球孢白僵菌致死宿主后合成卵孢素拮抗细菌的调节机制研究

一些昆虫病原真菌的次生代谢物具杀虫、抑菌活性，在真菌-宿主-环境微生物相互作用过程中发挥了重要作用。在上一个基金资助下，课题组发现球孢白僵菌合成的卵孢素在抑制死亡虫体上细菌生长、保障真菌完成产孢过程中具有关键作用，但其诱导因子及调节机制尚不清楚。我们发现，锌指蛋白Bbsmr1通过负调节卵孢素基因簇中转录因子OpS3的表达来调控卵孢素合成，但该蛋白并不与OpS3启动子直接作用。OpS3启动子中具有酸碱响应子PacC和逆境调控蛋白Msn2结合位点，是否二者与Bbsmr1共同参与了卵孢素的调节或存在其它调控蛋白？本研究将围绕球孢白僵菌在死亡虫体上合成卵孢素的调节机制展开研究，寻找其理化诱导因子并进一步发掘卵孢素合成调节子，同时分析PacC、Msn2或其它调控蛋白与Bbsmr1及卵孢素合成的关系，构建球孢白僵菌合成卵孢素的调控网络，深入了解死亡虫体上真菌与细菌的相互作用，促进真菌杀虫剂的应用推广。

Some secondary metabolites produced by entomopathogenic fungi played important roles during the interactions among fungi, host and environmental microorganisms. Under the support of last NSFC grant, we have found the entomopathogenic fungus Beauveria bassiana produces secondary metabolite oosporein to outcompete bacterial challenges for assimilation of host nutrients after host death, however, its inducer(s) and full regulatory mechanism kept unclear. A zinc finger protein Bbsmr1 regulated oosporein production by negatively regulated the expression of a positive regulator OpS3 of the oosporein biosynthesis gene cluster. But no direct binding of Bbsmr1 to OpS3 promoter was observed by EMSA analysis, indicating there is (are) other regulator(s) involved in the regulatory network of oosporein synthesis. The binding sites for regulatory proteins PacC and Msn2 which regulate general stress responses in fungi were found in the promoter region of OpS3. To understand the regulatory network of oosporein synthesis, we plan to analyze the inducers of oosporein synthesis and explore regulators. Furthermore, the regulatory cascade on oosporein production, including Bbsmr1, PacC, Msn2 and other regulators, will also be analyzed. These studies will help us to understand the regulatory network of oosporein synthesis and the interaction between entomopathogenic fungi and bacteria in cadavers, and will accelerate the development of fungal insecticides.