Current Opinion in Plant Biology

Functional diversifications of cyanogenic glucosides.

Publication Date: 2010 Feb 28 PMID: 20197238
Authors: Moller, B. L.
Journal: Curr Opin Plant Biol

Cyanogenic glucosides are present in many plants and their ability to liberate toxic HCN offers an immediate chemical defense response to herbivores and pathogens causing damage of the plant tissue. Countermeasures have evolved to overcome this type of defense and in some cases herbivores and pathogens are able to exploit the presence of cyanogenic glucosides to their own advantage. In plants, cyanogenic glucosides have gained additional functionalities as transporters of nitrogen and operation of an endogenous turnover pathway may enable plants to withdraw the nitrogen and glucose deposited in cyanogenic glucosides for use in primary metabolism. The aim of this review is to provide an overview of the new knowledge on these diverse functionalities of cyanogenic glucosides.

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Plastid transport and metabolism of C(3) and C(4) plants-comparative analysis and possible biotechnological exploitation.

Publication Date: 2010 Feb 24 PMID: 20188622
Authors: Weber, A. P. - von Caemmerer, S.
Journal: Curr Opin Plant Biol

Recent progress in genomics has provided complete or near complete genome sequences of several C(3) (e.g. Arabidopsis, rice, and poplar) and C(4) (e.g. sorghum and maize) plant species. These genome sequences enabled comparative quantitative proteomic and transcriptomic analyses of C(3) and C(4) plants, in particular of their chloroplasts. Such analyses have revealed a comprehensive picture of the distribution of C(4) pathway components between bundle sheath and mesophyll cell chloroplasts and they permitted the prediction of novel pathway components. A comprehensive understanding of the C(4) photosynthetic mechanism is required for the transfer of C(4)-like photosynthesis into C(3) crop plants, such as rice.

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Tailoring plant lipid composition: designer oilseeds come of age.

Publication Date: 2010 Feb 23 PMID: 20185359
Authors: Napier, J. A. - Graham, I. A.
Journal: Curr Opin Plant Biol

Plant neutral lipids such as seed oil triacylglycerols play a key role in many aspects of human life, ranging from providing essential nutrition to acting as biolubricants. There is also growing interest in using plant oils as a replacement for petrochemicals, either for fuel or as a chemical feedstock. Considerable effort has been focused on modifying the fatty acid composition of seed oils and/or increasing the levels of storage triacylglycerol. Certainly, it is now possible to successfully modify the profile of plant oils via transgenic metabolic engineering to generate something approaching a 'designer oil'. This is specifically true for the accumulation of omega-3 long chain polyunsaturated fatty acids that now stand at levels equivalent to those found in native marine organisms. However, it is equally clear that a holistic understanding of plant lipid metabolism is still lacking, mainly owing to the continually emerging complexity and interplay between pathways, recently exemplified by the identification of the ROD1 phosphatidylcholine:diacylglycerol cholinephosphotransferase involved in the channelling of unsaturated fatty acids into storage oil. The new approaches and outcomes described here will inform new paradigms and hasten the arrival of truly predictive biology in this vital field.

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Photorespiration: current status and approaches for metabolic engineering.

Publication Date: 2010 Feb 23 PMID: 20185358
Authors: Maurino, V. G. - Peterhansel, C.
Journal: Curr Opin Plant Biol

Photorespiration results from the oxygenase reaction catalysed by ribulose-1,5-bisphosphate carboxylase/oxygenase and serves as a carbon recovery system. It comprises enzymatic reactions distributed in chloroplasts, peroxisomes and mitochondria. The recent discovery of a cytosolic bypass and the requirement of complex formation between some photorespiratory proteins added additional levels of complexity to the known pathway. Photorespiration may have evolved in both, C(3) and C(4) plants, to prevent an accumulation of toxic levels of glycolate. Moreover, it is suggested that photorespiration evolved in cyanobacteria before the origin of chloroplasts. Synthetic detours, reminiscent of secondary photorespiratory pathways naturally occurring in cyanobacteria, were installed in Arabidopsis thaliana to bypass photorespiration. An enrichment of CO(2) in the chloroplast and positive effects on plant growth raised the question why these pathways have been lost from higher plants.

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Regulation of starch metabolism: the age of enlightenment?

Publication Date: 2010 Feb 18 PMID: 20171927
Authors: Kotting, O. - Kossmann, J. - Zeeman, S. C. - Lloyd, J. R.
Journal: Curr Opin Plant Biol

Starch and sucrose are the primary products of photosynthesis in the leaves of most plants. Starch represents the major plant storage carbohydrate providing energy during the times of heterotrophic growth. Starch metabolism has been studied extensively, leading to a good knowledge of the numerous enzymes involved. In contrast, understanding of the regulation of starch metabolism is fragmentary. This review summarises briefly the known steps in starch metabolism, highlighting recent discoveries. We also focus on evidence for potential regulatory mechanisms of the enzymes involved. These mechanisms include allosteric regulation by metabolites, redox regulation, protein-protein interactions and reversible protein phosphorylation. Modern systems biology and bioinformatic approaches are uncovering evidence for extensive post-translational protein modifications that may underlie enzyme regulation and identify novel proteins which may be involved in starch metabolism.

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Tailoring plant metabolism for the production of novel polymers and platform chemicals.

Publication Date: 2010 Feb 17 PMID: 20171137
Authors: Bornke, F. - Broer, I.
Journal: Curr Opin Plant Biol

Genetic engineering of plants for the production of novel polymers and platform chemicals can help to alleviate the demands for limited resources and potentially provide a platform to produce valuable compounds in bulk quantities. However, the success of transgenic plants as bioreactors depends on competitive high-yield production capacities. Recent advances in enhancing the production of novel compounds in transgenic plants include multigene transformation and the direction of biosynthetic pathways to specific intracellular compartments. It now appears feasible to produce interesting proteins such as spider silk or collagen, novel carbohydrates, and biopolymers that could replace petroleum-based plastics using transgenic plants. Direct production of novel compounds in biomass crops with the aim to produce bioenergy as a coproduct provides a promising way to improve economics of transgenic plants as biofactories.

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Accessing genetic diversity for crop improvement.

Publication Date: 2010 Feb 16 PMID: 20167531
Authors: Glaszmann, J. - Kilian, B. - Upadhyaya, H. - Varshney, R.
Journal: Curr Opin Plant Biol

Vast germplasm collections are accessible but their use for crop improvement is limited-efficiently accessing genetic diversity is still a challenge. Molecular markers have clarified the structure of genetic diversity in a broad range of crops. Recent developments have made whole-genome surveys and gene-targeted surveys possible, shedding light on population dynamics and on the impact of selection during domestication. Thanks to this new precision, germplasm description has gained analytical power for resolving the genetic basis of trait variation and adaptation in crops such as major cereals, chickpea, grapevine, cacao, or banana. The challenge now is to finely characterize all the facets of plant behavior in carefully chosen materials. We suggest broadening the use of 'core reference sets' so as to facilitate material sharing within the scientific community.

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Hybrid sterility in plant: stories from rice.

Publication Date: 2010 Feb 10 PMID: 20153244
Authors: Ouyang, Y. - Liu, Y. G. - Zhang, Q.
Journal: Curr Opin Plant Biol

Hybrid sterility is the most common form of postzygotic reproductive isolation in plants. The best-known example is perhaps the hybrid sterility between indica and japonica subspecies of Asian cultivated rice (Oryza sativa L.). Major progress has been reported recently in rice in identifying and cloning hybrid sterility genes at two loci regulating female and male fertility, respectively. Genetic analyses and molecular characterization of these genes, together with the results from other model organisms especially Drosophila, have advanced the understanding of the processes underlying reproductive isolation and speciation. These findings also have significant implications for crop genetic improvement, by providing the feasibility and strategies for overcoming intersubspecific hybrid sterility thus allowing the development of intersubspecific hybrids.

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