ORCID Profile
0000-0003-4756-0411
Current Organisation
Monash University
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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.
Plant Biology | Plant Physiology | Crop and Pasture Biochemistry and Physiology | Plant Cell and Molecular Biology | Plant Biology not elsewhere classified | Biochemistry and Cell Biology | Plant Improvement (Selection, Breeding And Genetic Engineering) | Global Change Biology | Protein Trafficking | Genomics | Crop and Pasture Improvement (Selection and Breeding) | Plant Physiology | Medical Parasitology | Genetic Technologies: Transformation, Site-Directed Mutagenesis, Etc. | Ecological Physiology
Sorghum | Climate Change Adaptation Measures | Plant Production and Plant Primary Products not elsewhere classified | Higher education | Flora, Fauna and Biodiversity of environments not elsewhere classified | Industrial Crops not elsewhere classified | Primary plant products not elsewhere classified | Climate and Climate Change not elsewhere classified | Field crops not elsewhere classified | Fodder crops | Health not elsewhere classified | Other environmental aspects |
Publisher: Wiley
Date: 04-08-2016
DOI: 10.1111/GCB.13380
Abstract: Cassava is an important dietary component for over 1 billion people, and its ability to yield under drought has led to it being promoted as an important crop for food security under climate change. Despite its known photosynthetic plasticity in response to temperature, little is known about how temperature affects plant toxicity or about interactions between temperature and drought, which is important because cassava tissues contain high levels of toxic cyanogenic glucosides, a major health and food safety concern. In a controlled glasshouse experiment, plants were grown at 2 daytime temperatures (23 °C and 34 °C), and either well-watered or subject to a 1 month drought prior to harvest at 6 months. The objective was to determine the separate and interactive effects of temperature and drought on growth and toxicity. Both temperature and drought affected cassava physiology and chemistry. While temperature alone drove differences in plant height and above-ground biomass, drought and temperature × drought interactions most affected tuber yield, as well as foliar and tuber chemistry, including C : N, nitrogen and cyanide potential (CNp total cyanide released from cyanogenic glucosides). Conditions that most stimulated growth and yield (well-watered × high temperature) effected a reduction in tuber toxicity, whereas drought inhibited growth and yield, and was associated with increased foliar and tuber toxicity. The magnitude of drought effects on tuber yield and toxicity were greater at high temperature thus, increases in tuber CNp were not merely a consequence of reduced tuber biomass. Findings confirm that cassava is adaptable to forecast temperature increases, particularly in areas of adequate or increasing rainfall however, in regions forecast for increased incidence of drought, the effects of drought on both food quality (tuber toxicity) and yield are a greater threat to future food security and indicate an increasing necessity for processing of cassava to reduce toxicity.
Publisher: Springer Science and Business Media LLC
Date: 11-2002
DOI: 10.1007/S00442-002-1055-9
Abstract: The effect of light on the partitioning of resources between photosynthesis and chemical defence was studied in Eucalyptus cladocalyx F. Muell. This species allocates up to 15% of leaf nitrogen to the constitutive cyanogenic glycoside, prunasin, making it an ideal system for studying resource allocation. By controlling the level of leaf nitrogen we were able to test the hypothesis that light limitation would result in the effective reallocation of nitrogen from the defensive to the photosynthetic apparatus. Seedlings were grown in full light or shade and supplied with 1.5 mM or 6 mM nitrogen in a 2×2 factorial design. We found that shading effected a decrease in the concentration of the cyanogenic glycoside, prunasin, and little if any change in the concentration of carbon-based secondary metabolites (total phenolics and condensed tannins). There was also significantly less prunasin, relative to total leaf nitrogen, chlorophyll concentration and carbon assimilation rates, when grown plants were grown in shade, particularly when there was an le supply of nitrogen. This pattern is likely to be the result of relative changes in the energetic and resource costs of photosynthesis and defensive compounds at different photon flux densities.
Publisher: SAGE Publications
Date: 02-2019
Publisher: F1000 Research Ltd
Date: 24-09-2015
DOI: 10.12688/F1000RESEARCH.7032.1
Abstract: Making material available through learning management systems is standard practice in most universities, but this is generally seen as an adjunct to the ‘real’ teaching, that takes place in face-to-face classes. Lecture attendance is poor, and it is becoming increasingly difficult to engage students, both in the material being taught and c us life. This paper describes the redevelopment of a large course in scientific practice and communication that is compulsory for all science students studying at our Melbourne and Malaysian c uses, or by distance education. Working with an educational designer, a blended learning methodology was developed, converting the environment provided by the learning management system into a teaching space, rather than a filing system. To ensure focus, topics are clustered into themes with a ‘question of the week’, a pre-class stimulus and follow up activities. The content of the course did not change, but by restructuring the delivery using educationally relevant design techniques, the content was contextualised resulting in an integrated learning experience. Students are more engaged intellectually, and lecture attendance has improved. The approach we describe here is a simple and effective approach to bringing this university’s teaching and learning into the 21 st century.
Publisher: Elsevier BV
Date: 02-2012
Publisher: CRC Press
Date: 07-10-2016
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/FP05304
Abstract: The deployment of secondary metabolites, such as terpenes, as anti-herbivore defences is thought to be costly for plants in terms of primary metabolism. Moreover, it is assumed that the cost of this deployment is modified by resource availability. In this study we examined the impact of terpenoid oil accumulation on the growth of Eucalyptus polybractea R.T.Baker seedlings from four maternal half-sib families, under conditions of sufficient and limiting nitrogen. The foliar oil concentration measured was extremely variable, varying almost 20-fold to a maximum of 13% (w / DW). Oil concentration was higher in plants grown under high nitrogen than in low-nitrogen plants, and it was positively correlated with foliar nitrogen concentration. Oil concentration was related to maternal concentration, although this relationship was weak because of the variation encountered. The composition of oil, dominated by monoterpenes, was also extremely variable, although this variation could not be adequately explained by either nitrogen availability or the seedling parentage. Importantly, we detected no negative correlations between oil concentration and relative growth rate (RGR), net assimilation rate (NAR), or leaf nitrogen productivity (LNP). Rather, under nitrogen limiting conditions, positive correlations were detected between oil concentration and all three indices. We conclude that oil accumulation is associated with factors that promote growth and if there is a cost to oil deployment, it could not be detected using the experimental design employed here.
Publisher: Wiley
Date: 28-02-2022
DOI: 10.1111/NPH.18018
Abstract: Geographical variation in the environment underpins selection for local adaptation and evolutionary ergence among populations. Because many environmental conditions vary across species' ranges, identifying the specific environmental variables underlying local adaptation is profoundly challenging. We tested whether natural selection mediated by aridity predicts clinal ergence among invasive populations of capeweed (Arctotheca calendula) that established and spread across southern Australia during the last two centuries. Using common garden experiments with two environmental treatments (wet and dry) that mimic aridity conditions across capeweed's invasive range, we estimated clinal ergence and effects of aridity on fitness and multivariate phenotypic selection in populations s led along aridity gradients in Australia. We show that: (1) capeweed populations have relatively high fitness in aridity environments similar to their s ling locations (2) the magnitude and direction of selection strongly differs between wet and dry treatments, with drought stress increasing the strength of selection and (3) differences in directional selection between wet and dry treatments predict patterns of clinal ergence across the aridity gradient, particularly for traits affecting biomass, flowering phenology and putative antioxidant expression. Our results suggest that aridity-mediated selection contributes to trait ersification among invasive capeweed populations, possibly facilitating the expansion of capeweed across southern Australia.
Publisher: CSIRO Publishing
Date: 1982
DOI: 10.1071/BT9820185
Abstract: Invading Pittosporum undulaturn tends to be clumped around the butts of established trees. This is due to the preferential deposition of seeds in these sites by the European blackbird (Turdus merula) which is believed to be the main vector of dispersal. Native silvereyes (Zosterops lateralis) eat some seed but are not considered important in dispersal. The high mortality of seedlings in exposedsites reinforces the patchy pattern originally dictated by seed dispersal. Seeds may germinate after seed fall in spring but most seeds germinate in autumn. No seeds germinate during summer because of the low rainfall and high temperatures, the optimum germination temperature being 18-21°C . After 16 months' storage at moderate temperatures and humidities, 80% of seed was still viable but viability was reduced to 30% at very low humidities. Seedlings of P. undulatum have three growth stages. The juvenile and transitional stages last 6-12 months and have alternate leaves. In the adult phase a terminal vegetative bud forms at the stem apex. Bud burst may occur several times a year in seedlings and twice a year in fruiting adults. The seedling root habit varies with soil type. The seedlings are able to coppice if the shoot is removed P. undulatum is an aggressive invader of eucalypt forests despite the poor survival of the initial colonizers. The formation of a regeneration niche ensures the survival of succeeding generations. Consequently, P. undulatum is a permanent threat to the Victorian vegetation.
Publisher: Informa UK Limited
Date: 03-08-2015
Publisher: Springer Science and Business Media LLC
Date: 04-2009
DOI: 10.1007/S10886-009-9617-5
Abstract: Global food security in a changing climate depends on both the nutritive value of staple crops as well as their yields. Here, we examined the direct effect of atmospheric carbon dioxide on the toxicity of the important pasture crop, Trifolium repens L. (clover). Shoots of T. repens contain cyanogenic glycosides that break down to release toxic hydrogen cyanide when damaged. The ability of animals to tolerate cyanogenic compounds is dependent, in part, on their overall protein intake. We grew T. repens communities at ambient and approximately twice-ambient CO(2) in a controlled environment greenhouse experiment. We found that the ratio of total cyanogenic glycosides to total protein ratio was nearly two times higher in leaves of T. repens grown at elevated CO(2). This study highlights the importance of assessing the nutritive value of this and other plants in response to rising CO(2) so that steps can be taken to address any adverse consequences for herbivores.
Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 2016
Publisher: Informa UK Limited
Date: 05-2018
DOI: 10.2216/17-82.1
Publisher: Springer Science and Business Media LLC
Date: 11-11-2021
DOI: 10.1007/S00425-021-03774-2
Abstract: Developmental and organ-specific expression of genes in dhurrin biosynthesis, bio-activation, and recycling offers dynamic metabolic responses optimizing growth and defence responses in Sorghum . Plant defence models evaluate the costs and benefits of resource investments at different stages in the life cycle. Poor understanding of the molecular regulation of defence deployment and remobilization h ers accuracy of the predictions. Cyanogenic glucosides, such as dhurrin are phytoanticipins that release hydrogen cyanide upon bio-activation. In this study, RNA-seq was used to investigate the expression of genes involved in the biosynthesis, bio-activation and recycling of dhurrin in Sorghum bicolor . Genes involved in dhurrin biosynthesis were highly expressed in all young developing vegetative tissues (leaves, leaf sheath, roots, stems), tiller buds and imbibing seeds and showed gene specific peaks of expression in leaves during diel cycles. Genes involved in dhurrin bio-activation were expressed early in organ development with organ-specific expression patterns. Genes involved in recycling were expressed at similar levels in the different organ during development, although post-floral initiation when nutrients are remobilized for grain filling, expression of GSTL1 decreased tenfold in leaves and NITB2 increased tenfold in stems. Results are consistent with the establishment of a pre-emptive defence in young tissues and regulated recycling related to organ senescence and increased demand for nitrogen during grain filling. This detailed characterization of the transcriptional regulation of dhurrin biosynthesis, bioactivation and remobilization genes during organ and plant development will aid elucidation of gene regulatory networks and signalling pathways that modulate gene expression and dhurrin levels. In-depth knowledge of dhurrin metabolism could improve the yield, nitrogen use efficiency and stress resilience of Sorghum .
Publisher: SAGE Publications
Date: 28-11-2018
Publisher: Elsevier BV
Date: 03-2007
Publisher: MDPI AG
Date: 28-10-2021
Abstract: Taro (Colocasia esculenta (L.) Schott) is a staple food crop in the Asia-Pacific region in areas where rising sea levels are threatening agricultural production. However, little is known about its response to salinity. In this study, we investigated the effects of salinity on the growth, morphology, physiology, and chemical traits of taro to predict the impacts of rising sea levels on taro production and nutritional value in the Pacific. We grew taro (approximately 4 months old) with a range of NaCl treatments (0–200 mM) for 12 weeks. Full nutrient, micronutrient, and secondary metabolite analyses were conducted, including measures of calcium oxalate (CaOx), an irritant that reduces palatability. Significant reductions in growth and biomass were observed at and above 100 mM NaCl. Concentrations of macro- and micronutrients, including sodium, were higher on a per mass basis in corms of plants experiencing salt stress. Foliar sodium concentrations remained stable, indicating that taro may utilize a salt exclusion mechanism. There was a large amount of in idual variation in the concentrations of oxalate and phenolics, but overall, the concentrations were similar in the plants grown with different levels of salt. The total contents of CaOx and phenolics decreased in plants experiencing salt stress. Taro’s ability to survive and produce corms when watered with a 200 mM NaCl solution places it among the salt-tolerant non-halophytes. The nutritional quality of the crop is only marginally affected by salt stress. Taro is, therefore, likely to remain a useful staple in the Pacific region in the future.
Publisher: MDPI
Date: 30-12-2019
Publisher: Wiley
Date: 09-2008
DOI: 10.1002/FFJ.1880
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/FPV40N2_FO
Abstract: The papers in this special issue were mainly derived from sessions at the International Botanical Congress in July 2011 in Melbourne, and at the ComBio meeting in Cairns, September 2011. They make contributions towards one of the most burning issues we face today: increasing sustainable crop production to provide sufficient high quality food to feed an ever increasing global human population, all in the face of climate change. Plant and crop science will have a major part in ensuring that agricultural production can meet these multiple demands. Contributions in this volume go beyond raising issues and highlighting potential effects of climate change factors, but also point out ways to better adapt to the inevitable.
Publisher: Wiley
Date: 14-06-2012
DOI: 10.1002/JSFA.5752
Abstract: Cyanogenic glucosides are common bioactive products that break down to release toxic hydrogen cyanide (HCN) when combined with specific β-glucosidases. In forage sorghum, high concentrations of the cyanogenic glucoside dhurrin lead to reduced productivity and sometimes death of grazing animals, especially in times of drought, when the dhurrin content of stunted crops is often higher. The aim of this study was to develop harvesting protocols suitable for s ling in remote areas. Dhurrin concentration in air- and oven-dried leaves was the same as in fresh leaves, with no subsequent losses during storage. Dhurrin concentration was halved when leaves were freeze-dried, although activity of the endogenous dhurrinase was preserved. Direct measurement of dhurrin concentration in methanolic extracts using liquid chromatography/mass spectrometry (LC/MS) gave similar results to methods that captured evolved cyanide. A single freezing event was as effective as fine grinding in facilitating complete conversion of dhurrin to cyanide. Direct measurement of dhurrin using LC/MS is accurate but expensive and not appropriate for fieldwork. Air drying provides an accurate, low-cost method for preparing tissue for dhurrin analysis, so long as the specific β-glucosidase is added. It is recommended that comparative studies like the one presented here be extended to other cyanogenic species.
Publisher: Portland Press Ltd.
Date: 14-11-2019
DOI: 10.1042/ETLS20190063
Abstract: Food security and the sustainability of native ecosystems depends on plant-insect interactions in countless ways. Recently reported rapid and immense declines in insect numbers due to climate change, the use of pesticides and herbicides, the introduction of agricultural monocultures, and the destruction of insect native habitat, are all potential contributors to this grave situation. Some researchers are working towards a future where natural insect pollinators might be replaced with free-flying robotic bees, an ecologically problematic proposal. We argue instead that creating environments that are friendly to bees and exploring the use of other species for pollination and bio-control, particularly in non-European countries, are more ecologically sound approaches. The computer simulation of insect-plant interactions is a far more measured application of technology that may assist in managing, or averting, ‘Insect Armageddon' from both practical and ethical viewpoints.
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/FP07241
Abstract: A protocol for the micropropagation of Eucalyptus polybractea R.T. Baker (blue mallee) using axillary bud proliferation from lignotuber-derived explants is described. Three different ages of plants were used as explant sources: glasshouse-grown seedlings, field-grown saplings, and coppice of field-grown mature lignotubers. Explants from each source initiated successfully and no significant difference was observed for shoot proliferation, rooting success or hardening success between explant sources. Leaf oil quantity and quality for hardened clones transplanted to a field plantation were assessed after 3 months of growth. Ramets of all clones contained high quality oil with over 80% 1,8-cineole. For seedling-derived clones, foliar oil concentrations of ramets were higher than those of the ortets from which they were derived. For sapling and mature lignotuber derived clones the opposite was the case. This suggests that ontogenetic and physiological constraints may be influencing yield in the young ramets. The age of the explant source did not appear to influence the success of micropropagation, and as a result older plants (for which key oil traits are known) can be selected as elite plants for multiplying selected genotypes via micropropagation.
Publisher: Oxford University Press (OUP)
Date: 19-02-2015
DOI: 10.1093/JXB/ERU526
Publisher: Elsevier BV
Date: 07-2003
DOI: 10.1016/S0031-9422(03)00245-0
Abstract: Cyanogenesis (i.e. the evolution of HCN from damaged plant tissue) requires the presence of two biochemical pathways, one controlling synthesis of the cyanogenic glycoside and the other controlling the production of a specific degradative beta-glucosidase. The sole cyanogenic glycoside in Eucalyptus nobilis was identified as prunasin (D-mandelonitrile beta-D-glucoside) using HPLC and GC-MS. Seedlings from three populations of E. nobilis were grown under controlled conditions and 38% were found to be acyanogenic, a proportion far greater than reported for any other cyanogenic eucalypt. A detailed study of the acyanogenic progeny from a single open-pollinated parent found that 23% lacked a cyanogenic beta-glucosidase, 32% lacked prunasin and 9% lacked both. Of the remaining seedlings initially identified as acyanogenics, 27% contained either trace amounts of beta-glucosidase or prunasin, while 9% contained trace amounts of both. Results support the hypothesis that the two components necessary for cyanogenesis are inherited independently. Trace amounts are likely to result from the presence of non-specific beta-glucosidases or the glycosylation of the cyanohydrin intermediate by non-specific UDP glycosyl transferases.
Publisher: Wiley
Date: 22-02-2019
DOI: 10.1111/JBI.13532
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.PLAPHY.2013.09.001
Abstract: Sorghum (Sorghum bicolor L. Moench) is a valuable forage crop in regions with low soil moisture. Sorghum may accumulate high concentrations of the cyanogenic glucoside dhurrin when drought stressed resulting in possible cyanide (HCN) intoxication of grazing animals. In addition, high concentrations of nitrate, also potentially toxic to ruminants, may accumulate during or shortly after periods of drought. Little is known about the degree and duration of drought-stress required to induce dhurrin accumulation, or how changes in dhurrin concentration are influenced by plant size or nitrate metabolism. Given that finely regulating soil moisture under controlled conditions is notoriously difficult, we exposed sorghum plants to varying degrees of osmotic stress by growing them for different lengths of time in hydroponic solutions containing polyethylene glycol (PEG). Plants grown in medium containing 20% PEG (-0.5 MPa) for an extended period had significantly higher concentrations of dhurrin in their shoots but lower dhurrin concentrations in their roots. The total amount of dhurrin in the shoots of plants from the various treatments was not significantly different on a per mass basis, although a greater proportion of shoot N was allocated to dhurrin. Following transfer from medium containing 20% PEG to medium lacking PEG, shoot dhurrin concentrations decreased but nitrate concentrations increased to levels potentially toxic to grazing ruminants. This response is likely due to the resumption of plant growth and root activity, increasing the rate of nitrate uptake. Data presented in this article support a role for cyanogenic glucosides in mitigating oxidative stress.
Publisher: Wiley
Date: 1998
Publisher: American Chemical Society (ACS)
Date: 12-06-2012
DOI: 10.1021/JF205030B
Abstract: Hydrogen cyanide (HCN) is a toxic chemical that can potentially cause mild to severe reactions in animals when grazing forage sorghum. Developing technologies to monitor the level of HCN in the growing crop would benefit graziers, so that they can move cattle into paddocks with acceptable levels of HCN. In this study, we developed near-infrared spectroscopy (NIRS) calibrations to estimate HCN in forage sorghum and hay. The full spectral NIRS range (400-2498 nm) was used as well as specific spectral ranges within the full spectral range, i.e., visible (400-750 nm), shortwave (800-1100 nm) and near-infrared (NIR) (1100-2498 nm). Using the full spectrum approach and partial least-squares (PLS), the calibration produced a coefficient of determination (R(2)) = 0.838 and standard error of cross-validation (SECV) = 0.040%, while the validation set had a R(2) = 0.824 with a low standard error of prediction (SEP = 0.047%). When using a multiple linear regression (MLR) approach, the best model (NIR spectra) produced a R(2) = 0.847 and standard error of calibration (SEC) = 0.050% and a R(2) = 0.829 and SEP = 0.057% for the validation set. The MLR models built from these spectral regions all used nine wavelengths. Two specific wavelengths 2034 and 2458 nm were of interest, with the former associated with C═O carbonyl stretch and the latter associated with C-N-C stretching. The most accurate PLS and MLR models produced a ratio of standard error of prediction to standard deviation of 3.4 and 3.0, respectively, suggesting that the calibrations could be used for screening breeding material. The results indicated that it should be feasible to develop calibrations using PLS or MLR models for a number of users, including breeding programs to screen for genotypes with low HCN, as well as graziers to monitor crop status to help with grazing efficiency.
Publisher: Wiley
Date: 23-10-2015
DOI: 10.1111/TPJ.13023
Abstract: The biosynthetic pathway for the cyanogenic glucoside dhurrin in sorghum has previously been shown to involve the sequential production of (E)- and (Z)-p-hydroxyphenylacetaldoxime. In this study we used microsomes prepared from wild-type and mutant sorghum or transiently transformed Nicotiana benthamiana to demonstrate that CYP79A1 catalyzes conversion of tyrosine to (E)-p-hydroxyphenylacetaldoxime whereas CYP71E1 catalyzes conversion of (E)-p-hydroxyphenylacetaldoxime into the corresponding geometrical Z-isomer as required for its dehydration into a nitrile, the next intermediate in cyanogenic glucoside synthesis. Glucosinolate biosynthesis is also initiated by the action of a CYP79 family enzyme, but the next enzyme involved belongs to the CYP83 family. We demonstrate that CYP83B1 from Arabidopsis thaliana cannot convert the (E)-p-hydroxyphenylacetaldoxime to the (Z)-isomer, which blocks the route towards cyanogenic glucoside synthesis. Instead CYP83B1 catalyzes the conversion of the (E)-p-hydroxyphenylacetaldoxime into an S-alkyl-thiohydroximate with retention of the configuration of the E-oxime intermediate in the final glucosinolate core structure. Numerous microbial plant pathogens are able to detoxify Z-oximes but not E-oximes. The CYP79-derived E-oximes may play an important role in plant defense.
Publisher: Springer Science and Business Media LLC
Date: 28-02-2022
DOI: 10.1007/S00425-022-03844-Z
Abstract: Droughted sorghum had higher concentrations of ROS in both wildtype and dhurrin-lacking mutants. Dhurrin increased in wildtype genotypes with drought. Dhurrin does not appear to mitigate oxidative stress in sorghum. Sorghum bicolor is tolerant of high temperatures and prolonged droughts. During droughts, concentrations of dhurrin, a cyanogenic glucoside, increase posing a risk to livestock of hydrogen cyanide poisoning. Dhurrin can also be recycled without the release of hydrogen cyanide presenting the possibility that it may have functions other than defence. It has been hypothesised that dhurrin may be able to mitigate oxidative stress by scavenging reactive oxygen species (ROS) during biosynthesis and recycling. To test this, we compared the growth and chemical composition of S. bicolor in total cyanide deficient sorghum mutants ( tcd1 ) with wild-type plants that were either well-watered or left unwatered for 2 weeks. Plants from the adult cyanide deficient class of mutant ( acdc1 ) were also included. Foliar dhurrin increased in response to drought in all lines except tcd1 and acdc1 , but not in the roots or leaf sheaths. Foliar ROS concentration increased in drought-stressed plants in all genotypes. Phenolic concentrations were also measured but no differences were detected. The total amounts of dhurrin, ROS and phenolics on a whole plant basis were lower in droughted plants due to their smaller biomass, but there were no significant genotypic differences. Up until treatments began at the 3-leaf stage, tcd1 mutants grew more slowly than the other genotypes but after that they had higher relative growth rates, even when droughted. The findings presented here do not support the hypothesis that the increase in dhurrin commonly seen in drought-stressed sorghum plays a role in reducing oxidative stress by scavenging ROS.
Publisher: Oxford University Press (OUP)
Date: 09-08-2016
DOI: 10.1093/JXB/ERW302
Abstract: Rising sea levels are threatening agricultural production in coastal regions due to inundation and contamination of groundwater. The development of more salt-tolerant crops is essential. Cassava is an important staple, particularly among poor subsistence farmers. Its tolerance to drought and elevated temperatures make it highly suitable for meeting global food demands in the face of climate change, but its ability to tolerate salt is unknown. Cassava stores nitrogen in the form of cyanogenic glucosides and can cause cyanide poisoning unless correctly processed. Previous research demonstrated that cyanide levels are higher in droughted plants, possibly as a mechanism for increasing resilience to oxidative stress. We determined the tolerance of cassava to salt at two different stages of development, and tested the hypothesis that cyanide toxicity would be higher in salt-stressed plants. Cassava was grown at a range of concentrations of sodium chloride (NaCl) at two growth stages: tuber initiation and tuber expansion. Established plants were able to tolerate 100mM NaCl but in younger plants 40mM was sufficient to retard plant growth severely. Nutrient analysis showed that plants were only able to exclude sodium at low concentrations. The foliar cyanogenic glucoside concentration in young plants increased under moderate salinity stress but was lower in plants grown at high salt. Importantly, there was no significant change in the cyanogenic glucoside concentration in the tubers. We propose that the mechanisms for salinity tolerance are age dependent, and that this can be traced to the relative cost of leaves in young and old plants.
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.PHYTOCHEM.2008.03.018
Abstract: In this study approximately 420 of the described species of Eucalyptus were examined for cyanogenesis. Our work has identified an additional 18 cyanogenic species, 12 from living tissues and a further six from herbarium s les. This brings the total of known cyanogenic species to 23, representing approximately 4% of the genus. The taxonomic distribution of the species within the genus is restricted to the subgenus Symphyomyrtus, with only two exceptions. Within Symphyomyrtus, the species are in three closely related sections. The cyanogenic glycoside was found to be predominantly prunasin (1) in the 11 species where this was examined. We conclude that cyanogenesis is plesiomorphic in Symphyomyrtus (i.e. a common basal trait) but has probably arisen independently in the other two subgenera, consistent with recent phylogenetic treatments of the genus. The results of this study have important implications for the selection of trees for plantations to support wildlife, and to preserve genetic ersity.
Publisher: Wiley
Date: 30-06-2022
DOI: 10.1111/PLB.13447
Abstract: Domesticated sorghum ( Sorghum bicolor [L.] Moench subsp. bicolor ) erts significant amounts of nitrogen away from primary metabolism to the synthesis of cyanogenic glucosides (CNglc) – specialized metabolites that release toxic hydrogen cyanide (HCN). Our aim was to identify the point in the genus Sorghum Moench at which plants gained the ability to maintain hazardous concentrations of cyanogenic glucosides in their leaves into maturity (HCN potential .4 mg g −1 ). This ability occurs in domesticated sorghum (in the subgenus Eusorghum ), but not in wild taxa in other Sorghum subgenera. Eight accessions from the subgenus Eusorghum were grown in a common garden: an improved sorghum line, five sorghum landraces, the crop's wild progenitor ( S. bicolor subsp. verticilliflorum [Steud.] de Wet ex Wiersema & J. Dahlb.) and wild Sorghum propinquum (Kunth) Hitchc. HCN potential was measured in plants (n = 80) at the three‐leaf stage and at 6 weeks old. All study accessions, including the wild taxa, had hazardous CNglc concentrations in the leaves at both the three‐leaf stage (mean HCN potentials = 2.5 mg g −1 ) and at 6 weeks old (mean HCN potentials = 0.68 mg g −1 ), greatly contrasting the much lower mature leaf HCN potentials previously found in wild Sorghum taxa outside subgenus Eusorghum (generally = 0.01 mg g −1 ). Our results suggest that the ability to maintain hazardous leaf HCN potentials into maturity might have arisen during the ergence of Eusorghum from other Sorghum subgenera, rather than during the speciation or domestication of S. bicolor , and highlights the value of utilizing Sorghum taxa outside Eusorghum in efforts to improve the crop safety of sorghum.
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/FP10124
Abstract: Producing enough food to meet the needs of an increasing global population is one of the greatest challenges we currently face. The issue of food security is further complicated by impacts of elevated CO2 and climate change. In this viewpoint article, we begin to explore the impacts of elevated CO2 on two specific aspects of plant nutrition and resource allocation that have traditionally been considered separately. First, we focus on arbuscular mycorrhizas, which play a major role in plant nutrient acquisition. We then turn our attention to the allocation of resources (specifically N and C) in planta, with an emphasis on the secondary metabolites involved in plant defence against herbivores. In doing so, we seek to encourage a more integrated approach to investigation of all aspects of plant responses to eCO2.
Publisher: BMJ
Date: 16-05-2017
DOI: 10.1136/BMJ.J2234
Publisher: Springer Science and Business Media LLC
Date: 30-08-2006
Publisher: Wiley
Date: 11-10-2006
DOI: 10.1111/J.1469-8137.2006.01881.X
Abstract: * Here, a new approach to macromolecular imaging of leaf tissue using a multichannel focal plane array (FPA) infrared detector was compared with the proven method of infrared mapping with a synchrotron source, using transverse sections of leaves from a species of Eucalyptus. * A new histological method was developed, ideally suited to infrared spectroscopic analysis of leaf tissue. Spatial resolution and the signal-to-noise ratio of the FPA imaging and synchrotron mapping methods were compared. * An area of tissue 350 microm(2) required approx. 8 h to map using the synchrotron technique and approx. 2 min to image using the FPA. The two methods produced similar infrared images, which differentiated all tissue types in the leaves according to their macromolecular chemistry. * The synchrotron and FPA methods produced similar results, with the synchrotron method having superior signal-to-noise ratio and potentially better spatial resolution, whereas the FPA method had the advantage in terms of data acquisition time, expense and ease of use. FPA imaging offers a convenient, laboratory-based approach to microscopic chemical imaging of leaves.
Publisher: Oxford University Press (OUP)
Date: 23-06-2010
Abstract: Plants have evolved a vast array of defence mechanisms to avoid or minimize damage caused by herbivores and pathogens. The costs and benefits of defences are thought to vary with the availability of resources, herbivore pressure and plant functional traits. We investigated the resource (nitrogen) and growth cost of deploying cyanogenic glycosides in seedlings of Eucalyptus cladocalyx (Myrtaceae). To do this, we grew the plants under a range of soil N conditions, from levels that were limiting for growth to those that were saturating for growth, and we measured correlations between foliar chemical and performance attributes. Within each N treatment, we found evidence that, for every N invested in cyanogenic glycosides, additional N is added to the leaf. For the lowest N treatment, the additional N was less than one per cyanogenic glycoside, rising to some two Ns for the other treatments. The interaction between cyanogenic glycosides and both condensed tannins and total phenolic compounds was also examined, but we did not detect correlations between these compounds under constant leaf N concentrations. Finally, we did not detect a correlation between net assimilation rate, relative growth rate and cyanogenic glycoside concentrations under any soil N treatment. We conclude that the growth cost of cyanogenic glycosides was likely too low to detect and that it was offset to some degree by additional N that was allocated alongside the cyanogenic glycosides.
Publisher: Wiley
Date: 05-05-2023
DOI: 10.1111/PLB.13522
Abstract: The cyanogenic glucoside, dhurrin, present in Sorghum bicolor is thought to have multiple functions, including in defence against herbivory. The hormone methyl jasmonate (MeJA) is also induced by herbivory and is key to instigating defence processes in plants. To investigate whether dhurrin is induced in response to herbivore attack and also to the associated presence of MeJA, sorghum plants were either wounded or exogenous MeJA was applied. We show that specific wounding (pin board and perforation) and the application of MeJA increases dhurrin concentration in leaves and sheath tissue 12 h after treatment. Quantitative PCR shows that the expression of two genes, SbCYP79A1 and SbUGT85B1 , involved in the synthesis of dhurrin are significantly induced by exogenous MeJA and by wounding. Analysis of 2 kb of sequence upstream of the start codon of SbCYP79A1 identifies several cis ‐acting elements that have been linked to MeJA induction. A promoter deletion series, coupled to GFP, and transiently expressed in Nicotiana benthamiana suggests that there are potentially three sequence motifs (~−925 to −976) involved in the binding of transcription factors that result in increased expression of SbCYP79A1 and the synthesis of dhurrin in response to MeJA.
Publisher: MDPI AG
Date: 11-05-2022
Abstract: In 2009, Food Standards Australia New Zealand set a total cyanide content limit of 10 ppm for ready-to-eat cassava products to address food safety concerns about cyanogenic glucosides in cassava. This study surveys a range of cassava food products available in Melbourne, Australia, ten years after the implementation of these regulations. Of all the products tested, the mean cyanide content was greatest in ready-to-eat cassava chips (48.4 ppm), although imported ready-to-eat products had a higher mean cyanide content (95.9 ppm) than those manufactured in Australia (1.0 ppm). Cyanide was detected in frozen cassava products (grated mean = 12.9 ppm whole root mean = 19.8 ppm), but was significantly reduced through processing according to packet instructions in both product types. Three methods were used to quantify total cyanide content: the evolved cyanide method, the picrate absorbance method and the picrate chart method, with satisfactory agreement between methods. The picrate absorbance and chart methods reported mean cyanide contents 13.7 ppm and 23.1 ppm higher, respectively, than the evolved cyanide method. Our results reaffirm the need for the ongoing testing of cassava food products, especially ready-to-eat products whose cyanide content will not be reduced before consumption.
Publisher: Informa UK Limited
Date: 11-2017
DOI: 10.2216/17-45.1
Publisher: Springer Science and Business Media LLC
Date: 27-03-2019
Publisher: Elsevier BV
Date: 04-2021
Publisher: Wiley
Date: 08-2006
DOI: 10.1111/J.1469-8137.2006.01842.X
Abstract: The accumulation of terpenoid oil was examined in the leaves of Eucalyptus polybractea at scales ranging from in idual oil glands to the whole plant. Variations in oil composition and concentration of oil were measured and related to both morphological and physiological parameters. Within a plant, all glands produced oil of broadly similar composition that was not regulated by leaf age or the position of the gland within the leaf. There were, however, distinct differences between plants, suggesting that composition is controlled primarily at the whole-plant level. Oil concentration, too, was regulated primarily at the whole-plant level and was limited by gland capacity. Gland capacity was linked to leaf area and thickness, the final products of leaf expansion. Leaf and plant oil composition is determined not by a mosaic of glands specializing in producing a single or a small group of compounds, but rather by glands with remarkably similar capacities for terpenoid biosynthesis, although oil concentration, limited by gland capacity, may be linked to leaf expansion rather than biosynthetic capacity.
Publisher: Springer Science and Business Media LLC
Date: 18-04-2016
DOI: 10.1038/NBT.3535
Abstract: Cassava (Manihot esculenta) provides calories and nutrition for more than half a billion people. It was domesticated by native Amazonian peoples through cultivation of the wild progenitor M. esculenta ssp. flabellifolia and is now grown in tropical regions worldwide. Here we provide a high-quality genome assembly for cassava with improved contiguity, linkage, and completeness almost 97% of genes are anchored to chromosomes. We find that paleotetraploidy in cassava is shared with the related rubber tree Hevea, providing a resource for comparative studies. We also sequence a global collection of 58 Manihot accessions, including cultivated and wild cassava accessions and related species such as Ceará or India rubber (M. glaziovii), and genotype 268 African cassava varieties. We find widespread interspecific admixture, and detect the genetic signature of past cassava breeding programs. As a clonally propagated crop, cassava is especially vulnerable to pathogens and abiotic stresses. This genomic resource will inform future genome-enabled breeding efforts to improve this staple crop.
Publisher: Oxford University Press (OUP)
Date: 05-2000
DOI: 10.1093/TREEPHYS/20.9.591
Abstract: The release of hydrogen cyanide from endogenous cyanide-containing compounds in plants is an effective herbivore deterrent. We investigated temporal and spatial variations in cyanogenic glycoside concentration in greenhouse-grown seedlings and 6-year-old plantation trees of Eucalyptus cladocalyx F. Muell., which allocates up to 20% of leaf nitrogen to the cyanogenic glycoside, prunasin. The highest cyanogenic glycoside concentrations were in the young, developing vegetative and reproductive tissues. Both the overall cyanogenic glycoside concentration and the proportion of nitrogen allocated to cyanogenic glycoside decreased as tissues matured. Cyanogenic glycoside and nitrogen concentrations were similar at all positions on the leaf blade. There was no change in concentration of cyanogenic glycosides either diurnally or following wounding of the tissue, suggesting that these compounds are constitutive. Cyanogenic glycoside concentration varied seasonally in young leaf tips of field-grown E. cladocalyx, but not in mature, fully expanded leaves. Although some of the changes in cyanogenic glycoside concentration in young leaf tips may have been driven by changes in leaf nitrogen, there was a significant decrease in the proportion of nitrogen allocated to cyanogenic glycosides in young leaves during the summer, coinciding with the peak flowering period. Mobilization of cyanogenic glycosides may have occurred to provide nitrogen for reproduction. Most of the observed temporal and spatial variations in cyanogenic glycosides are consistent with the optimal use of resources, particularly nitrogen.
Publisher: MDPI AG
Date: 17-12-2020
Abstract: In plants, the production of secondary metabolites is considered to be at the expense of primary growth. Sorghum produces a cyanogenic glycoside (dhurrin) that is believed to act as its chemical defence. Studies have shown that acyanogenic plants are smaller in size compared to the wildtype. This study aimed to investigate whether the small plant size is due to delayed germination or due to the lack of dhurrin derived nitrogen. A novel plant system consisting of totally cyanide deficient class 1 (tcd1) and adult cyanide deficient 1 (acdc1) mutant lines was employed. The data for germination, plant height and developmental stage during seedling development and final plant reproductive fitness was recorded. The possible role of phytohormones in recovering the wildtype phenotype, especially in developmentally acyanogenic acdc1 line, was also investigated. The data on plant growth have shown that the lack of dhurrin is disadvantageous to growth, but only at the early developmental stage. The tcd1 plants also took longer to mature probably due to delayed flowering. None of the tested hormones were able to recover the wildtype phenotype. We conclude that the generation of dhurrin is advantageous for plant growth, especially at critical growth stages like germinating seed by providing a ready source of reduced nitrogen.
Publisher: MDPI AG
Date: 14-01-2022
Abstract: Domestication has resulted in a loss of genetic ersity in our major food crops, leading to susceptibility to biotic and abiotic stresses linked with climate change. Crop wild relatives (CWR) may provide a source of novel genes potentially important for re-gaining climate resilience. Sorghum bicolor is an important cereal crop with wild relatives that are endemic to Australia. Sorghum bicolor is cyanogenic, but the cyanogenic status of wild Sorghum species is not well known. In this study, leaves of wild species endemic in Australia are screened for the presence of the cyanogenic glucoside dhurrin. The direct measurement of dhurrin content and the potential for dhurrin-derived HCN release (HCNp) showed that all the tested Australian wild species were essentially phenotypically acyanogenic. The unexpected low dhurrin content may reflect the variable and generally nutrient-poor environments in which they are growing in nature. Genome sequencing of six CWR and PCR lification of the CYP79A1 gene from additional species showed that a high conservation of key amino acids is required for correct protein function and dhurrin synthesis, pointing to the transcriptional regulation of the cyanogenic phenotype in wild sorghum as previously shown in elite sorghum.
Publisher: MDPI AG
Date: 19-11-2010
DOI: 10.3390/SU2113572
Publisher: CSIRO Publishing
Date: 1981
DOI: 10.1071/BT9810705
Abstract: Pittosporum undulatum is invading eucalypt open forests in south-central Victoria, 200 km west of its native habitat in eastern Australia. This is due to horticultural plantings of P. unduiatum and to the suppression of wildfires: it has thin bark and is killed by fires which most eucalypts can survive. Near Melbourne, P. undulatum preferentially establishes around the butts of eucalypts and other established trees although in denser forests this clumping is not so obvious. Seedlings of other weed species such as Ilex aquifolium and Cotoneaster pannosa similarly aggregate around established shrubs and trees. Classification of quadrats by monothetic ision showed P. undulatum to be the most important species in the community. The weedy nature of P. undulatum is clear from its rapid dispersal, early seed production and fast growth. The dense canopy dramatically reduces the light intensity and completely suppresses the original sclerophyllous understorey: only Gahnia radula remains. Soil beneath the canopy is fertile and the litter is high in nutrients but bioassays indicate that inhibitors may be present. The root system is variable, depending on soil texture and compaction. The invasion of forest remnants by P. undulatum and other weeds is threatening the survival of the eucalypt forests in urban areas.
Publisher: Springer Science and Business Media LLC
Date: 10-10-2015
Publisher: Elsevier BV
Date: 03-2021
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/FP12179
Abstract: Cassava (Manihot esculenta Crantz) is the staple food source for over 850 million people worldwide. Cassava contains cyanogenic glucosides and can be toxic to humans, causing paralysing diseases such as konzo, and even death if not properly processed. Konzo epidemics are often associated with times of drought. This may be due to a greater reliance on cassava as it is drought tolerant, but it may also be due to an increase in cyanogenic glucosides. Episodic droughts are forecast to become more common in many cassava-growing regions. We therefore sought to quantify the effect of water-stress on both yield and cyanogenic glucoside concentration (CNc) in the developing tubers of cassava. Five-month-old plants were grown in a glasshouse and either well watered or droughted for 28 days. A subset of droughted plants was re-watered half way through the experiment. Droughted plants had 45% fewer leaves and lower tuber yield, by 83%, compared with well-watered plants. CNc was 2.9-fold higher in the young leaves of droughted plants, whereas CNc in tubers from droughted plants was 4-fold greater than in tubers from well-watered plants. Re-watered plants had a similar biomass to control plants, and lower CNc than droughted plants. These findings highlight the important link between food quality and episodic drought.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/FP17227
Abstract: Long-standing growth/defence theories state that the production of defence compounds come at a direct cost to primary metabolism when resources are limited. However, such trade-offs are inherently difficult to quantify. We compared the growth and nitrogen partitioning in wild type Sorghum bicolor (L.) Moench, which contains the cyanogenic glucoside dhurrin, with unique mutants that vary in dhurrin production. The totally cyanide deficient 1 (tcd1) mutants do not synthesise dhurrin at all whereas mutants from the adult cyanide deficient class 1 (acdc1) have decreasing concentrations as plants age. Sorghum lines were grown at three different concentrations of nitrogen. Growth, chemical analysis, physiological measurements and expression of key genes in biosynthesis and turnover were determined for leaves, stems and roots at four developmental stages. Nitrogen supply, ontogeny, tissue type and genotype were all important determinants of tissue nitrate and dhurrin concentration and turnover. The higher growth of acdc1 plants strongly supports a growth/defence trade-off. By contrast, tcd1 plants had slower growth early in development, suggesting that dhurrin synthesis and turnover may be beneficial for early seedling growth rather than being a cost. The relatively small trade-off between nitrate and dhurrin suggests these may be independently regulated.
Publisher: Springer Science and Business Media LLC
Date: 2002
Abstract: Cyanogenesis is the process by which hydrogen cyanide is released from endogenous cyanide containing compounds. Many cyanogenic plants release HCN in sufficient quantities to be toxic and, as a result, tend to be avoided by herbivores. However, there are many exceptions with some herbivores either immune to the cyanogenic status of the plant, or in some cases attracted to cyanogenic plants. This has led to a certain degree of scepticism regarding the role of cyanogenic glycosides as defense compounds. In this review, we examine evidence showing that differences in the effectiveness of cyanogenic glycosides in deterring herbivory can usually be reconciled when the morphology, physiology, and behavior of the animals, together with the concentration of cyanogenic glycosides in the host plant, are taken into account. Cyanogenic glycosides are not effective against all herbivores, and not all cyanogenic plants release enough cyanide to be considered toxic. Nevertheless, they do form part of the broad spectrum of toxic and distasteful compounds that herbivores must accommodate if they are to feed on cyanogenic plants.
Publisher: Wiley
Date: 31-08-2011
DOI: 10.1111/J.1467-7652.2011.00646.X
Abstract: Cyanogenic glucosides are present in several crop plants and can pose a significant problem for human and animal consumption, because of their ability to release toxic hydrogen cyanide. Sorghum bicolor L. contains the cyanogenic glucoside dhurrin. A qualitative biochemical screen of the M2 population derived from EMS treatment of sorghum seeds, followed by the reverse genetic technique of Targeted Induced Local Lesions in Genomes (TILLING), was employed to identify mutants with altered hydrogen cyanide potential (HCNp). Characterization of these plants identified mutations affecting the function or expression of dhurrin biosynthesis enzymes, and the ability of plants to catabolise dhurrin. The main focus in this study is on acyanogenic or low cyanide releasing lines that contain mutations in CYP79A1, the cytochrome P450 enzyme catalysing the first committed step in dhurrin synthesis. Molecular modelling supports the measured effects on CYP79A1 activity in the mutant lines. Plants harbouring a P414L mutation in CYP79A1 are acyanogenic when homozygous for this mutation and are phenotypically normal, except for slightly slower growth at early seedling stage. Detailed biochemical analyses demonstrate that the enzyme is present in wild-type amounts but is catalytically inactive. Additional mutants capable of producing dhurrin at normal levels in young seedlings but with negligible leaf dhurrin levels in mature plants were also identified. No mutations were detected in the coding sequence of dhurrin biosynthetic genes in this second group of mutants, which are as tall or taller, and leafier than nonmutated lines. These sorghum mutants with reduced or negligible dhurrin content may be ideally suited for forage production.
Publisher: CSIRO Publishing
Date: 1983
DOI: 10.1071/BT9830151
Abstract: Seedlings of Pittosporum undulatum were grown under shade screens for 16 days at four flux densities: 97.8, 18.2, 3.4 and 0.4% full daylight, i.e. c. 420, 78, 14 and 2 W m-2. Seedlings showed moderate tolerance of shade: the growth compensation point for light was 1 .6% daylight, the leaf area ratio in full daylight was low (48.96 cm2 g-1) and when plants grown at 0.4% were compared with those grown at 97.8% full daylight and there was a fourfold increase in chlorophyll concentration. Leaves were thinner at the lowest flux density because the cells were deflated and there appeared to be only one row of palisade mesophyll cells. On the other hand, there was no large increase in leaf area ratio with shading, no alteration in the chlorophyll a/b ratio and no depression of net assimilation rate in full daylight. P. undulatum can endure shade but has a higher growth rate when grown at higher photon flux densities. P. undulatum is found predominantly in shade owing to the uneven dispersal of seed and the site-dependent survival of seedlings and not because shade is required for maximum growth.
Publisher: Wiley
Date: 11-11-2014
DOI: 10.1111/PCE.12209
Abstract: Arbuscular mycorrhizas (AM) can increase plant acquisition of P and N. No published studies have investigated the impact of P and AM on the allocation of N to the plant defence, cyanogenic glucosides. We investigated the effects of soil P and AM on cyanogenic glucoside (dhurrin) concentration in roots and shoots of two forage sorghum lines differing in cyanogenic potential (HCNp). Two harvest times allowed plants grown at high and low P to be compared at the same age and the same size, to take account of known ontogenetic changes in shoot HCNp. P responses were dependent on ontogeny and tissue type. At the same age, P-limited plants were smaller and had higher shoot HCNp but lower root HCNp. Ontogenetically controlled comparisons showed a P effect of lesser magnitude, and that there was also an increase in the allocation of N to dhurrin in shoots of P-limited plants. Colonization by AM had little effect on shoot HCNp, but increased root HCNp and the allocation of N to dhurrin in roots. Divergent responses of roots and shoots to P, AM and with ontogeny demonstrate the importance of broadening the predominantly foliar focus of plant defence studies/theory, and of ontogenetically controlled comparisons.
Publisher: Springer Science and Business Media LLC
Date: 09-02-2018
DOI: 10.1038/S41598-018-20928-7
Abstract: Localisation of metabolites in sorghum coleoptiles using Raman hyperspectral imaging analysis was compared in wild type plants and mutants that lack cyanogenic glucosides. This novel method allows high spatial resolution in situ localization by detecting functional groups associated with cyanogenic glucosides using vibrational spectroscopy. Raman hyperspectral imaging revealed that dhurrin was found mainly surrounding epidermal, cortical and vascular tissue, with the greatest amount in cortical tissue. Numerous “hotspots” demonstrated dhurrin to be located within both cell walls and cytoplasm adpressed towards the plasmamembrane and not in the vacuole as previously reported. The high concentration of dhurrin in the outer cortical and epidermal cell layers is consistent with its role in defence against herbivory. This demonstrates the ability of Raman hyperspectral imaging to locate cyanogenic glucosides in intact tissues, avoiding possible perturbations and imprecision that may accompany methods that rely on bulk tissue extraction methods, such as protoplast isolation.
Publisher: MDPI AG
Date: 25-12-2022
DOI: 10.3390/F14010039
Abstract: Climate change is a driver of bio ersity loss, often favouring invasive species such as in the case of Pittosporum undulatum in Eucalyptus forests of south-eastern Australia. We tested whether the invasiveness of P. undulatum is due to the release of secondary metabolites with allelopathic action inhibiting other species germination or to the content of antioxidant secondary metabolites. We compared the germination of P. undulatum and Eucalyptus ovata seeds on different substrates watered with different leachates. Polyphenolic compounds, saponins and tannins of Eucalyptus spp. and P. undulatum leaf extracts were quantified. Biogenic Volatile Organic Compounds were collected in the field and analyzed to compare the emissions in eucalypt forests with and without P. undulatum. Eucalyptus germination rates were not affected by different leachates and no allelopathic compounds were identified in P. undulatum leachate. Flavonoids and tannins characterized Eucalyptus leachates, while P. undulatum leachates showed high hydroxycinnamic acids content. The forests invaded by P. undulatum were characterized by high levels of monoterpenes, whereas the forest lacking P. undulatum were dominated by sesquiterpenes. Our results suggest that the invasiveness of P. undulatum may be due to the high content in secondary metabolites that play a protective role against abiotic stresses rather than the release of allelopathic compounds.
Publisher: Elsevier BV
Date: 2020
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/PP01116
Abstract: Cyanogenesis in many plant species is an effective herbivore deterrent, which appears to be influenced by a range of environmental variables. There is evidence that one such variable, soil water availability, increases cyanogenic capacity (i.e. leaf cyanogenic glycoside concentration), but it is not clear whether this is a relatively direct or indirect effect. To shed light on this issue, we compared the cyanogenic capacity of in iduals from two populations of Eucalyptus cladocalyx F.Muell. from areas of South Australia that differ markedly in rainfall. Stable carbon isotope analysis confirmed that trees at the drier site were more water-stressed. We found a large range in leaf cyanogenic capacities, from 0 to 1.01 mg cyanide g–1 dry weight. Importantly, this is the first record of acyanogenic E. cladocalyx. Mean cyanogenic capacity was 30% higher in trees from the drier site, and they suffered less damage from herbivores. However, these trees also contained higher concentrations of leaf nitrogen (N). Correlative analysis of data for in idual plants from both sites showed that leaf N was able to account for a significant amount of the variation in cyanogenic glycoside concentration (28%). Water availability on its own, however, was not able to account significantly for any such variation. We conclude that most of the variation in cyanogenic capacity is due to genetic differences between in iduals, while the remaining variation is due to differences in leaf N.
Publisher: Oxford University Press (OUP)
Date: 29-04-2020
DOI: 10.1104/PP.19.01357
Publisher: Springer Science and Business Media LLC
Date: 17-05-2009
Publisher: American Chemical Society (ACS)
Date: 04-05-2012
DOI: 10.1021/JF2047288
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/FPV33N5_FO
Publisher: Informa UK Limited
Date: 03-2017
DOI: 10.2216/16-49.1
Publisher: Informa UK Limited
Date: 05-05-2016
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/FP03217
Abstract: Terpene deployment was examined in a population of Eucalyptus polybractea (R.Baker) trees. Eucalyptus polybractea is a terpene-accumulating species, which stores terpenes in oil glands beneath the leaf surface. Using regression analysis, we showed that leaf thickness, measured as leaf mass per area (LMA), influenced terpene content, apparently through regulation of gland dimensions, and thus, gland volume. We also examined how environmental factors affected terpene content through regulation of both LMA, and therefore, storage capacity, and the supply of resources for terpene synthesis. Neither water stress, measured using carbon isotope ratios as an indicator, nor nutrient stress, measured as foliar nitrogen and phosphorus content, accounted for observed variation in either terpene content or LMA. Phenolic content, measured as a possible competing carbon sink, did not account for variation in terpene content, and variation in environmental stresses could not account for differences in growth rate. However, both terpenes and total carbon-based secondary metabolites (terpenes and phenolics) showed positive correlations with growth, suggesting plants gain a growth advantage by deploying greater amounts of secondary metabolites.
Publisher: Springer Science and Business Media LLC
Date: 14-03-2019
DOI: 10.1038/S41396-019-0393-0
Abstract: Most aerobic bacteria exist in dormant states within natural environments. In these states, they endure adverse environmental conditions such as nutrient starvation by decreasing metabolic expenditure and using alternative energy sources. In this study, we investigated the energy sources that support persistence of two aerobic thermophilic strains of the environmentally widespread but understudied phylum Chloroflexi. A transcriptome study revealed that Thermomicrobium roseum (class Chloroflexia) extensively remodels its respiratory chain upon entry into stationary phase due to nutrient limitation. Whereas primary dehydrogenases associated with heterotrophic respiration were downregulated, putative operons encoding enzymes involved in molecular hydrogen (H 2 ), carbon monoxide (CO), and sulfur compound oxidation were significantly upregulated. Gas chromatography and microsensor experiments showed that T. roseum aerobically respires H 2 and CO at a range of environmentally relevant concentrations to sub-atmospheric levels. Phylogenetic analysis suggests that the hydrogenases and carbon monoxide dehydrogenases mediating these processes are widely distributed in Chloroflexi genomes and have probably been horizontally acquired on more than one occasion. Consistently, we confirmed that the sporulating isolate Thermogemmatispora sp. T81 (class Ktedonobacteria) also oxidises atmospheric H 2 and CO during persistence, though further studies are required to determine if these findings extend to mesophilic strains. This study provides axenic culture evidence that atmospheric CO supports bacterial persistence and reports the third phylum, following Actinobacteria and Acidobacteria, to be experimentally shown to mediate the biogeochemically and ecologically important process of atmospheric H 2 oxidation. This adds to the growing body of evidence that atmospheric trace gases are dependable energy sources for bacterial persistence.
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/FP03218
Abstract: This study characterised three aspects of cyanogenesis in the late successional tropical rainforest species Prunus turneriana (F.M.Bailey) Kalkman. First, all tissues were found to be highly cyanogenic, containing combinations of the cyanogenic glycosides (R)-prunasin, (S)-sambunigrin, and amygdalin. Second, the progeny of a single parent tree varied markedly and continuously in their cyanogenic glycoside content, indicating that this variation is genetically based. Third, we investigated resource allocation to cyanogenic glycosides in light treatments representative of rainforest understorey and gap environments. Contrary to our hypothesis that under low light, photosynthetic gain would be maximised by the reallocation of nitrogen from defence to the photosynthetic system, we found no difference in cyanogenic glycoside concentration, or the proportion of nitrogen allocated to cyanogenic glycoside, between high and low light. However, within the plant, shade affected a significant change in distribution of cyanogenic glycosides between young and old leaves. There was an increased allocation of cyanogenic glycosides to old, expanded and photosynthetically productive leaves, a pattern which appears inconsistent with predictions of optimal defence theories, and the results of other studies. We suggest that such a strategy may be advantageous for seedlings of tree species that can only reach a reproductive stage following the creation of a canopy gap.
Publisher: CSIRO Publishing
Date: 1982
DOI: 10.1071/BT9820347
Abstract: The clumping of invading seedlings of Pittosporum undulatum Vent. around the butts of established trees is due partly to the site-dependent survival of seedlings. particularly during summer. P. undulatum seedlings were very drought-tolerant when grown at moderately low temperatures (21.4°C day/17.8°C night compared with 27.4°C day/23.9°C night) and in deep shade. Plants droughted at 5°C higher temperatures and higher photon flux densities stopped transpiring and wilted 10-13 days earlier than those droughted under cooler, densely shaded conditions. Well watered seedlings had higher relative growth rates and net assimilation rates when grown under higher temperatures and photon flux densities. Control seedlings were more leafy when grown under low light. as reflected by the specific leaf area, leaf area ratio and root/shoot ratios. The adverse effects of higher photon flux densities and temperatures on the drought tolerance of P. undulatum seedlings support the hypothesis that survlval of invading seedlings in their first year is dependent on the microclimate.
Publisher: Springer Science and Business Media LLC
Date: 27-01-2022
DOI: 10.1007/S00425-022-03831-4
Abstract: Australian native species of sorghum contain negligible amounts of dhurrin in their leaves and the cyanogenesis process is regulated differently under water-stress in comparison to domesticated sorghum species. Cyanogenesis in forage sorghum is a major concern in agriculture as the leaves of domesticated sorghum are potentially toxic to livestock, especially at times of drought which induces increased production of the cyanogenic glucoside dhurrin. The wild sorghum species endemic to Australia have a negligible content of dhurrin in the above ground tissues and thus represent a potential resource for key agricultural traits like low toxicity. In this study we investigated the differential expression of cyanogenesis related genes in the leaf tissue of the domesticated species Sorghum bicolor and the Australian native wild species Sorghum macrospermum grown in glasshouse-controlled water-stress conditions using RNA-Seq analysis to analyse gene expression. The study identified genes, including those in the cyanogenesis pathway, that were differentially regulated in response to water-stress in domesticated and wild sorghum. In the domesticated sorghum, dhurrin content was significantly higher compared to that in the wild sorghum and increased with stress and decreased with age whereas in wild sorghum the dhurrin content remained negligible. The key genes in dhurrin biosynthesis, CYP79A1 , CYP71E1 and UGT85B1 , were shown to be highly expressed in S. bicolor . DHR and HNL encoding the dhurrinase and α-hydroxynitrilase catalysing bio-activation of dhurrin were also highly expressed in S. bicolor . Analysis of the differences in expression of cyanogenesis related genes between domesticated and wild sorghum species may allow the use of these genetic resources to produce more acyanogenic varieties in the future.
Publisher: Annual Reviews
Date: 29-04-2014
DOI: 10.1146/ANNUREV-ARPLANT-050213-040027
Abstract: Cyanogenic glycosides (CNglcs) are bioactive plant products derived from amino acids. Structurally, these specialized plant compounds are characterized as α-hydroxynitriles (cyanohydrins) that are stabilized by glucosylation. In recent years, improved tools within analytical chemistry have greatly increased the number of known CNglcs by enabling the discovery of less abundant CNglcs formed by additional hydroxylation, glycosylation, and acylation reactions. Cyanogenesis—the release of toxic hydrogen cyanide from endogenous CNglcs—is an effective defense against generalist herbivores but less effective against fungal pathogens. In the course of evolution, CNglcs have acquired additional roles to improve plant plasticity, i.e., establishment, robustness, and viability in response to environmental challenges. CNglc concentration is usually higher in young plants, when nitrogen is in ready supply, or when growth is constrained by nonoptimal growth conditions. Efforts are under way to engineer CNglcs into some crops as a pest control measure, whereas in other crops efforts are directed toward their removal to improve food safety. Given that many food crops are cyanogenic, it is important to understand the molecular mechanisms regulating cyanogenesis so that the impact of future environmental challenges can be anticipated.
Publisher: Oxford University Press (OUP)
Date: 28-04-2016
DOI: 10.1093/JXB/ERW166
Publisher: Wiley
Date: 23-09-2009
Publisher: CSIRO Publishing
Date: 1984
DOI: 10.1071/PP9840553
Abstract: The effects of two levels of temperature and of water supply on grain development of wheat (cv. Warigal) were studied by imposing treatments during the early or late period of cell ision. High temperature (28°C day/20°C night) accelerated development of the grain. Dry matter accumulation and cell ision proceeded at a higher rate but had a shorter duration in the high temperature treatments. Maximum cell number, final cell size and the number of large starch granules per cell were not significantly reduced by high temperature. Drought and drought × high temperature reduced the storage capacity of the grain, with a decrease in number of cells and starch granules in the endosperm. Cell size was also reduced when treatments were imposed late during cell ision. Duration of dry matter accumulation and cell ision was reduced in the drought and drought × high temperature treatments. The combined effects of drought and high temperature were much more severe than those of each separate treatment. The amount of sucrose per cell was similar in all treatments. It appears unlikely that the supply of sucrose to the endosperm cells is the main limiting factor of dry matter accumulation in both drought and high temperature treatments.
Publisher: Springer Science and Business Media LLC
Date: 28-03-2010
Publisher: Wiley
Date: 06-2012
Publisher: Elsevier BV
Date: 09-2021
Publisher: Oxford University Press (OUP)
Date: 22-10-2015
DOI: 10.1093/PCP/PCV153
Abstract: Many important food crops produce cyanogenic glucosides as natural defense compounds to protect against herbivory or pathogen attack. It has also been suggested that these nitrogen-based secondary metabolites act as storage reserves of nitrogen. In sorghum, three key genes, CYP79A1, CYP71E1 and UGT85B1, encode two Cytochrome P450s and a glycosyltransferase, respectively, the enzymes essential for synthesis of the cyanogenic glucoside dhurrin. Here, we report the use of targeted induced local lesions in genomes (TILLING) to identify a line with a mutation resulting in a premature stop codon in the N-terminal region of UGT85B1. Plants homozygous for this mutation do not produce dhurrin and are designated tcd2 (totally cyanide deficient 2) mutants. They have reduced vigor, being dwarfed, with poor root development and low fertility. Analysis using liquid chromatography-mass spectrometry (LC-MS) shows that tcd2 mutants accumulate numerous dhurrin pathway-derived metabolites, some of which are similar to those observed in transgenic Arabidopsis expressing the CYP79A1 and CYP71E1 genes. Our results demonstrate that UGT85B1 is essential for formation of dhurrin in sorghum with no co-expressed endogenous UDP-glucosyltransferases able to replace it. The tcd2 mutant suffers from self-intoxication because sorghum does not have a feedback mechanism to inhibit the initial steps of dhurrin biosynthesis when the glucosyltransferase activity required to complete the synthesis of dhurrin is lacking. The LC-MS analyses also revealed the presence of metabolites in the tcd2 mutant which have been suggested to be derived from dhurrin via endogenous pathways for nitrogen recovery, thus indicating which enzymes may be involved in such pathways.
Publisher: Oxford University Press (OUP)
Date: 09-2002
DOI: 10.1093/TREEPHYS/22.13.939
Abstract: Cyanogenesis is a widespread and effective defense mechanism in plants. Published evidence suggests that cyanogenic capacity (i.e., cyanogenic glycoside concentration) is enhanced in response to water stress, although potentially confounding variables preclude a definite conclusion. We used highly cyanogenic Eucalyptus cladocalyx var. nana F. Muell. seedlings grown with varying amounts of water and nitrogen (N) to determine the relationship between cyanogenic capacity and water stress. We also examined whether variation in cyanogenic capacity affects phenolic biosynthesis because both pathways use phenylalanine as a substrate. Cyanogenic capacity in fully expanded leaves increased 70% in response to moderate water stress when N availability was high but only 30% when growth was N-limited. Absolute cyanogenic capacity also increased with increasing N supply. Total phenolics and condensed tannins decreased with increasing N supply, but these compounds were unaffected by water stress. We conclude that, under the influence of water stress, the enhanced demand for phenylalanine for cyanogenic glycoside biosynthesis can be sustained by enhanced shikimate pathway flux without affecting phenolic metabolism.
Start Date: 08-2010
End Date: 08-2013
Amount: $270,000.00
Funder: Australian Research Council
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End Date: 12-2021
Amount: $470,707.00
Funder: Australian Research Council
View Funded ActivityStart Date: 04-2021
End Date: 04-2024
Amount: $436,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2007
End Date: 10-2010
Amount: $210,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2013
End Date: 08-2017
Amount: $395,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2015
End Date: 06-2016
Amount: $346,439.00
Funder: Australian Research Council
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