致病杆菌中新型T3SS效应蛋白XopA在共生和致病中的功能研究

Ⅲ型分泌系统在多种G-细菌与宿主相互作用中扮演重要角色。通过异源表达来自发光杆菌的Ⅲ型分泌系统合成基因簇，课题组从致病杆菌中鉴定到一种新型T3SS效应蛋白——XopA，与副溶血弧菌中的III型效应蛋白VopA具有30.6%的相似性；XopA蛋白在致病杆菌中普遍存在，而与致病杆菌近源发光杆菌中均不存在。本项目拟研究XopA效应蛋白的细胞毒性、对细胞自噬的诱导作用、对MAPK和NF-κB信号通路的抑制作用；体内、体外研究鞭毛运输装置对XopA蛋白的分泌情况；研究XopA蛋白对共生菌与线虫共生行为、对昆虫致病能力的影响。本研究将阐明XopA蛋白的作用机制，掌握T3SS在细菌与宿主相互作用中的功能及作用机制，进一步揭示昆虫病原线虫共生菌与宿主相互作用的分子机制，为更好利用昆虫病原线虫共生菌进行生物防治提供理论依据；同时，本研究有望为T3SS分泌装置和鞭毛运输装置功能互补性、进化同源性提供证据。

The type III secretion system plays an important role in the interaction between various G-bacteria and host. Through heterologous expression of T3SS synthetic gene cluster from Photorhabdus luminescens, a new type of T3SS effector protein, XopA, which was 30.6% similar to the T3SS effector protein VopA in Vibrio parahaemolyticus, was identified from Xenorhabdus stockiae. XopA effector was commonly found in Xenorhabdus bacteria, but not in the Photorhabdus bacteria which was closely related to Xenorhabdus. This project aims to study the cytotoxicity of XopA effector, the induction of autophagy, the inhibition of MAPK and NF-κB signaling pathway. The secretion of XopA protein via flagellum transport device will be studied in vivo and in vitro. The effects of XopA protein on symbiotic behavior between symbiotic bacteria and nematodes and the pathogenicity against insects will then be evaluated. This study will clarify the mechanism of XopA protein, better grasp the function and mechanism of T3SS in the interaction between bacteria and host, further reveal the molecular mechanism of the interaction between entomopathogenic nematode symbiont and host, and provide theoretical basis for better use of entomopathogenic nematode symbiont for biological control. Meanwhile, this study is expected to provide evidence for the functional complementarity and evolutionary homology for T3SS secretion device and flagellum transport device.