ORCID Profile
0000-0002-9819-1372
Current Organisation
Australian National University
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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)
Plant Cell and Molecular Biology | Plant Biology | Plant Developmental and Reproductive Biology | Crop and Pasture Improvement (Selection and Breeding) | Biochemistry and Cell Biology | Gene Expression | Plant Physiology | Genetics | Crop and Pasture Production | Biotechnology Not Elsewhere Classified | Receptors and Membrane Biology | Signal Transduction | Quantitative Genetics (incl. Disease and Trait Mapping Genetics) | Cellular Interactions (incl. Adhesion, Matrix, Cell Wall) | Protein Trafficking | Plant Pathology | Analytical Biochemistry | Protein Targeting And Signal Transduction | Genetic Development (Incl. Sex Determination) | Crop and Pasture Biochemistry and Physiology |
ANZSRC Socio-Economic Objective (SEO)
Environmentally Sustainable Plant Production not elsewhere classified | Expanding Knowledge in the Biological Sciences | Grain legumes | Biological sciences | Summer Grains and Oilseeds not elsewhere classified | Winter Grains and Oilseeds not elsewhere classified | Barley | Native forests | Wheat | Oats | Wheat | Health related to ageing | Cardiovascular system and diseases | Cancer and related disorders | Chemical sciences | Climate change | Primary plant products not elsewhere classified | Preventive medicine
Related Links
Publications
Analysis of central Hox protein types across bilaterian clades: On the diversification of central Hox proteins from an Antennapedia/Hox7-like protein
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.YDBIO.2013.09.009
Abstract: Hox proteins are among the most intensively studied transcription factors and represent key factors in establishing morphological differences along the anterior-posterior axis of animals. They are generally regarded as highly conserved in function, a view predominantly based on experiments comparing a few (anterior) Hox proteins. However, the extent to which central or abdominal Hox proteins share conserved functions and sequence signatures remains largely unexplored. To shed light on the functional ergence of the central Hox proteins, we present an easy to use resource aimed at predicting the functional similarities of central Hox proteins using sequence elements known to be relevant to Hox protein functions. We provide this resource both as a stand-alone download, including all information, as well as via a simplified web-interface that facilitates an accurate and fine-tuned annotation of novel Hox sequences. The method used in the manuscript is, so far, the only published sequence-based method capable of differentiating between the functionally distinct central Hox proteins with near-identical homeodomains (such as the Drosophila Antp, Ubx and Abd-A Hox proteins). In this manuscript, a pairwise-sequence-similarity based approach (using the bioinformatics tool CLANS) is used to analyze all available central Hox protein sequences. The results are combined with a large-scale species phylogeny to depict the presence/absence of central Hox sequence-types across the bilaterian lineage. The obtained pattern of distribution of the Hox sequence-types throughout the species tree enables us to infer at which branching point a specific type of central Hox protein was present. Based on the Hox sequences currently available in public databases, seven sequence-similarity groups could be identified for the central Hox proteins, two of which have never been described before (Echi/Hemi7 and Echi/Hemi8). Our work also shows, for the first time, that Antp/Hox7-like sequences are present throughout all bilaterian clades and that all other central Hox protein groups are specific to sub-lineages in the protostome or deuterostome branches only.
The Peptide Hormone Receptor CEPR1 Functions in the Reproductive Tissue to Control Seed Size and Yield
Publisher: Oxford University Press (OUP)
Date: 21-04-2020
DOI: 10.1104/PP.20.00172
Architectural phenotypes in the transparent testa mutants of Arabidopsis thaliana
Publisher: Oxford University Press (OUP)
Date: 03-2009
DOI: 10.1093/JXB/ERN323
Characterization of the Secretome of Suspension Cultures of Medicago Species Reveals Proteins Important for Defense and Development
Publisher: American Chemical Society (ACS)
Date: 10-09-2008
DOI: 10.1021/PR800291Z
Abstract: Molecular events occurring in the plant apoplast contribute to important developmental and defense responses. To define the secretome of Medicago, we used suspension cultures to isolate and identify secreted proteins as a first step to determining their functions. Proteins in the extracellular medium of the suspension cultures were examined using SDS-PAGE, tandem mass spectrometry (MALDI-TOF/TOF) and bioinformatics tools. There were 39 proteins identified in the cultures derived from M. sativa, M. truncatula 2HA (an embryogenic line), and M. truncatula sickle (an ethylene-insensitive mutant). N-Terminal secretion signals were detected in 34 proteins and five other proteins were predicted to be secreted via a nonclassical (ER-independent) route. All s les possessed defense related proteins including pathogenesis related (PR) proteins. The glycoprotein, SIEP1L, was found only in M. sativa. Three secreted proteinases were identified in M. truncatula, including a serine carboxypeptidase detected only in 2HA. Some proteins were unique to a cell culture line. Quantitative real time RT-PCR was used to determine mRNA expression of selected genes corresponding to proteins found only in 2HA or sickle or in both. The results correlate well with the proteomic data. For instance, a GDSL-lipase gene known to be regulated by ethylene was found only in 2HA but not in the ethylene insensitive mutant. Similarly, the PR1a protein, expressed from a well recognized ethylene-regulated gene, was found in 2HA but not sickle. These experiments indicate that the suspension culture systems established here are useful to avoid contamination from cytoplasmic proteins and to identify secreted proteins in Medicago, and should have application in other plant systems.
Regulation of Arabidopsis root development by small signaling peptides
Publisher: Frontiers Media SA
Date: 2013
Sinorhizobium meliloti metabolism in the root nodule: A proteomic perspective
Publisher: Wiley
Date: 07-2004
Abstract: The proteome of the model symbiotic bacterium, Sinorhizobium meliloti was examined to determine the enzymatic reactions and cell processes that occur when S. meliloti occupies the root nodules of Medicago truncatula and Melilotus alba. The proteomes of the nodule bacteria were compared to that of S. meliloti grown under laboratory cultured conditions as an additional control. All the detectable protein spots on the two-dimensional (2-D) gels between pH 4-7 were analyzed. In total, the identity of proteins in 1545 spots from 2-D gels was determined using peptide mass fingerprinting. There were clear differences in the proteome of nodule bacteria and cultured bacteria and putative nodule-specific and nodule suppressed proteins were identified. The data were analyzed using metabolic pathway prediction programs and used to review the biochemical and genetic studies that had been done previously on S. meliloti over several decades. There was a broad congruency between the proteomic and biochemical data when the overall pathways of central carbon and nitrogen metabolism were considered. A selective suite of ABC-type transporters was present in nodule bacteria that were biased towards the transport of amino acids and inorganic ions (P and Fe) suggesting that a highly specialized nutrient exchange was occurring between the nodule bacteria and the host. Proteins prominent in nodule bacteria were those involved in the pathways for vitamin synthesis and stress-related processes (chaperoning, heat shock, detoxification of reactive oxygen species, regulation of stress and osmo-regulation). Some of these proteins were found only in nodule bacteria. These results show the extent of the shift in metabolism that occurs when S. meliloti invades legume plants and establishes a nitrogen fixing symbiosis.
Novel MtCEP1 peptides producedin vivodifferentially regulate root development inMedicago truncatula
Publisher: Oxford University Press (OUP)
Date: 22-02-2015
DOI: 10.1093/JXB/ERV008
Crosstalk between the nodulation signaling pathway and the autoregulation of nodulation in Medicago truncatula
Publisher: Wiley
Date: 20-04-2011
DOI: 10.1111/J.1469-8137.2011.03738.X
Abstract: A subset of CLAVATA3/endosperm-surrounding region-related (CLE) peptides are involved in autoregulation of nodulation (AON) in Medicago truncatula (e.g. MtCLE12 and MtCLE13). However, their linkage to other components of the AON pathways downstream of the shoot-derived inhibitor (SDI) is not understood. We have ectopically expressed the putative peptide ligand encoding genes MtCLE12 and MtCLE13 in M. truncatula which abolished nodulation completely in wild-type roots but not in the supernodulating null mutant sunn-4. Further, root growth inhibition was detected when MtCLE12 was ectopically expressed in wild-type roots or synthetic CLE12 peptide was applied exogenously. To identify downstream genes, roots of wild-type and sunn-4 mutant overexpressing MtCLE12 were used for quantitative gene expression analysis. We found that, in 35S:MtCLE12 roots, NODULE INCEPTION (NIN, a central regulator of nodulation) was down-regulated, whereas MtEFD (ethylene response factor required for nodule differentiation) and MtRR8 (a type-A response regulator thought to be involved in the negative regulation of cytokinin signaling), were up-regulated. Moreover, we found that the up-regulation of MtEFD and MtRR8 caused by overexpressing MtCLE12 is SUNN-dependent. Hence, our data link for the first time the pathways for Nod factor signaling, cytokinin perception and AON.
microRNA profiling of root tissues and root forming explant cultures in Medicago truncatula
Publisher: Springer Science and Business Media LLC
Date: 10-04-2013
DOI: 10.1007/S00425-013-1871-7
Abstract: Plant root architecture is regulated by the initiation and modulation of cell ision in regions containing pluripotent stem cells known as meristems. In roots, meristems are formed early in embryogenesis, in the case of the root apical meristem (RAM), and during organogenesis at the site of lateral root or, in legumes, nodule formation. Root meristems can also be generated in vitro from leaf explants cultures supplemented with auxin. microRNAs (miRNAs) have emerged as regulators of many key biological functions in plants including root development. To identify key miRNAs involved in root meristem formation in Medicago truncatula, we used deep sequencing to compare miRNA populations. Comparisons were made between: (1) the root tip (RT), containing the RAM and the elongation zone (EZ) tissue and (2) root forming callus (RFC) and non-root forming callus (NRFC). We identified 83 previously reported miRNAs, 24 new to M. truncatula, in 44 families. For the first time in M. truncatula, members of conserved miRNA families miR165, miR181 and miR397 were found. Bioinformatic analysis identified 38 potential novel miRNAs. Selected miRNAs and targets were validated using Taqman miRNA assays and 5' RACE. Many miRNAs were differentially expressed between tissues, particularly RFC and NRFC. Target prediction revealed a number of miRNAs to target genes previously shown to be differentially expressed between RT and EZ or RFC and NRFC and important in root development. Additionally, we predict the miRNA/target relationships for miR397 and miR160 to be conserved in M. truncatula. Amongst the predictions, were AUXIN RESPONSE FACTOR 10, targeted by miR160 and a LACCASE-like gene, targeted by miR397, both are miRNA/target pairings conserved in other species.
CEP–CEPR1 signalling inhibits the sucrose-dependent enhancement of lateral root growth
Publisher: Oxford University Press (OUP)
Date: 06-05-2019
DOI: 10.1093/JXB/ERZ207
Abstract: Lateral root (LR) proliferation is a major determinant of soil nutrient uptake. How resource allocation controls the extent of LR growth remains unresolved. We used genetic, physiological, transcriptomic, and grafting approaches to define a role for C-TERMINALLY ENCODED PEPTIDE RECEPTOR 1 (CEPR1) in controlling sucrose-dependent LR growth. CEPR1 inhibited LR growth in response to applied sucrose, other metabolizable sugars, and elevated light intensity. Pathways through CEPR1 restricted LR growth by reducing LR meristem size and the length of mature LR cells. RNA-sequencing of wild-type (WT) and cepr1-1 roots with or without sucrose treatment revealed an intersection of CEP–CEPR1 signalling with the sucrose transcriptional response. Sucrose up-regulated several CEP genes, supporting a specific role for CEP–CEPR1 in the response to sucrose. Moreover, genes with basally perturbed expression in cepr1-1 overlap with WT sucrose-responsive genes significantly. We found that exogenous CEP inhibited LR growth via CEPR1 by reducing LR meristem size and mature cell length. This result is consistent with CEP–CEPR1 acting to curtail the extent of sucrose-dependent LR growth. Reciprocal grafting indicates that LR growth inhibition requires CEPR1 in both the roots and shoots. Our results reveal a new role for CEP–CEPR1 signalling in controlling LR growth in response to sucrose.
CEP peptide and cytokinin pathways converge on CEPD glutaredoxins to inhibit root growth
Publisher: Springer Science and Business Media LLC
Date: 27-03-2023
DOI: 10.1038/S41467-023-37282-6
Abstract: C - TERMINALLY ENCODED PEPTIDE (CEP) and cytokinin hormones act over short and long distances to control plant responses to environmental cues. CEP and cytokinin pathway mutants share phenotypes, however, it is not known if these pathways intersect. We show that CEP and cytokinin signalling converge on CEP DOWNSTREAM (CEPD) glutaredoxins to inhibit primary root growth. CEP inhibition of root growth was impaired in mutants defective in trans -zeatin ( t Z)-type cytokinin biosynthesis, transport, perception, and output. Concordantly, mutants affected in CEP RECEPTOR 1 showed reduced root growth inhibition in response to t Z, and altered levels of t Z-type cytokinins. Grafting and organ-specific hormone treatments showed that t Z-mediated root growth inhibition involved CEPD activity in roots. By contrast, root growth inhibition by CEP depended on shoot CEPD function. The results demonstrate that CEP and cytokinin pathways intersect, and utilise signalling circuits in separate organs involving common glutaredoxin genes to coordinate root growth.
CEP peptide hormones: key players in orchestrating nitrogen-demand signalling, root nodulation, and lateral root development
Publisher: Oxford University Press (OUP)
Date: 20-03-2018
DOI: 10.1093/JXB/ERY037
Abstract: Secreted peptide hormones play pivotal roles in plant growth and development. So far, CEPs (C-TERMINALLY ENCODED PEPTIDEs) have been shown to act through CEP receptors (CEPRs) to control nitrogen (N)-demand signalling, nodulation, and lateral root development. Secreted CEP peptides can enter the xylem stream to act as long-distance signals, but evidence also exists for CEPs acting in local circuits. Recently, CEP peptide species varying in sequence, length, and post-translational modifications have been identified. A more comprehensive understanding of CEP biology requires insight into the in planta function of CEP genes, CEP peptide biogenesis, the components of CEP signalling cascades and, finally, how CEP peptide length, amino-acid composition, and post-translational modifications affect biological activity. In this review, we highlight recent studies that have advanced our understanding in these key areas and discuss some future directions.
Molecular genetic analysis of subterranean clover-microbe interactions
Publisher: Elsevier BV
Date: 04-1995
nodT, a positively-acting cultivar specificity determinant controlling nodulation of Trifolium subterraneum by Rhizobium leguminosarum biovar trifolii
Publisher: Springer Science and Business Media LLC
Date: 04-1991
DOI: 10.1007/BF00023418
Abstract: The brain is the main target in congenital cytomegalovirus (CMV) infection and immunocompromised patients. No definite evidence that a CMV has special affinity for the central nervous system (CNS) has been published. Here, we generated transgenic mice with an e1 promoter/enhancer region connected to the reporter gene lacZ. Surprisingly, expression of the transgene was completely restricted to the CNS in all lines of transgenic mice. The transgene was expressed in subpopulation of neurons in the cerebral cortex, hippoc us, diencephalon, brainstem, cerebellum, and spinal cord in all of the lines. Non-neuronal cells in the CNS were negative for transgene expression. Activation of the transgene was first observed in neurons of mesencephalon in late gestation, and then the number of positive neurons increased in various parts of the brain as development proceeded. Upon infection of the transgenic mouse brains with MCMV, the location of the activated neurons became more extensive, and the number of such neurons increased. These results suggest that there are host factor(s) that directly activate the MCMV early gene promoter in neurons. This neuron-specific activation may be associated with persistent infection in the brain and may be responsible for the neuronal dysfunction and neuronal cell loss caused by CMV infection.
The Glycine max Xylem Sap and Apoplast Proteome
Publisher: American Chemical Society (ACS)
Date: 14-08-2007
DOI: 10.1021/PR0606833
Abstract: Molecular signaling interactions in the plant apoplast are important for defense and developmental responses. We examined the soybean proteome of the apoplastic conduit of root-to-shoot communication, the xylem stream, using gel electrophoresis combined with two types of tandem mass spectrometry. We examined soybeans for the presence of a Bradyrhizobium japonicum-induced, long distance developmental signal that controls autoregulation of nodulation (AON) to determine if xylem proteins (XPs) were involved directly or indirectly in AON. The xylem and apoplast fluids collected in hypocotyl, epicotyl, and stem tissue contained a highly similar set of secreted proteins. The XPs were different from those secreted from imbibing seed implying they play important basic roles in xylem function. The XPs of wild-type and nts1007 plants were indistinguishable irrespective of plant age, inoculation status, or time after inoculation suggesting that none was directly involved in AON. XPs were continuously loaded into the xylem stream, as they were present even 28 h after shoot decapitation. These results were consistent with semiquantitative RT-PCR studies that examined the expression of genes corresponding to the XPs under inoculated or uninoculated conditions. Monitoring the expression of XP genes by RT-PCR showed that four possessed root biased expression. This suggested that the corresponding protein products could be produced in roots and travel long distances to shoots. Of these, a species of lipid transfer protein is a candidate for a water-soluble, long-distance signal-carrier due to the presence of hydrophobic clefts that bind known plant signals in vitro. Two soybean XPs identified in this study, lipid transfer protein and Kunitz trypsin inhibitor (KTI), have known roles in plant signaling.
Temperature modulation of fatty acid profiles for biofuel production in nitrogen deprived Chlamydomonas reinhardtii
Publisher: Elsevier BV
Date: 2013
DOI: 10.1016/J.BIORTECH.2012.09.090
Abstract: This study investigated the changes in the fatty acid content and composition in the nitrogen-starved Chlamydomonas reinhardtii starchless mutant, BAF-J5, grown at different temperatures. The optimal temperature for vegetative growth under nitrogen sufficient conditions was found to be 32 °C. Shifting temperature from 25 to 32 °C, in conjunction with nitrogen starvation, resulted in BAF-J5 storing the maximum quantity of fatty acid (76% of dry cell weight). Shifting to temperatures lower than 25 °C, reduced the total amount of stored fatty acid content and increased the level of desaturation in the fatty acids. The optimal fatty acid composition for biodiesel was at 32 °C. This study demonstrates how a critical environmental factor, such as temperature, can modulate the amount and composition of fatty acids under nitrogen deprivation and reduce the requirement for costly refining of biofuels.
The NIN transcription factor coordinates CEP and CLE signaling peptides that regulate nodulation antagonistically
Publisher: Springer Science and Business Media LLC
Date: 23-06-2020
DOI: 10.1038/S41467-020-16968-1
Abstract: Legumes tightly regulate nodule number to balance the cost of supporting symbiotic rhizobia with the benefits of nitrogen fixation. C-terminally Encoded Peptides (CEPs) and CLAVATA3-like (CLE) peptides positively and negatively regulate nodulation, respectively, through independent systemic pathways, but how these regulations are coordinated remains unknown. Here, we show that rhizobia, Nod Factors, and cytokinins induce a symbiosis-specific CEP gene, MtCEP7 , which positively regulates rhizobial infection. Via grafting and split root studies, we reveal that MtCEP7 increases nodule number systemically through the MtCRA2 receptor. MtCEP7 and MtCLE13 expression in rhizobia-inoculated roots rely on the MtCRE1 cytokinin receptor and on the MtNIN transcription factor. MtNIN binds and transactivates Mt CEP7 and MtCLE13 , and a NIN Binding Site (NBS) identified within the proximal MtCEP7 promoter is required for its symbiotic activation. Overall, these results demonstrate that a cytokinin-MtCRE1-MtNIN regulatory module coordinates the expression of two antagonistic, symbiosis-related, peptide hormones from different families to fine-tune nodule number.
Plant factors induce expression of nodulation and host-range genes in Rhizobium trifolii
Publisher: Springer Science and Business Media LLC
Date: 12-1985
DOI: 10.1007/BF00331334
Rhizobium nodulation genes involved in root hair curling (Hac) are functionally conserved
Publisher: Springer Science and Business Media LLC
Date: 03-1985
DOI: 10.1007/BF02418762
Diversification of the C-TERMINALLY ENCODED PEPTIDE (CEP) gene family in angiosperms, and evolution of plant-family specific CEP genes
Publisher: Springer Science and Business Media LLC
Date: 2014
Five genetic loci involved in the synthesis of acidic exopolysaccharides are closely linked in the genome of Rhizobium sp strain NGR234
Publisher: Springer Science and Business Media LLC
Date: 05-1988
DOI: 10.1007/BF00334701
Stability of a biomembrane tube covered with proteins
Publisher: Cold Spring Harbor Laboratory
Date: 29-09-2022
Proteomic analysis of legume-microbe interactions
Publisher: Hindawi Limited
Date: 2003
DOI: 10.1002/CFG.263
New role for a CEP peptide and its receptor: complex control of lateral roots
Publisher: Oxford University Press (OUP)
Date: 08-2016
DOI: 10.1093/JXB/ERW306
Soybean Nodule Autoregulation Receptor Kinase Phosphorylates Two Kinase-associated Protein Phosphatases in Vitro
Publisher: Elsevier BV
Date: 09-2008
A molecular linkage map of nitrogenase and nodulation genes in Rhizobium trifolii
Publisher: Springer Science and Business Media LLC
Date: 11-1983
DOI: 10.1007/BF00392191
The production of species-specific highly unsaturated fatty acyl-containing LCOs from Rhizobium leguminosarum bv. trifolii is stringently regulated by nodD and involves the nodRL genes
Publisher: Scientific Societies
Date: 03-2006
DOI: 10.1094/MPMI-19-0215
Abstract: A proportion of the Nod factors of some Rhizobium leguminosarum bv. trifolii strains is characterized by the presence of highly unsaturated fatty acyl chains containing trans double bonds in conjugation with the carbonyl group of the glycan oligosaccharide backbone. These fatty acyl chains are C 18:3 , C 20:3 , C 18:4 , or C 20:4 and have UV-absorption maxima at 303 and 330 nm. These Nod factors are presumed to be important for host-specific nodulation on clover species. However, in wild-type R. leguminosarum bv. trifolii ANU843, Nod factors with these characteristic acyl chains were not observed using standard growth conditions. They were observed only when nod genes were present in multiple copies or when transcription was artificially increased to higher levels by introduction of extra copies of the transcriptional regulator gene nodD. In a screen for the genetic requirements for production of the Nod factors with these characteristic structures, it was found that the region downstream of nodF and nodE is essential for the presence of highly unsaturated fatty acyl moieties. Mu-lacZ insertion in this region produced a mutant that did not produce detectable levels of the highly unsaturated fatty acyl-bearing Nod factors. The Mu-lacZ insertion was translationally fused to a putative new gene, designated nodR, in the nodE-nodL intergenic region however, no predicted function for the putative NodR protein has been obtained from data-base homology searches. In a set of 12 wild-type strains of R. leguminosarum bv. trifolii originating from various geographical regions that were analyzed for the presence of a nodR-like gene, it was found that seven strains carry a homologous NodR open reading frame. Taken together, our results suggest a tightly controlled regulation of nod genes, in which we propose that it is the balance of transcriptional levels of nodFE and the nodRL genes that is critical for determining the presence of highly unsaturated fatty acyl moieties in the Nod factors produced by R. leguminosarum bv. trifolii.
Solution NMR studies of the plant peptide hormone CEP inform function
Publisher: Wiley
Date: 05-11-2013
DOI: 10.1016/J.FEBSLET.2013.10.033
Abstract: The C-terminally Encoded Peptide (CEP) family of regulatory peptides controls root development in vascular plants. Here, we present the first NMR structures of CEP. We show that root-knot nematode (RKN: Meloidogyne spp.) also encodes CEP, presumably to mimic plant CEP as part of their stereotypic, parasitic interaction with vascular plants. Molecular dynamics simulations of plant- and nematode-encoded CEP displaying known posttranslational modifications (PTM) provided insight into the structural effects of PTM and the conformational plasticity and rigidity of CEP. Potential mechanisms of action are discussed with respect to the structure and s ling of conformational space.
CEP peptide and cytokinin pathways converge on CEPD glutaredoxins to inhibit root growth
Publisher: Cold Spring Harbor Laboratory
Date: 06-07-2022
DOI: 10.1101/2022.07.05.498042
Abstract: C-TERMINALLY ENCODED PEPTIDE (CEP) and cytokinin hormones act over short and long distances to control plant responses to environmental cues. CEP and cytokinin pathway mutants share phenotypes, however, it is not known if these pathways intersect. We show that CEP and cytokinin signalling converge on CEP DOWNSTREAM (CEPD) glutaredoxins to inhibit primary root growth. CEP inhibition of root growth was impaired in mutants defective in trans -zeatin ( t Z)-type cytokinin biosynthesis, transport, perception, and output. Concordantly, mutants affected in CEP RECEPTOR 1 showed reduced root growth inhibition in response to t Z, and altered levels of t Z-type cytokinins. Grafting and organ-specific hormone treatments showed that t Z-mediated root growth inhibition required CEPD activity in roots. By contrast, root growth inhibition by CEP depended on shoot CEPD function. The results demonstrate that CEP and cytokinin pathways intersect, and utilise signalling circuits in separate organs involving common glutaredoxin genes to coordinate root growth.
CEP receptor signalling controls root system architecture in Arabidopsis and Medicago
Publisher: Wiley
Date: 17-03-2020
DOI: 10.1111/NPH.16483
Alteration of flavonoid accumulation patterns in transparent testa mutants disturbs auxin transport, gravity responses, and imparts long-term effects on root and shoot architecture
Publisher: Springer Science and Business Media LLC
Date: 27-04-2013
DOI: 10.1007/S00425-013-1883-3
Abstract: Flavonoids have broad cross-kingdom biological activity. In Arabidopsis, flavonoid accumulation in specific tissues, notably the root elongation zone and root/shoot junction modulate auxin transport, affect root gravitropism, and influence overall plant architecture. The relative contribution made by aglycones and their glycosides remains undetermined, and the longer-term phenotypic effects of altered flavonoid accumulation are not fully assessed. We tested Arabidopsis thaliana mutants that accumulate different flavonoids to determine which flavonoids were causing these affects. Tandem mass spectrometry and in situ fluorescence localisation were used to determine the in vivo levels of aglycones in specific tissues of 11 transparent testa mutants. We measured rootward and shootward auxin transport, gravitropic responses, and identified the long-term changes to root and shoot architecture. Unexpected aglycone species accumulated in vivo in several flavonoid-pathway mutants, and lower aglycone levels occurred in transcription factor mutants. Mutants accumulating more quercetin and quercetin-glycosides changed the greatest in auxin transport, gravitropism, and aerial tissue growth. Early flavonoid-pathway mutants showed aberrant lateral root initiation patterns including clustered lateral root initiations at a single site. Transcription factor mutants had multiple phenotypes including shallow root systems. These results confirm that aglycones are present at very low levels, show that lateral root initiation is perturbed in early flavonoid-pathway mutants, and indicate that altered flavonoid accumulation affects multiple aspects of plant architecture.
The Medicago truncatula Small Protein Proteome and Peptidome
Publisher: American Chemical Society (ACS)
Date: 07-11-2006
DOI: 10.1021/PR060336T
Abstract: The small protein and native peptide component of plant tissues is a neglected area of proteomic studies. We have used fractionation techniques for denatured and nondenatured protein preparations combined with 2-D LC tandem mass spectrometry to examine the sequences of small proteins and peptides in four tissues of the model legume, Medicago truncatula: the root tip and root of germinating seedlings, nitrogen fixing nodules, and young leaves. The isolation and fractionation strategies successfully enriched the small protein and native peptide content of the s les. Eighty-one small M. truncatula proteins and native peptides were identified. Most s les were dominated by ribosomal and histone proteins, and leaf s les possessed photosynthesis-related proteins. Secreted proteins such as lipid transfer proteins were common to several tissues. Twenty-four hours after germination, the roots and root tip tissues possessed several "seed-specific" and late-embryogenesis proteins. We conclude that these proteins are present in cells prior to germination and that they are subsequently used as a nutritional source for the young tissues. Native UV absorbing peptides were detected in very low molecular weight fractions and sequenced. Each peptide shared C-terminal residues and showed homology to the seed storage protein legumin. The strategies used here would be suitable for combining bioassays and mass spectrometry to identify bioactive peptides in the M. truncatula peptidome.
Improving Hox protein classification across the major model organisms
Publisher: Public Library of Science (PLoS)
Date: 25-05-2010
Probing for pH-Regulated Proteins in <i>Sinorhizobium medicae </i>Using Proteomic Analysis
Publisher: S. Karger AG
Date: 2004
DOI: 10.1159/000078657
Abstract: To elucidate the mechanisms of pH response in an acid-tolerant i Sinorhizobium medicae /i strain we have identified acid-activated gene transcription and now complement this approach by using a proteomic analysis to identify the changes that occur following exposure to acidity. Protein profiles of persistently or transiently acid-stressed i S. medicae /i cells were compared to those grown in pH neutral, buffered media. Fifty pH-regulated proteins were identified N-terminal sequences for 15 of these were obtained using the Edman degradation. Transient acid exposure downregulated GlnA and GlnK and upregulated a hypothetical protein. Continuing acid exposure downregulated ClpP, an ABC transporter, a hypothetical protein, a lipoprotein, the Trp-like repressor WrbA1 and upregulated DegP, fructose bisphosphate aldolase, GroES, malate dehydrogenase and two hypothetical proteins. These findings implicate proteolytic, chaperone and transport processes as key components of pH response in i S. medicae /i .
Microscopic analysis of the effect of Rhizobium leguminosarum biovar trifolii host specific nodulation genes in the infection of white clovers
Publisher: Springer Science and Business Media LLC
Date: 06-1993
DOI: 10.1007/BF01379375
Influence of Rhizobium leguminosarum biovar trifolii host specific nodulation genes on the ontogeny of clover nodulation
Publisher: Springer Science and Business Media LLC
Date: 06-1993
DOI: 10.1007/BF01379374
Proteome analysis of the model microsymbiont sinorhizobium meliloti: isolation and characterisation of novel proteins
Publisher: Wiley
Date: 25-11-2007
Characterization of Aberrant Infection Events Induced on Trifolium subterraneum by Rhizobium trifolii Region II Mutants
Publisher: Elsevier BV
Date: 08-1988
Fatty acid profiling of Chlamydomonas reinhardtii under nitrogen deprivation
Publisher: Elsevier BV
Date: 02-2011
DOI: 10.1016/J.BIORTECH.2010.11.051
Abstract: The Chlamydomonas reinhardtii starch-less mutant, BAF-J5, was found to store lipids up to 65% of dry cell weight when grown photoheterotrophically and subjected to nitrogen starvation. Fourier transform infrared spectroscopy was used as a high-throughput method for semi-quantitative measurements of protein, carbohydrate and lipid content. The fatty acids of wild-type and starch mutants were identified and quantified by gas chromatography mass spectrometry. C. reinhardtii starch mutants, BAF-J5 and I7, produce significantly elevated levels of 16:0, 18:1(Δ9), 18:2(Δ9,12) and 18:3(Δ9,12,15) fatty acids. Long-chain saturated, mono- and polyunsaturated fatty acids were found under nitrogen starvation. Oleosin-like and caleosin-like genes were identified in the C. reinhardtii genome. However, proteomic analysis of isolated lipid bodies only identified a key lipid droplet associated protein. This study shows it is possible to manipulate algal biosynthetic pathways to produce high levels of lipid that may be suitable for conversion to liquid fuels.
The inhibition of infection thread development in the cultivar-specific interaction of Rhizobium and subterranean clover is not caused by a hypersensitive response
Publisher: Springer Science and Business Media LLC
Date: 03-1995
DOI: 10.1007/BF01272754
Lipo-chitin oligosaccharides, plant symbiosis signalling molecules that modulate mammalian angiogenesis in vitro
Publisher: Public Library of Science (PLoS)
Date: 23-12-2014
Comparative proteomic profiles of the soybean (Glycine max) root apex and differentiated root zone
Publisher: Wiley
Date: 22-03-2011
Abstract: The root apical meristem (RAM) is responsible for the growth of the plant root system. Because of the importance of root architecture in the performance of crop plants, we established a proteome reference map of the soybean root apex and compared this with the proteome of the differentiated root zone. The root apex s les contained the apical 1 mm of the root, comprising the RAM, quiescent center and root cap. We identified 342 protein spots from 550 excised proteins (∼62%) of root apex s les by MALDI-TOF MS/MS analysis. All these proteins were also present in the differentiated root, but differed in abundance. Functional classification showed that the most numerous protein categories represented in the root were those of stress response, glycolysis, redox homeostasis and protein processing. Using DIGE, we identified 73 differentially accumulated proteins between root apex and differentiated root. Proteins overrepresented in the root apex belonged primarily to the pathways for protein synthesis and processing, cell redox homeostasis and flavonoid biosynthesis. Proteins underrepresented in the root apex were those of glycolysis, tricarboxylic acid metabolism and stress response. Our results highlight the importance of stress and defense response, redox control and flavonoid metabolism in the root apex.
Root-to-shoot signalling: integration of diverse molecules, pathways and functions
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/FP15252
Abstract: Plant adaptive potential is critically dependent upon efficient communication and co-ordination of resource allocation and signalling between above- and below-ground plant parts. Plant roots act as gatekeepers that sense and encode information about soil physical, chemical and biological factors, converting them into a sophisticated network of signals propagated both within the root itself, and also between the root and shoot, to optimise plant performance for a specific set of conditions. In return, plant roots receive and decode reciprocal information coming from the shoot. The communication modes are highly erse and include a broad range of physical (electric and hydraulic signals, propagating Ca2+ and ROS waves), chemical (assimilates, hormones, peptides and nutrients), and molecular (proteins and RNA) signals. Further, different signalling systems operate at very different timescales. It remains unclear whether some of these signalling systems operate in a priming mode(s), whereas others deliver more specific information about the nature of the signal, or whether they carry the same ‘weight’. This review summarises the current knowledge of the above signalling mechanisms, and reveals their hierarchy, and highlights the importance of integration of these signalling components, to enable optimal plant functioning in a dynamic environment.
A new method to visualize CEP hormone–CEP receptor interactions in vascular tissue in vivo
Publisher: Oxford University Press (OUP)
Date: 31-05-2021
DOI: 10.1093/JXB/ERAB244
Abstract: C-TERMINALLY ENCODED PEPTIDEs (CEPs) control erse responses in plants including root development, root system architecture, nitrogen demand signalling, and nutrient allocation that influences yield, and there is evidence that different ligands impart different phenotypic responses. Thus, there is a need for a simple method that identifies bona fide CEP hormone–receptor pairings in vivo and examines whether different CEP family peptides bind the same receptor. We used formaldehyde or photoactivation to cross-link fluorescently tagged group 1 or group 2 CEPs to receptors in semi-purified Medicago truncatula or Arabidopsis thaliana leaf vascular tissues to verify that COMPACT ROOT ARCHITECTURE 2 (CRA2) is the Medicago CEP receptor, and to investigate whether sequence ersity within the CEP family influences receptor binding. Formaldehyde cross-linked the fluorescein isothiocyanate (FITC)-tagged Medicago group 1 CEP (MtCEP1) to wild-type Medicago or Arabidopsis vascular tissue cells, but not to the CEP receptor mutants, cra2 or cepr1. Binding competition showed that unlabelled MtCEP1 displaces FITC–MtCEP1 from CRA2. In contrast, the group 2 CEP, FITC–AtCEP14, bound to vascular tissue independently of CEPR1 or CRA2, and AtCEP14 did not complete with FITC–MtCEP1 to bind CEP receptors. The binding of a photoactivatable FITC–MtCEP1 to the periphery of Medicago vascular cells suggested that CRA2 localizes to the plasma membrane. We separated and visualized a fluorescent 105 kDa protein corresponding to the photo-cross-linked FITC–MtCEP1–CRA2 complex using SDS–PAGE. Mass spectrometry identified CRA2-specific peptides in this protein band. The results indicate that FITC–MtCEP1 binds to CRA2, MtCRA2 and AtCEPR1 are functionally equivalent, and the binding specificities of group 1 and group 2 CEPs are distinct. Using formaldehyde or photoactivated cross-linking of biologically active, fluorescently tagged ligands may find wider utility by identifying CEP–CEP receptor pairings in erse plants.
The peptide-encoding CEP1 gene modulates lateral root and nodule numbers in Medicago truncatula
Publisher: Oxford University Press (OUP)
Date: 20-11-2013
DOI: 10.1093/JXB/ERT369
Abstract: The role of MtCEP1, a member of the CEP (C-terminally encoded peptide) signaling peptide family, was examined in Medicago truncatula root development. MtCEP1 was expressed in root tips, vascular tissue, and young lateral organs, and was up-regulated by low nitrogen levels and, independently, by elevated CO2. Overexpressing MtCEP1 or applying MtCEP1 peptide to roots elicited developmental phenotypes: inhibition of lateral root formation, enhancement of nodulation, and the induction of periodic circumferential root swellings, which arose from cortical, epidermal, and pericycle cell isions and featured an additional cortical cell layer. MtCEP peptide addition to other legume species induced similar phenotypes. The enhancement of nodulation by MtCEP1 is partially tolerant to high nitrate, which normally strongly suppresses nodulation. These nodules develop faster, are larger, and fix more nitrogen in the absence and presence of inhibiting nitrate levels. At 25mM nitrate, nodules formed on pre-existing swelling sites induced by MtCEP1 overexpression. RNA interference-mediated silencing of several MtCEP genes revealed a negative correlation between transcript levels of MtCEP1 and MtCEP2 with the number of lateral roots. MtCEP1 peptide-dependent phenotypes were abolished or attenuated by altering or deleting key residues in its 15 amino acid domain. RNA-Seq analysis revealed that 89 and 116 genes were significantly up- and down-regulated, respectively, by MtCEP1 overexpression, including transcription factors WRKY, bZIP, ERF, and MYB, homologues of LOB29, SUPERROOT2, and BABY BOOM. Taken together, the data suggest that the MtCEP1 peptide modulates lateral root and nodule development in M. truncatula.
The Expression of Genes Encoding Secreted Proteins in Medicago truncatula A17 Inoculated Roots
Publisher: Bogor Agricultural University
Date: 09-2013
DOI: 10.4308/HJB.20.3.105
A convenient set of vectors for expression of multiple gene combinations in plants
Publisher: Springer Science and Business Media LLC
Date: 06-1997
DOI: 10.1007/BF02812263
Border sequences of Medicago truncatula CLE36 are specifically cleaved by endoproteases common to the extracellular fluids of Medicago and soybean
Publisher: Oxford University Press (OUP)
Date: 06-2011
DOI: 10.1093/JXB/ERR185
C-TERMINALLY ENCODED PEPTIDE (CEP) and cytokinin hormone signaling intersect to promote shallow lateral root angles
Publisher: Oxford University Press (OUP)
Date: 09-09-2023
DOI: 10.1093/JXB/ERAD353
Elevated Levels of Synthesis of over 20 Proteins Results after Mutation of the Rhizobium leguminosarum Exopolysaccharide Synthesis Gene pssA
Publisher: American Society for Microbiology
Date: 15-08-2000
DOI: 10.1128/JB.182.16.4521-4532.2000
Abstract: The protein expression profiles of Rhizobium leguminosarum strains in response to specific genetic perturbations in exopolysaccharide (EPS) biosynthesis genes were examined using two-dimensional gel electrophoresis. Lesions in either pssA , pssD , or pssE of R. leguminosarum bv. viciae VF39 or in pssA of R. leguminosarum bv. trifolii ANU794 not only abolished the capacity of these strains to synthesize EPS but also had a pleiotropic effect on protein synthesis levels. A minimum of 22 protein differences were observed for the two pssA mutant strains. The differences identified in the pssD and pssE mutants of strain VF39 were a distinct subset of the same protein synthesis changes that occurred in the pssA mutant. The pssD and pssE mutant strains shared identical alterations in the proteins synthesized, suggesting that they share a common function in the biosynthesis of EPS. In contrast, a pssC mutant that produces 38% of the EPS level of the parental strain showed no differences in its protein synthesis patterns, suggesting that the absence of EPS itself was contributing to the changes in protein synthesis and that there may be a complex interconnection of the EPS biosynthetic pathway with other metabolic pathways. Genetic complementation of pssA can restore wild-type protein synthesis levels, indicating that many of the observed differences in protein synthesis are also a specific response to a dysfunctional PssA. The relevance of these proteins, which are grouped as members of the pssA mutant stimulon, remains unclear, as the majority lacked a homologue in the current sequence databases and therefore possibly represent a novel functional network(s). These findings have illustrated the potential of proteomics to reveal unexpected higher-order processes of protein function and regulation that arise from mutation. In addition, it is evident that enzymatic pathways and regulatory networks are more interconnected and more sensitive to structural changes in the cell than is often appreciated. In these cases, linking the observed phenotype directly to the mutated gene can be misleading, as the phenotype could be attributable to downstream effects of the mutation.
Tn 5 mutagenesis of Rhizobium trifolii host-specific nodulation genes result in mutants with altered host-range ability
Publisher: Springer Science and Business Media LLC
Date: 08-1985
DOI: 10.1007/BF00425732
Diverse Peptide Hormones Affecting Root Growth Identified in the Medicago truncatula Secreted Peptidome
Publisher: Elsevier BV
Date: 2018
Auxin transport inhibition precedes root nodule formation in white clover roots and is regulated by flavonoids and derivatives of chitin oligosaccharides
Publisher: Wiley
Date: 04-1998
Factors Altering Pyruvate Excretion in a Glycogen Storage Mutant of the Cyanobacterium, Synechococcus PCC7942
Publisher: Frontiers Media SA
Date: 05-04-2016
Global gene expression analysis of in vitro root formation in Medicago truncatula
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/FP10159
Abstract: Medicago truncatula Gaertn. can generate roots in vitro through the formation of root stem cells from leaf explants cultured with auxin. To identify key genes involved in the early processes of root initiation, we compared gene expression in root-forming cultures (RFC) enriched for root stem cells with non-root-forming cultures (NRFC) and untreated leaves using the Affymetrix Medicago GeneChip. Comparing RFC (at 1 week, before root primordium formation) to normal leaf tissue, we identified 904 and 993 up- and downregulated probe sets. Comparing RFC and NRFC, we identified 92 and 182 up- and downregulated probe sets. By comparing all the s les we identified a set of 76 and 42 probe sets up- and downregulated that may be crucial to root stem cell formation and subsequent root initiation. Upregulated probe sets in RFC include Arabidopsis orthologs that are involved in root stem cell formation and root initiation. To validate the GeneChip results, quantitative real-time RT–PCR analysis was used to examine the expression of specific up- and downregulated genes, all of which positively correlated with the microarray data. We used bioinformatic tools developed to functionally annotate the Medicago genome array. This showed significant changes in metabolism, signalling and the expression of transcription factors including some with described roles in root organogenesis and other genes not previously linked to this process. This data facilitates the mapping of regulatory and metabolic networks in M. truncatula and provides candidates for further functional analysis of root initiation in vitro and in planta.
Effects of pH, Ca and Al on the exudation from clover seedlings of compounds that induce the expression of nodulation genes in Rhizobium trifolii
Publisher: Springer Science and Business Media LLC
Date: 06-1988
DOI: 10.1007/BF02197578
Host Specific Nodulation of Plants of the Pea Cross-inoculation Group is Influenced by Genes in Fast Growing Rhizobium downstream nodC
Publisher: Elsevier BV
Date: 05-1988
Macroptilium atropurpureum (siratro) host specificity genes are linked to a nodD-like gene in the broad host range Rhizobium strain NGR234
Publisher: Springer Science and Business Media LLC
Date: 04-1986
DOI: 10.1007/BF00330383
Nitrogen modulation of legume root architecture signaling pathways involves phytohormones and small regulatory molecules
Publisher: Frontiers Media SA
Date: 2013
Flavones induce expression of nodulation genes in Rhizobium
Publisher: Springer Science and Business Media LLC
Date: 10-1986
DOI: 10.1038/323632A0
Flavonoids Are Differentially Taken Up and Transported Long Distances in Arabidopsis
Publisher: Oxford University Press (OUP)
Date: 24-08-2007
Abstract: Flavonoids are synthesized in response to developmental and environmental signals and perform many functions in plants. Arabidopsis (Arabidopsis thaliana) roots grown in complete darkness do not accumulate flavonoids since the expression of genes encoding enzymes of flavonoid biosynthesis is light dependent. Yet, flavonoids accumulate in root tips of plants with light-grown shoots and light-shielded roots, consistent with shoot-to-root flavonoid movement. Using fluorescence microscopy, a selective flavonoid stain, and localized aglycone application to transparent testa mutants, we showed that flavonoids accumulated in tissues distal to the application site, indicating uptake and movement systems. This was confirmed by time-course fluorescence experiments and high-performance liquid chromatography. Flavonoid applications to root tips resulted in basipetal movement in epidermal layers, with subsequent fluorescence detected 1 cm from application sites after 1 h. Flavonoid application to midroot or cotyledons showed movement of flavonoids toward the root tip mainly in vascular tissue. Naringenin, dihydrokaempferol, and dihydroquercetin were taken up at the root tip, midroot, or cotyledons and traveled long distances via cell-to-cell movement to distal tissues, followed by conversion to quercetin and kaempferol. In contrast, kaempferol and quercetin were only taken up at the root tip. Using ATP-binding cassette (ABC) transporter and H+-ATPase inhibitors suggested that a multidrug resistance-associated protein ABCC transporter facilitated flavonoid movement away from the application site.
Nodulation of specific legumes is controlled by several distinct loci in Rhizobium trifolii
Publisher: Springer Science and Business Media LLC
Date: 1986
DOI: 10.1007/BF00027132
Unintended changes in protein expression revealed by proteomic analysis of seeds from transgenic pea expressing a bean alpha-amylase inhibitor gene.
Publisher: Wiley
Date: 09-2009
Abstract: Seeds of genetically modified (GM) peas (Pisum sativum L.) expressing the gene for alpha-amylase inhibitor-1 (alphaAI1) from the common bean (Phaseolus vulgaris L. cv. Tendergreen) exhibit resistance to the pea weevil (Bruchus pisorum). A proteomic analysis was carried out to compare seeds from GM pea lines expressing the bean alphaAI1 protein and the corresponding alphaAI1-free segregating lines and non-GM parental line to identify unintended alterations to the proteome of GM peas due to the introduction of the gene for alphaAI1. Proteomic analysis showed that in addition to the presence of alphaAI1, 33 other proteins were differentially accumulated in the alphaAI1-expressing GM lines compared with their non-GM parental line and these were grouped into five expression classes. Among these 33 proteins, only three were found to be associated with the expression of alphaAI1 in the GM pea lines. The accumulation of the remaining 30 proteins appears to be associated with Agrobacterium-mediated transformation events. Sixteen proteins were identified after MALDI-TOF-TOF analysis. About 56% of the identified proteins with altered accumulation in the GM pea were storage proteins including legumin, vicilin or convicilin, phaseolin, cupin and valosin-containing protein. Two proteins were uniquely expressed in the alphaAI1-expressing GM lines and one new protein was present in both the alphaAI1-expressing GM lines and their alphaAI1-free segregating lines, suggesting that both transgenesis and transformation events led to demonstrable changes in the proteomes of the GM lines tested.
Different Pathways Act Downstream of the CEP Peptide Receptor CRA2 to Regulate Lateral Root and Nodule Development
Publisher: Oxford University Press (OUP)
Date: 24-06-2016
DOI: 10.1104/PP.16.00113
Is there gold at the top of the beanstalk?
Publisher: Springer Science and Business Media LLC
Date: 2006
Mining the genome of Arabidopsis thaliana as a basis for the identification of novel bioactive peptides involved in oxidative stress tolerance
Publisher: Oxford University Press (OUP)
Date: 16-09-2013
DOI: 10.1093/JXB/ERT295
Abstract: Although evidence has accumulated on the role of plant peptides in the response to external conditions, the number of peptide-encoding genes in the genome is still underestimated. Using tiling arrays, we identified 176 unannotated transcriptionally active regions (TARs) in Arabidopsis thaliana that were induced upon oxidative stress generated by the herbicide paraquat (PQ). These 176 TARs could be translated into 575 putative oxidative stress-induced peptides (OSIPs). A high-throughput functional assay was used in the eukaryotic model organism Saccharomyces cerevisiae allowing us to test for bioactive peptides that increase oxidative stress tolerance. In this way, we identified three OSIPs that, upon overexpression in yeast, resulted in a significant rise in tolerance to hydrogen peroxide (H2O2). For one of these peptides, the decapeptide OSIP108, exogenous application to H2O2-treated yeast also resulted in significantly increased survival. OSIP108 is contained within a pseudogene and is induced in A. thaliana leaves by both the reactive oxygen species-inducer PQ and the necrotrophic fungal pathogen Botrytis cinerea. Moreover, infiltration and overexpression of OSIP108 in A. thaliana leaves resulted in increased tolerance to treatment with PQ. In conclusion, the identification and characterization of OSIP108 confirms the validity of our high-throughput approach, based on tiling array analysis in A. thaliana and functional screening in yeast, to identify bioactive peptides.
Small-peptide signals that control root nodule number, development, and symbiosis
Publisher: Oxford University Press (OUP)
Date: 08-2015
DOI: 10.1093/JXB/ERV357
Abstract: Many legumes have the capacity to enter into a symbiotic association with soil bacteria generically called 'rhizobia' that results in the formation of new lateral organs on roots called nodules within which the rhizobia fix atmospheric nitrogen (N). Up to 200 million tonnes of N per annum is fixed by this association. Therefore, this symbiosis plays an integral role in the N cycle and is exploited in agriculture to support the sustainable fixation of N for cropping and animal production in developing and developed nations. Root nodulation is an expendable developmental process and competency for nodulation is coupled to low-N conditions. Both nodule initiation and development is suppressed under high-N conditions. Although root nodule formation enables sufficient N to be fixed for legumes to grow under N-deficient conditions, the carbon cost is high and nodule number is tightly regulated by local and systemic mechanisms. How legumes co-ordinate nodule formation with the other main organs of nutrient acquisition, lateral roots, is not fully understood. Independent mechanisms appear to regulate lateral roots and nodules under low- and high-N regimes. Recently, several signalling peptides have been implicated in the local and systemic regulation of nodule and lateral root formation. Other peptide classes control the symbiotic interaction of rhizobia with the host. This review focuses on the roles played by signalling peptides during the early stages of root nodule formation, in the control of nodule number, and in the establishment of symbiosis. Here, we highlight the latest findings and the gaps in our understanding of these processes.
Promotion of mammalian angiogenesis by neolignans derived from soybean extracellular fluids
Publisher: Public Library of Science (PLoS)
Date: 08-05-2018
CEP genes regulate root and shoot development in response to environmental cues and are specific to seed plants
Publisher: Oxford University Press (OUP)
Date: 31-10-2013
DOI: 10.1093/JXB/ERT332
Abstract: The manifestation of repetitive developmental programmes during plant growth can be adjusted in response to various environmental cues. During root development, this means being able to precisely control root growth and lateral root development. Small signalling peptides have been found to play roles in many aspects of root development. One member of the CEP (C-TERMINALLY ENCODED PEPTIDE) gene family has been shown to arrest root growth. Here we report that CEP genes are widespread among seed plants but are not present in land plants that lack true branching roots or root vasculature. We have identified 10 additional CEP genes in Arabidopsis. Expression analysis revealed that CEP genes are regulated by environmental cues such as nitrogen limitation, increased salt levels, increased osmotic strength, and increased CO2 levels in both roots and shoots. Analysis of synthetic CEP variants showed that both peptide sequence and modifications of key amino acids affect CEP biological activity. Analysis of several CEP over-expression lines revealed distinct roles for CEP genes in root and shoot development. A cep3 knockout mutant showed increased root and shoot growth under a range of abiotic stress, nutrient, and light conditions. We demonstrate that CEPs are negative regulators of root development, slowing primary root growth and reducing lateral root formation. We propose that CEPs are negative regulators that mediate environmental influences on plant development.
The Medicago SymCEP7 hormone increases nodule number via shoots without compromising lateral root number
Publisher: Oxford University Press (OUP)
Date: 19-01-2023
Abstract: Legumes acquire soil nutrients through nitrogen-fixing root nodules and lateral roots. To balance the costs and benefits of nodulation, legumes negatively control root nodule number by autoregulatory and hormonal pathways. How legumes simultaneously coordinate root nodule and lateral root development to procure nutrients remains poorly understood. In Medicago (Medicago truncatula), a subset of mature C-TERMINALLY ENCODED PEPTIDE (CEP) hormones can systemically promote nodule number, but all CEP hormones tested to date negatively regulate lateral root number. Here we showed that Medicago CEP7 produces a mature peptide, SymCEP7, that promotes nodulation from the shoot without compromising lateral root number. Rhizobial inoculation induced CEP7 in the susceptible root nodulation zone in a Nod factor-dependent manner, and, in contrast to other CEP genes, its transcription level was elevated in the ethylene signaling mutant sickle. Using mass spectrometry, fluorescence microscopy and expression analysis, we demonstrated that SymCEP7 activity requires the COMPACT ROOT ARCHITECTURE 2 receptor and activates the shoot-to-root systemic effector, miR2111. Shoot-applied SymCEP7 rapidly promoted nodule number in the pM to nM range at concentrations up to five orders of magnitude lower than effects mediated by root-applied SymCEP7. Shoot-applied SymCEP7 also promoted nodule number in White Clover (Trifolium repens) and Lotus (Lotus japonicus), which suggests that this biological function may be evolutionarily conserved. We propose that SymCEP7 acts in the Medicago shoot to counter balance the autoregulation pathways induced rapidly by rhizobia to enable nodulation without compromising lateral root growth, thus promoting the acquisition of nutrients other than nitrogen to support their growth.
CLE peptide tri‐arabinosylation and peptide domain sequence composition are essential for SUNN‐dependent autoregulation of nodulation in Medicago truncatula
Publisher: Wiley
Date: 02-02-2018
DOI: 10.1111/NPH.15019
Abstract: MtCLE12 and MtCLE13 encode CLAVATA3/EMBRYO-SURROUNDING REGION RELATED (CLE) peptides which regulate autoregulation of nodulation (AON) in Medicago through the shoot receptor, SUNN (SUPER NUMERIC NODULES). Genetics suggests RDN1 (ROOT-DETERMINED NODULATION 1) arabinosylates MtCLE12 to enable SUNN perception. The functional structures of MtCLE12 and MtCLE13 peptides, however, remain elusive. We combined genetic and chemical synthesis approaches to determine if glyco-modifications of three nodule-expressed CLE peptides are essential for AON. We also examined how root and shoot applied AON-CLEs inhibit nodulation. MtCLE12, MtCLE13 and MtCLE42 peptides were synthesized with hydroxylation, mono-arabinosylation or tri-arabinosylation (TaP) at proline 7. Only MtCLE12-TaP and MtCLE13-TaP peptides induced AON in wild-type (WT) and rdn1-1, but not in sunn-4. The application of MtCLE13-TaP to cotyledons 1 d before rhizobial inoculation completely inhibited both rhizobial infection and nodulation. By contrast, MtCLE12-TaP induced significant AON without abolishing rhizobial infection. The results indicate that key CLE domain amino acids and TaP modifications to MtCLE12 and MtCLE13 are essential for SUNN-dependent AON. We also show evidence that RDN1 does not tri-arabinosylate MtCLE13. Finally, MtCLE13-TaP can induce a strong AON response in shoots that inhibits the entire symbiotic processes in roots. We present a new model for AON in Medicago.
CEP3 levels affect starvation-related growth responses of the primary root
Publisher: Oxford University Press (OUP)
Date: 06-06-2019
DOI: 10.1093/JXB/ERZ270
Abstract: CEPs (C-TERMINALLY ENCODED PEPTIDEs) inhibit Arabidopsis primary root growth by unknown mechanisms. We investigated how CEP3 levels control primary root growth. CEP3 peptide application decreased cell ision, S-phase cell number, root meristematic cell number, and meristem zone (MZ) size in a dose- and CEP RECEPTOR1-dependent manner. Grafting showed that CEP3-dependent growth inhibition requires root and shoot CEPR1. CEP3 induced mitotic quiescence in MZ cells significantly faster than that induced by nutrient limitation alone. CEP3 also inhibited the restoration of S-phase to mitotically quiescence cells by nutrient resupply without quantitatively reducing TARGET OF RAPAMYCIN (TOR) kinase activity. In contrast, cep3-1 had an increased meristem size and S-phase cell number under nitrogen (N)-limited conditions, but not under N-sufficient conditions. Furthermore, cep3-1 meristematic cells remained in S-phase longer than wild-type cells during a sustained carbon (C) and N limitation. RNA sequencing showed that CEP3 peptide down-regulated genes involved in S-phase entry, cell wall and ribosome biogenesis, DNA replication, and meristem expansion, and up-regulated genes involved in catabolic processes and proteins and peptides that negatively control meristem expansion and root growth. Many of these genes were reciprocally regulated in cep3-1. The results suggest that raising CEP3 induces starvation-related responses that curtail primary root growth under severe nutrient limitation.
ELECTRODE: An electrochemistry package for atomistic simulations
Publisher: AIP Publishing
Date: 25-08-2022
DOI: 10.1063/5.0099239
Abstract: Constant potential methods (CPMs) enable computationally efficient simulations of the solid–liquid interface at conducting electrodes in molecular dynamics. They have been successfully used, for ex le, to realistically model the behavior of ionic liquids or water-in-salt electrolytes in supercapacitors and batteries. CPMs model conductive electrodes by updating charges of in idual electrode atoms according to the applied electric potential and the (time-dependent) local electrolyte structure. Here, we present a feature-rich CPM implementation, called ELECTRODE, for the Large-scale Atomic/Molecular Massively Parallel Simulator, which includes a constrained charge method and a thermo-potentiostat. The ELECTRODE package also contains a finite-field approach, multiple corrections for nonperiodic boundary conditions of the particle–particle particle–mesh solver, and a Thomas–Fermi model for using nonideal metals as electrodes. We demonstrate the capabilities of this implementation for a parallel-plate electrical double-layer capacitor, for which we have investigated the charging times with the different implemented methods and found an interesting relationship between water and ionic dipole relaxations. To prove the validity of the one-dimensional correction for the long-range electrostatics, we estimated the vacuum capacitance of two coaxial carbon nanotubes and compared it to structureless cylinders, for which an analytical expression exists. In summary, the ELECTRODE package enables efficient electrochemical simulations using state-of-the-art methods, allowing one to simulate even heterogeneous electrodes. Moreover, it allows unveiling more rigorously how electrode curvature affects the capacitance with the one-dimensional correction.
Flavonoids: New Roles for Old Molecules
Publisher: Wiley
Date: 2010
DOI: 10.1111/J.1744-7909.2010.00905.X
Abstract: Flavonoids are ubiquitous in the plant kingdom and have many erse functions including defense, UV protection, auxin transport inhibition, allelopathy, and flower coloring. Interestingly, these compounds also have considerable biological activity in plant, animal and bacterial systems - such broad activity is accomplished by few compounds. Yet, for all the research over the last three decades, many of the cellular targets of these secondary metabolites are unknown. The many mutants available in model plant species such as Arabidopsis thaliana and Medicago truncatula are enabling the intricacies of the physiology of these compounds to be deduced. In the present review, we cover recent advances in flavonoid research, discuss deficiencies in our understanding of the physiological processes, and suggest approaches to identify the cellular targets of flavonoids.
The plant detectives: innovative undergraduate teaching to inspire the next generation of plant biologists
Publisher: Frontiers Media SA
Date: 15-09-2015
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