水稻转录因子SAE1提高耐盐性的分子基础

Salt stress is one of the major impediments to the production increase in rice, thus breeding new rice varieties with improved salt tolerance is essential for ensuring food security in China, whereas studying the molecular mechanism of plant salt tolerance is the premise of breeding new salt tolerant rice varieties using modern plant biotechnology. ..In our preliminary experiments, by analyzing rice gene expression data, we found SAE1, an ERF transcription factor gene, is responsive to salt and ABA at transcriptional level. Silencing SAE1 increases salt and ABA sensitivity in rice, and SAE1 binds ABI5 promoter to influence the transcription of ABI5, but it is unclear how SAE1 regulates the expression of downstream target genes in response to salt stress in rice. ..In this project, we will (1) overexpress SAE1 or knockout SAE1 in rice and evaluate the physiological function of SAE1 in rice salt tolerance; (2) analyze the characteristics of SAE1, including expression profile, binding activity to cis-elements, transcriptional activation/repression, subcellular localization, critical domains/sites for its function; (3) identify the direct target genes of SAE1 by Chromatin Immunoprecipitation-sequencing (ChIP-seq), and analyze the transcriptional activation/repression on ABI5 by transient or stable co-expression of SAE1 gene and ABI5 promoter driven luciferase reporter gene; (4) dissect the genetic relationship between SAE1 and its target genes. ..Through the implementation of this project, we expect to provide a theoretical basis and breeding materials for the improvement of rice salt tolerance by uncovering the molecular basis of salt tolerance regulated by SAE1, and creating new rice breeding materials with improved salt tolerance.

盐胁迫是限制作物稳产高产的重要因素，剖析植物耐盐性调控的分子机理是开展作物耐盐分子育种的基础。在前期研究中，我们通过分析水稻基因表达谱发现ERF基因SAE1的表达受盐胁迫和ABA诱导，生理表型分析发现SAE1基因沉默的转基因水稻在种子萌发期和幼苗生长期对高盐胁迫和外源ABA的敏感性增加，ChIP分析表明SAE1可以结合ABI5基因的启动子，瞬时表达实验发现SAE1抑制ABI5启动子的转录活性，这些结果表明SAE1可能通过ABA信号调控水稻的盐胁迫反应。本项目拟在以上研究基础上，通过基因过表达和突变体分析确认SAE1在水稻耐盐性调控中的生理功能，并结合转录组、EMSA、酵母单杂交及ChIP-seq等分子生物学方法，解析SAE1调控水稻耐盐性的分子途径。通过本项目的实施，我们期望解析SAE1调控靶基因表达的分子遗传基础，诠释SAE1调控水稻耐盐性的途径，为水稻遗传改良提供理论指导和育种材料。

盐胁迫是限制作物稳产高产的重要因素，鉴定植物耐盐相关基因、剖析植物盐胁迫应答调控网络，有助于利用分子育种技术培育耐盐作物新品种。在本项目中，我们研究了转录因子OsSAE1通过转录抑制OsABI5的转录从而影响水稻发芽期和幼苗期耐盐性的分子机制，发现OsSAE1的表达受盐胁迫诱导，EMSA实验证实OsSAE1可以直接结合OsABI5启动子的GCC盒，瞬时表达实验表明OsSAE1因为其EAR基序而具有转录抑制活性，可以抑制OsABI5启动子的转录活性。对sae1突变体及SAE1过表达水稻株系的转录组分析发现OsSAE1下调ABI5等基因的转录。在sae1、abi5突变体及SAE1过表达水稻株系对外源ABA敏感性和耐盐性分析中发现，SAE1负调控水稻对外源ABA的敏感性、正调控耐盐性，ABI5正调控水稻对外源ABA的敏感性、负调控耐盐性。以上结果表明，盐胁迫应答中，SAE1表达增加，抑制ABI5的表达，从而引起下游胁迫应答相关基因的表达改变，提高水稻的耐盐性。SAE1-ABI5调控水稻盐胁迫应答途径可以作为水稻耐盐育种的改良靶点。