蜕皮液介导的昆虫体壁免疫机理研究

化学农药的使用给人类健康带来了危害，人们对无污染生物农药的使用日益重视，昆虫致病真菌白僵菌是一种具有潜力的生物农药，但是其主动逃避宿主免疫的能力制约了推广和应用。前期发表的结果表明在蜕皮期间的家蚕体壁（包括新旧表皮和蜕皮液）免疫可以有效防御球孢白僵菌感染，但其分子机制不清楚。预实验显示在蜕皮后蜕皮液若被水清洗，家蚕幼虫对白僵菌感染抵抗力下降，表明蜕皮液中存在抑制白僵菌侵染的因子。初步研究还发现蜕皮液多酚氧化酶等多种蛋白可以结合到白僵菌分生孢子上，纯化的多酚氧化酶结合到孢子后被激活，而白僵菌分生孢子又可以分泌未知蛋白酶来剪切游离的多酚氧化酶，和孢子结合的蜕皮液蛋白对白僵菌侵染的抑制功能有待于深入研究。本项目拟解析蜕皮液中抑制白僵菌侵染的因子，以期揭示眠期昆虫有效对抗真菌的分子机理。昆虫蜕皮液抑制因子有可能作为新型靶标，为害虫生物防治和益虫保护提供参考作用，具有重要的科学研究和应用价值。

The application of chemical pesticides brings damage to human health. Thus, people are paying much more attention to the non-pollution biological pesticides. The entomopathogenic fungi Beauveria bassiana is a type of bio-pesticide. However, the application of Beauveria bassiana is limited due to its capacity of evading the host innate immunity. Our previous published paper demonstrates that the silkworm Bombyx mori are very effective to fight against Beauveria bassiana infection in unknown mechanism during the molting stages. Preliminary experiments demonstrate that when the molting fluids were removed by washing after ecdysis, the insects show low resistance to Beauveria bassiana infection, which indicates that there are inhibition factors in the molting fluids. Further works show that prophenoloxidase and some other proteins in the molting fluids including purified prophenoloxidase can bind to the spores of Beauveria bassiana. To our surprise, prophenoloxidase was activated to show enzyme activity if it was bound to the spores. Very interestingly, proteinase was secreted by spores of Beauveria bassiana to degrade free prophenoloxidase in the solution. In this project, we work on the molecular mechanism of inhibition factors on Beauveria bassiana infection derived from the molting fluids, by which to disclose the special epidermis immunity response during ecdysis. In the future, these inhibition factors may be targets in the fields of pest biological control or economical insect production. We believe that this work is important due to the important scientific problems and potential agricultural application.