Current Opinion in Plant Biology

Physiology and metabolism 'Tear down this wall'

Publication Date: 2008 May 7 PMID: 18468479
Authors: Pauly, M. - Keegstra, K.
Journal: Curr Opin Plant Biol

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Wood cell walls: biosynthesis, developmental dynamics and their implications for wood properties.

Publication Date: 2008 Apr 21 PMID: 18434240
Authors: Mellerowicz, E. J. - Sundberg, B.
Journal: Curr Opin Plant Biol

Progress has been made toward understanding the biosynthesis and modifications of the cellulose and the hemicellulose/pectin matrix of woody cell walls (and hence wood properties) by identifying 1600 carbohydrate active enzymes (CAZYmes) in Populus, and pinpointing key candidates involved in various developmental stages of wood formation. Transgenic modifications of primary wall modifying enzymes have demonstrated on the possibility of shaping the dimension of wood cells. Candidates for the biosynthesis of secondary wall matrix have been identified, and the cellulose microfibril angle of wood fibers has been modified. In addition, molecular analysis of the plastic development of wood cell walls has provided further information regarding the mechanisms regulating their structure.

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Unique aspects of the grass cell wall.

Publication Date: 2008 Apr 21 PMID: 18434239
Authors: Vogel, J.
Journal: Curr Opin Plant Biol

Grasses are amongst the most important crops worldwide, and the composition of their cell walls is critical for uses as food, feed, and energy crops. Grass cell walls differ dramatically from dicot cell walls in terms of the major structural polysaccharides present, how those polysaccharides are linked together, and the abundance and importance of pectins, proteins and phenolic compounds. Recent advances, spurred by the availability of genomic resources for several plant species, include the characterization of cellulose synthase like (Csl) gene families that are unique to the grasses and the demonstration that members of one of those gene families, CslF, are responsible for making the mixed linkage glucans that are unique to the order Poales.

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Lignin engineering.

Publication Date: 2008 Apr 21 PMID: 18434238
Authors: Vanholme, R. - Morreel, K. - Ralph, J. - Boerjan, W.
Journal: Curr Opin Plant Biol

Lignins are aromatic polymers that are present mainly in secondarily thickened plant cell walls. Several decades of research have elucidated the main biosynthetic routes toward the monolignols and demonstrated that lignin amounts can be engineered and that plants can cope with large shifts in p-hydroxyphenyl/guaiacyl/syringyl (H/G/S) lignin compositional ratios. It has also become clear that lignins incorporate many more units than the three monolignols described in biochemistry textbooks. Together with the theory that lignin polymerization is under chemical control, observations hint at opportunities to design lignin structure to the needs of agriculture. An increasing number of examples illustrates that lignin engineering can improve the processing efficiency of plant biomass for pulping, forage digestibility and biofuels. Systems approaches, in which the plant's response to engineering of a single gene in the pathway is studied at the organismal level, are beginning to shed light on the interaction of lignin biosynthesis with other metabolic pathways and processes.

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How the walls come crumbling down: recent structural biochemistry of plant polysaccharide degradation.

Publication Date: 2008 Apr 20 PMID: 18430603
Authors: Gilbert, H. J. - Stalbrand, H. - Brumer, H.
Journal: Curr Opin Plant Biol

The recent years have witnessed considerable developments in the interpretation of the three-dimensional structures of plant polysaccharide-degrading enzymes in the context of their functional specificity. A plethora of new structures of catalytic, carbohydrate-binding and protein-scaffolding modules involved in (hemi)cellulose catabolism has emerged in harness with sophisticated biochemical analysis. Despite significant advances, a full understanding of the intricacies of substrate recognition and catalysis by these diverse and specialised enzymes remains an important goal, especially if the application potential of these biocatalysts is to be fully realised.

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Revealing the structural and functional diversity of plant cell walls.

Publication Date: 2008 Apr 17 PMID: 18424171
Authors: Knox, J. P.
Journal: Curr Opin Plant Biol

The extensive knowledge of the chemistry of isolated cell wall polymers, and that relating to the identification and partial annotation of gene families involved in their synthesis and modification, is not yet matched by a sophisticated understanding of the occurrence of the polymers within cell walls of the diverse cell types within a growing organ. Currently, the main sets of tools that are used to determine cell-type-specific configurations of cell wall polymers and aspects of cell wall microstructures are antibodies, carbohydrate-binding modules (CBMs) and microspectroscopies. As these tools are applied we see that cell wall polymers are extensively developmentally regulated and that there is a range of structurally distinct primary and secondary cell walls within organs and across species. The challenge now is to document cell wall structures in relation to diverse cell biological events and to integrate this knowledge with the emerging understanding of polymer functions.

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