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Title: Molecular Characterization of PoGT8D and PoGT43B, Two Secondary Wall-Associated Glycosyltransferases in Popular

Author
item ZHOU, GONG-KE - UGA
item ZHONG, RULQUIN - UGA
item Himmelsbach, David
item McPhail, Brooks
item YE, ZHENG-HUA - UGA

Submitted to: Plant and Cell Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2007
Publication Date: 3/22/2007
Citation: Zhou, G., Zhong, R., Himmelsbach, D.S., Mcphail, B.T., Ye, Z. 2007. Molecular Characterization of PoGT8D and PoGT43B, Two Secondary Wall-Associated Glycosyltransferases in Popular. Plant And Cell Physiology.

Interpretive Summary: Two genes have been identified in a hybrid popular that show similarity to those in Arabidopsis that are associated with the production of hemi-cellulosic components of wood. These genes express themselves in secondary cell wall thickening of xylem and phloem tissues. They have been shown to have the ability to repair plant defects that lead to reduction in plant size and secondary cell wall thickness. This provides increased understanding of the biosynthesis of woody tissue that can lead to potential repair of plant defects and thus increase biomass production.

Technical Abstract: Dicot wood is mainly composed of cellulose, lignin and glucuronoxylan (GX). Although the biosynthetic genes for cellulose and lignin have been studied intensively, little is known about the genes involved in the biosynthesis of GX during wood formation. Here, we report the molecular characterization of two genes, PoGT8D and PoGT43B, which encode putative glycosyltransferases, in the hybrid poplar Populus alba x tremula. The predicted amino acid sequences of PoGT8D and PoGT43B exhibit 89 and 75% similarity to the Arabidopsis thaliana IRREGULAR XYLEM8 (IRX8) and IRX9, respectively, both of which have been shown to be required for GX biosynthesis. The PoGT8D and PoGT43B genes were found to be expressed in cells undergoing secondary wall thickening, including the primary xylem, secondary xylem and phloem fibers in stems, and the secondary xylem in roots. Both PoGT8D and PoGT43B are predicted to be type II membrane proteins and shown to be targeted to Golgi. Overexpression of PoGT43B in the irx9 mutant was able to rescue the defects in plant size and secondary wall thickness and partially restore the xylose content. Taken together, our results demonstrate that PoGT8D and PoGT43B are Golgi-localized, secondary wall-associated proteins, and PoGT43B is a functional ortholog of IRX9 involved in GX biosynthesis during wood formation.