病原真菌在侵染早期就被昆虫感应而启动免疫防御途径，而有关病原菌逃避早期免疫防御反应的机制，鲜有报道。Bbmpk1-Bbste12是介导昆虫病原真菌球孢白僵菌穿透昆虫体壁的关键途径，是探索病原菌穿透宿主体壁调控机制的重要线索。申请人在解析该途径调控的靶标基因时发现两个Bas2类小分子蛋白参与穿透体壁过程，干扰宿主免疫反应。该发现为探究病原菌逃避昆虫早期免疫防御反应提供了新线索。本项目拟结合异源表达的Bas2蛋白及获得遗传转化菌株，进一步明确Bas2蛋白在穿透体壁过程中与宿主免疫反应的关系，采用融合GFP标签和免疫组化，探究Bas2蛋白在侵染过程中在昆虫组织的分泌及分布特征，利用蛋白免疫共沉淀等蛋白互作及昆虫RNAi技术，分离鉴定Bas2蛋白的作用靶标并解析其作用机制。项目的开展不仅为揭示病原真菌逃避昆虫早期免疫防御反应提供新的理论依据，而且研究结果将可能为改良和提升真菌生防效果提供理论支撑。

Insect senses fungal pathogens during/at the early stage of infection and initiates immune defense pathway. However, little is known that the fungal pathogens evade the immune response of the host before or during penetration of cuticle. Bbmpk1-Bbste12 has been found to be a crucial pathway that control penetration of cuticle in the insect fungal pathogen Beauveria bassiana. Two Bas2-like small molecule proteins Bas2a/b were identified as the targets of Bbste12 and involved in cuticle penetration via interfering with host immune response, which provides an important clue to explore the mechanism of the fungus to evade immune response during penetration of cuticle. In this project, we would further clarify effects of the two Bas2-like proteins on evasion of immune response during penetration of cuticle using the yeast-expressed proteins and constructed genetically modified strains (gene disruption/overexpression). Furthermore, distribution of GFP-tagged Bas2a/b during cuticle penetration are monitored using immunohistochemistry method. And then, the target proteins of Bas2a/b in the insect cells would be identified using protein-protein interaction methods of protein immunoprecipitation, yeast-two hybrid and pull-down methods and insect RNAi technology, to elucidate mechanism of immune evasion would be further revealed. The goals of the project are to expand our understanding of evasion of immune response during penetration in fungal pathogens. Moreover, we hope to provide a theoretical basis for the improvement of fungal agents using genetic engineering.