ORCID Profile
0000-0003-2545-6939
Current Organisations
Arizona State University
,
University of Western Australia
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Natural Products Chemistry | Separation Science | Plant Biology | Organic Chemistry | Biologically Active Molecules | Plant Cell and Molecular Biology | Organic Chemical Synthesis | Genetics | Population, Ecological and Evolutionary Genetics | Plant Biology not elsewhere classified | Biological And Medical Chemistry | Biochemistry and Cell Biology | Geochemistry | Organic Chemical Synthesis | Evolutionary Biology | Synthetic Biology | Organometallic Chemistry | Genomics | Conservation and Biodiversity | Analytical Chemistry | Analytical Spectrometry | Medicinal and Biomolecular Chemistry | Separation Science | Other Instrumental Methods | Medical Biochemistry and Metabolomics not elsewhere classified | Organic Geochemistry | Industrial Chemistry | Evolution of Developmental Systems | Microbial Ecology | Proteomics and Intermolecular Interactions (excl. Medical Proteomics) | Plant Physiology | Materials Engineering Not Elsewhere Classified | Agronomy | Biological Sciences not elsewhere classified | Biological Adaptation
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Biological Sciences | Plant Production and Plant Primary Products not elsewhere classified | Field crops | Flora, Fauna and Biodiversity at Regional or Larger Scales | Organic industrial chemicals not classified elsewhere | Wheat | Rehabilitation of degraded farmland | Flora, Fauna and Biodiversity of environments not elsewhere classified | Horticultural Crops not elsewhere classified | Manufactured products not elsewhere classified | Treatments (e.g. chemicals, antibiotics) | Environmentally Sustainable Plant Production not elsewhere classified | Rehabilitation of degraded mining lands | Water Services and Utilities | Industrial chemicals and related products | Oil and Gas Exploration | Coastal and Estuarine Soils | Winter Grains and Oilseeds not elsewhere classified | Expanding Knowledge in the Environmental Sciences | Expanding Knowledge in the Agricultural and Veterinary Sciences |
Related Links
Publications
Substrate-Induced Degradation of the α/β-Fold Hydrolase KARRIKIN INSENSITIVE2 Requires a Functional Catalytic Triad but Is Independent of MAX2
Publisher: Elsevier BV
Date: 05-2015
Early human impacts and ecosystem reorganization in southern-central Africa
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-05-2021
Abstract: Early modern humans fundamentally altered ecology and landscapes in southern-central Africa using fire.
Pollination by sexual deception — it takes chemistry to work
Publisher: Elsevier BV
Date: 08-2016
DOI: 10.1016/J.PBI.2016.06.004
Abstract: Semiochemicals are of paramount importance in sexually deceptive plants. These plants sexually lure specific male insects as pollinators by chemical and physical mimicry of the female of the pollinator. The strategy has evolved repeatedly in orchids, with a wide ersity of insect groups exploited. Chemical communication systems confirmed by field bioassays include: alkenes and alkanes in bee pollinated Ophrys species, keto-acid and hydroxy-acids in scoliid wasp pollinated O. speculum, and cyclohexanediones and pyrazines in thynnine wasp pollinated Chiloglottis and Drakaea orchids, respectively. In Ophrys, stearoyl-acyl carrier protein desaturase (SAD) enzymes have been confirmed to control species level variation in alkene double bond position. The production of cyclohexanediones in Chiloglottis unexpectedly depends on UVB light, a phenomenon unknown for other plant specialised metabolites. Potential biosynthetic pathways for other systems are explored, and alternative approaches to further accelerate chemical discovery in sexually deceptive plants are proposed.
Effects of a butenolide present in smoke on light-mediated germination of Australian Asteraceae
Publisher: Cambridge University Press (CUP)
Date: 03-2006
DOI: 10.1079/SSR2005232
Abstract: This study investigated the effects of 3-methyl-2 H -furo[2,3- c ]pyran-2-one, a germination active butenolide present in plant-derived smoke, gibberellic acid and smoke water on seeds of Australian Asteraceae exposed to different light regimes. Seeds of all species required light, with maximum germination occurring under white light, or light dominated by 640 nm. Compared to untreated seeds, butenolide increased germination of Angianthus tomentosus , Gnephosis tenuissima , Myriocephalus guerinae , Podolepis canescens and Rhodanthe citrina at suboptimal light wavelengths and in the dark to a level equal to, or greater than, smoke water. Germination of Erymophyllum glossanthus and Gnephosis acicularis was not promoted by butenolide or smoke water under any light regime. The action of gibberellic acid was compared to that of butenolide for three species ( Angianthus tomentosus , Myriocephalus guerinae and Podolepis canescens ), and both compounds were found to stimulate germination. This study provides evidence that butenolide can act in a similar fashion as gibberellic acid in promoting seed germination of light-sensitive seeds. The ecological significance of these findings is discussed.
Parental environment changes the dormancy state and karrikinolide response of Brassica tournefortii seeds
Publisher: Oxford University Press (OUP)
Date: 03-04-2012
DOI: 10.1093/AOB/MCS067
Type-I Hemins and Free Porphyrins from a Western Australian Sponge Isabela sp.
Publisher: MDPI AG
Date: 03-01-2023
DOI: 10.3390/MD21010041
Abstract: Two novel free porphyrins, isabellins A and B, as well as the known compounds corallistin D and deuteroporphyrin IX were isolated from a marine sponge Isabela sp. LC-MS analysis of the crude extract revealed that the natural products were present both as free porphyrins and iron(III) coordinated hemins, designated isabellihemin A, isabellihemin B, corallistihemin D and deuterohemin IX, respectively. Structures were determined via high-resolution mass spectrometry, UV-Vis spectroscopy and extensive NOESY NMR spectroscopic experiments. The type-I alkyl substitution pattern of isabellin A and isabellihemin A was assigned unambiguously by single crystal X-ray diffraction. Biological evaluation of the metabolites revealed potent cytotoxicity for isabellin A against the NS-1 murine myeloma cell line.
Dirhodium-Catalyzed Transannulation of N-Sulfonyl-1,2,3-triazoles to 2,3-Dehydropiperazines
Publisher: American Chemical Society (ACS)
Date: 31-07-2023
Investigation of an Unusual Crystal Habit of Hydrochlorothiazide Reveals Large Polar Enantiopure Domains and a Possible Crystal Nucleation Mechanism
Publisher: Wiley
Date: 24-06-2019
Abstract: The observation of an unusual crystal habit in the common diuretic drug hydrochlorothiazide (HCT), and identification of its subtle conformational chirality, has stimulated a detailed investigation of its crystalline forms. Enantiomeric conformers of HCT resolve into an unusual structure of conjoined enantiomorphic twin crystals comprising enantiopure domains of opposite chirality. The purity of the domains and the chiral molecular conformation are confirmed by spatially revolved synchrotron micro-XRD experiments and neutron diffraction, respectively. Macroscopic inversion twin symmetry observed between the crystal wings suggests a pseudoracemic structure that is not a solid solution or a layered crystal structure, but an unusual structural variant of conglomerates and racemic twins. Computed interaction energies for molecular pairs in the racemic and enantiopure polymorphs of HCT, and the observation of large opposing unit-cell dipole moments for the enantiopure domains in these twin crystals, suggest a plausible crystal nucleation mechanism for this unusual crystal habit.
Pyroxasulfone-Resistant Annual Ryegrass (Lolium rigidum) Has Enhanced Capacity for Glutathione Transferase-Mediated Pyroxasulfone Conjugation
Publisher: American Chemical Society (ACS)
Date: 03-06-2021
Carlactone-independent seedling morphogenesis in Arabidopsis
Publisher: Wiley
Date: 25-07-2013
DOI: 10.1111/TPJ.12265
Abstract: Strigolactone hormones are derived from carotenoids via carlactone, and act through the α/β-hydrolase D14 and the F-box protein D3/MAX2 to repress plant shoot branching. While MAX2 is also necessary for normal seedling development, D14 and the known strigolactone biosynthesis genes are not, raising the question of whether endogenous, canonical strigolactones derived from carlactone have a role in seedling morphogenesis. Here, we report the chemical synthesis of the strigolactone precursor carlactone, and show that it represses Arabidopsis shoot branching and influences leaf morphogenesis via a mechanism that is dependent on the cytochrome P450 MAX1. In contrast, both physiologically active Z-carlactone and the non-physiological E isomer exhibit similar weak activity in seedlings, and predominantly signal through D14 rather than its paralogue KAI2, in a MAX2-dependent but MAX1-independent manner. KAI2 is essential for seedling morphogenesis, and hence this early-stage development employs carlactone-independent morphogens for which karrikins from wildfire smoke are specific surrogates. While the commonly employed synthetic strigolactone GR24 acts non-specifically through both D14 and KAI2, carlactone is a specific effector of strigolactone signalling that acts through MAX1 and D14.
The substrate-dependent stereoselectivity of the multicopper oxidase (MCO)-catalyzed oxidative coupling in the biosynthesis of the bisnaphthopyrone viriditoxin
Publisher: Cold Spring Harbor Laboratory
Date: 18-11-2019
DOI: 10.1101/846196
Abstract: VdtB, the multiple-copper oxidase (MCO) from the bisnaphthopyrone ( M )-viriditoxin biosynthetic pathway in Paecilomyces variotii , was shown to catalyze regioselective 6,6′-coupling of semi-viriditoxin ( 1 ). The stereoselectivity of the oxidative coupling reaction for the production of the atropisomer ( M )-viriditoxin, however, was controlled by VdtD, a non-catalytic dirigent protein from the pathway. In this work, VdtB either alone or together with VdtD were investigated for its stereoselective control upon coupling of other monomeric naphthopyrone derivatives from the pathway with different minor structural variations in terms of presence/absence of O -methylation at C7-position and C3-C4 Δ 2 double bond on the pyrone ring, and the different side-chain modifications. We showed that VdtB could favour either M - or P -form coupling in a substrate-dependent manner. For some substrates, VdtB could catalyze oxidative coupling in an enantiomerically selective manner. The efficiency of the VdtD in exerting stereoselective control of the oxidative coupling reaction also varies between substrates. The results point to a model whereby VdtB and VdtD form a VdtB-ligand-VdtD complex in which the stereochemical outcome of the coupling reaction depends on how the substrate interacts with both proteins, based on the substrate structure. Our findings contributed to a more comprehensive understanding of dirigent protein-mediated MCO-catalyzed stereoselective oxidative coupling reactions in fungi.
Volatile Combustion Products of Wood Attract Acanthocnemus nigricans (Coleoptera: Acanthocnemidae)
Publisher: Springer Science and Business Media LLC
Date: 14-11-2014
Seed germination of agricultural weeds is promoted by the butenolide 3-methyl-2H-furo[2,3-c]pyran-2-one under laboratory and field conditions
Publisher: Springer Science and Business Media LLC
Date: 08-08-2007
An Artificial Yeast Genetic Circuit Enables Deep Mutational Scanning of an Antimicrobial Resistance Protein
Publisher: American Chemical Society (ACS)
Date: 06-07-2018
DOI: 10.1021/ACSSYNBIO.8B00121
Abstract: Understanding the molecular mechanisms underlying antibiotic resistance requires concerted efforts in enzymology and medicinal chemistry. Here we describe a new synthetic biology approach to antibiotic development, where the presence of tetracycline antibiotics is linked to a life-death selection in Saccharomyces cerevisiae. This artificial genetic circuit allowed the deep mutational scanning of the tetracycline inactivating enzyme TetX, revealing key functional residues. We used both positive and negative selections to confirm the importance of different residues for TetX activity, and profiled activity hotspots for different tetracyclines to reveal substrate-specific activity determinants. We found that precise positioning of FAD and hydrophobic shielding of the tetracycline are critical for enzymatic inactivation of doxycycline. However, positioning of FAD is suboptimal in the case of anhydrotetracycline, potentially explaining its comparatively poor degradation and potential as an inhibitor for this family of enzymes. By combining artificial genetic circuits whose function can be modulated by antimicrobial resistance determinants, we establish a framework to select for the next generation of antibiotics.
Lateral branching oxidoreductase acts in the final stages of strigolactone biosynthesis in Arabidopsis
Publisher: Proceedings of the National Academy of Sciences
Date: 18-05-2016
Abstract: Strigolactone hormones regulate many plant growth and developmental processes and are particularly important in regulating growth in response to nonoptimal conditions. Plants produce a range of bioactive strigolactone-like compounds, suggesting that the biosynthesis pathway is complex. Despite this complexity, only one type of enzyme, the MORE AXILLARY GROWTH1 (MAX1) cytochrome P450, has been attributed to the ersity of strigolactones. Using transcriptomics and reverse genetics, we discovered a previously uncharacterized gene that encodes a 2-oxoglutarate and Fe(II)-dependent dioxygenase involved in strigolactone production downstream of MAX1. Studies with the corresponding mutant have shown that previously identified strigolactone-type compounds in Arabidopsis are not the major strigolactone-type shoot branching hormone in this model species.
Synthesis of the seed germination stimulant 3-methyl-2H-furo[2,3-c]pyran-2-one
Publisher: Elsevier BV
Date: 08-2005
Specialisation within the DWARF14 protein family confers distinct responses to karrikins and strigolactones in Arabidopsis
Publisher: The Company of Biologists
Date: 04-2012
DOI: 10.1242/DEV.074567
Abstract: Karrikins are butenolides derived from burnt vegetation that stimulate seed germination and enhance seedling responses to light. Strigolactones are endogenous butenolide hormones that regulate shoot and root architecture, and stimulate the branching of arbuscular mycorrhizal fungi. Thus, karrikins and strigolactones are structurally similar but physiologically distinct plant growth regulators. In Arabidopsis thaliana, responses to both classes of butenolides require the F-box protein MAX2, but it remains unclear how discrete responses to karrikins and strigolactones are achieved. In rice, the DWARF14 protein is required for strigolactone-dependent inhibition of shoot branching. Here, we show that the Arabidopsis DWARF14 orthologue, AtD14, is also necessary for normal strigolactone responses in seedlings and adult plants. However, the AtD14 paralogue KARRIKIN INSENSITIVE 2 (KAI2) is specifically required for responses to karrikins, and not to strigolactones. Phylogenetic analysis indicates that KAI2 is ancestral and that AtD14 functional specialisation has evolved subsequently. Atd14 and kai2 mutants exhibit distinct subsets of max2 phenotypes, and expression patterns of AtD14 and KAI2 are consistent with the capacity to respond to either strigolactones or karrikins at different stages of plant development. We propose that AtD14 and KAI2 define a class of proteins that permit the separate regulation of karrikin and strigolactone signalling by MAX2. Our results support the existence of an endogenous, butenolide-based signalling mechanism that is distinct from the strigolactone pathway, providing a molecular basis for the adaptive response of plants to smoke.
Karrikins force a rethink of strigolactone mode of action
Publisher: Informa UK Limited
Date: 08-2012
DOI: 10.4161/PSB.20977
Mycotoxins produced by Fusarium spp. associated with Fusarium head blight of wheat in Western Australia
Publisher: Springer Science and Business Media LLC
Date: 02-02-2012
DOI: 10.1007/S12550-011-0122-7
Abstract: An isolated occurrence of Fusarium head blight (FHB) of wheat was detected in the south-west region of Western Australia during the 2003 harvest season. The molecular identity of 23 isolates of Fusarium spp. collected from this region during the FHB outbreak confirmed the associated pathogens to be F. graminearum, F. acuminatum or F. tricinctum. Moreover, the toxicity of their crude extracts from Czapek-Dox liquid broth and millet seed cultures to brine shrimp (Artemia franciscana) was associated with high mortality levels. The main mycotoxins detected were type B trichothecenes (deoxynivalenol and 3-acetyldeoxynivalenol), enniatins, chlamydosporol and zearalenone. This study is the first report on the mycotoxin profiles of Fusarium spp. associated with FHB of wheat in Western Australia. This study highlights the need for monitoring not just for the presence of the specific Fusarium spp. present in any affected grain but also for their potential mycotoxin and other toxic secondary metabolites.
Oxidation of hydroxymethylpyrazines and hydroxylated phenyl compounds in a gas chromatography inlet
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4AY02958E
Abstract: Large proportions of aldehydes were formed when hydroxymethylpyrazines, and benzyl- and cinnamyl alcohols were analysed by gas chromatography-mass spectrometry using a heated inlet with a used glass inlet liner.
The Spider Orchid Caladenia crebra Produces Sulfurous Pheromone Mimics to Attract its Male Wasp Pollinator
Publisher: Wiley
Date: 06-2017
Abstract: One of the most intriguing natural observations is the pollination of orchids by sexual deception. Chemicals underpin this interaction between the orchid and its sexually attracted male insect pollinator, with the signaling compounds involved, called semiochemicals, predicted to mimic the chemical composition of the sex pheromone. We identified floral semiochemicals from Caladenia (spider orchids) for the first time. We further demonstrate that C. crebra attracts its single pollinator species with a unique system of (methylthio)phenols, three of which are new natural products. Furthermore, as predicted, the same compounds constitute the sex pheromone of the pollinator, the thynnine wasp C ylothynnus flavopictus, representing the first occurrence of sulfurous sex pheromones in Hymenoptera.
Acclimation-induced changes in cell membrane composition and influence on cryotolerance of in vitro shoots of native plant species
Publisher: Springer Science and Business Media LLC
Date: 04-03-2013
Karrikins Identified in Biochars Indicate Post-Fire Chemical Cues Can Influence Community Diversity and Plant Development
Publisher: Public Library of Science (PLoS)
Date: 18-08-2016
An unusual tricosatriene is crucial for male fungus gnat attraction and exploitation by sexually deceptive Pterostylis orchids
Publisher: Elsevier BV
Date: 05-2021
DOI: 10.1016/J.CUB.2021.01.095
Abstract: Cross-kingdom mimicry of female insect sex pheromones by sexually deceptive orchids has evolved multiple times.
Inhibition of ruminal bacteria involved in lactic acid metabolism by extracts from Australian plants
Publisher: Elsevier BV
Date: 09-2012
A Direct Pre-screen for Marine Bacteria Producing Compounds Inhibiting Quorum Sensing Reveals Diverse Planktonic Bacteria that are Bioactive
Publisher: Springer Science and Business Media LLC
Date: 08-2014
DOI: 10.1007/S10126-014-9592-X
Abstract: A promising new strategy in antibacterial research is inhibition of the bacterial communication system termed quorum sensing. In this study, a novel and rapid pre-screening method was developed to detect the production of chemical inhibitors of this system (quorum-quenching compounds) by bacteria isolated from marine and estuarine waters. This method involves direct screening of mixed populations on an agar plate, facilitating specific isolation of bioactive colonies. The assay showed that between 4 and 46 % of culturable bacteria from various s les were bioactive, and of the 95 selectively isolated bacteria, 93.7 % inhibited Vibrio harveyi bioluminescence without inhibiting growth, indicating potential production of quorum-quenching compounds. Of the active isolates, 21 % showed further activity against quorum-sensing-regulated pigment production by Serratia marcescens. The majority of bioactive isolates were identified by 16S ribosomal DNA (rDNA) lification and sequencing as belonging to the genera Vibrio and Pseudoalteromonas. Extracts of two strongly bioactive Pseudoalteromonas isolates (K1 and B2) were quantitatively assessed for inhibition of growth and quorum-sensing-regulated processes in V. harveyi, S. marcescens and Chromobacterium violaceum. Extracts of the isolates reduced V. harveyi bioluminescence by as much as 98 % and C. violaceum pigment production by 36 % at concentrations which had no adverse effect on growth. The activity found in the extracts indicated that the isolates may produce quorum-quenching compounds. This study further supports the suggestion that quorum quenching may be a common attribute among culturable planktonic marine and estuarine bacteria.
Methyl t-butyl ether-degrading bacteria for bioremediation and biocontrol purposes
Publisher: Public Library of Science (PLoS)
Date: 21-02-2020
Secondary metabolites produced by a root-inhabiting sterile fungus antagonistic towards pathogenic fungi
Publisher: Oxford University Press (OUP)
Date: 04-2010
A Specific Blend of Drakolide and Hydroxymethylpyrazines: An Unusual Pollinator Sexual Attractant Used by the Endangered Orchid Drakaea micrantha
Publisher: Wiley
Date: 12-12-2019
Abstract: Bioactive natural products underpin the intriguing pollination strategy used by sexually deceptive orchids. These compounds, which mimic the sex pheromones of the female insect, are emitted in particular blends to lure male insect pollinators of specific species. By combining methods from field biology, analytical chemistry, electrophysiology, crystallography, and organic synthesis, we report that an undescribed β‐hydroxylactone, in combination with two specific hydroxymethylpyrazines, act as pollinator attractants in the rare hammer orchid Drakaea micrantha . This discovery represents an unusual case of chemically unrelated compounds being used together as a sexual attractant. Furthermore, this is the first ex le of the identification of pollinator attractants in an endangered orchid, enabling the use of chemistry in orchid conservation. Our synthetic blend is now available to be used in pollinator surveys to locate suitable sites for plant conservation translocations.
Metabolites of a Drechslera sp. endophyte with potential as biocontrol and bioremediation agent
Publisher: Informa UK Limited
Date: 11-03-2020
Rice cytochrome P450 MAX1 homologs catalyze distinct steps in strigolactone biosynthesis
Publisher: Springer Science and Business Media LLC
Date: 26-10-2014
Abstract: Strigolactones (SLs) are a class of phytohormones and rhizosphere signaling compounds with high structural ersity. Three enzymes, carotenoid isomerase DWARF27 and carotenoid cleavage dioxygenases CCD7 and CCD8, were previously shown to convert all-trans-β-carotene to carlactone (CL), the SL precursor. However, how CL is metabolized to SLs has remained elusive. Here, by reconstituting the SL biosynthetic pathway in Nicotiana benthamiana, we show that a rice homolog of Arabidopsis More Axillary Growth 1 (MAX1), encodes a cytochrome P450 CYP711 subfamily member that acts as a CL oxidase to stereoselectively convert CL into ent-2'-epi-5-deoxystrigol (B-C lactone ring formation), the presumed precursor of rice SLs. A protein encoded by a second rice MAX1 homolog then catalyzes the conversion of ent-2'-epi-5-deoxystrigol to orobanchol. We therefore report that two members of CYP711 enzymes can catalyze two distinct steps in SL biosynthesis, identifying the first enzymes involved in B-C ring closure and a subsequent structural ersification step of SLs.
Plant growth stage and Phoma medicaginis inoculum concentration together determine severity of Phoma black stem and leaf spot and consequent phytoestrogen production in annual Medicago spp.
Publisher: Wiley
Date: 26-06-2023
DOI: 10.1111/PPA.13770
Abstract: Phoma black stem and leaf spot disease ( Phoma medicaginis ) not only destroys annual Medicago spp. forage and seed yield but also reduces herbage quality by consequent phytoestrogen production that reduces ovulation of grazing animals. Two controlled environment studies evaluated the effects of plant developmental stage in annual Medicago rugosa ‘Paraponto’ and M . scutellata ‘Sava’ and different inoculum concentrations of P . medicaginis in M . littoralis ‘Harbinger’ and M . polymorpha ‘Serena’ on disease development and coumestrol production. Disease incidence and severity and coumestrol production were dependent on plant developmental stage, cultivar and inoculum level (all p ≤ 0.001). Disease was least in 4‐week‐old plants highest coumestrol was in inoculated 10‐week‐old Sava (1353 mg/kg) and least coumestrol in uninoculated 4‐week‐old Paraponto (87 mg/kg) and there was a positive correlation of disease incidence/severity factors with coumestrol across cultivars and plant growth stages ( p 0.001). Disease levels and coumestrol production were determined by inoculum concentration and cultivar (both p ≤ 0.001). Highest coumestrol was in Serena inoculated with 10 7 conidia/mL (265 mg/kg) lowest coumestrol was in uninoculated Harbinger (6 mg/kg) and there was a significant positive correlation of disease incidence/severity factors with coumestrol across cultivars and inoculum concentrations ( p 0.001). These studies emphasize both the opportunity for farmers to better use annual Medicago spp. stands for grazing reproducing animals early in the growing season when both disease and coumestrol levels are lowest, and the need for heightened farmer vigilance at later growth stages with greater disease and consequent phytoestrogen risk for grazing animals.
Phoma black stem severity and phytoestrogen production in annual Medicago spp. is primarily determined by interaction of cultivar and pathogen isolate
Publisher: Wiley
Date: 09-02-2022
DOI: 10.1111/PPA.13533
Abstract: Phoma black stem and leaf spot disease (caused by Phoma medicaginis ) not only diminishes forage and seed yield but stimulates production of detrimental phytoestrogens in annual Medicago spp. This study aimed to evaluate relationships between disease development from five isolates of P . medicaginis on 16 cultivars with production of coumestrol and 4′‐ O ‐methylcoumestrol. In the presence of P . medicaginis , Sava had the highest coumestrol and 4′‐ O ‐methylcoumestrol (640 and 85 mg/kg, respectively) followed by Caliph (253 and 15 mg/kg, respectively). In the absence of P . medicaginis , Jemalong and Paragosa showed highest and lowest coumestrol (137 and 0 mg/kg, respectively). 4′‐ O ‐methylcoumestrol was not produced in disease‐free plants, but coumestrol was. Disease incidence and severity on leaves and on petiole/stems, and consequent leaf yellowing severity ranged from 5%–98.7%, 0%–100%, 4.4%–98.7%, 1.7%–100%, and 0%–85%. Sava, Paraponto, Harbinger, and Serena were most susceptible, while Tornafield and Caliph were least susceptible. There was significant overall positive correlation of disease incidence/severity factors across cultivars ( p 0.01) with both coumestrol and 4′‐ O ‐methylcoumestrol. Jemalong was least responsive and Paragosa and Sava most responsive to coumestrol production following P . medicaginis inoculation. Coumestrol in inoculated Paragosa increased to 373 mg/kg in comparison with 0 mg/kg in controls. These findings are of critical importance towards developing less disease‐susceptible annual Medicago spp. producing less detrimental phytoestrogens. Least susceptible cultivars like Tornafield and Caliph can be used to manage yield loss, whilst least responsive cultivars to phytoestrogen production like Caliph also can help to reduce phytoestrogen production.
Exploring the molecular mechanism of karrikins and strigolactones
Publisher: Elsevier BV
Date: 06-2012
DOI: 10.1016/J.BMCL.2012.04.016
Abstract: Karrikins and strigolactones are novel plant growth regulators that contain similar molecular features, but very little is known about how they elicit responses in plants. A tentative molecular mechanism has previously been proposed involving a Michael-type addition for both compounds. Through structure-activity studies with karrikins, we now propose an alternative mechanism for karrikin and strigolactone mode of action that involves hydrolysis of the butenolide ring.
Structure of a class III engineered cephalosporin acylase: comparisons with class I acylase and implications for differences in substrate specificity and catalytic activity
Publisher: Portland Press Ltd.
Date: 28-03-2013
DOI: 10.1042/BJ20121715
Abstract: The crystal structure of the wild-type form of glutaryl-7-ACA (7-aminocephalosporanic acid) acylase from Pseudomonas N176 and a double mutant of the protein (H57βS/H70βS) that displays enhanced catalytic efficiency on cephalosporin C over glutaryl-7-aminocephalosporanic acid has been determined. The structures show a heterodimer made up of an α-chain (229 residues) and a β-chain (543 residues) with a deep cavity, which constitutes the active site. Comparison of the wild-type and mutant structures provides insights into the molecular reasons for the observed enhanced specificity on cephalosporin C over glutaryl-7-aminocephalosporanic acid and offers the basis to evolve a further improved enzyme variant. The nucleophilic catalytic serine residue, Ser1β, is situated at the base of the active site cavity. The electron density reveals a ligand covalently bound to the catalytic serine residue, such that a tetrahedral adduct is formed. This is proposed to mimic the transition state of the enzyme for both the maturation step and the catalysis of the substrates. A view of the transition state configuration of the enzyme provides important insights into the mechanism of substrate binding and catalysis.
Volatiles from Merino fleece evoke antennal and behavioural responses in the Australian sheep blow fly Lucilia cuprina
Publisher: Wiley
Date: 28-05-2019
DOI: 10.1111/MVE.12383
Abstract: To identify flystrike‐related volatile compounds in wool from Merino sheep, the attractiveness of wool to Lucilia cuprina Wiedmann (Diptera: Calliphoridae) was examined. First, a selection of wool s les guided by previous knowledge of sheep lines, predicted to be more susceptible or more resistant to flystrike, was tested. The attractiveness of the 10 s les selected was not associated with field susceptibility: two s les from the more resistant line were identified as most attractive and two s les from the more susceptible line were identified as least attractive, based on the behavioural assays with gravid flies. Comparison of the headspace volatiles of these s les, using solid phase microextraction and gas chromatography‐mass spectrometry‐electroantennographic detection, revealed octanal and nonanal to be present in the attractive wool s les that elicited responses from the fly antenna. Furthermore, the two compounds were not present in wool that was least attractive to L. cuprina . In laboratory bioassays, octanal and nonanal evoked antennal and behavioural responses in gravid L. cuprina , thus confirming their potential role as semiochemicals responsible for attracting L. cuprina to Merino sheep.
Critical pollination chemistry: Specific sesquiterpene floral volatiles in carrot inhibit honey bee feeding
Publisher: Cold Spring Harbor Laboratory
Date: 11-10-2022
DOI: 10.1101/2022.10.11.511710
Abstract: Although many plant species are reliant on insect pollination, agricultural plant breeding programs have primarily focused on traits that appeal to growers and consumers, rather than on floral traits that enhance pollinator attraction. In some vegetable seed production systems, this has led to declining pollinator attraction and poor seed yields. We predicted that low-yielding crop varieties would be less attractive to pollinators due to deficiencies in nectar rewards or volatile floral attractants. To test our prediction, we used a chemical phenotyping approach to examine how floral chemical traits of five carrot lines affect honey bee visitation. In bioassays, honey bees avoided feeders containing nectar from all carrot lines indicating a general non-attractant effect. Certain compounds in carrot flowers and nectar not only failed to elicit attraction but functioned as repellents, including the sesquiterpenes α-selinene and β-selinene. Others enhanced attraction, e.g. β-ocimene. The repellent sesquiterpenes have previously been implicated in plant defense suggesting a fine balance between pollination and plant protection, which when disrupted in artificial selection in plant breeding programs can impact the crop yield. These new insights highlight the importance of bioactive compounds in attracting pollinators toward floral resources in both ecological and agricultural settings.
Karrikins: A new family of plant growth regulators in smoke
Publisher: Elsevier BV
Date: 10-2009
Bioactive fractions from the pasture legume Biserrula pelecinus L. have an anti-methanogenic effect against key rumen methanogens
Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.ANAEROBE.2016.04.004
Abstract: Methanogenic archaea (methanogens) are common inhabitants of the mammalian intestinal tract. In ruminants, they are responsible for producing abundant amounts of methane during digestion of food, but selected bioactive plants and compounds may inhibit this activity. Recently, we have identified that, Biserrula pelecinus L. (biserrula) is one such plant and the current study investigated the specific anti-methanogenic activity of the plant. Bioassay-guided extraction and fractionation, coupled with in vitro fermentation batch culture were used to select the most bioactive fractions of biserrula. The four fractions were then tested against five species of methanogens grown in pure culture. Fraction bioactivity was assessed by measuring methane production and lification of the methanogen mcrA gene. Treatments that showed bioactivity were subcultured in fresh broth without the bioactive fraction to distinguish between static and cidal effects. All four fractions were active against pure cultures, but the F2 fraction was the most consistent inhibitor of both methane production and cell growth, affecting four species of methanogens and also producing equivocal-cidal effects on the methanogens. Other fractions had selective activity affecting only some methanogens, or reducing either methane production or methanogenic cell growth. In conclusion, the anti-methanogenic activity of biserrula can be linked to compounds contained in selected bioactive fractions, with the F2 fraction strongly affecting key rumen methanogens. Further study is required to identify the specific plant compounds in biserrula that are responsible for the anti-methanogenic activity. These findings will help devise novel strategies to control methanogen populations and activity in the rumen, and consequently contribute in reducing greenhouse gas emissions from ruminants.
The volatile chemistry of orchid pollination
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2NP00060A
Abstract: Orchids are amongst the most erse of all plant families, and produce a wide array of volatile compounds for pollinator attraction.
Regulation of seed germination and seedling growth by chemical signals from burning vegetation
Publisher: Annual Reviews
Date: 02-06-2012
DOI: 10.1146/ANNUREV-ARPLANT-042811-105545
Abstract: It is well known that burning of vegetation stimulates new plant growth and landscape regeneration. The discovery that char and smoke from such fires promote seed germination in many species indicates the presence of chemical stimulants. Nitrogen oxides stimulate seed germination, but their importance in post-fire germination has been questioned. Cyanohydrins have been recently identified in aqueous smoke solutions and shown to stimulate germination of some species through the slow release of cyanide. However, the most information is available for karrikins, a family of butenolides related to 3-methyl-2H-furo[2,3-c]pyran-2-one. Karrikins stimulate seed germination and influence seedling growth. They are active in species not normally associated with fire, and in Arabidopsis they require the F-box protein MAX2, which also controls responses to strigolactone hormones. We hypothesize that chemical similarity between karrikins and strigolactones provided the opportunity for plants to employ a common signal transduction pathway to respond to both types of compound, while tailoring specific developmental responses to these distinct environmental signals.
Discovery of Tetrasubstituted Pyrazines As Semiochemicals in a Sexually Deceptive Orchid
Publisher: American Chemical Society (ACS)
Date: 18-09-2012
DOI: 10.1021/NP300388Y
Abstract: Sexually deceptive orchids employ mimicry of insect sex pheromones to exploit a erse group of pollinators. The chemical structures of five semiochemicals (1-3, 7, 8) produced by populations of the warty hammer orchid, Drakaea livida, pollinated by a thynnine wasp in the genus Catocheilus were elucidated. With the exception of (2,5-dimethylpyrazin-3-yl)methyl 3-methylbutanoate (7), all active compounds were tetrasubstituted pyrazines, including hydroxymethyl (1) and ester (2 and 3) trimethylpyrazine derivatives. Male Catocheilus wasps were responsive to all of these compounds in GC-EAD experiments.
Structural Analysis of a Potent Seed Germination Stimulant
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/CH05086
Abstract: A single-crystal X-ray crystallographic study of a seed germination stimulant isolated from plant-derived smoke confirms it to be 3-methyl-2H-furo[2,3-c]pyran-2-one 1.
Karrikins promote germination of physiologically dormant seeds of Chrysanthemoides monilifera ssp. monilifera (boneseed)
Publisher: Wiley
Date: 23-11-2014
DOI: 10.1111/WRE.12051
Marine Natural Products from Flora and Fauna of the Western Australian Coast: Taxonomy, Isolation and Biological Activity
Publisher: MDPI AG
Date: 02-02-2023
DOI: 10.3390/MOLECULES28031452
Abstract: Marine natural products occurring along the Western Australian coastline are the focus of this review. Western Australia covers one-third of the Australian coast, from tropical waters in the far north of the state to cooler temperate and Antarctic waters in the south. Over 40 years of research has resulted in the identification of a number of different types of secondary metabolites including terpenoids, alkaloids, polyketides, fatty acid derivatives, peptides and arsenic-containing natural products. Many of these compounds have been reported to display a variety of bioactivities. A description of the compound classes and their associated bioactivities from marine organisms found along the Western Australian coastline is presented.
2-(Tetrahydrofuran-2-yl)acetic Acid and Ester Derivatives as Long-Range Pollinator Attractants in the Sexually Deceptive Orchid Cryptostylis ovata
Publisher: American Chemical Society (ACS)
Date: 28-03-2019
DOI: 10.1021/ACS.JNATPROD.8B00772
Abstract: Sexually deceptive orchids achieve pollination by luring male insects to flowers through chemical and sometimes visual mimicry of females. An extreme ex le of this deception occurs in Cryptostylis, one of only two genera where sexual deception is known to induce pollinator ejaculation. In the present study, bioassay-guided fractionations of Cryptostylis solvent extracts in combination with field bioassays were implemented to isolate and identify floral volatiles attractive to the pollinator Lissopimpla excelsa. ( S)-2-(Tetrahydrofuran-2-yl)acetic acid [( S)-1] and the ester derivatives methyl ( S)-2-(tetrahydrofuran-2-yl)acetate [( S)-2] and ethyl ( S)-2-(tetrahydrofuran-2-yl)acetate [( S)-3], all previously unknown semiochemicals, were confirmed to attract L. excelsa males in field bioassays. Chiral-phase GC and HPLC showed that the natural product 1 comprised a single enantiomer, its S-configuration being confirmed by synthesis of the two enantiomers from known enantiomers of tetrahydrofuran-2-carboxylic acid.
Synthesis of R- and S-MDMA via nucleophilic ring-opening of homochiral N-tosylaziridines
Publisher: CSIRO Publishing
Date: 12-07-2023
DOI: 10.1071/CH23064
Abstract: Homochiral (R)- and (S)-3,4-methylenedioxymeth hetamine (MDMA) were prepared in six steps (each) from the chiral pool precursors d- and l-alanine, respectively. The key step, copper-catalysed regioselective ring-opening of an N-tosylaziridine with an aryl Grignard reagent, proceeded in high yield with complete regioselectivity. Elaboration was achieved with preservation of configurational integrity, affording R- and S-MDMA hydrochlorides with enantiopurities of .5%, as determined by enantioselective HPLC with fluorescence detection. Attempts to apply the synthetic methodology to the synthesis of the homochiral enantiomers of the α-phenyl analogue of MDMA (UWA-001) were thwarted by a switch in regioselectivity in the key step.
Identification of hydroxymethylpyrazines using mass spectrometry
Publisher: Wiley
Date: 23-06-2015
DOI: 10.1002/JMS.3612
Abstract: Pyrazines are well-known natural products that are present in bacterial odours and food flavouring agents and are used as insect pheromones. Recently, a number of hydroxymethylpyrazines have been identified as thynnine wasp pheromones and orchid semiochemicals that are essential for pollination in sexually deceptive plants. These compounds are present in low amounts in complex blends, making GC-MS (including high-resolution techniques) the method of choice for their structure elucidation. We report the EI mass spectra for 14 representative compounds and have found that based on characteristic fragmentations, it is possible to distinguish between different positional isomers of hydroxymethylpyrazines. The presence or absence of either [M - 17]
Mechanism of the dehydrogenase reaction of DmpFG and analysis ofinter-subunit channeling efficiency and thermodynamic parametersin the overall reaction
Publisher: Elsevier BV
Date: 08-2013
DOI: 10.1016/J.BIOCEL.2013.05.028
Abstract: The bifunctional, microbial enzyme DmpFG is comprised of two subunits: the aldolase, DmpG, and the dehydrogenase, DmpF. DmpFG is of interest due to its ability to channel substrates between the two spatially distinct active sites. While the aldolase is well studied, significantly less is known about the dehydrogenase. Steady-state kinetic measurements of the reverse reaction of DmpF confirmed that the dehydrogenase uses a ping-pong mechanism, with substrate inhibition by acetyl CoA indicating that NAD(+)/NADH and CoA/acetyl CoA bind to the same site in DmpF. The Km of DmpF for exogenous acetaldehyde as a substrate was 23.7 mM, demonstrating the necessity for the channel to deliver acetaldehyde directly from the aldolase to the dehydrogenase active site. A channeling assay on the bifunctional enzyme gave an efficiency of 93% indicating that less than 10% of the toxic acetaldehyde leaks out of the channel into the bulk media, prior to reaching the dehydrogenase active site. The thermodynamic activation parameters of the reactions catalyzed by the aldolase, the dehydrogenase and the DmpFG complex were determined. The Gibb's free energy of activation for the dehydrogenase reaction was lower than that obtained for the full DmpFG reaction, in agreement with the high kcat obtained for the dehydrogenase reaction in isolation. Furthermore, although both the DmpF and DmpG reactions occur with small, favorable entropies of activation, the full DmpFG reaction occurs with a negative entropy of activation. This supports the concept of allosteric structural communication between the two enzymes to coordinate their activities.
Antimicrobial Activity of Several Cineole-Rich Western Australian Eucalyptus Essential Oils
Publisher: MDPI AG
Date: 03-12-2018
DOI: 10.3390/MICROORGANISMS6040122
Abstract: Essential oils from the Western Australian (WA) Eucalyptus mallee species Eucalyptus loxophleba, Eucalyptus polybractea, and Eucalyptus kochii subsp. plenissima and subsp. borealis were hydrodistilled from the leaves and then analysed by gas chromatography–mass spectrometry in addition to a commercial Eucalyptus globulus oil and 1,8-cineole. The main component of all oils was 1,8-cineole at 97.32% for E. kochii subsp. borealis, 96.55% for E. kochii subsp. plenissima, 82.95% for E. polybractea, 78.78% for E. loxophleba 2, 77.02% for E. globulus, and 66.93% for E. loxophleba 1. The Eucalyptus oils exhibited variable antimicrobial activity determined by broth microdilution, with E. globulus and E. polybractea oils showing the highest activities. The majority of microorganisms were inhibited or killed at concentrations ranging from 0.25% to 8.0% (v/v). Enterococcus faecalis and Candida albicans were the least susceptible organisms, whilst Acinetobacter baumannii was the most sensitive. In conclusion, all oils from WA Eucalyptus species showed microorganism inhibitory activity, although this varied according to both the Eucalyptus species and the microorganism tested. These data demonstrate that WA Eucalyptus oils show activity against a range of medically important pathogens and therefore have potential as antimicrobial agents.
(Methylthio)phenol semiochemicals are exploited by deceptive orchids as sexual attractants for Campylothynnus thynnine wasps
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.FITOTE.2017.09.022
Abstract: Until recently, (methylthio)phenols as natural products had only been reported from bacteria. Now, four representatives of this class of sulfurous aromatic compounds have been discovered as semiochemicals in the orchid Caladenia crebra, which secures pollination by sexual deception. In this case, field bioassays confirmed that a 10:1 blend of 2-(methylthio)benzene-1,4-diol (1) and 4-hydroxy-3-(methylthio)benzaldehyde (2) sexually attracts the male thynnine wasp C ylothynnus flavopictus (Tiphiidae:Thynnineae), the exclusive pollinator of C. crebra. Here we show with field bioassays that another undescribed species of C ylothynnus (sp. A) is strongly sexually attracted to a 1:1 blend of compounds 1 and 2, which elicits very high attempted copulation rates (88%). We also confirm that this C ylothynnus species is a pollinator of Caladenia attingens subsp. attingens. Chemical analysis of the flowers of this orchid revealed two (methylthio)phenols, compound 2 and 2-(methylthio)phenol (3), as candidate semiochemicals involved in pollinator attraction. Thus, (methylthio)phenols are likely to be more widely used than presently known. The confirmation of this C ylothynnus as a pollinator of C. attingens subsp. attingens at our study sites was unexpected, since elsewhere this orchid is pollinated by a different thynnine wasp (Thynnoides sp). In general, sexually deceptive Caladenia only use a single species of pollinator, and as such, this unusual case may offer a tractable study system for understanding the chemical basis of pollinator switching in sexually deceptive orchids.
Molecular weight of a germination-enhancing compound in smoke†
Publisher: Springer Science and Business Media LLC
Date: 06-0003
Stereospecificity in strigolactone biosynthesis and perception
Publisher: Springer Science and Business Media LLC
Date: 22-04-2016
DOI: 10.1007/S00425-016-2523-5
Abstract: Plants produce strigolactones with different structures and different stereospecificities which provides the potential for ersity and flexibility of function. Strigolactones (SLs) typically comprise a tricyclic ABC ring system linked through an enol-ether bridge to a butenolide D-ring. The stereochemistry of the butenolide ring is conserved but two alternative configurations of the B-C ring junction leads to two families of SLs, exemplified by strigol and orobanchol. Further modifications lead to production of many different strigolactones within each family. The D-ring structure is established by a carotenoid cleavage dioxygenase producing a single stereoisomer of carlactone, the likely precursor of all SLs. Subsequent oxidation involves cytochrome P450 enzymes of the MAX1 family. In rice, MAX1 enzymes act stereospecifically to produce 4-deoxyorobanchol and orobanchol. Strigol- and orobanchol-type SLs have different activities in the control of seed germination and shoot branching, depending on plant species. This can partly be explained by different stereospecificity of SL receptors which includes the KAI2/HTL protein family in parasitic plants and the D14 protein functioning in shoot development. Many studies use chemically synthesised SL analogues such as GR24 which is prepared as a racemic mixture of two stereoisomers, one with the same stereo-configuration as strigol, and the other its enantiomer, which does not correspond to any known SL. In Arabidopsis, these two stereoisomers are preferentially perceived by AtD14 and KAI2, respectively, which activate different developmental pathways. Thus caution should be exercised in the use of SL racemic mixtures, while conversely the use of specific stereoisomers can provide powerful tools and yield critical information about receptors and signalling pathways in operation.
Comparative enhancement of germination and vigor in seed and somatic embryos by the smoke chemical 3-methyl-2H-furo[2,3-c]pyran-2-one in Baloskion tetraphyllum (Restionaceae)
Publisher: Springer Science and Business Media LLC
Date: 05-2006
DOI: 10.1079/IVP2006758
The Structure of the Karrikin-Insensitive Protein (KAI2) in Arabidopsis thaliana
Publisher: Public Library of Science (PLoS)
Date: 18-01-2013
Crambescidin 800, isolated from the marine sponge monanchora viridis, induces cell cycle arrest and apoptosis in triple-negative breast cancer cells
Publisher: MDPI AG
Date: 08-02-2018
DOI: 10.3390/MD16020053
Practical one-pot stereospecific preparation of vicinal and 1,3-diols
Publisher: Elsevier BV
Date: 2017
Phoma medicaginis Isolate Differences Determine Disease Severity and Phytoestrogen Production in Annual Medicago spp.
Publisher: Scientific Societies
Date: 10-2021
DOI: 10.1094/PDIS-03-21-0606-RE
Abstract: Phoma black stem and leaf spot disease of annual Medicago spp., caused by Phoma medicaginis, not only can devastate forage and seed yield but can reduce herbage quality by inducing production of phytoestrogens (particularly coumestrol and 4′-O-methylcoumestrol), which can also reduce the ovulation rates of animals grazing infected forage. We determined the consequent phytoestrogen levels on three different annual Medicago species/cultivars (Medicago truncatula cultivar Cyprus, Medicago polymorpha var. brevispina cultivar Serena, and Medicago murex cultivar Zodiac) after inoculation with 35 isolates of P. medicaginis. Across the isolate × cultivar combinations, leaf disease incidence, petiole/stem disease incidence, leaf disease severity, petiole disease severity, and leaf yellowing severity ranged up to 100, 89.4, 100, 58.1, and 61.2%, respectively. Cultivars Cyprus and Serena were the most susceptible and cultivar Zodiac was the most resistant to P. medicaginis. Isolates WAC3653, WAC3658, and WAC4252 produced the most severe disease. Levels of phytoestrogens in stems ranged from 25 to 1,995 mg/kg for coumestrol and from 0 to 418 mg/kg for 4′-O-methylcoumestrol. There was a significant positive relationship of disease incidence and severity parameters with both coumestrol and 4′-O-methylcoumestrol contents, as noted across in idual cultivars and across the three cultivars overall, where r = 0.39 and 0.37 for coumestrol and 4′-O-methylcoumestrol, respectively (P 0.05). Although cultivar Serena was most susceptible to P. medicaginis and produced the highest levels of phytoestrogens in the presence of P. medicaginis, cultivar Zodiac contained the highest levels of phytoestrogens in comparison with other cultivars in the absence of P. medicaginis. There was a 15-fold increase in coumestrol in cultivar Serena but only a 7-fold increase in cultivar Zodiac from infection of P. medicaginis. The study highlights that the intrinsic ability of a particular cultivar to produce phytoestrogens in the absence of the pathogen, and its comparative ability to produce phytoestrogens in the presence of the P. medicaginis, are both important and highly relevant to developing new annual Medicago spp. cultivars that offer improved disease resistance and better animal reproductive outcomes.
Investigation of an Unusual Crystal Habit of Hydrochlorothiazide Reveals Large Polar Enantiopure Domains and a Possible Crystal Nucleation Mechanism
Publisher: Wiley
Date: 24-06-2019
The karrikin response system of Arabidopsis
Publisher: Wiley
Date: 24-02-2014
DOI: 10.1111/TPJ.12430
Abstract: Arabidopsis thaliana provides a powerful means to investigate the mode of action of karrikins, compounds produced during wildfires that stimulate germination of seeds of fire-following taxa. These studies have revealed close parallels between karrikin signalling and strigolactone signalling. The two perception systems employ similar mechanisms involving closely related α/β-fold hydrolases (KAI2 and AtD14) and a common F-box protein (MAX2). However, karrikins and strigolactones may be distinguished from each other and elicit different responses. The karrikin response requires a newly discovered protein (SMAX1), a homologue of rice protein D53 that is required for the strigolactone response. Mutants defective in the response to karrikins have seeds with increased dormancy, altered seedling photomorphogenesis and modified leaf shape. As the karrikin and strigolactone response mechanisms are so similar, it is speculated that the endogenous signalling compound for the KAI2 system may be a specific strigolactone. However, new results show that the proposed endogenous signalling compound is not produced by the known strigolactone biosynthesis pathway via carlactone. Structural studies of KAI2 protein and its interaction with karrikins and strigolactone analogues provide some insight into possible protein-ligand interactions, but are h ered by lack of knowledge of the endogenous ligand. The KAI2 system appears to be present throughout angiosperms, implying a fundamentally important function in plant biology.
Seed germination of Solanum spp. (Solanaceae) for use in rehabilitation and commercial industries
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/BT07209
Abstract: Effective methods for propagation of native Solanum species are required for mine rehabilitation and the native food industry in Australia. This study investigated seed germination of eight native Solanum species with respect to incubation temperature and the efficacy of germination-promoting compounds gibberellic acid (GA3), the butenolide isolated from smoke (karrikinolide, KAR1) and smoke water (SW). Seeds of all species were tested under a temperature regime of 26/13°C or 33/18°C. In these conditions, seeds of only two species, S. cunninghamii Benth. and S. phlomoides Benth. germinated to high levels without treatment. Of the remaining six species, GA3 alone promoted germination in S. chippendalei Symon, S. ersiflorum F.Muell. and S. sturtianum F.Muell., whereas GA3, KAR1 and SW were effective at promoting germination of S. centrale J.M.Black, S. dioicum W.Fitzg. and S. orbiculatum Dunal ex Poir. to varying degrees. Additional incubation temperatures (10, 15, 20, 25 and 30°C) were examined for S. centrale and S. orbiculatum. For both species, broadly similar patterns were noted in the response of seeds to GA3, KAR1 and SW across all temperatures. However, for S. centrale seeds, germination percentages were higher at 26/13°C than at any of the constant temperatures, and there was a trend of increasing germination with increasing constant temperature for S. orbiculatum seeds. Analysis of seed embryo type and imbibition characteristics and consideration of the subsequent germination results indicates that dormant Solanum seeds possess physiological dormancy.
Lipidomic features of honey bee and colony health during limited supplementary feeding
Publisher: Wiley
Date: 21-07-2023
DOI: 10.1111/IMB.12864
Abstract: Honey bee nutritional health depends on nectar and pollen, which provide the main source of carbohydrates, proteins and lipids to in idual bees. During malnutrition, insect metabolism accesses fat body reserves. However, this process in bees and its repercussions at the colony level are poorly understood. Using untargeted lipidomics and gene expression analysis, we examined the effects of different feeding treatments (starvation, sugar feeding and sugar + pollen feeding) on bees and correlated them with colony health indicators. We found that nutritional stress led to an increase in unsaturated triacylglycerols and diacylglycerols, as well as a decrease in free fatty acids in the bee fat body. Here, we hypothesise that stored lipids are made available through a process where unsaturations change lipid's structure. Increased gene expression of three lipid desaturases in response to malnutrition supports this hypothesis, as these desaturases may be involved in releasing fatty acyl chains for lipolysis. Although nutritional stress was evident in starving and sugar‐fed bees at the colony and physiological level, only starved colonies presented long‐term effects in honey production.
Procyanidin A2 in the Australian plant Alectryon oleifolius has anthelmintic activity against equine cyathostomins in vitro
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.VETPAR.2017.11.008
Abstract: There is a need to investigate new methods of controlling cyathostomins in horses due to increasing anthelmintic resistance amongst these parasites. In a previous study we identified the Australian plant Alectryon oleifolius as having anthelmintic activity towards cyathostomins. This study aimed to isolate and identify the bioactive compound(s) responsible for all or part of this anthelmintic activity and quantify its activity in vitro. The condensed tannin procyanidin A2 was isolated from the plant through a process of bioassay guided fractionation and identified using 1D and 2D nuclear magnetic resonance spectroscopy and high performance liquid chromatography with mass spectrometry. Procyanidin A2 demonstrated significant anthelmintic activity in larval development assays, completely inhibiting development from egg to third larval stage at concentrations as low as 50μg/mL and having an IC
Karrikin and Cyanohydrin Smoke Signals Provide Clues to New Endogenous Plant Signalling Compounds
Publisher: Elsevier BV
Date: 2013
DOI: 10.1093/MP/SSS132
Abstract: Two new types of signaling compounds have been discovered in wildfire smoke due to their ability to stimulate seed germination. The first discovered were karrikins, which share some structural similarity with the strigolactone class of plant hormones, and both signal through a common F-box protein. However, karrikins and strigolactones operate through otherwise distinct signaling pathways, each distinguished by a specific α/β hydrolase protein. Genetic analysis suggests that plants contain endogenous compounds that signal specifically through the karrikin pathway. The other active compounds discovered in smoke are cyanohydrins that release germination-stimulating cyanide upon hydrolysis. Cyanohydrins occur widely in plants and have a role in defense against other organisms, but an additional role in endogenous cyanide signaling should also now be considered.
A Selaginella moellendorffii ortholog of KARRIKIN INSENSITIVE2 functions in Arabidopsis development but cannot mediate responses to karrikins or strigolactones
Publisher: Oxford University Press (OUP)
Date: 07-2015
DOI: 10.1105/TPC.15.00146
Behavior and Electrophysiological Response of Gravid and Non-Gravid Lucilia cuprina (Diptera: Calliphoridae) to Carrion-Associated Compounds
Publisher: Oxford University Press (OUP)
Date: 04-05-2018
DOI: 10.1093/JEE/TOY115
Abstract: The Australian blow fly, Lucilia cuprina Wiedmann (Diptera: Calliphoridae), is a major cause of myiasis (flystrike) in Merino sheep in Australia and New Zealand and, as a primary colonizer of fresh carrion, also an important species in forensic investigations. Olfaction is considered the most important cue for insects to rapidly locate carrion over long distances, so the first carrion visitors are predicted to be very sensitive to carrion-related volatile compounds. We studied the responses of the Australian blow fly, Lucilia cuprina, to the carrion-associated compounds dimethyl trisulfide (DMTS), butyric acid, 1-octen-3-ol and indole. We also tested 2-mercaptoethanol, a compound commonly used in fly traps in Australia. We investigated whether responses of the flies are affected by their ovarian status by comparing responses of gravid and non-gravid L. cuprina in electroantennography (EAG) and two-choice laboratory bioassays. All four compounds evoked an EAG response, while only DMTS evoked responses in gas chromatography-mass spectrometry electroantennographic detection (GCMS-EAD) analyses and two-choice bioassays. Gravid flies detected lower doses of the test compounds than non-gravid flies. Our results indicate that DMTS is an important semiochemical for L. cuprina to locate carrion resources, and has potential for use in fly traps for flystrike control. Our observations also suggest that the greater sensitivity of gravid L. cuprina allows them to find fresh carrion quickly to maximize reproductive success by avoiding unsuitable degraded carrion.
Biochar-Derived Smoke Waters Affect Bactrocera oleae Behavior and Control the Olive Fruit Fly under Field Conditions
Publisher: MDPI AG
Date: 13-11-2022
Abstract: Bactrocera oleae is the key pest of olive production. Several attempts have been carried out over time to control it using biological solutions but with results rarely comparable to those obtained with chemical applications. The purpose of this work was to identify and test new compounds from s les of various Smoke Waters (SWs) for their effect on the fly, and given their low impact on the environment. SWs obtained from different feedstocks were used in in vitro and open field applications. SWs were shown to alter B. oleae fitness, acting on its microbiome, particularly on the presence and activity of the primary endosymbiont “Ca. Erwinia dacicola”, and also to affect the behavior of the adult flies, altering the attractiveness of the drupes susceptible to attack. The effects recorded were concentration-dependent and varied among repulsion, up to 87% towards females, indecision, up to 70% towards males, and attraction, comparable to fresh green olives, based on the starting materials. These responses were confirmed in electroantennography trials and during two-years of field trials carried out in South and Central Italy. Gas Chromatography–Mass Spectrometry highlighted the presence of compounds such as guaiacol and hydroquinone as potentially important for the observed activity. Principal Component Analyses confirmed the proximity among SWs obtained from similar feedstocks. In controlled conditions, females appear to be more sensitive to the SW treatments. Field trials have shown how the effects of SWs can lead depression of infestation levels obtainable with other well-known compounds, such as kaolin clay and isopropyl-myristate (repulsive), or pheromones (attractive).
Complex Sexual Deception in an Orchid Is Achieved by Co-opting Two Independent Biosynthetic Pathways for Pollinator Attraction
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.CUB.2017.05.065
Abstract: Sexually deceptive orchids lure their specific male pollinators using volatile semiochemicals that mimic female sex pheromones. To date, the semiochemicals known to be involved consist of blends of chemically and biosynthetically related compounds. In contrast, we report that (S)-β-citronellol and 2-hydroxy-6-methylacetophenone, two biosynthetically distinct compounds, are the active semiochemicals in Caladenia plicata, which is pollinated by male Zeleboria sp. thynnine wasps. They are also sex pheromone components of the female Zeleboria. A 1:4 blend elicits a high rate of attempted copulation (∼70%) in bioassays, equivalent to rates observed at orchid flowers. Whereas β-citronellol is well known, 2-hydroxy-6-methylacetophenone appears to be previously unknown as a floral volatile. Production of the two compounds is restricted to glandular sepal tips thus, differential expression analysis of contrasting floral tissue transcriptomes was employed to illuminate the biosynthesis. As expected, production of (S)-β-citronellol commences with the terpene synthase GES1 catalyzing the irreversible conversion of geranyl diphosphate (GPP) to geraniol. Contrary to prediction, biosynthesis subsequently proceeds in three steps, commencing with the oxidation of geraniol to geranial by alcohol dehydrogenase ADH3, followed by the enantioselective reduction of a double bond in geranial by geranial reductase GER1 to give (S)-β-citronellal. Finally, ADH3-catalyzed reduction of (S)-β-citronellal results in (S)-β-citronellol. In line with previous work on insects showing that 2-hydroxy-6-methylacetophenone is derived from a polyketide pathway, we report a differentially expressed polyketide synthase (PKS) gene candidate. Thus, in this unique ex le of sexual deception, pollination is achieved by co-opting and regulating two independent biosynthetic pathways of floral volatile compounds. VIDEO ABSTRACT.
Three Chemically Distinct Floral Ecotypes in Drakaea livida, an Orchid Pollinated by Sexual Deception of Thynnine Wasps
Publisher: MDPI AG
Date: 19-01-2022
Abstract: Sexually deceptive orchids are unusual among plants in that closely related species typically attract different pollinator species using contrasting blends of floral volatiles. Therefore, intraspecific variation in pollinator attraction may also be underpinned by differences in floral volatiles. Here, we tested for the presence of floral ecotypes in the sexually deceptive orchid Drakaea livida and investigated if the geographic range of floral ecotypes corresponded to variation in pollinator availability. Pollinator choice trials revealed the presence of three floral ecotypes within D. livida that each attracts a different species of thynnine wasp as a pollinator. Surveys of pollinator distribution revealed that the distribution of one of the ecotypes was strongly correlated with that of its pollinator, while another pollinator species was present throughout the range of all three ecotypes, demonstrating that pollinator availability does not always correlate with ecotype distribution. Floral ecotypes differed in chemical volatile composition, with a high degree of separation evident in principal coordinate analysis. Some compounds that differed between ecotypes, including pyrazines and (methylthio)phenols, are known to be electrophysiologically active in thynnine wasp antennae. Based on differences in pollinator response and floral volatile profile, the ecotypes represent distinct entities and should be treated as such in conservation management.
Nickel‐Catalyzed C−N Cross‐Coupling of Primary Imines with Subsequent In Situ [2+2] Cycloaddition or Alkylation
Publisher: Wiley
Date: 09-10-2017
Behavioral differences among domestic cats in the response to cat-attracting plants and their volatile compounds reveal a potential distinct mechanism of action for actinidine
Publisher: Cold Spring Harbor Laboratory
Date: 07-03-2022
DOI: 10.1101/2022.03.05.483118
Abstract: It has been known for centuries that cats respond euphorically to Nepeta cataria (catnip). Recently, we have shown that Lonicera tatarica (Tatarian honeysuckle), Actinidia polygama (silver vine) and Valeriana officinalis (valerian) can also elicit this “catnip response”. The aim of this study was to learn if the behavior seen in response to these plants is similar to the response to catnip. Furthermore, we studied if these responses are fixed or if there are differences between cats. While nepetalactone was identified decades ago as the molecule responsible for the “catnip response”, we know that this volatile is found almost exclusively in catnip. Therefore, we also aimed to identify other compounds in these alternative plants that can elicit the blissful behavior in cats. Bioassays with 6 cats were performed in a stress-free environment, where 6 plants and 13 single compounds were each tested for at least 100 and 17 hours, respectively. All responses were video recorded and BORIS software was used to analyze the cats’ behavior. Both response duration and behavior differed significantly between the cats. While in idual cats had preferences for particular plants, the behavior of in idual cats was consistent among all plants. About half a dozen lactones similar in structure to nepetalactone were able to elicit the “catnip response”, as were the structurally more distinct molecules actinidine and dihydroactinidiolide. Most cats did not respond to actinidine, whereas those who did, responded longer to this volatile than any of the other secondary plant metabolites, and different behavior was observed. Interestingly, dihydroactinidiolide was also found in excretions and secretions of the red fox, making this the first report of a compound produced by a mammal, that can elicit the “catnip response”. A range of different cat-attracting compounds was detected by chemical analysis of plant materials but differences in cat behavior could not be directly related to differences in chemical composition of the plants. Together with among other results of habituation / dishabituation experiments, this indicates that additional cat-attracting compounds may be present in the plant materials that remain to be discovered. Collectively, these findings suggest that both the personality of the cat and genetic variation in the genes encoding olfactory receptors may play a role in how cats respond to cat-attracting plants. Furthermore, the data suggest a potential distinct mechanism of action for actinidine.
Albanitriles A–G: Antiprotozoal Polyacetylene Nitriles from a Mycale Marine Sponge
Publisher: American Chemical Society (ACS)
Date: 13-12-2019
DOI: 10.1021/ACS.JNATPROD.9B00840
Abstract: Seven new nitrile-bearing polyacetylenes, named albanitriles A-G, were isolated from a marine sponge of the
A Compound from Smoke That Promotes Seed Germination
Publisher: American Association for the Advancement of Science (AAAS)
Date: 13-08-2004
Abstract: Exposure of seeds to aerosol smoke or crude smoke extracts stimulates the germination of a number of fire-dependent and fire-independent plant species. We now report the identity of a germination-promoting compound present in plant- and cellulose-derived smoke. The structure of this compound, deduced from spectroscopic analysis and confirmed by synthesis, was shown to be that of the butenolide 3-methyl-2 H -furo[2,3- c ]pyran-2-one ( 1 ). Here we show that 1 promotes germination of a number of plant species at a level similar to that observed with plant-derived smoke water.
Assaying germination and seedling responses of arabidopsis to karrikins
Publisher: Springer New York
Date: 19-11-2016
DOI: 10.1007/978-1-4939-6469-7_4
Abstract: Karrikins are a small family of naturally occurring plant growth regulators present in the smoke and char produced from burning plant material in wildfires. They can stimulate germination of dormant seed and can influence seedling morphogenesis. Although Arabidopsis thaliana is not considered to be a smoke-responsive species, karrikins will stimulate seed germination under the appropriate circumstances and will cause repression of hypocotyl elongation in low light. This chapter describes how to conduct assays of the activity of karrikins on Arabidopsis seeds and seedlings. The methods presented can potentially be modified for use in a range of Arabidopsis genotypes or in other plant species.
Harzianic Acid, an Antifungal and Plant Growth Promoting Metabolite from Trichoderma harzianum
Publisher: American Chemical Society (ACS)
Date: 06-11-2009
DOI: 10.1021/NP900548P
Abstract: A Trichoderma harzianum strain, isolated from composted hardwood bark in Western Australia, was found to produce a metabolite with antifungal and plant growth promoting activity. The structure and absolute configuration of the fungal compound, harzianic acid (1), were determined by X-ray diffraction studies. Harzianic acid showed antibiotic activity against Pythium irregulare, Sclerotinia sclerotiorum, and Rhizoctonia solani. A plant growth promotion effect was observed at low concentrations of 1.
Symbiodinium Genotypic and Environmental Controls on Lipids in Reef Building Corals
Publisher: Public Library of Science (PLoS)
Date: 26-05-2011
The origins and mechanisms of karrikin signalling
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.PBI.2013.07.005
Abstract: Karrikins are butenolides in smoke and char that stimulate seed germination. Karrikin action in Arabidopsis requires the F-box protein MAX2 and the α/β-hydrolase KAI2, a paralogue of D14 that is required for perception of strigolactones (SL). SL response involves hydrolysis by D14, whereas karrikins bind to KAI2 without apparent hydrolysis. We discuss the current understanding of the mechanisms of karrikin perception and response. The usual function of KAI2 is unclear, but we hypothesise that the similarity between karrikins and the endogenous ligand for KAI2 made adaptation of some plants to karrikins possible.
Identification of (Z)-8-Heptadecene and n-Pentadecane as Electrophysiologically Active Compounds in Ophrys insectifera and Its Argogorytes Pollinator
Publisher: MDPI AG
Date: 17-01-2020
DOI: 10.3390/IJMS21020620
Abstract: Sexually deceptive orchids typically depend on specific insect species for pollination, which are lured by sex pheromone mimicry. European Ophrys orchids often exploit specific species of wasps or bees with carboxylic acid derivatives. Here, we identify the specific semiochemicals present in O. insectifera, and in females of one of its pollinator species, Argogorytes fargeii. Headspace volatile s les and solvent extracts were analysed by GC-MS and semiochemicals were structurally elucidated by microderivatisation experiments and synthesis. (Z)-8-Heptadecene and n-pentadecane were confirmed as present in both O. insectifera and A. fargeii female extracts, with both compounds being found to be electrophysiologically active to pollinators. The identified semiochemicals were compared with previously identified Ophrys pollinator attractants, such as (Z)-9 and (Z)-12-C27-C29 alkenes in O. sphegodes and (Z)-9-octadecenal, octadecanal, ethyl linoleate and ethyl oleate in O. speculum, to provide further insights into the biosynthesis of semiochemicals in this genus. We propose that all these currently identified Ophrys semiochemicals can be formed biosynthetically from the same activated carboxylic acid precursors, after a sequence of elongation and decarbonylation reactions in O. sphegodes and O. speculum, while in O. insectifera, possibly by decarbonylation without preceding elongation.
Sequential infections by 32 isolates of
Publisher: CSIRO Publishing
Date: 13-07-2022
DOI: 10.1071/CP22098
Abstract: Context Studies of Phoma black stem and leaf spot disease (caused by Phoma medicaginis) in annual medics (Medicago spp.) normally involve a ‘once-only’ inoculation not reflecting multiple pathogen infection and phytoestrogen production cycles in the field. Phytoestrogen production by plants can result in lower ovulation rates in grazing animals. Aims We aimed to determine whether sequential infections by P. medicaginis increase production of phytoestrogens in annual medics, and to measure the genetic ersity of isolates. Methods In a greenhouse experiment, pathogenicity and virulence were investigated across 32 isolates of P. medicaginis following one, two or three rounds of inoculation of M. polymorpha var. brevispina. Production of the phytoestrogens coumestrol and 4′-O-methyl coumestrol was measured, and correlation with disease parameters assessed. DNA sequencing using ITS, β-tubulin, calmodulin and P. medicaginis-specific EFNI-1α was applied for phylogenetic analysis of isolates from Western Australia and elsewhere. Key results Across isolates, highest leaf disease incidence was 76%, petiole disease incidence 61%, leaf disease severity 52% and petiole disease severity 53%. Stem coumestrol content range was 45–1247 mg kg−1, and 4′-O-methyl coumestrol 0–344 mg kg−1. All measures were highest after three rounds of inoculation. Overall, there was a positive correlation of leaf disease incidence with coumestrol content (P 0.05) and of both leaf and petiole disease incidence with 4′-O-methylcoumestrol content (P 0.01, P 0.05, respectively). Phylogenetic analysis revealed a high degree of genetic similarity among Western Australian isolates, generally grouping into a single separate cluster across the four markers, and genetically distinct from isolates sourced outside Australia. Conclusions Leaf disease incidence was the best discriminating disease parameter for coumestrol and 4′-O-methylcoumestrol content. Western Australian isolates of P. medicaginis were genetically similar and unique, possibly due to geographic separation. Implications The study emphasised the importance of sequential inoculations when screening annual Medicago genotypes towards developing cultivars with superior disease resistance and enhanced animal reproductive outcomes.
Ethynylbenzenoid metabolites of Antrodia camphorata: synthesis and inhibition of TNF expression
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3OB42333F
Abstract: Antroc hin A and B, and (±)- epi -antrodioxolanone have been synthesised from a common precursor. Antroc hin A displays anti-inflammatory activity but is also cytotoxic.
Drakolide Structure-activity Relationships for Sexual Attraction of Zeleboria Wasp Pollinator
Publisher: Springer Science and Business Media LLC
Date: 31-01-2022
DOI: 10.1007/S10886-021-01324-4
Abstract: Orchids pollinated by sexual deception lure their specific male pollinators by sex pheromone mimicry. Despite the growing list of chemically erse semiochemicals known to be involved, the chemical basis and flexibility of this extreme pollinator specificity are not fully understood. One promising but rarely applied tool is the synthesis and field testing of chemically related variants for investigating the structural specificity of the pheromone mimics. Here, we build on the discovery of the unusual semiochemical blend used by Drakaea micrantha to sexually lure its male Zeleboria thynnine wasp pollinator. This blend consists of a β-ketolactone (drakolide) and two specific hydroxymethylpyrazines, presumably drawn from two distinct biosynthetic pathways. Here, we synthesized and tested the activity of various stereo- and structural isomers of the naturally occurring drakolide. Our study confirmed that in blends with the two pyrazines, both a mixture of stereoisomers, and the specific stereoisomer of the natural drakolide, elicit high rates of landings and attempted copulations. However, in the absence of pyrazines, both the number of responses and the level of sexual attraction were significantly reduced. When structural analogs were substituted for the natural drakolide, attractiveness and degree of sexual behaviour varied but were generally reduced. Based on our findings, and prior knowledge that related hydroxymethylpyrazines are active in other Drakaea spp., we conclude that the dual sex pheromone mimicry of D. micrantha likely evolved via initial changes in just one of the two biosynthetic pathways. Most plausibly, this involved modifications in the drakolides, with the pyrazines as a 'pre-adaption' enhancing the sexual response.
Strigolactone hormones and their stereoisomers signal through two related receptor proteins to induce different physiological responses in arabidopsis
Publisher: Oxford University Press (OUP)
Date: 07-05-2014
Abstract: Two α/β-fold hydrolases, KARRIKIN INSENSITIVE2 (KAI2) and Arabidopsis thaliana DWARF14 (AtD14), are necessary for responses to karrikins (KARs) and strigolactones (SLs) in Arabidopsis (Arabidopsis thaliana). Although KAI2 mediates responses to KARs and some SL analogs, AtD14 mediates SL but not KAR responses. To further determine the specificity of these proteins, we assessed the ability of naturally occurring deoxystrigolactones to inhibit Arabidopsis hypocotyl elongation, regulate seedling gene expression, suppress outgrowth of secondary inflorescences, and promote seed germination. Neither 5-deoxystrigol nor 4-deoxyorobanchol was active in KAI2-dependent seed germination or hypocotyl elongation, but both were active in AtD14-dependent hypocotyl elongation and secondary shoot growth. However, the nonnatural enantiomer of 5-deoxystrigol was active through KAI2 in growth and gene expression assays. We found that the four stereoisomers of the SL analog GR24 had similar activities to their deoxystrigolactone counterparts. The results suggest that AtD14 and KAI2 exhibit selectivity to the butenolide D ring in the 2′R and 2′S configurations, respectively. However, we found, for nitrile-debranone (CN-debranone, a simple SL analog), that the 2′R configuration is inactive but that the 2′S configuration is active through both AtD14 and KAI2. Our results support the conclusion that KAI2-dependent signaling does not respond to canonical SLs. Furthermore, racemic mixtures of chemically synthesized SLs and their analogs, such as GR24, should be used with caution because they can activate responses that are not specific to naturally occurring SLs. In contrast, the use of specific stereoisomers might provide valuable information about the specific perception systems operating in different plant tissues, parasitic weed seeds, and arbuscular mycorrhizae.
A RE-EVALUATION OF CINEOLE AS A GERMINATION PROMOTER OFLACTUCA SATIVAL. GRAND RAPIDS
Publisher: Informa UK Limited
Date: 31-08-2001
DOI: 10.1081/AL-100106852
Identification of Alkyl Substituted 2H-Furo[2,3-c]pyran-2-ones as Germination Stimulants Present in Smoke
Publisher: American Chemical Society (ACS)
Date: 28-10-2009
DOI: 10.1021/JF9028128
Abstract: The butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one (1), is a major compound in smoke responsible for promoting the seed germination of a wide range of plant species. We now report the structure of five alkyl substituted variants of 1 that are also present in smoke. The concentrations of these analogues, as well as that of 1, in a typical smoke-water solution have been determined using high-performance liquid chromatography (HPLC) purification followed by gas chromatography-mass spectrometry (GC-MS) analysis. The analogue, 3,5-dimethyl-2H-furo[2,3-c]pyran-2-one (3), was identified at levels that indicate that it is a contributor to the overall germination-promoting activity of crude smoke extracts.
Destabilization of strigolactone receptor DWARF14 by binding of ligand and E3-ligase signaling effector DWARF3
Publisher: Springer Science and Business Media LLC
Date: 16-10-2015
DOI: 10.1038/CR.2015.122
The synthesis and biological evaluation of labelled karrikinolides for the elucidation of the mode of action of the seed germination stimulant
Publisher: Elsevier BV
Date: 2011
Pollination by nectar-foraging thynnine wasps: evidence of a new specialized pollination system for Australian orchids
Publisher: Oxford University Press (OUP)
Date: 08-09-2018
Preparation of 2H-Furo[2,3-c]pyran-2-one Derivatives and Evaluation of Their Germination-Promoting Activity
Publisher: American Chemical Society (ACS)
Date: 23-02-2007
DOI: 10.1021/JF0633241
Abstract: The butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one (1), has recently been identified as the germination stimulant present in smoke that promotes the germination of seeds from a wide range of plant species. In this paper, we describe the preparation of a number of analogues of 1 and compare their efficacy in promoting seed germination of three highly smoke-responsive plant species, Lactuca sativa L. cv. Grand Rapids (Asteraceae), Emmenanthe penduliflora Benth. (Hydrophyllaceae), and Solanum orbiculatum Poir. (Solanaceae). The results show that the methyl substituent at C-3 in 1 is important for germination-promoting activity while substitution at C-7 reduces activity. In contrast, bioactivity is mostly retained with analogues substituted at C-4 or C-5.
Reporter gene-facilitated detection of compounds in Arabidopsis leaf extracts that activate the karrikin signaling pathway
Publisher: Frontiers Media SA
Date: 02-12-2016
Volatile biomarkers for non-invasive detection of American foulbrood, a threat to honey bee pollination services
Publisher: Elsevier BV
Date: 11-2022
DOI: 10.1016/J.SCITOTENV.2022.157123
Abstract: Honey bees provide essential environmental services, pollinating both agricultural and natural ecosystems that are crucial for human health. However, these pollination services are under threat by outbreaks of the bacterial honey bee disease American foulbrood (AFB). Caused by the bacterium, Paenibacillus larvae, AFB kills honey bee larvae, converting the biomass to a foul smelling, spore-laden mass. Due to the bacterium's tough endospores, which are easily spread and extremely persistent, AFB management requires the destruction of infected colonies in many countries. AFB detection remains a significant problem for beekeepers: diagnosis is often slow, relying on beekeepers visually identifying symptoms in the colony and molecular confirmation. Delayed detection can result in large outbreaks during high-density beekeeping pollination events, jeopardising livelihoods and food security. In an effort to improve diagnostics, we investigated volatile compounds associated with AFB-diseased brood in vitro and in beehive air. Using Solid Phase Microextraction and Gas Chromatography Mass-Spectrometry, we identified 40 compounds as volatile biomarkers for AFB infections, including 16 compounds previously unreported in honey bee studies. In the field, we detected half of the biomarkers in situ (in beehive air) and demonstrated their sensitivity and accuracy for diagnosing AFB. The most sensitive volatile biomarker, 2,5-dimethylpyrazine, was exclusively detected in AFB-disease larvae and hives, and was detectable in beehives with <10 AFB-symptomatic larvae. These, to our knowledge, previously undescribed biomarkers are prime candidates to be targeted by a portable sensor device for rapid and non-invasive diagnosis of AFB in beehives.
A new selective fluorescent probe based on tamoxifen
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.BMCL.2016.09.028
Abstract: Developing targeted validation probes that can interrogate biology is of interest for both chemists and biologists. The synthesis of suitable compounds provides a means for avoiding the costly labeling of cells with specific antibodies and the bias associated with the interpretation of biological validation experiments. The chemotherapeutic agent, tamoxifen has been routinely used in the treatment of breast cancer for decades. Once metabolized, the active form of tamoxifen (4-hydroxytamoxifen) competes with the binding of estrogens to the estrogen receptors (ER). Its selectivity in ER modulation makes it an ideal candidate for the development of materials to be used as chemical probes. Here we report the synthesis of a fluorescent BODIPY®FL conjugate of tamoxifen linked through an ethylene glycol moiety, and present proof-of-principle results in ER positive and ER negative cell lines. Optical microscopy indicates that the fluorescent probe binds selectively to tamoxifen sensitive breast cancer cell lines. The compound showed no affinity for the tamoxifen resistant breast cancer lines. The specificity of the new compound make it a valuable addition to the chemical probe tool kit for estrogen receptors.
Divergent receptor proteins confer responses to different karrikins in two ephemeral weeds
Publisher: Springer Science and Business Media LLC
Date: 09-03-2020
DOI: 10.1038/S41467-020-14991-W
Abstract: Wildfires can encourage the establishment of invasive plants by releasing potent germination stimulants, such as karrikins. Seed germination of Brassica tournefortii , a noxious weed of Mediterranean climates, is strongly stimulated by KAR 1 , the archetypal karrikin produced from burning vegetation. In contrast, the closely-related yet non-fire-associated ephemeral Arabidopsis thaliana is unusual because it responds preferentially to KAR 2 . The α/β-hydrolase KARRIKIN INSENSITIVE 2 (KAI2) is the putative karrikin receptor identified in Arabidopsis . Here we show that B. tournefortii expresses three KAI2 homologues, and the most highly-expressed homologue is sufficient to confer enhanced responses to KAR 1 relative to KAR 2 when expressed in Arabidopsis . We identify two amino acid residues near the KAI2 active site that explain the ligand selectivity, and show that this combination has arisen independently multiple times within dicots. Our results suggest that duplication and ersification of KAI2 proteins could confer differential responses to chemical cues produced by environmental disturbance, including fire.
Production of the Seed Germination Stimulant Karrikinolide from Combustion of Simple Carbohydrates
Publisher: American Chemical Society (ACS)
Date: 31-01-2011
DOI: 10.1021/JF1041728
Abstract: The naturally occurring seed germination stimulant karrikinolide is formed from the combustion of plant material including cellulose. It has previously been reported that combustion of simple carbohydrates such as d-glucose does not produce extracts containing karrikinolide. Moreover, it was reported that extracts with germination-promoting ability could be obtained only by combustion of simple carbohydrates in the presence of amino acids such as l-glycine. By employing a (13)C-labeled karrikinolide to physically quantify natural karrikinolide, we now show that it is produced from combustion of simple carbohydrates in similar amounts regardless of whether l-glycine is present or not. The addition of l-glycine appears to be beneficial in reducing the inhibitory effect of smoke extracts and provides a greater concentration range for effective germination-promoting activity.
Toxigenicity of enniatins from Western Australian Fusarium species to brine shrimp (Artemia franciscana)
Publisher: Elsevier BV
Date: 04-2011
DOI: 10.1016/J.TOXICON.2011.02.019
Abstract: The high prevalence (14 of 24 isolates) of enniatin-producing isolates from Western Australian Fusarium species isolated from pasture legumes associated with sheep feed refusal and rat deaths, and the high toxicity of their crude extracts to brine shrimp (Artemia franciscana) from a previous study warranted further investigation of this class of mycotoxin. Crude extracts from Fusarium acuminatum, Fusarium avenaceum, Fusarium tricinctum and Fusarium sambucinum, along with enniatins A, A1, B and B1 purified from a Western Australian strain of F. acuminatum using semi-preparative HPLC, were bioassayed using brine shrimp. All Fusarium isolates produced both enniatins B and B1, except for F. tricinctum WAC 8019, and 11 of the 17 isolates produced enniatin A1. Overall, all of the F. avenaceum isolates produced high amounts of enniatins, in particular enniatin B. One isolate of F. acuminatum (WAC 5715) and of F. tricinctum (WAC 11486) also produced high amounts of both enniatins B and B1. Only F. acuminatum WAC 5715 produced enniatin A among the tested isolates. All four purified enniatins A, A1, B, B1, in idually and in combination, caused brine shrimp toxicity after 6 h of exposure, implicating that this emerging class of mycotoxin as a cause of the acute toxicity to brine shrimp observed. The mixture of all four enniatins was the most toxic to brine shrimp compared to purified in idual enniatins, where the relative toxicity order was B > B1 > A1 > A. Enniatin B was the in idual most toxic enniatin with some bioactivity at 5 μg/mL and almost 100% brine shrimp death at 50 μg/mL after 24 h of exposure. This study is the first report to confirm the acute toxicity of enniatins A, A1, B and B1 to brine shrimp, and also highlights the need for further investigation of the potential toxicity of these cyclic hexadepsipeptides to animals and humans.
Structure-Activity Relationship of Karrikin Germination Stimulants
Publisher: American Chemical Society (ACS)
Date: 09-07-2010
DOI: 10.1021/JF101690A
Abstract: Karrikins (2H-furo[2,3-c]pyran-2-ones) are potent smoke-derived germination promoters for a erse range of plant species but, to date, their mode of action remains unknown. This paper reports the structure-activity relationship of numerous karrikin analogues to increase understanding of the key structural features of the molecule that are required for biological activity. The results demonstrate that modification at the C5 position is preferred over modification at the C3, C4, or C7 positions for retaining the highest bioactivity.
The Discovery of 2-Hydroxymethyl-3-(3-methylbutyl)-5-methylpyrazine: A Semiochemical in Orchid Pollination
Publisher: American Chemical Society (ACS)
Date: 03-05-2012
DOI: 10.1021/OL300864U
Abstract: Drakaea livida (Orchidaceae) is pollinated by sexual deception of the wasp Zaspilothynnus nigripes (Thynnidae). It is shown that the orchid emits the same compound, 2-hydroxymethyl-3-(3-methylbutyl)-5-methylpyrazine, that females emit when calling for mates. This novel pyrazine was isolated and identified by GC-EAD and GC-MS and confirmed by synthesis. This compound may represent the first known case of pyrazines as sex pheromones in Hymenoptera.
F-box protein MAX2 has dual roles in karrikin and strigolactone signaling in Arabidopsis thaliana
Publisher: Proceedings of the National Academy of Sciences
Date: 09-05-2011
Abstract: Smoke is an important abiotic cue for plant regeneration in postfire landscapes. Karrikins are a class of compounds discovered in smoke that promote seed germination and influence early development of many plants by an unknown mechanism. A genetic screen for karrikin-insensitive mutants in Arabidopsis thaliana revealed that karrikin signaling requires the F-box protein MAX2, which also mediates responses to the structurally-related strigolactone family of phytohormones. Karrikins and the synthetic strigolactone GR24 trigger similar effects on seed germination, seedling photomorphogenesis, and expression of a small set of genes during these developmental stages. Karrikins also repress MAX4 and IAA1 transcripts, which show negative feedback regulation by strigolactone. We demonstrate that all of these common responses are abolished in max2 mutants. Unlike strigolactones, however, karrikins do not inhibit shoot branching in Arabidopsis or pea, indicating that plants can distinguish between these signals. These results suggest that a MAX2 -dependent signal transduction mechanism was adapted to mediate responses to two chemical cues with distinct roles in plant ecology and development.
How plants make cats happy
Publisher: ScienceOpen
Date: 04-2022
DOI: 10.14293/S2199-1006.1.SOR-.PPGVZYF.V1
Abstract: It has been known for centuries that cats respond euphorically tocatnip. We showed that among others Tatarian honeysuckle and silver vine can also elicit this “catnip response”. The behavior seen during the responses was different between cats. While in idual cats had preferences for particular plants, the behavior of in idual cats was consistent among all plants. About half a dozen lactones similar in structure to nepetalactone were able to elicit the “catnip response”, as were the structurally more distinct molecules actinidine and dihydroactinidiolide. Most cats did not respond to actinidine, whereas those who did, responded longer to this volatile than any of the other secondary plant metabolites, and different behavior was observed. A range of different cat-attracting compounds was detected by chemical analysis of plant materials but differences in cat behavior could not be directly related to differences in chemical composition of the plants. Collectively, these findings suggest that both the personality of the cat and genetic variation in the genes encoding olfactory receptors may play a role in how cats respond to cat-attracting plants. Furthermore, the data suggest a potential distinct mechanism of action for actinidine.
Discovery of pyrazines as pollinator sex pheromones and orchid semiochemicals: implications for the evolution of sexual deception
Publisher: Wiley
Date: 03-04-2014
DOI: 10.1111/NPH.12800
Abstract: Sexually deceptive orchids employ floral volatiles to sexually lure their specific pollinators. How and why this pollination system has evolved independently on multiple continents remains unknown, although preadaptation is considered to have been important. Understanding the chemistry of sexual deception is a crucial first step towards solving this mystery. The combination of gas chromatography‐electroantennographic detection ( GC ‐ EAD ), GC ‐ MS , synthesis and field bioassays allowed us to identify the volatiles involved in the interaction between the orchid D rakaea glyptodon and its sexually attracted male thynnine wasp pollinator, Z aspilothynnus trilobatus . Three alkylpyrazines and one novel hydroxymethyl pyrazine were identified as the sex pheromone of Z . trilobatus and are also used by D . glyptodon for pollinator attraction. Given that our findings revealed a new chemical system for plants, we surveyed widely across representative orchid taxa for the presence of these compounds. With one exception, our chemical survey failed to detect pyrazines in related genera. Collectively, no evidence for preadaptation was found. The chemistry of sexual deception is more erse than previously known. Our results suggest that evolutionary novelty may have played a key role in the evolution of sexual deception and highlight the value of investigating unusual pollination systems for advancing our understanding of the role of chemistry in evolution.
What are karrikins and how were they `discovered? by plants?
Publisher: Springer Science and Business Media LLC
Date: 12-2015
Solar irradiation of the seed germination stimulant karrikinolide produces two novel head-to-head cage dimers
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2OB25090J
Abstract: Karrikinolide is a naturally derived potent seed germination stimulant that is responsible for triggering the germination of numerous plant species from various habitats around the world. We now report that solar irradiation of karrikinolide yields two novel head-to-head cage photodimers with the formation, stability and bioactivity of both presented herein.
Structure–Function Analysis of SMAX1 Reveals Domains That Mediate Its Karrikin-Induced Proteolysis and Interaction with the Receptor KAI2
Publisher: Oxford University Press (OUP)
Date: 20-05-2020
DOI: 10.1105/TPC.19.00752
Burning vegetation produces cyanohydrins that liberate cyanide and stimulate seed germination
Publisher: Springer Science and Business Media LLC
Date: 21-06-2011
DOI: 10.1038/NCOMMS1356
Abstract: Cyanide is well known for its toxicity towards living organisms. Many plants use cyanide as a defensive agent against herbivores, releasing it through the enzymatic hydrolysis of endogenous cyanogenic compounds. At low concentrations, cyanide has been proposed to have a regulatory role in many plant processes including stimulation of seed germination. However, no ecological role for cyanide in seed germination has been established. In the present study, we show that burning plant material produces the cyanohydrin, glyceronitrile. We also show that, in the presence of water, glyceronitrile is slowly hydrolysed to release cyanide that stimulates seed germination of a erse range of fire-responsive species from different continents. We propose that glyceronitrile serves as an ecological store for cyanide and is an important cue for stimulating seed germination and landscape regeneration after fires.
Aurantoside C Targets and Induces Apoptosis in Triple Negative Breast Cancer Cells
Publisher: MDPI AG
Date: 10-2018
DOI: 10.3390/MD16100361
Abstract: Triple negative breast cancer (TNBC) is a subtype of breast cancers that currently lacks effective targeted therapy. In this study, we found that aurantoside C (C828), isolated from the marine sponge Manihinea lynbeazleyae collected from Western Australia, exhibited higher cytotoxic activities in TNBC cells compared with non-TNBC (luminal and normal-like) cells. The cytotoxic effect of C828 was associated to the accumulation of cell at S-phase, resulting in the decline of cyclin D1, cyclin E1, CDK4, and CDK6, and an increase in p21. We also found that C828 inhibited the phosphorylation of Akt/mTOR and NF-kB pathways and increased the phosphorylation of p38 MAPK and SAPK/JNK pathways, leading to apoptosis in TNBC cells. These effects of C828 were not observed in non-TNBC cells at the concentrations that were cytotoxic to TNBC cells. When compared to the cytotoxic effect with the chemotherapeutic drugs doxorubicin and cisplatin, C828 was found to be 20 times and 35 times more potent than doxorubicin and cisplatin, respectively. These results indicate that C828 could be a promising lead for developing new anticancer agents that target TNBC cells.
Access to 1,2,3,4-Tetraoxygenated Benzenes via a Double Baeyer–Villiger Reaction of Quinizarin Dimethyl Ether: Application to the Synthesis of Bioactive Natural Products from Antrodia camphorata
Publisher: American Chemical Society (ACS)
Date: 04-2016
Abstract: The first systematic investigation into the Baeyer-Villiger reaction of an anthraquinone is presented. The double Baeyer-Villiger reaction of quinizarin dimethyl ether is viable, directly providing the dibenzo[b,f][1,4]-dioxocin-6,11-dione ring-system, which is otherwise difficult to prepare. This methodology provides rapid access to 1,2,3,4-tetraoxygenated benzenes, and has been exploited by application to the total synthesis of a natural occurring benzodioxole and its biphenyl dimer, which both display noteworthy biological activity. Interestingly, the axially chiral biphenyl was found to be configurationally stable, but the resolved enantiomers exhibit no optical activity at the αD-line.
Behavioral differences among domestic cats in the response to cat-attracting plants and their volatile compounds reveal a potential distinct mechanism of action for actinidine
Publisher: Springer Science and Business Media LLC
Date: 25-08-2022
DOI: 10.1186/S12915-022-01369-1
Abstract: It has been known for centuries that cats respond euphorically to Nepeta cataria (catnip). Recently, we have shown that Lonicera tatarica (Tatarian honeysuckle), Actinidia polygama (silver vine), and Valeriana officinalis (valerian) can also elicit this “catnip response”. The aim of this study was to learn if the behavior seen in response to these plants is similar to the response to catnip. Furthermore, we studied if these responses are fixed or if there are differences between cats. While nepetalactone was identified decades ago as the molecule responsible for the “catnip response”, we know that this volatile is found almost exclusively in catnip. Therefore, we also aimed to identify other compounds in these alternative plants that can elicit the blissful behavior in cats. Bioassays with 6 cats were performed in a low-stress environment, where 5 plants and 13 single compounds were each tested for at least 100 and 17 h, respectively. All responses were video recorded and BORIS software was used to analyze the cats’ behavior. Both response duration and behavior differed significantly between the cats. While in idual cats had preferences for particular plants, the behavior of in idual cats was consistent among all plants. About half a dozen lactones similar in structure to nepetalactone were able to elicit the “catnip response”, as were the structurally more distinct molecules actinidine and dihydroactinidiolide. Most cats did not respond to actinidine, whereas those who did, responded longer to this volatile than any of the other secondary plant metabolites, and different behavior was observed. Interestingly, dihydroactinidiolide was also found in excretions and secretions of the red fox, making this the first report of a compound produced by a mammal that can elicit the “catnip response”. A range of different cat-attracting compounds was detected by chemical analysis of plant materials but differences in cat behavior could not be directly related to differences in chemical composition of the plants. Together with results of, among others, habituation / dishabituation experiments, this indicates that additional cat-attracting compounds may be present in the plant materials that remain to be discovered. Collectively, these findings suggest that both the personality of the cat and genetic variation in the genes encoding olfactory receptors may play a role in how cats respond to cat-attracting plants. Furthermore, the data suggest a potential distinct mechanism of action for actinidine.
Critical Pollination Chemistry: Specific Sesquiterpene Floral Volatiles in Carrot Inhibit Honey Bee Feeding
Publisher: American Chemical Society (ACS)
Date: 23-10-2023
Stable triazolylphosphonate analogues of phosphohistidine
Publisher: Springer Science and Business Media LLC
Date: 22-11-2012
DOI: 10.1007/S00726-011-1145-2
Abstract: Histidine-phosphorylated proteins and the corresponding kinases are important components of bacterial and eukaryotic cell-signalling pathways, and are therefore potential drug targets. The study of these biomolecules has been h ered by the lability of the phosphoramidate functional group in the phosphohistidines and the lack of generic antibodies. Herein, the design and concise synthesis of stable triazolylphosphonate analogues of N1- and N3-phosphohistidine, and derivatives suitable for bioconjugation, are described.
Harzianic acid: a novel siderophore fromTrichoderma harzianum
Publisher: Oxford University Press (OUP)
Date: 09-2013
Abstract: Agriculture-relevant microorganisms are considered to produce secondary metabolites during processes of competition with other micro- and macro-organisms, symbiosis, parasitism or pathogenesis. Many different strains of the genus Trichoderma, in addition to a direct activity against phytopathogens, are well-known producers of secondary metabolites and compounds that substantially affect the metabolism of the host plant. Harzianic acid is a Trichoderma secondary metabolite, showing antifungal and plant growth promotion activities. This report demonstrates the ability of this tetramic acid to bind with a good affinity essential metals such as Fe(3+) , which may represent a mechanism of iron solubilisation that significantly alters nutrient availability in the soil environment for other microorganisms and the host plant.
A systematic approach to recycling organics for horticulture: comparing emerging and conventional technologies
Publisher: International Society for Horticultural Science (ISHS)
Date: 03-2016
Dendrillic Acids A and B: Nitrogenous, Rearranged Spongian Nor-Diterpenes from a Dendrilla sp. Marine Sponge
Publisher: American Chemical Society (ACS)
Date: 16-03-2023
Establishing alighting preferences and species transmission differences for Pea seed-borne mosaic virus aphid vectors
Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.VIRUSRES.2017.04.005
Abstract: Pea seed-borne mosaic virus (PSbMV) infection causes a serious disease of field pea (Pisum sativum) crops worldwide. The PSbMV transmission efficiencies of five aphid species previously found landing in south-west Australian pea crops in which PSbMV was spreading were studied. With plants of susceptible pea cv. Kaspa, the transmission efficiencies of Aphis craccivora, Myzus persicae, Acyrthosiphon kondoi and Rhopalosiphum padi were 27%, 26%, 6% and 3%, respectively. Lipaphis erysimi did not transmit PSbMV in these experiments. The transmission efficiencies found for M. persicae and A. craccivora resembled earlier findings, but PSbMV vector transmission efficiency data were unavailable for A. kondoi, R. padi and L. erysimi. With plants of partially PSbMV resistant pea cv. PBA Twilight, transmission efficiencies of M. persicae, A. craccivora and R. padi were 16%, 12% and 1%, respectively, reflecting putative partial resistance to aphid inoculation. To examine aphid alighting preferences over time, free-choice assays were conducted with two aphid species representing efficient (M. persicae) and inefficient (R. padi) vector species. For this, alatae were set free on multiple occasions (10-15 repetitions each) amongst PSbMV-infected and mock-inoculated pea or faba bean (Vicia faba) plants. Following release, non-viruliferous R. padi alatae exhibited a general preference for PSbMV-infected pea and faba bean plants after 30min-4h, but preferred mock-inoculated plants after 24h. In contrast, non-viruliferous M. persicae alatae alighted on mock-inoculated pea plants preferentially for up to 48h following their release. With faba bean, M. persicae preferred infected plants at the front of assay cages, but mock-inoculated ones their backs, apparently due to increased levels of natural light there. When preliminary analyses were performed to detect PSbMV-induced changes in the volatile organic compound profiles of pea and faba bean plants, higher numbers of volatiles representing a range of compound groups (such as aldehydes, ketones and esters) were found in the headspaces of PSbMV-infected than of mock-inoculated pea or faba bean plants. This indicates PSbMV induces physiological changes in these hosts which manifest as altered volatile emissions. These alterations could be responsible for the differences in alighting preferences. Information from this study enhances understanding of virus-vector relationships in the PSbMV-pea and faba bean pathosystems.
Identity and Activity of 2,4-Dichlorophenoxyacetic Acid Metabolites in Wild Radish (Raphanus raphanistrum)
Publisher: American Chemical Society (ACS)
Date: 05-12-2018
Abstract: Synthetic auxin herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), are widely used for selective control of broadleaf weeds in cereals and transgenic crops. Although the troublesome weed wild radish ( Raphanus raphanistrum) has developed resistance to 2,4-D, no populations have yet displayed an enhanced capacity for metabolic detoxification of the herbicide, with both susceptible and resistant wild radish plants readily metabolizing 2,4-D. Using mass spectrometry and nuclear magnetic resonance, the major 2,4-D metabolite was identified as the glucose ester, and its structure was confirmed by synthesis. As expected, both the endogenous and synthetic compounds retained auxin activity in a bioassay. The lack of detectable 2,4-D hydroxylation in wild radish and the lability of the glucose ester suggest that metabolic 2,4-D resistance is unlikely to develop in this species.
Temperature and Soil Moisture Drive Coumestrol Concentration in Annual Medicago spp. in the Presence but Not Absence of Phoma Black Stem and Leaf Spot (Phoma medicaginis)
Publisher: MDPI AG
Date: 07-08-2022
Abstract: Studies were undertaken to determine the impact of environmental variables temperature (12.5/9.5, 20/17, 27/24 °C day/night) and soil moisture (100, 50% WHC), and their interaction with Phoma medicaginis infection, on production of the phytoestrogen coumestrol in annual Medicago rugosa cv. Paraponto and M. scutellata cv. Sava. Disease factors measured included leaf disease incidence/severity, petiole/stem disease incidence/severity, and leaf yellowing severity. Coumestrol levels were determined using gas chromatography–mass spectrometry (GC–MS). Increasing temperature from 12.5/9.5 °C to 27/24 °C in inoculated plants significantly (p 0.05) increased coumestrol from 193 mg kg−1 to 390 mg kg−1, but there were no differences in coumestrol production across all three temperatures in uninoculated plants. Reducing soil moisture from 100% to 50% WHC at the highest temperature (27/24 °C) caused the greatest increase in coumestrol production from 156 to 269 mg kg−1 in inoculated plants. The greatest coumestrol production (600 mg kg−1) was under 27/24 °C/50% WHC for Sava infected with P. medicaginis and least coumestrol (1.6 mg kg−1) was Sava under 20/17 °C/50% WHC in the absence of P. medicaginis. Clearly, situations of higher temperatures in conjunction with lower soil moisture levels cause greatest elevation in coumestrol in the presence of P. medicaginis, levels far exceeding the animal risk threshold of 25 mg kg−1.
Karrikins Discovered in Smoke Trigger Arabidopsis Seed Germination by a Mechanism Requiring Gibberellic Acid Synthesis and Light
Publisher: Oxford University Press (OUP)
Date: 12-12-2009
Abstract: Discovery of the primary seed germination stimulant in smoke, 3-methyl-2H-furo[2,3-c]pyran-2-one (KAR1), has resulted in identification of a family of structurally related plant growth regulators, karrikins. KAR1 acts as a key germination trigger for many species from fire-prone, Mediterranean climates, but a molecular mechanism for this response remains unknown. We demonstrate that Arabidopsis (Arabidopsis thaliana), an ephemeral of the temperate northern hemisphere that has never, to our knowledge, been reported to be responsive to fire or smoke, rapidly and sensitively perceives karrikins. Thus, these signaling molecules may have greater significance among angiosperms than previously realized. Karrikins can trigger germination of primary dormant Arabidopsis seeds far more effectively than known phytohormones or the structurally related strigolactone GR-24. Natural variation and depth of seed dormancy affect the degree of KAR1 stimulation. Analysis of phytohormone mutant germination reveals suppression of KAR1 responses by abscisic acid and a requirement for gibberellin (GA) synthesis. The reduced germination of sleepy1 mutants is partially recovered by KAR1, which suggests that germination enhancement by karrikin is only partly DELLA dependent. While KAR1 has little effect on sensitivity to exogenous GA, it enhances expression of the GA biosynthetic genes GA3ox1 and GA3ox2 during seed imbibition. Neither abscisic acid nor GA levels in seed are appreciably affected by KAR1 treatment prior to radicle emergence, despite marked differences in germination outcome. KAR1 stimulation of Arabidopsis germination is light-dependent and reversible by far-red exposure, although limited induction of GA3ox1 still occurs in the dark. The observed requirements for light and GA biosynthesis provide the first insights into the karrikin mode of action.
The Crystal Structure of a Homodimeric Pseudomonas Glyoxalase I Enzyme Reveals Asymmetric Metallation Commensurate with Half‐of‐Sites Activity
Publisher: Wiley
Date: 19-11-2014
Abstract: The Zn inactive class of glyoxalase I (Glo1) metalloenzymes are typically homodimeric with two metal-dependent active sites. While the two active sites share identical amino acid composition, this class of enzyme is optimally active with only one metal per homodimer. We have determined the X-ray crystal structure of GloA2, a Zn inactive Glo1 enzyme from Pseudomonas aeruginosa. The presented structures exhibit an unprecedented metal-binding arrangement consistent with half-of-sites activity: one active site contains a single activating Ni(2+) ion, whereas the other contains two inactivating Zn(2+) ions. Enzymological experiments prompted by the binuclear Zn(2+) site identified a novel catalytic property of GloA2. The enzyme can function as a Zn(2+) /Co(2+) -dependent hydrolase, in addition to its previously determined glyoxalase I activity. The presented findings demonstrate that GloA2 can accommodate two distinct metal-binding arrangements simultaneously, each of which catalyzes a different reaction.
A Merry Dance Across the π-Cloud: Tracking the Transformation of a 2,7-Substituted Dihydropyrene Through a Thermally Stimulated Single-Crystal-to-Single-Crystal Reaction
Publisher: American Chemical Society (ACS)
Date: 21-10-2021
Prior hydration of Brassica tournefortii seeds reduces the stimulatory effect of karrikinolide on germination and increases seed sensitivity to abscisic acid
Publisher: Oxford University Press (OUP)
Date: 25-03-2010
DOI: 10.1093/AOB/MCQ061
Desmethyl butenolides are optimal ligands for karrikin receptor proteins
Publisher: Wiley
Date: 10-02-2021
DOI: 10.1111/NPH.17224
Structure Reassignment of Echinosulfone A and the Echinosulfonic Acids A–D Supported by Single-Crystal X-ray Diffraction and Density Functional Theory Analysis
Publisher: American Chemical Society (ACS)
Date: 14-01-2020
DOI: 10.1021/ACS.JNATPROD.9B00902
Abstract: Two previously reported bis-indole alkaloids, echinosulfone A and echinosulfonic acid B, have been isolated for the first time from a Western Australian marine sponge,
Antibacterial compounds from the Australian native plant Eremophila glabra
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.FITOTE.2017.11.008
Abstract: Recent reports of Eremophila glabra (R.Br.) Ostenf. (Scrophulariaceae) displaying antibacterial activity has led us to investigate the bioactive secondary metabolites responsible for this activity. Bioassay-directed fractionation of solvent extracts prepared from the leaves of E. glabra led to the isolation of seven serrulatane diterpenes, three flavonoids and the caffeoyl ester disaccharide verbascoside. Among these, four serrulatanes, namely 18-acetoxy-8, 20-dihydroxyserrulat-14-en-19-oic acid (14), 18,20-diacetoxy-8-hydroxyserrulat-14-en-19-oic acid (16), 8,18,20-triacetoxyserrulat-14-en-19-oic acid (17) and 18-acetoxy-8-hydroxyserrulat-14-en-19-oic acid (18) are described for the first time, while 8,20-diacetoxyserrulat-14-en-19-oic acid (3), 8,18,20-trihydroxyserrulat-14-en-19-oic acid (5) and 20-acetoxy-8-hydroxyserrulat-14-en-19-oic acid (19) were previously reported. All three flavonoids hispidulin (12), jaceosidin (13) and cirsimaritin (15) are known but reported for the first time in E. glabra. All compounds were tested in an agar diffusion antimicrobial assay against Staphylococcus aureus (NCTC 10442) and Staphylococcus epidermidis (ATCC 14990). Compounds 12, 13, 17, 18 and 19 exhibited moderate activity, with minimum inhibitory concentrations (MICs) ranging from 32 to 512μg/mL. Compound 19 demonstrated the highest activity against S. epidermidis ATCC 14990 with MIC of 32μg/mL, while 13 demonstrated the highest activity against S. aureus NCTC 10442 with MIC of 128μg/mL.
Karrikins enhance light responses during germination and seedling development in Arabidopsis thaliana
Publisher: Proceedings of the National Academy of Sciences
Date: 29-03-2010
Abstract: Karrikins are a class of seed germination stimulants identified in smoke from wildfires. Microarray analysis of imbibed Arabidopsis thaliana seeds was performed to identify transcriptional responses to KAR 1 before germination. A small set of genes that are regulated by KAR 1 , even when germination is prevented by the absence of gibberellin biosynthesis or light, were identified. Light-induced genes, putative HY5-binding targets, and ABRE-like promoter motifs were overrepresented among KAR 1 -up-regulated genes. KAR 1 transiently induced the light signal transduction transcription factor genes HY5 and HYH . Germination of afterripened Arabidopsis seed was triggered at lower fluences of red light when treated with KAR 1 . Light-dependent cotyledon expansion and inhibition of hypocotyl elongation were enhanced in the presence of germination-active karrikins. HY5 is important for the Arabidopsis hypocotyl elongation, but not seed germination, response to karrikins. These results reveal a role for karrikins in priming light responses in the emerging seedling, and suggest that the influence of karrikins on postfire ecology may not be limited to germination recruitment.
Mycotoxins produced by Fusarium species associated with annual legume pastures and ‘sheep feed refusal disorders’ in Western Australia
Publisher: Springer Science and Business Media LLC
Date: 12-01-2011
DOI: 10.1007/S12550-010-0085-0
Abstract: Sheep grazing in Western Australia can partially or completely refuse to consume annual Medicago pods contaminated with a number of different Fusarium species. Many Fusarium species are known to produce trichothecenes as part of their array of toxigenic secondary metabolites, which are known to cause feed refusal in animals. This study reports the identity of Fusarium species using species-specific PCR primers and a characterization of the toxigenic secondary metabolites produced by 24 Fusarium isolates associated with annual legume-based pastures and particularly those associated with sheep feed refusal disorders in Western Australia. Purification of the fungal extracts was facilitated by a bioassay-guided fractionation using brine shrimp. A number of trichothecenes (3-acetyldeoxynivalenol, deoxynivalenol, fusarenon-X, monoacetoxyscirpenols, diacetoxyscirpenol, scirpentriol, HT-2 toxin and T-2 toxin), enniatins (A, A1, B, and B1), chlamydosporol and zearalenone were identified using GC/MS and/or NMR spectroscopy. Some of the crude extracts and fractions showed significant activity against brine shrimp at concentrations as low as 5 μg ml(-1), and are likely to be involved in the sheep feed refusal disorders. This is the first report of chlamydosporol production by confirmed Fusarium spp. of the incidence of F. brachygibbosum and F. venenatum in Australia and of F. tricinctum in Western Australia and of mycotoxin production by Fusarium species from Western Australia.
Identification of the Cat Attractants Isodihydronepetalactone and Isoiridomyrmecin from Acalypha indica
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/CH15476
Abstract: Acalypha indica is a herb that grows throughout the tropical regions of the world. As well as being exploited for medicinal use, the roots of this plant are known to elicit a drug-like effect in cats. Recent research into feral cat control on Christmas Island has investigated whether a preparation of the roots of A. indica might be effective in traps to attract feral cats. However, the volatile nature of the attractants made it unviable for use in traps for more than a few days. In this study, we investigated the volatile components emitted by the plant roots and identified two iridoid compounds, (4R,4aR,7S,7aR)-isodihydronepetalactone and (4R,4aS,7S,7aR)-isoiridomyrmecin, which are known to affect behavioural activity in cats. Synthesis of standards confirmed the stereochemistry of both compounds emitted by the plant. Potential application of these compounds in feral cat control is discussed.
Investigation of volatile organic biomarkers derived from Plasmodium falciparum in vitro
Publisher: Springer Science and Business Media LLC
Date: 07-09-2012
Abstract: There remains a need for techniques that improve the sensitive detection of viable Plasmodium falciparum as part of diagnosis and therapeutic monitoring in clinical studies and usual-care management of malaria infections. A non-invasive breath test based on P. falciparum- associated specific volatile organic compounds (VOCs) could fill this gap and provide insights into parasite metabolism and pathogenicity. The aim of this study was to determine whether VOCs are present in the headspace above in vitro P. falciparum cultures. A novel, custom-designed apparatus was developed to enable efficient headspace s ling of infected and non-infected cultures. Conditions were optimized to support cultures of high parasitaemia ( %) to improve the potential detection of parasite-specific VOCs. A number of techniques for VOC analysis were investigated including solid phase micro-extraction using two different polarity fibres, and purge and trap/thermal desorption, each coupled to gas chromatography–mass spectrometry. Each experiment and analysis method was performed at least on two occasions. VOCs were identified by comparing their mass spectra against commercial mass spectral libraries. No unique malarial-specific VOCs could be detected relative to those in the control red blood cell cultures. This could reflect sequestration of VOCs into cell membranes and/or culture media but solvent extractions of supernatants and cell lysates using hexane, dichloromethane and ethyl acetate also showed no obvious difference compared to control non-parasitized cultures. Future in vivo studies analysing the breath of patients with severe malaria who are harbouring a parasite biomass that is significantly greater than achievable in vitro may yet reveal specific clinically-useful volatile chemical biomarkers.
An allelic series at the KARRIKIN INSENSITIVE 2 locus of Arabidopsis thaliana decouples ligand hydrolysis and receptor degradation from downstream signalling
Publisher: Wiley
Date: 23-07-2018
DOI: 10.1111/TPJ.14017
Abstract: Karrikins are butenolide compounds present in post-fire environments that can stimulate seed germination in many species, including Arabidopsis thaliana. Plants also produce endogenous butenolide compounds that serve as hormones, namely strigolactones (SLs). The receptor for karrikins (KARRIKIN INSENSITIVE 2 KAI2) and the receptor for SLs (DWARF14 D14) are homologous proteins that share many similarities. The mode of action of D14 as a dual enzyme receptor protein is well established, but the nature of KAI2-dependent signalling and its function as a receptor are not fully understood. To expand our knowledge of how KAI2 operates, we screened ethyl methanesulphonate (EMS)-mutagenized populations of A. thaliana for mutants with kai2-like phenotypes and isolated 13 new kai2 alleles. Among these alleles, kai2-10 encoded a D184N protein variant that was stable in planta. Differential scanning fluorimetry assays indicated that the KAI2 D184N protein could interact normally with bioactive ligands. We developed a KAI2-active version of the fluorescent strigolactone analogue Yoshimulactone Green to show that KAI2 D184N exhibits normal rates of ligand hydrolysis. KAI2 D184N degraded in response to treatment with exogenous ligands, suggesting that receptor degradation is a consequence of ligand binding and hydrolysis, but is insufficient for signalling activity. Remarkably, KAI2 D184N degradation was hypersensitive to karrikins, but showed a normal response to strigolactone analogues, implying that these butenolides may interact differently with KAI2. These results demonstrate that the enzymatic and signalling functions of KAI2 can be decoupled, and provide important insights into the mechanistic events that underpin butenolide signalling in plants.
Hit-to-Lead Optimization of a Novel Class of Potent, Broad-Spectrum Trypanosomacides
Publisher: American Chemical Society (ACS)
Date: 19-09-2016
DOI: 10.1021/ACS.JMEDCHEM.6B00442
Abstract: The parasitic trypanosomes Trypanosoma brucei and T. cruzi are responsible for significant human suffering in the form of human African trypanosomiasis (HAT) and Chagas disease. Drugs currently available to treat these neglected diseases leave much to be desired. Herein we report optimization of a novel class of N-(2-(2-phenylthiazol-4-yl)ethyl)amides, carbamates, and ureas, which rapidly, selectively, and potently kill both species of trypanosome. The mode of action of these compounds is unknown but does not involve CYP51 inhibition. They do, however, exhibit clear structure-activity relationships, consistent across both trypanosome species. Favorable physicochemical parameters place the best compounds in CNS drug-like chemical space but, as a class, they exhibit poor metabolic stability. One of the best compounds (64a) cleared all signs of T. cruzi infection in mice when CYP metabolism was inhibited, with sterile cure achieved in one mouse. This family of compounds thus shows significant promise for trypanosomiasis drug discovery.
Structure-Activity Studies of Semiochemicals from the Spider Orchid Caladenia plicata for Sexual Deception
Publisher: Springer Science and Business Media LLC
Date: 17-03-2018
DOI: 10.1007/S10886-018-0946-0
Abstract: Sexually deceptive orchids attract specific pollinators by mimicking insect sex pheromones. Normally this mimicry is very specific and identical compounds have been identified from orchids and matching females of the pollinators. In this study, we conduct a detailed structure-activity investigation on isomers of the semiochemicals involved in the sexual attraction of the male pollinator of the spider orchid Caladenia plicata. This orchid employs an unusual blend of two biosynthetically unrelated compounds, (S)-β-citronellol and 2-hydroxy-6-methylacetophenone, to lure its Zeleboria sp. thynnine wasp pollinator. We show that the blend is barely attractive when (S)-β-citronellol is substituted with its enantiomer, (R)-β-citronellol. Furthermore, none of the nine-possible alternative hydroxy-methylacetophenone regioisomers of the natural semiochemical are active when substituted for the natural 2-hydroxy-6-methylacetophenone. Our results were surprising given the structural similarity between the active compound and some of the analogues tested, and results from previous studies in other sexually deceptive orchid/wasp systems where substitution with analogues was possible. Interestingly, high-level ab initio and density functional theory calculations of the hydroxy-methylacetophenones revealed that the active natural isomer, 2-hydroxy-6-methylacetophenone, has the strongest intramolecular hydrogen bond of all regioisomers, which at least in part may explain the specific activity.
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