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First published online September 1, 2006; 10.1104/pp.106.086678 Plant Physiology 142:1233-1245 (2006) © 2006 American Society of Plant Biologists OPEN ACCESS ARTICLE
The Cellulose Synthase Gene Superfamily and Biochemical Functions of Xylem-Specific Cellulose Synthase-Like Genes in Populus trichocarpa1,[W],[OA]Forest Biotechnology Group, Department of Forestry and Environmental Resources, College of Natural Resources, North Carolina State University, Raleigh, North Carolina 27695
Wood from forest trees modified for more cellulose or hemicelluloses could be a major feedstock for fuel ethanol. Xylan and glucomannan are the two major hemicelluloses in wood of angiosperms. However, little is known about the genes and gene products involved in the synthesis of these wood polysaccharides. Using Populus trichocarpa as a model angiosperm tree, we report here a systematic analysis in various tissues of the absolute transcript copy numbers of cellulose synthase superfamily genes, the cellulose synthase (CesA) and the hemicellulose-related cellulose synthase-like (Csl) genes. Candidate Csl genes were characterized for biochemical functions in Drosophila Schneider 2 (S2) cells. Of the 48 identified members, 37 were found expressed in various tissues. Seven CesA genes are xylem specific, suggesting gene networks for the synthesis of wood cellulose. Four Csl genes are xylem specific, three of which belong to the CslA subfamily. The more xylem-specific CslA subfamily is represented by three types of members: PtCslA1, PtCslA3, and PtCslA5. They share high sequence homology, but their recombinant proteins produced by the S2 cells exhibited distinct substrate specificity. PtCslA5 had no catalytic activity with the substrates for xylan or glucomannan. PtCslA1 and PtCslA3 encoded mannan synthases, but PtCslA1 further encoded a glucomannan synthase for the synthesis of (1
1 This work was supported by the Japan Society for the Promotion of Science (2004–2006; postdoctoral fellowship for research abroad to S.S.), by the National Research Initiative of the U.S. Department of Agriculture Cooperative State Research, Education, and Extension Service (grant no. 2004–35504–14652 to V.L.C.), and by the North Carolina State University Forest Biotechnology Industrial Research Consortium (grant no. 524450 to L.L. and S.S.). 2 Present address: Institute of Sustainability Science, Kyoto University, Gokasho, Uji, Kyoto 611–0011, Japan. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Vincent L. Chiang (vincent_chiang{at}ncsu.edu). [W] The online version of this article contains Web-only data. [OA] Open Access articles can be viewed online without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.106.086678 * Corresponding author; e-mail vincent_chiang{at}ncsu.edu; fax 919–515–7801. Received July 12, 2006; accepted August 28, 2006; published September 1, 2006. This article has been cited by other articles:
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-D-glucomannan. The expression of PtCslA1 is most highly xylem specific, suggesting a key role for it in the synthesis of wood glucomannan. The results may help guide further studies to learn about the regulation of cellulose and hemicellulose synthesis in wood. 
