蛋白OsRac1的单泛素化修饰对水稻免疫反应的调控作用

小GTP酶OsRac1是重要的免疫调控因子，但并不清楚单泛素化修饰是否参与其免疫活性调节。申请人前期发现AAA型ATP酶LRD6-6调控多囊泡体（Multivesicular body，MVB）介导的胞内运输并抑制水稻免疫反应；在免疫反应自激活的广谱抗病突变体lrd6-6中，蛋白OsRac1的单泛素化增强，OsRac1大量积累。由于单泛素化是MVB途径识别和转运蛋白底物的关键信号，因此推测OsRac1的单泛素化与LRD6-6介导的免疫反应有关。在此基础上，本项目拟开展如下研究：1）检测单泛素化修饰是否调控MVB介导的OsRac1转运；2）分析OsRac1的单泛素化修饰与免疫反应的关系；3）解析MVB介导的OsRac1单泛素化蛋白转运对免疫反应的调控机理。通过上述研究，揭示OsRac1的单泛素化修饰对水稻免疫反应的调控作用，丰富水稻免疫机理，为培育具有广谱抗性的农作物新品种提供新的理论指导。

The small GTPase OsRac1 is an important immunity regulator. However, little is known about how mono-ubiquitination regulates its immune activity. Previously, we identified an AAA type ATPase LRD6-6 which regulates the multivesicular body (MVB) trafficking pathway and inhibits rice immune response. The lrd6-6 mutant in loss of LRD6-6 ATPase activity displays autoimmunity and confers to broad-spectrum disease resistance to diverse pathogens. We find that OsRac1 is mono-ubiquitinated and the ubiquitinated OsRac1 accumulates in lrd6-6. Since mono-ubiquitination is a key signal for MVB transportation of cargos, we presume that the accumulation of mono-ubiquitinated OsRac1 may regulate LRD6-6 mediated immunity. To test this hypothesis, we will conduct the following studies: 1) to test whether mono-ubiquitination of OsRac1 is required for its MVB mediated transportation; 2) to determine the relationship between OsRac1’s mono-ubiquitination and immune response; 3) to uncover the mechanism of MVB mediated transportation of mono-ubiquitinated OsRac1 on rice immunity regulation. These studies will enrich the mechanism of broad-spectrum disease resistance and provide new theoretical guidance for breeding of broad-spectrum resistant rice varieties.