水稻OsBAG4-OsMYB106转录复合体调控盐胁迫应答的分子机制

植物在盐胁迫环境中，通过有效地调控钠离子分布来降低对细胞的损伤。然而，参与此调控过程的核心转录调控复合体及其分子调控机制尚不清楚。前期工作中我们发现具有保守BAG结构域的osbag4突变体呈现出对盐胁迫敏感的表型。通过Co-IP和LC-MS/MS鉴定多肽的实验发现OsBAG4与OsMYB106转录因子互作，并且结合在OsHKT1;5的启动子，激活其表达。同时，发现OsBAG4还能与潜在具有H3K9甲基转移酶活性的OsSUVH1互作。在此基础上，我们拟利用ChIP-seq和RNA-seq等技术，在全基因组范围内鉴定OsBAG4-OsMYB106转录调控因子的靶基因，解析其转录调控模式。同时，将进一步解析OsSUVH1是否直接参与OsBAG4-OsMYB106靶基因位点的染色质组成和状态。研究结果将发现水稻盐胁迫应答转录调控过程全新的分子调控机制，为基于分子设计培育耐盐水稻新育种提供理论依据。

Under the soil salinity condition, plants effectively control the sodium distribution to protect the cellular integrity. However, the key transcriptional complex governing this process and the underlying molecular mechanism remain unknown. Our previous efforts to perform a genetic screening of a CRISPR/Cas9-rice-mutant pool have identified a loss-of-function mutant osbag4 which displayed clear salt stress-sensitive phenotypes. By performing co-immunoprecipitation-coupled LC-MS/MS, we further uncovered a novel R2R3 MYB transcription factor, OsMYB106, interacts with OsBAG4 both in vitro and in vivo. Moreover, we found that OsBAG4 and OsMYB106 can directly bind to the consensus MYB binding element located at OsHKT1;5 promoter in vivo, which was confirmed by ChIP-qPCR, thereby activating its transcription. Additionally, we identified a putative H3K9 methyltransferase, OsSUVH1, interacts with OsBAG4. Based on these previous work, we proposed this grant application. We are planning to perform genome-wide chromatin immunoprecipitation-coupled massively paralleled DNA sequencing and RNA-sequencing analysis to dissect the direct transcriptional targets of the OsBAG4-OsMYB106 transcriptional module and further propose a new molecular mechanism by which a novel transcriptional complex controls salt stress-responsive gene expression. In parallel, we will examine whether another putative binding partner of OsBAG4, OsSUVH1, which is predicted to play a role in histone modification, functions in regulating chromatin conformational changes in the OsBAG4-OsMYB106 target loci. Collectively, we expect that our proposed studies will shed new light on a novel OsBAG4-OsMYB106 transcription module and its roles in regulating the expression of salt stress-responsive genes. Our results may also provide new theoretical clues for generating salinity stress-tolerant rice germplasms by the “breeding by molecular design” strategy.