杀虫真菌通过附着胞主动穿透昆虫体壁实现侵染，附着胞内膨压形成所依赖的高浓度甘油来源于脂滴的降解。杀虫真菌胞内脂滴积累与正常代谢是感染昆虫寄主的重要保障，然而脂滴的形态和分布是否影响绿僵菌对脂滴的利用，进而影响杀虫毒力仍然未知。申请人前期研究发现绿僵菌内质网膜蛋白seipin的功能缺失不仅导致脂滴大小不一，而且出现大量核内脂滴。本项目将构建seipin缺失和截短的突变体用于分析seipin蛋白不同区域对脂滴形态和分布的调控；通过透射电镜观察和标记不同的脂滴相关蛋白，分析seipin如何影响脂滴的核内外分布；检测seipin缺失菌株内脂类含量和脂滴降解水平，分析脂滴大小和分布是否影响绿僵菌对脂滴的利用；最后结合生物测定，阐释seipin蛋白如何调控脂滴生成进而影响绿僵菌的致病性。本项目的研究成果将为改造提高杀虫真菌的毒力以应用于农业害虫绿色防治提供理论支撑。

Entomopathogenic fungi infect insects via direct penetration of the host cuticle, the accumulation and metabolism of lipid droplets (LDs) are important guarantees for turgor pressure building up in the appressorium. However, it is still unknown that whether the morphology and distribution of LDs affect the utilization of LDs and virulence in Metarhizium. Our previous studies found that deletion of seipin, an endoplasmic reticulum membrane protein that regulate the size of LDs, results in aberrant LD size but also the formation of nuclear LDs in M. robertsii. In this project, we will use seipin deletion and truncated mutants to investigate the domain that regulate the morphology and distribution of LDs, study how seipin affects the distribution of nuclear and cytoplasmic LDs by transmission electron microscopy and labeling of LD proteins, detect lipid content and LD degradation to evaluate the utilization of LDs in Metarhizium, perform bioassays and elucidate the mechanism by which seipin regulates lipid droplet and insecticidal virulence. Results from this project will offer theoretical support for improving the virulence of insecticidal fungi used in ecological control of agricultural pests.