Two Trichome Birefringence-like proteins Mediate Xylan Acetylation, Which Is Essential for Leaf Blight Resistance in Rice
| 作者： |
Yaping Gao, Congwu He, Dongmei Zhang, Xiangling Liu, Zuopeng Xu, Tian Yanbao, Xue-Hui Liu, Shanshan Zang, Markus Pauly, Yihua Zhou and Baocai Zhang |
| 刊物名称： |
Plant Physiology |
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| 发表年度： |
2016-11-19 |
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| 摘要： |
Acetylation is a ubiquitous modification on cell wall polymers, which play a structural role in plant growth and stress defenses. However, the mechanisms for how crop plants accomplish cell-wall polymer O-acetylation are largely unknown. Here, we report on the isolation and characterization of two trichome birefringence-like (tbl) mutants in rice, which are affected in xylan O-acetylation. ostbl1 and ostbl2 single mutant and the tbl1 tbl2 double mutant displayed a stunted growth phenotype with varied degree of dwarfism. As shown by chemical assays, the wall acetylation level is affected in the mutants and the knock-down and overexpression transgenic plants. Furthermore, nuclear magnetic resonance (NMR) spectroscopy analyses showed that all those mutants have varied decreases in xylan monoacetylation. The divergent expression level of OsTBL1 and OsTBL2 explained the chemotype difference and indicated that OsTBL1 is a functionally dominant gene. OsTBL1 was found to be Golgi-localized. The recombinant OsTBL1 protein incorporates acetyl groups onto xylan. By using xylopentaose (X5), a preferring acceptor substrate, OsTBL1 can transfer up to four acetyl residues onto X5 and this activity showed saturable kinetics. 2D-NMR spectroscopy specified that OsTBL1 transfers acetate to both 2-O and 3-O site of xylosyl residues. In addition, ostbl1 and tbl1 tbl2 displayed susceptibility to rice blight disease, indicating that this xylan modification is required for pathogen resistance. This study offers us the insights into the mechanisms and functions of xylan acetylation in crop plants. |
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