组蛋白乙酰转移酶OsglHAT1调控水稻粒型和粒重的分子机制

Enhancing grain yield is important in view of the increasing global population. Grain weight is a key determinant of crop yield; however, its underlying molecular mechanisms are largely unknown. Here, by using a map-based cloning approach, we identified a grain weight/yield quantitative trait locus OsglHAT1 that encodes a novel histone H4 acetyltransferase. We revealed that OsglHAT1 functions as a positive regulator of grain weight, and that the allelic variation is attributed to its altered promoter activities. Furthermore, RNA-Seq and microarray experiments indicated that OsglHAT1 likely functions through the regulation of transcription, involving a variety of signaling pathways. We have been still wondering up to date how OsglHAT1 involved in the regulation of transcription, and which signaling pathway is closely related to its controlling of grain weight in rice. Based on these results, this project was specifically designed to shed light on the molecular bases of its regulation of grain weight, which would be revealed from three different aspects: (1) the molecular basis of altered OsglHAT1's promoter activities; (2) its conserved protein domains and biological functions; and (3) the signaling pathways and factors directly and/or indirectly influenced by OsglHAT1's actions.

在世界人口持续增长的现实背景下，提高作物产量显得尤为重要。粒重是作物产量的构成要素之一；不过，人们对其分子调控机理了解很有限。利用图位克隆技术，我们分离到一个调控水稻粒重/产量的数量性状位点(QTL)/基因OsglHAT1；其编码一个新类型的组蛋白H4乙酰转移酶。我们发现，OsglHAT1是一个水稻粒重性状正向调节因子，启动子活性差异是造成亲本等位基因间功能不同的主要原因。同时，RNA-Seq和基因芯片实验结果表明，OsglHAT1可能参与了基因转录调控，介导诸多信号途径。但目前为止，我们仍不清楚：该基因是如何参与基因转录的？其参与的哪个/类信号途径调控粒重性状？在前期工作基础上，本项目将深入探索该基因调控水稻粒重的分子机制。拟从三个不同角度揭示其分子作用机理：（1）启动子活性差异的分子基础；（2）编码蛋白的保守结构域和其生物学功能；以及（3）该基因参与调控的直接或间接信号途径和信号分子。

染色质结构的变化影响细胞核内的很多重要生理过程，如修复、重组和转录。组蛋白乙酰化是对染色质组蛋白的特定氨基酸的一种共价修饰，可以调节组蛋白与DNA间的互作，改变染色质的结构进而影响转录因子与顺式作用元件的结合。在前期工作中我们揭示一个新的调控水稻粒长、粒重和产量的分子模块GW6a, 其编码一个新类型的组蛋白H4乙酰化酶（OsglHAT1）。在此研究基础上，本项目在以下几个方面取得了重要进展：（1）发现GW6a的新的结构域LOOP调控水稻粒型；（2）找到了与GW6a互作的、调控水稻粒型的LC360和LC490等遗传因子；（3）初步鉴定到导致差异GW6a启动子驱动活性的如E-box等顺式作用元件；（4）发现GW6a是一个油菜素内酯（BR）响应基因，可能通过改变生长素信号途径调控水稻粒型。总之，这些进展让我们对组蛋白乙酰化酶GW6a调控水稻粒型的分子机制有了较好的理解，也为更深入的相关粒型调控的遗传调控网络研究奠定了良好基础。