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Abstract Detail


Cell Walls

Zeng, Wei [1], Chatterjee, Mohor [2], Faik, Ahmed [2].

Glucurono(Arabino)Xylan biosynthesis in wheat.

Glucurono(Arabino)Xylan (GAX) is an important hemicellulose in type II cell walls. It consists of a β-(1, 4)-D-xylan backbone substituted with α-Araf and α-glucuronic acid residues. Nothing is known about GAX biosynthesis pathway and none of the biosynthetic genes, i.e. xylan synthase (XylS), arabinosyltransferase, and glucuronosyltransferase (GlcAT) have been identified. Two strategies were used to identify putative GAX biosynthetic genes. The first strategy is based on expression profiling of putative glycosyltransferase genes using cereal endosperm as a model. The walls of wheat endosperm contain up to 70% of arabinoxylan. The development of wheat seed was divided in several stages to cover endosperm cell wall formation. Twenty-four putative wheat glycosyltransferase genes were identified using an in-house bioinformatics script and the expression patterns of these genes were semi-quantitatively analyzed by RT-PCR. The data indicate that the expression of at least ten of these putative glycosyltransferase genes coincide with endosperm cell wall elaboration. The second strategy is based on the development of a biochemical assay for GAX biosynthesis. Golgi-enriched microsomes were prepared from etiolated wheat seedlings and an enzymatic assay was optimized where incorporation of [14C]Xyl, [14C]GlcA, and [14C]Ara into ethanol-insoluble products was obtained. These products were susceptible to a wheat arabinoxylan-specific endoxylanase. The synthesis of these GAX-like polymers required cooperative action between XylS and GlcAT activities. The GAX-synthesizing activity was solublized with detergents and purification procedures were developed to purify the complex.


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1 - Ohio University, Environmental and Plant Biology, Molecular Cellular Biology Program, 315 Porter Hall, Athens, Ohio, 45701, USA
2 - Ohio University, Environmental and Plant Biology, Molecular Cellular Biology Program

Keywords:
cell wall
cereal
glucoronoarabinoxylan
biosynthesis.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P17022
Abstract ID:1088


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