组蛋白甲基化修饰调控寡孢节丛孢捕食器官形成的分子机制

Nematode-trapping fungi are important bio-control species which can effectively reduce nematode population in nature. The formation of trapping devices is an important indicator of their switch from the saprophytic to the predacious lifestyles and also key tools to capture nematodes. It is important to do researches on the molecular mechanisms of trapping formations, which may help us to understand the switching of its lifestyles from saprophytic to predacious, and also to develop high effective bio-control agents in the future. However, there are little studies related to the epigenetic modification mechanisms during trap formation. In our previous study, we found that five histone lysine methyltransfereses (HKMTs) in A. oligospora may be involved in the regulation of trap formation. In order to elucidate the regulation mechanism of histone modifications in A. oligospora, we plan to study the biological function of these five HKMTs and to identify and study the target genes regulated by HKMTs during trap formations. Our results will provide a basis for understanding the molecular mechanism of nematode-trapping fungi switching its lifestyles from saprophytic to predacious, for elucidating the mechanism of fungi pathogenicity and provide theoretical foundation for utilizing these fungi as potential bio-control agents.

捕食线虫真菌是重要的线虫生防菌，捕食器官既是捕食线虫真菌从腐生过渡到寄生的关键标志，也是其对线虫进行有效捕捉的重要工具。阐明捕食器官形成的分子机制对于了解食线虫真菌侵染线虫的分子机制和构建高效生防制剂具有十分重要的意义。然而，关于表观遗传修饰在捕食器官形成过程中的调控机制研究甚少。我们前期研究发现寡孢节丛孢中的5个含有SET结构域的组蛋白甲基化转移酶（HKMTs）可能参与调控捕食器官形成。本研究拟利用分子生物学手段和高通量测序技术，进一步诠释HKMTs在捕食器官形成过程中的生物学功能，对受到HKMTs调控的目标基因进行鉴定及功能研究，揭示组蛋白甲基化修饰对寡孢节丛孢捕食器官形成过程进行调控的分子机制，从表观遗传学角度揭示捕食线虫真菌通过产生捕食器官侵染线虫的分子机制，为理解真菌通过形态学改变完成侵染的致病机理奠定理论基础，也为开发高效的线虫生防制剂提供理论指导。

本项目完成了4个SET结构域HKMTs的基因（AoSet1，AoSUV39，AoSet2和AoSet7）的敲除，并进一步获得组蛋白H3上对应的四个甲基化位点（K4、K9、K27、K36）的点突变株。通过RNA-seq对∆AoSet1、∆AoSet7、∆AoSUV39和∆AoSet2敲除菌株及点突变菌株进行转录组高通量测序，Western blot分析基因敲除以及点突变后甲基化水平的变化，由此证实HKMTs在捕食器官形成过程中具有重要的功能。此外，结合RT-PCR以及ChIP-qPCR结果，发现在∆AoSet1及点突变菌株 AoH3K4A中，一个bZip转录因子AobZip129的表达量明显减少，提示介导H3K4me3 的组蛋白甲基化转移酶AoSET1能够调控AobZip129的表达。进一步对AobZip129进行敲除，发现该基因的敲除同样导致寡孢节丛孢产捕食器官的能力减少，且杀线虫活性减弱。由此可见，AoSet1通过介导H3K4me调控转录因子AobZip129的表达，从而影响捕食线虫真菌寡孢节丛孢捕食器官的形成，并进一步影响其杀线虫的能力。本研究从表观遗传学的角度探讨捕食器官形成的机制，为全面理解捕食线虫真菌通过产生捕食器官侵染线虫的分子机制奠定基础，也为高效生防制剂的开发提供理论指导。