氮调控捕食线虫真菌生活史转变的分子机制

Nematode-trapping fungi play important roles in the bio-control of nematode population in the environment. These fungi are capable of developing specific trapping devices to capture and kill nematode prey. Many studies have discovered that traps can be induced in the responsiveness to signals from the environment, including nematodes, nematode extracts, amino acids, small peptides, and ascarosides, etc.. However, the detailed molecular mechanism of trap formation remains unknown. Based on our precious studies, urea, released by bacteria, could trigger a lifestyle switch in the nematode-trapping fungi with the formation adhesive nets, constricting rings, adhesive knobs and adhesive branches. Furthermore, the urea metabolite ammonia functions as a downstream signal molecule to initiate the formation of trapping devices. This project will be worked on the molecular mechanism of adhesive nets in Arthrobotrys oligospora induced by ammonia. Comparative transcriptome method will be used to analyze the differential mycelia genes in Arthrobotrys oligospora, which treated by ammonia at different time. And then, we will study the key differentially expressed genes through bioinformatics analysis and qPCR. Using the techniques of gene-knockout, over-expression, reverse-mutation, as well as yeast two-hybrid system, the function of the key genes related to adhesive net formation will be identified. The project will be a preliminary elucidated the molecular mechanism of adhesive net formation in Arthrobotrys oligospora. So, the results will lay important foundation for understanding the regulatory mechanism of nitrogen-inducing lifestyle switch in nematode-trapping fungi, and will facilitate the genetic improvement of Arthrobotrys oligospora and other nematode-trapping fungi. Moreover, it can provide new solutions for the biological control of nematode population.

捕食线虫真菌是自然界控制线虫种群数量的主要生物因子，捕食器官（捕器）是其捕杀线虫的工具，也是真菌从腐生转变为寄生的典型标志。国内外研究报道线虫及提取液、氨基酸、小肽和蛔苷等可以诱导捕器产生，但对其分子水平诱导机制仍知之甚少。申请人前期研究发现细菌分泌的尿素及其产物-氨能诱导捕食线虫真菌产生粘性网、收缩环、粘球、粘性分枝等捕器，提示氨可能在捕器形成中发挥重要作用。本课题以少孢节丛孢为研究对象，通过转录组技术和Real time PCR技术比较在氨诱导和非诱导条件下基因表达的差异，确定参与捕器形成的候选基因；通过基因敲除、过表达、回复突变和酵母杂交等方法鉴定候选基因的功能，阐明参与氨调控少孢节丛孢捕器形态建成的关键基因及相关信号途径。最终从分子水平揭示氮调控捕食线虫真菌捕器形成的分子机制，为捕食线虫真菌遗传改良和挖掘线虫生防高效菌剂奠定基础。

捕食线虫真菌是自然界控制线虫种群数量的主要生物因子，捕食器官（捕器）是其捕杀线虫的工具，也是真菌从腐生转变为寄生的典型标志。国内外研究报道线虫及提取液、氨基酸、小肽和蛔苷等可以诱导捕器产生，但对其分子水平诱导机制仍知之甚少。前期研究发现细菌分泌的尿素及其产物-氨能诱导捕食线虫真菌产生粘性网、收缩环、粘球、粘性分枝等捕器，提示氨可能在捕器形成中发挥重要作用。该课题以少孢节丛孢为研究对象，以少孢节丛孢（A. oligospora）为研究对象，氨作为诱导因子，利用组学分析、qRT-PCR、基因敲除以及酵母双杂交等手段，首次证实了“Torc1-Npr1-Art-Rsp5”、ESCRT以及去泛素化酶DUBs调控的胞吞通路参与了捕食线虫真菌捕器形成，并发现胞吞和细胞膜破裂再修复参与捕器形成。最终从分子水平揭示氮调控捕食线虫真菌捕器形成的分子机制，为捕食线虫真菌遗传改良和挖掘线虫生防高效菌剂奠定基础。