Poster: Cell Walls
Abs #
1265: Efforts to identify xylan biosynthetic enzymes
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Presenter: |
Liepman, Aaron H., liepmana@msu.edu |
Authors | Liepman, Aaron H. (A) Leykam, Joseph (A) Wilkerson, Curtis G. (A) Keegstra, Kenneth (A) | | Affiliations: |
(A): Michigan State University
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Glucuronoarabinoxylan (GAX) is a non-cellulosic polysaccharide found in the secondary cell walls of all plants, and is particularly abundant in the primary cell walls of commelinoid monocots, including grasses. Structurally, a stereotypical GAX consists of a b-1,4 linked xylan backbone decorated with a-1,3 linked arabinose, and a-1,2 linked glucuronic acid sidechains. GAX content and composition in plant tissues is of great economic importance since it influences their suitability for processing into foods, fuels and many other products. Like other soluble fibers, consumption of GAX has been demonstrated to promote cardiovascular health. Although a number of groups have studied GAX biosynthesis in a variety of plant species, to date no genes encoding GAX biosynthetic enzymes have been identified. To identify the GAX backbone-synthesizing enzyme, xylan synthase (XylS; E.C. 2.4.2.24) candidates, we are pursuing a multifaceted strategy involving biochemistry, cell biology, genomic and proteomic techniques. Rice is being used for these studies because it is the only grass species with a fully sequenced genome. As a first step toward identifying XylS, two distinct types of in vitro assays (endogenous and exogenous acceptor-based) have been used to measure XylS activity in rice microsomal membrane preparations. These assays have been optimized, and assay products characterized. Sensitive MS-based proteomics techniques are being used to identify candidate protein sequences from Golgi-enriched membrane preparations of rice. Gene expression profiling is being pursued as a complementary approach to identify candidate XylS genes, and to test the hypothesis that a cellulose synthase-like (Csl) enzyme catalyzes xylan backbone biosynthesis. Results of our efforts will be presented.
