昆虫病原索科线虫是一类宝贵的昆虫天敌资源，在蔬菜、农林及卫生害虫生物防治方面具有很好的应用前景。该类线虫的性别决定较为特殊，寄生期的营养竞争压力决定其雌、雄性别分化(属环境决定型)，然而目前鲜见动物这一特殊性别决定机理的研究与报道。前期试验中，申请者筛选到索科线虫部分性别相关基因，分析发现与模式线虫C. elegans 的相差较大。据此，本项目拟选用两种索科线虫做比较研究，通过转录组测序和RACE 技术筛选其全部性别分化相关基因；利用Real-time PCR 分析这些基因在线虫发育中的时空表达模式；采用RNA干扰、Western blot 和免疫组化等确定线虫雌雄性别决定/特异基因的功能。初步探明索科线虫性别决定基因的分子调控网络和信号转导途径，进一步揭示营养决定线虫性别分化机制，并为实现大量体外培养生殖调控提供基础性资料。因此，本项目的开展不仅具有非常重要的理论意义，还有潜在的应用价值。

Mermithid nematodes are precious insect natural enemies and used to control the agricultural, forestry and medical pests. Their sex differentiation is environment-dependent sex determination (ESD) and influenced by the nutritional competitive pressure in parasitic period. So far, there is no detailed report about this special mechanism of sex differentiation in the animal kingdom. Therefore, in this study, we just focus on the molecular regulation mechanism, which will be of biological significance and practical value. The main contents of this study are: (1) to screen the sex determining genes of two species of mermithid nematodes (Ovomermis sinensis and Romanomermis wuchangemsis) by the methods such as, RNA-seq and RACE-PCR. (2) to detect the spatio-temporal expression patters of the specific genes of male and female with Real-time PCR. (3) to determine the function and regulatory network of the sex determining genes by RNAi, Western blot and Immunohistochemistry. After completing this study, the main regulation pathways for the sex determining genes of mermithidae can be made clear and the key regulation factors be finally confirmed. And then, a molecular regulation model can be further constructed for sex determination mechanism of mermithidae, and will also provide the theoretical basis and technical parameters for the controlling the sex ratio of male and female in vitro cultivation of the mermithid nematodes needed for field trials.