Plant and Cell Physiology Advance Access originally published online on March 22, 2007
Plant and Cell Physiology 2007 48(5):689-699; doi:10.1093/pcp/pcm037
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Molecular Characterization of PoGT8D and PoGT43B, Two Secondary Wall-Associated Glycosyltransferases in Poplar
1Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
2Richard B. Russell Agriculture Research Center, US Department of Agriculture, Agriculture Research Service, Athens, GA 30604, USA
*Corresponding author: E-mail, zhye{at}plantbio.uga.edu; Fax, +1-706-542-1805.
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Abstract |
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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.
Keywords: Glucuronoxylan - Glycosyltransferase - Poplar - Secondary wall synthesis
Abbreviations: CaMV, cauliflower mosaic virus; CFP, cyan fluorescent protein; fra8, fragile fiber8; GFP, green fluorescent protein; GlcA, glucuronic acid; GT, glycosyltransferase; GX, glucuronoxylan; irx8, irregular xylem8; irx9, irregular xylem9; MeGlcA, 4-O-methyl-glucuronic acid; RT–PCR, reverse transcription–PCR; YFP, yellow fluorescent protein
(Received January 19, 2007; Accepted March 13, 2007)
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