冬虫夏草寄主蝠蛾染菌机制的新研究

The infection mechanism that the cordyceps fungus parasitizes on Hepialus larvae still remains unrevealed. Based on our previous research, we speculated that the fungus might stay inside the insect early at the stage of fertilized-egg, furthermore, the co-effection of the fungi both in egg and the soil eventually cause the infection of larvae and the occurrence of Ophiocordyceps sinensis. This project intends to prove this hypothesis from a completely new prospect. Firstly, four sampling sites where the population density of Ophiocordyceps sinensis and Hepialus showed significant differences will be located, and soil and fertilized female moths at the sampling sites will be collected. Then, the fungus/bacteria diversity of the soil (outside environment) and the fertilized eggs (inside the environment) will be analyzed by 454 high-throughput sequencing. Finally, the relationship between the fungus/bacteria diversity (both internal and external environment) and the infection rate of Hepilaus are investigated by comprehensive analysis. Through the research, the parameters which can promote the infection rate can be established. Therefore, this project can elucidate the mechanism of infection and provide with an instruction for the improvement of the infection rate.

蝠蛾幼虫感染冬虫夏草菌的机制迄今仍是未解决的难题。根据前期研究基础，我们推测：蝠蛾昆虫早在受精卵期就与冬虫夏草菌接触，而受精卵和土壤中菌群的协同作用最终导致蝠蛾幼虫染菌并发生为冬虫夏草。本项目拟从全新的角度来证明这一推测：先采用野外科学考察，确定蝠蛾幼虫与冬虫夏草数量相差迥异的4个地段，然后运用先进的454高通量测序平台，对相应地段的土壤（外环境）和蝠蛾遗腹受精卵（内环境）中菌群结构的时空分布开展系统的研究。综合分析内、外环境中菌群结构与蝠蛾幼虫染菌率和冬虫夏草发生率之间的关系，获得能影响蝠蛾幼虫感染冬虫夏草菌的感染率参数，探讨冬虫夏草菌侵染蝠蛾幼虫的途径，为阐明蝠蛾幼虫感染冬虫夏草的机制提供重要理论依据，为大幅度提高蝠蛾幼虫感染率及冬虫夏草发生率提供技术支持。

蝠蛾幼虫感染冬虫夏草菌的机制迄今仍是未解决的难题。根据前期研究基础，我们推测：蝠蛾昆虫早在受精卵期就与冬虫夏草菌接触，而受精卵和土壤中菌群的协同作用最终导致蝠蛾幼虫染菌并发生为冬虫夏草。我们依据研究计划，在2014、2015、2016年5-8月间，采用野外科学考察，在西藏色季拉山虫草适生地选择了确定蝠蛾幼虫与冬虫夏草数量相差迥异的3个地段（A：虫多草多，B：虫多草少，C：虫多无草），并相应地段上采集了蝠蛾幼虫、受精的蝠蛾对、蝠蛾虫卵和土壤样本。在实验室内，首先运用基因文库和定量PCR的方法研究了冬虫夏草的菌核（即虫体）、子座和其包裹土壤中的微生物组成，发现这三类样品中存在大量的真菌和细菌，证实了冬虫夏草菌的多元性。然后运用illumila Hiseq测序平台，对比分析了A、B、C三地土壤、遗腹受精卵、初产卵中菌群结构，证实了这些样本中存在大量的微生物菌群，且微生物组成与冬虫夏草的发生密切相关。综合分析以上结果，在实验室内诱导蝠蛾幼虫自然发生成冬虫夏草，并推演了冬虫夏草菌侵染蝠蛾幼虫及发生的机制，也证实了“受精卵与土壤中的冬虫夏草菌的协同作用，促使了蝠蛾幼虫的染菌及冬虫夏草的发生”这一命题。这些研究结果为探讨冬虫夏草菌侵染蝠蛾幼虫的途径，为阐明蝠蛾幼虫感染冬虫夏草的机制提供重要理论依据，为大幅度提高蝠蛾幼虫感染率及冬虫夏草发生率提供技术支持。