真菌杀虫剂具有对环境友好和寄主难以产生抗性等优点，但它们所占市场份额较小，一个主要原因是昆虫病原真菌的杀虫速度慢。昆虫病原真菌致病过程主要分为穿透体壁和定植血腔两个阶段，杀死昆虫所需时间主要消耗在血腔定植阶段；因此，定植昆虫血腔时间的长短，是决定杀虫速度快慢的主要因素。为此，本项目以罗伯茨绿僵菌为材料，研究昆虫病原真菌定植昆虫血腔的机制。首先，利用正向遗传学（筛选突变体库）和反向遗传学（转录组分析）等手段，鉴定系列血腔定植基因：包括信号转导途径，转录因子和它们所调控的下游血腔定植基因。然后，研究下游血腔定植基因的功能和基因间的互作理。最后，研究信号转导途径和转录因子对下游血腔定植基因的调控机理。项目的完成，将阐明罗伯茨绿僵菌定植昆虫血腔的关键机理，为缩短昆虫病原真菌定植昆虫血腔的时间、提高真菌杀虫剂的杀虫速度提供理论支撑。

Mycoinsecticides are environmentally friendly alternatives to chemical insecticides in biocontrol programs for agricultural pests and vectors of disease. In addition, it is hard for insect pests to develop resistance to mycoinsecticides. However, mycoinsecticides currently have a small market share, mainly due to slow killing speed. Entomopathogenic fungi initiate infection via conidia that adhere to the insect cuticle and produce germ tubes that meander across the cuticle until they find a suitable site for penetration into the insect hemocoel. During hemocoel colonization, the fungi change from filament to blastospores, and the insect is killed by a combination of the proliferation of blastospores and the production of toxins. For many entomopathogenic fungi such as Metarhizium robertsii, penetration of the insect cuticle is quick, and most of time for the whole pathogenesis is spent on colonization of the hemocoel. The ability to colonize hemocoel largely determines the killing speed of the entomopathogenic fungi. Therefore, we propose to investigate the mechanisms for hemocoel colonization by entomopathogenic fungi using M. robertsii as a model. Firstly, a series of genes involved in hemocoel colonization will be identified by screening relevant mutants from a random T-DNA insertion library and a mutant library constructed by genome-wide target gene disruption, and by genome-wide profiling of gene expression during pathogenesis with RNA-seq. These genes encode components in signaling pathways, transcription factors or their downstream effectors. Secondly, molecular and biochemical analyses will be conducted to characterize the functions of key downstream effectors and their interactions. Finally, we will investigate how the signaling pathways and transcription factors regulate the downstream effectors. Completion of this project will provide advanced insights into mechanisms for hemocoel colonization by entomopathogenic fungi, which will facilitate improving killing speed of mycoinsecticides by reducing the time for hemocoel colonization using genetic engineering.