Two Trichome Birefringence-Like Proteins Mediate Xylan Acetylation, Which Is Essential for Leaf Blight Resistance in Rice
Two Trichome Birefringence-Like Proteins Mediate Xylan Acetylation, Which Is Essential for Leaf Blight Resistance in Rice
复制标题
两种毛状双折射样蛋白介导木聚糖乙酰化，这对于水稻抗叶枯病至关重要
DOI：
10.1104/pp.16.01618
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发表时间：
2017-01-01
期刊：
影响因子：
7.4
通讯作者：
Zhang, Baocai
中科院分区：
文献类型：
--
作者：
Gao, Yaping;He, Congwu;Zhang, Baocai
乙酰化是一种普遍存在的对细胞壁聚合物的修饰，它在植物生长和逆境防御中发挥着结构性作用。然而，作物如何完成细胞壁聚合物O-乙酰化的机制在很大程度上是未知的。在这里，我们报道了两个水稻毛状体双折射(Tbl)突变体的分离和鉴定，这两个突变体在木聚糖O-乙酰化过程中受到影响。Ostbl1、ostbl2单突变体和tbl1、tbl2双突变体表现出不同程度的矮化生长表型。化学分析表明，在突变体和敲除和过表达的转基因植株中，壁乙酰化水平受到影响。此外，核磁共振波谱分析表明，所有这些突变体都有不同程度的木聚糖单乙酰化降低。OsTBL1和OsTBL2表达水平的差异解释了化学类型的差异，表明OsTBL1是一个功能显性基因。OsTBL1基因定位于高尔基体。重组的OsTBL1蛋白将乙酰基结合到木聚糖上。作为一种较好的受体底物，OsTBL1可以将最多四个乙酰基转移到木戊糖上，且该反应表现出饱和动力学。2D-核磁共振波谱表明，OsTBL1将乙酸酯转移到木醇残基的2-O和3-O位。此外，ostbl1和tbl1、tbl2对水稻枯萎病表现出感病特性，表明这种木聚糖修饰是水稻抗病所必需的。本研究确定了水稻木聚糖乙酰化的主要基因。
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 (Oryza sativa), 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, NMR spectroscopy analyses showed that all those mutants have varied decreases in xylan monoacetylation. The divergent expression levels 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, a preferred acceptor substrate, OsTBL1 can transfer up to four acetyl residues onto xylopentaose, and this activity showed saturable kinetics. 2D-NMR spectroscopy showed that OsTBL1 transfers acetate to both 2-O and 3-O sites 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 identifies the major genes responsible for xylan acetylation in rice plants.