拟南芥E3泛素连接酶FIT3调控植物天然免疫信号转导的分子机理研究

Plants heavily depend on innate immunity to protect themselves from infection. After the identification of pathogen, plant cell produces the immune response immediately. Post-translational modifications play an important role in the process of such rapid reaction. Ubiquitination-26S proteasome system is the key post-translational modification in plant innate immunity. In our previous work, We screened a E3 ubiquitin ligase gene, FIT3(flg22 induced E three ubiquitin-ligase 3), which responsed to bacterial flagellum protein flg22. FIT3 The expression and self ubiquitin level of FIT3 have rised significantly after the treatment of flg22. FIT3 overexpression plants appeared obvious growth inhibition after flg22 treatment, and ROS production amount higher than the wild type, the resistance of Pst DC3000 was also significantly enhanced. All the evidence indicated FIT3 play positive role in plant innate immunity. Our final goal is to uncover the function of FIT3 in regulating of plant innate immunity signaling pathway. It is not only let us better understand the mechanism of plant disease resistance response but also provides important theoretical value and realistic meaning in cultivating disease-resistant varieties.

植物主要通过天然免疫系统抵御病原菌的侵害。植物细胞识别病原菌后会迅速产生免疫反应，在免疫信号迅速传递过程中蛋白的翻译后修饰起重要作用。泛素-26S蛋白酶体系统是植物天然免疫中最为关键的翻译后修饰形式。前期工作中，我们筛选到一个响应细菌鞭毛蛋白flg22的拟南芥E3泛素连接酶FIT3(flg22 induced E three ubiquitin ligase 3)。flg22处理之后FIT3表达量和自我泛素化程度显著上升，FIT3超表达拟南芥植株在外施flg22后发生明显的生长抑制，ROS产生量比野生型升高，对Pst.DC3000菌的抗性也显著增强，说明FIT3参与植物天然免疫信号通路并起正调控作用。对FIT3参与植物天然免疫的作用机理进行深入的研究，不仅能完善植物与病原菌互做网络，更好地理解植物抗病应答机理，同时也为有效利用相关基因资源培育抗病植物品种提供重要的理论和指导。

植物主要依赖其天然免疫系统抵御病原微生物的入侵。当植物被病原微生物侵染时，包括免疫受体在内的一系列免疫信号通路组分进行磷酸化接力，从而激活天然免疫，产生免疫反应。而与此同时，植物又利用一些免疫抑制因子，如钙离子依赖的蛋白激酶CPK28等，对天然免疫信号进行严格控制，以防止过度免疫反应对细胞本身照成伤害。然而，人们对免疫激活过程中免疫抑制因子是否会被清除以及其背后的分子机制仍知之甚少。 . 本研究发现植物天然免疫负调控因子CPK28能够通过26S蛋白酶体被降解；而且，CPK28的降解在植物被细菌鞭毛蛋白处理后明显增强。进一步的研究发现，两个E3泛素连接酶ATL31和ATL6能够与CPK28相互作用；而细菌鞭毛蛋白的处理进一步促进了他们的互作。ATL31和ATL6直接介导CPK28的泛素化，导致CPK28通过26S蛋白酶体被降解，从而解除或减弱了其对免疫信号的抑制作用，使植物天然免疫反应得到增强。