TBL在植物细胞壁多糖乙酰化修饰中的功能研究

Acetylation widely exists in many organisms from bacteria to higher plants and human, indicating that this modification is highly conserved throughout evolution. Polysaccharides are important molecules that execute various vital functions in the lifecycle of plants and animals. Acetylation status of polysaccharides often has important affects on the physicochemical property. However, the molecular mechanism by which components control the polysaccharide acetylation status is poorly understood. To uncover the underlying molecular basis, we use cell wall polysaccharides as targets because many of them contain acetyl-substituents. Based on our previous studies on the genetic materials, we found that some plant-specific Trichome Birefringence-Like (TBL) genes are likely involved in acetylation of hemicellulose xylan. In this study, we aim to: 1. characterize the biochemical functions of 2-3 TBLs in polysaccharide acetylation in rice; 2. identify the position where the acetyl resides are added by TBLs. 3. characterize the biological functions of polysaccharide acetylation in rice plants, based on phenotypic and transcript profile analyses. Therefore, this study will shed light on the molecular mechanism of TBLs in the control of cell-wall polysaccharide acetylation level and on the significance of acetylated polysaccharides in plant growth and economic value.

乙酰化修饰现象在生命进化进程中极为保守。多糖作为一种重要的生命体基本物质，乙酰化修饰对多糖的理化性质有着重要的影响，但其分子机理仍相当不清楚。本项目拟围绕细胞壁多糖的乙酰化修饰机理及功能开展研究。我们前期工作已筛选并鉴定了水稻中十个TBL候选基因，对所获得的转基因和突变体材料进行化学成分分析，从中遴选出2-3个能调控细胞壁多糖、尤其是木聚糖乙酰化水平的TBL。本研究将利用遗传学、生物化学、分子生物学、植物化学等多学科交叉手段，系统解析这2-3个TBL的生化活性及产物特征，揭示细胞壁多糖乙酰化修饰的分子机制；开展表型分析和转录组等研究，明确其乙酰化修饰的生物学效应，为农业生产和秸秆生物质的工业化利用提供指导。

乙酰化作为细胞壁多糖的主要修饰形式，其修饰水平和位置对细胞壁的理化性质及结构具有重要影响。水稻是一种单子叶模式植物以及重要的粮食作物，水稻中乙酰化修饰的分子机理及对农艺性状的影响仍相当不清楚。本项目围绕水稻中TBL (Trichome Birefrigence-Like) A亚家族中的4个成员开展工作，通过系统深入的生物化学、遗传学、植物化学等研究，建立了TBL蛋白的酶活分析体系；明确了高尔基体定位的OsTBL15的功能为木聚糖主链乙酰基转移酶，但其酶学特性与OsTBL1不同；利用CRISPR/Cas9创制了ostbl5和ostbl6的单突变体，轻微的表型暗示二者可能存在功能冗余。通过对遗传材料的表型分析，发现细胞壁乙酰化改变影响了茎秆的支撑力、株型和抗病性，为相关农艺性状的改良提供靶标。