Molecular Dissection of Xylan Biosynthesis during Wood Formation in Poplar

作     者：Chanhui Lee Quincy Teng Ruiqin Zhong Zheng-Hua Ye 

作者机构：Department of Plant Biology University of Georgia Athens GA 30602 USA National Exposure Research Laboratory US Environmental Protection Agency Athens GA 30605 USA 

出 版 物：《Molecular Plant》 (分子植物（英文版）)

年 卷 期：2011年第4卷第4期

页      面：730-747页

核心收录：

学科分类：0710[理学-生物学] 071010[理学-生物化学与分子生物学] 082902[工学-木材科学与技术] 081704[工学-应用化学] 07[理学] 08[工学] 0817[工学-化学工程与技术] 0829[工学-林业工程] 

基　　金：Division of Chemical Sciences,Geosciences,and Biosciences Office of Basic Energy Sciences of the US Department of Energy through 

主　　题：Glycosyltransferase GT8 family GT43 family poplar wood formation xylan. 

摘      要：Xylan, being the second most abundant polysaccharide in dicot wood, is considered to be one of the factors contributing to wood biomass recalcitrance for biofuel production. To better utilize wood as biofuel feedstock, it is crucial to functionally characterize all the genes involved in xylan biosynthesis during wood formation. In this report, we investigated roles of poplar families GT43 and GT8 glycosyltransferases in xylan biosynthesis during wood formation. There exist seven GT43 genes in the genome of poplar （Populus trichocarpa）, five of which, namely PtrGT43A, PtrGT43B, PtrGT43C, PtrGT43D, and PtrGT43E, were shown to be highly expressed in the developing wood and their encoded proteins were localized in the Golgi. Comprehensive genetic complementation coupled with chemical analyses demonstrated that overexpression of PtrGT43A/B/E but not PtrGT43C/D was able to rescue the xylan defects conferred by the Arabidopsis irx9 mutant, whereas overexpression of PtrGT43C/D but not PtrGT43A/B/E led to a complementation of the xylan defects in the Arabidopsis irx14 mutant. The essential roles of poplar GT43 members in xylan biosynthesis was further substantiated by RNAi down-regulation of GT43B in the hybrid poplar （Populus alba x tremula） leading to reductions in wall thickness and xylan content in wood, and an elevation in the abundance of the xylan reducing end sequence. Wood digestibility analysis revealed that cellulase digestion released more glucose from the wood of poplar GT43B RNAi lines than the control wood, indicating a decrease in wood biomass recalcitrance. Furthermore, RNAi down-regulation of another poplar wood-associated glycosyltransferase, PoGTSD, was shown to cause decreases in wall thickness and xylan content as well as in the abundance of the xylan reducing end sequence. Together, these findings demonstrate that the poplar GT43 members form two functionally non-redundant groups, namely PtrGT43A/B/E as functional orthologs of Arabidopsis IRX9 and PtrG