拟南芥自噬调控ACBP1-ERF VII复合体稳态参与低氧响应的分子机理

Submergence-induced hypoxia is one of the most important abiotic stresses that affect the growth of plants. The physiological and biochemical regulation mechanism of plants in response to hypoxia stress remains to be further investigated. Studies have discovered that the E3 ligase SINAT1 and SINAT2 regulate the dynamic of autophagy by modulating the stability of ATG6 protein, and autophagy functioned in the hypoxia response in Arabidopsis by modulating SA-mediated cellular homeostasis. Preliminary data further showed that the transcription factors in ethylene signal including RAP2.12, RAP2.3 and HRE1 translocated to the puncta structure under hypoxia stress, and the stability of the transcription factors was related with autophagy and 26S proteasome pathway. Protein interaction assay showed that ATG8e and SINATs protein interact with RAP2.12 and ACBP1 respectively. Phenotype analysis showed that sinat1sinat2 double mutants diaplayed enhanced tolerance to hypoxia, while sinat6 mutant showed hypersensitivity. These results indicate that Arabidopsis SINATs protein may function as a key regulator in modulating RAP2.12 and ACBP1 stabitity in plant response to hypoxia. By genetic and biochemical approaches, we further intend to elucidate the mechanism of how autophagy and SINATs mediates the stability of RAP2.12 and ACBP1 to regulate hypoxia response in Arabidopsis.

水淹导致的低氧胁迫是影响植物生长最重要的非生物因素之一，植物响应低氧胁迫的分子与生理生化机制还不甚清楚。研究表明拟南芥E3泛素连接酶SINATs蛋白通过调节ATG6蛋白的稳定性调控自噬的动态平衡，而细胞自噬通过调控ROS的含量参与植物响应低氧胁迫。申请人近期研究发现，乙烯信号途径的转录因子包括RAP2.12，RAP2.3和HRE1在低氧条件下的亚细胞定位是点状结构，RAP2.12和ACBP1蛋白的稳定性与自噬途径和26S蛋白酶体途径相关。蛋白互作实验发现，自噬相关蛋白ATG8e和SINATs与RAP2.12和ACBP1蛋白相互作用。表型分析显示，sinat1sinat2双突变体对低氧胁迫表现出增强的耐受性，而sinat6突变体则异常敏感，说明SINATs蛋白是植物响应低氧胁迫的关键调控因子。本项目拟通过遗传学与生物化学手段，深入解析自噬途径和SINATs蛋白调控植物应答低氧胁迫的分子机理。

水淹导致的低氧胁迫给农作物的生长造成极大影响，在世界范围内造成粮食减产，严重威胁粮食安全。研究表明，低氧响应转录因子因ERF-VIIs的蛋白稳定性与E3泛素连接酶SINAT1/2密切相关，但其分子机制尚不清楚。本研究通过生理生化和遗传学手段，揭示了E3泛素连接酶SINATs在植物响应低氧胁迫中的功能及其作用机理。蛋白稳定性分析发现，ERF-VIIs蛋白在低氧条件下升高，在低氧后的恢复条件下降低，并且ERF-VIIs蛋白在低氧及复氧条件下的稳定性受26S蛋白酶体途径调控。蛋白互作及稳定性分析表明SINAT3通过与HRE1在体内和体外相互作用介导HRE1的泛素化降解。进一步研究发现，SINAT3在正常条件及低氧后的复氧条件下定位在细胞核，在低氧条件下转移至细胞质。遗传学分析表明，sinat12双突变体和sinat1234四突变体对低氧胁迫的耐受性增强，低氧胁迫下游响应因子ADH1和PDC1的转录水平和蛋白稳定性在sinat12和sinat1234突变体中升高。以上结果说明，E3泛素连接酶SINATs蛋白通过泛素化降解ERF-VIIs转录因子HRE1，参与植物响应低氧胁迫。