The cell wall and secretory proteome of a tobacco cell line synthesising secondary wall.

The utility of plant secondary cell wall biomass for industrial and biofuel purposes depends upon improving cellulose amount, availability and extractability. The possibility of engineering such biomass requires much more knowledge of the genes and proteins involved in the synthesis, modification and assembly of cellulose, lignin and xylans. Proteomic data are essential to aid gene annotation and understanding of polymer biosynthesis.

Modification of hemicellulose content by antisense down-regulation of UDP-glucuronate decarboxylase in tobacco and its consequences for cellulose extractability.

Extractability and recovery of cellulose from cell walls influences many industrial processes and also the utilisation of biomass for energy purposes. The utility of genetic manipulation of lignin has proven potential for optimising such processes and is also advantageous for the environment. Hemicelluloses, particularly secondary wall xylans, also influence the extractability of cellulose.

Molecular phenotyping of lignin-modified tobacco reveals associated changes in cell-wall metabolism, primary metabolism, stress metabolism and photorespiration.

Lignin is an important component of secondarily thickened cell walls. Cinnamoyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) are two key enzymes that catalyse the penultimate and last steps in the biosynthesis of the monolignols. Downregulation of CCR in tobacco (Nicotiana tabacum) has been shown to reduce lignin content, whereas lignin in tobacco downregulated for CAD incorporates more aldehydes.

Evolution and current status of research in phenolic compounds.

Phenolic compounds are ubiquitous in plants which collectively synthesize several thousand different chemical structures characterized by hydroxylated aromatic ring(s). These compounds play several important functions in plants. They represent a striking example of metabolic plasticity enabling plants to adapt to changing biotic and abiotic environments and provide to plant products colour, taste, technological properties and putative health promoting benefits.

Metabolite profiling reveals a role for atypical cinnamyl alcohol dehydrogenase CAD1 in the synthesis of coniferyl alcohol in tobacco xylem.

In angiosperms, lignin is built from two main monomers, coniferyl and sinapyl alcohol, which are incorporated respectively as G and S units in the polymer. The last step of their synthesis has so far been considered to be performed by a family of dimeric cinnamyl alcohol dehydrogenases (CAD2). However, previous studies on Eucalyptus gunnii xylem showed the presence of an additional, structurally unrelated, monomeric CAD form named CAD1.

hca: an Arabidopsis mutant exhibiting unusual cambial activity and altered vascular patterning.

By screening a T-DNA population of Arabidopsis mutants for alterations in inflorescence stem vasculature, we have isolated a mutant with a dramatic increase in vascular tissue development, characterized by a continuous ring of xylem/phloem. This phenotype is the consequence of premature and numerous cambial cell divisions in both the fascicular and interfascicular regions that result in the loss of the alternate vascular bundle/fiber organization typically observed in Arabidopsis stems. The mutant was therefore designated high cambial activity (hca).

The polymorphism of the genes/enzymes involved in the last two reductive steps of monolignol synthesis: what is the functional significance?

The polymorphism of genes and enzymes involved in the last two steps of monolignol synthesis is examined in the light of recent data coming from genomic studies and mutant/transformant analyses. The two catalytic activities considered--cinnamoyl-CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD)--are encoded by small multigene families. While some degree of diversification can be noted at the sequence level, it is often difficult to use this information to assign substrate specificities to each member of a gene family.

An efficient procedure to stably introduce genes into an economically important pulp tree (Eucalyptus grandis x Eucalyptus urophylla).

Regeneration problems are one of the main limitations preventing the wider application of genetic engineering strategies to the genus Eucalyptus. Seedlings from Eucalyptus grandis x Eucalyptus urophylla were selected according to their regeneration (adventitious organogenesis) and transformation capacity. After in vitro cloning, the best genotype of 250 tested was transformed via Agrobacterium tumefaciens.

Down-regulation of caffeic acid o-methyltransferase in maize revisited using a transgenic approach.

Transgenic maize (Zea mays) plants were generated with a construct harboring a maize caffeic acid O-methyltransferase (COMT) cDNA in the antisense (AS) orientation under the control of the maize Adh1 (alcohol dehydrogenase) promoter. Adh1-driven beta-glucuronidase expression was localized in vascular tissues and lignifying sclerenchyma, indicating its suitability in transgenic experiments aimed at modifying lignin content and composition. One line of AS plants, COMT-AS, displayed a significant reduction in COMT activity (15%-30% residual activity) and barely detectable amounts of COMT protein as determined by western-blot analysis.