Important new players in secondary wall synthesis. Trends Plant Sci

Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
Trends in Plant Science (Impact Factor: 12.93). 05/2006; 11(4):162-4. DOI: 10.1016/j.tplants.2006.02.001
Source: PubMed


Secondary walls in wood are the most abundant biomass produced by plants. Understanding how plants make wood is not only of interest in basic plant biology but also has important implications for tree biotechnology. Three recent papers report exciting findings regarding a group of novel glycosyltransferases (GTs) involved in secondary wall synthesis. Because little is known about genes involved in the synthesis of wood polysaccharides other than cellulose, the identification of these GTs is a breakthrough in the molecular dissection of wood formation.

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    • "Wood development has been characterized by expression profiling in aspen [9-11], Pinus [12,13], black locust [14], Eucalyptus [15,16] and spruce [17]. These studies, and investigations on vascular cell development in herbaceous species Arabidopsis and Zinnia, have identified several classes of important transcription regulators and structural genes involved in secondary cell wall biogenesis (reviewed in [8,18,7,19]). The developmental transition from primary to secondary growth that occurs along the stem has been used as a unique system to identify processes specific to secondary growth in sitka spruce [18] and aspen [20,21]. "
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    ABSTRACT: With its genome sequence and other experimental attributes, Populus trichocarpa has become the model species for genomic studies of wood development. Wood is derived from secondary growth of tree stems, and begins with the development of a ring of vascular cambium in the young developing stem. The terminal region of the developing shoot provides a steep developmental gradient from primary to secondary growth that facilitates identification of genes that play specialized functions during each of these phases of growth. Using a genomic microarray representing the majority of the transcriptome, we profiled gene expression in stem segments that spanned primary to secondary growth. We found 3,016 genes that were differentially expressed during stem development (Q-value </= 0.05; >2-fold expression variation), and 15% of these genes encode proteins with no significant identities to known genes. We identified all gene family members putatively involved in secondary growth for carbohydrate active enzymes, tubulins, actins, actin depolymerizing factors, fasciclin-like AGPs, and vascular development-associated transcription factors. Almost 70% of expressed transcription factors were upregulated during the transition to secondary growth. The primary shoot elongation region of the stem contained specific carbohydrate active enzyme and expansin family members that are likely to function in primary cell wall synthesis and modification. Genes involved in plant defense and protective functions were also dominant in the primary growth region. Our results describe the global patterns of gene expression that occur during the transition from primary to secondary stem growth. We were able to identify three major patterns of gene expression and over-represented gene ontology categories during stem development. The new regulatory factors and cell wall biogenesis genes that we identified provide candidate genes for further functional characterization, as well as new tools for molecular breeding and biotechnology aimed at improvement of tree growth rate, crown form, and wood quality.
    BMC Genomics 03/2010; 11(1):150. DOI:10.1186/1471-2164-11-150 · 3.99 Impact Factor
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    • "malting and brewing industries (Kuntz and Bamforth, 2007). Although there have been exciting new discoveries in the synthesis of cellulose, pectic polysaccharides, mannans, and xyloglucans in recent years, these discoveries have been made predominantly in dicotyledonous plants (Ye et al., 2006; Mohnen, 2008; Zabotina et al., 2008) and will not be covered here. This update, therefore, will be restricted to recent advances in our understanding of the biosynthesis of the characteristic and major wall polysaccharides of the grasses, namely the heteroxylans and (1,3;1,4)-b-D-glucans. "
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    ABSTRACT: A major part of the daily caloric intake of human societies around the world is derived from a diverse range of foods prepared from members of the grass family, including wheat (Triticum aestivum), rice (Oryza sativa), sorghum (Sorghum bicolor), the millets (Panicum miliaceum and Pennisetum americanum), barley (Hor- deum vulgare), and sugar cane (Saccharum officinarum). Grasses cover perhaps 20% or more of the earth's land surface (Gaut, 2002), and many of these are used as forage and fodder for the production of sheep, cattle, and other domesticated livestock. Maize (Zea mays )i s also used widely in animal feed diets, while sorghum, switchgrass (Panicum virgatum), and several other perennial grasses are attracting considerable attention as future biomass energy crops (McLaren, 2005). The grasses are noteworthy for the unusual compo- sition of their cell walls, because walls of grasses have less pectin and xyloglucan, but more heteroxylan, than walls from other higher plants. Most significantly, walls of the grasses contain as major constituents the (1,3;1,4)-b-D-glucans, which are not widely distributed outside the Poaceae. The compositions of walls from selected barley organs are shown in Table I. In many cases, constituents of cell walls in the grasses are closely linked with their widespread adoption, utility, and future potential in agricultural practice and en- ergy production. The noncellulosic polysaccharides of walls in grasses are important components of dietary fiber, which is highly beneficial for lowering the risk of serious human health conditions, including colorectal cancer, high serum cholesterol and cardiovascular disease, obesity, and non-insulin-dependent diabetes (Braaten et al., 1994; Brennan and Cleary, 2005). Con- versely, the noncellulosic wall polysaccharides from walls of cereals and grasses have antinutritive effects in monogastric animals such as pigs and poultry (Brennan and Cleary, 2005) and are often considered to be undesirable components of raw materials in the
    Plant physiology 02/2009; 149(1):27-37. DOI:10.1104/pp.108.130096 · 6.84 Impact Factor
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    • "Other functions include biosynthesis of glycan (GT31, GT34), and compounds involved in mobilisation of energy in the form of sucrose (GT8). Several genes were found to be homologous to poplar xylem-specific GT genes [42]. "
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    ABSTRACT: Different strategies (genetics, biochemistry, and proteomics) can be used to study proteins involved in cell biogenesis. The availability of the complete sequences of several plant genomes allowed the development of transcriptomic studies. Although the expression patterns of some Arabidopsis thaliana genes involved in cell wall biogenesis were identified at different physiological stages, detailed microarray analysis of plant cell wall genes has not been performed on any plant tissues. Using transcriptomic and bioinformatic tools, we studied the regulation of cell wall genes in Arabidopsis stems, i.e. genes encoding proteins involved in cell wall biogenesis and genes encoding secreted proteins. Transcriptomic analyses of stems were performed at three different developmental stages, i.e., young stems, intermediate stage, and mature stems. Many genes involved in the synthesis of cell wall components such as polysaccharides and monolignols were identified. A total of 345 genes encoding predicted secreted proteins with moderate or high level of transcripts were analyzed in details. The encoded proteins were distributed into 8 classes, based on the presence of predicted functional domains. Proteins acting on carbohydrates and proteins of unknown function constituted the two most abundant classes. Other proteins were proteases, oxido-reductases, proteins with interacting domains, proteins involved in signalling, and structural proteins. Particularly high levels of expression were established for genes encoding pectin methylesterases, germin-like proteins, arabinogalactan proteins, fasciclin-like arabinogalactan proteins, and structural proteins. Finally, the results of this transcriptomic analyses were compared with those obtained through a cell wall proteomic analysis from the same material. Only a small proportion of genes identified by previous proteomic analyses were identified by transcriptomics. Conversely, only a few proteins encoded by genes having moderate or high level of transcripts were identified by proteomics. Analysis of the genes predicted to encode cell wall proteins revealed that about 345 genes had moderate or high levels of transcripts. Among them, we identified many new genes possibly involved in cell wall biogenesis. The discrepancies observed between results of this transcriptomic study and a previous proteomic study on the same material revealed post-transcriptional mechanisms of regulation of expression of genes encoding cell wall proteins.
    BMC Plant Biology 02/2009; 9(1):6. DOI:10.1186/1471-2229-9-6 · 3.81 Impact Factor
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