Functional conservation and divergence of Miscanthus lutarioriparius GT43 gene family in xylan biosynthesis.
BACKGROUND
Xylan is the most abundant un-cellulosic polysaccharides of plant cell walls. Much progress in xylan biosynthesis has been gained in the model plant species Arabidopsis. Two homologous pairs Irregular Xylem 9 (IRX9)/9L and IRX14/14L from glycosyltransferase (GT) family 43 have been proved to play crucial roles in xylan backbone biosynthesis. However, xylan biosynthesis in grass such as Miscanthus remains poorly understood.


RESULTS
We characterized seven GT43 members in M. lutarioriparius, a promising bioenergy crop. Quantitative real-time RT-PCR (qRT-PCR) analysis revealed that the expression of MlGT43 genes was ubiquitously detected in the tissues examined. In-situ hybridization demonstrated that MlGT43A-B and MlGT43F-G were specifically expressed in sclerenchyma, while MlGT43C-E were expressed in both sclerenchyma and parenchyma. All seven MlGT43 proteins were localized to Golgi apparatus. Overexpression of MlGT43A-E but not MlGT43F and MlGT43G in Arabidopsis irx9 fully or partially rescued the mutant defects, including morphological changes, collapsed xylem and increased xylan contents, whereas overexpression of MlGT43F and MlGT43G but not MlGT43A-E complemented the defects of irx14, indicating that MlGT43A-E are functional orthologues of IRX9, while MlGT43F and MlGT43G are functional orthologues of IRX14. However, overexpression of all seven MlGT43 genes could not rescue the mucilage defects of irx14 seeds. Furthermore, transient transactivation analyses of MlGT43A-E reporters demonstrated that MlGT43A and MlGT43B but not MlGT43C-E were differentially activated by MlSND1, MlMYB46 or MlVND7.


CONCLUSIONS
The results demonstrated that all seven MlGT43s are functionally conserved in xylan biosynthesis during secondary cell wall formation but diversify in seed coat mucilage xylan biosynthesis. The results obtained provide deeper insight into xylan biosynthesis in grass, which lay the foundation for genetic modification of grass cell wall components and structure to better suit for next-generation biofuel production.
Qingdao Institute of Bioenergy and Bioprocess Technology, Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Chinese Academy of Sciences, Qingdao, 266101, PR China.|University of Chinese Academy of Sciences, Beijing, 100049, PR China.
Xiaoyu
X
Wang
Qingdao Institute of Bioenergy and Bioprocess Technology, Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Chinese Academy of Sciences, Qingdao, 266101, PR China.
Qi
Q
Tang
Qingdao Institute of Bioenergy and Bioprocess Technology, Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Chinese Academy of Sciences, Qingdao, 266101, PR China.|University of Chinese Academy of Sciences, Beijing, 100049, PR China.
Xun
X
Zhao
Shandong Institute of Agricultural Sustainable Development, Jinan, 250100, PR China.
Chunlin
C
Jia
Qingdao Institute of Bioenergy and Bioprocess Technology, Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Chinese Academy of Sciences, Qingdao, 266101, PR China.
Xuanwen
X
Yang
Qingdao Institute of Bioenergy and Bioprocess Technology, Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Chinese Academy of Sciences, Qingdao, 266101, PR China.
Guo
G
He
State Key Laboratory for Conservation and Utilization of Subtropical Agrobioresources, South China Agricultural University, Guangzhou, 510642, PR China.
Aimin
A
Wu
Tobacco Research Institute of Chinese Academy of Agricultural Sciences, Key laboratory of Tobacco Genetic Improvement and Biotechnology, Qingdao, 266101, PR China.
Yingzhen
Y
Kong
Qingdao Institute of Bioenergy and Bioprocess Technology, Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Chinese Academy of Sciences, Qingdao, 266101, PR China. hurb@qibebt.ac.cn.
Ruibo
R
Hu
Qingdao Institute of Bioenergy and Bioprocess Technology, Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Chinese Academy of Sciences, Qingdao, 266101, PR China. zhougk@qibebt.ac.cn.
Gongke
G
Zhou
D000595:Amino Acid Sequence; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D014644:Genetic Variation; D016695:Glycosyltransferases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D017403:In Situ Hybridization; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D005810:Multigene Family; D009154:Mutation; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018547:Plant Stems / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D006109:Poaceae / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014990:Xylans / Q000096:biosynthesis*
D008164:Luminescent Proteins; D010940:Plant Proteins; D014990:Xylans; D016695:Glycosyltransferases
Glycosyltransferase family 43; Miscanthus lutarioriparius; Secondary cell wall; Seed coat mucilage; Xylan biosynthesis