冬虫夏草菌与寄主蝠蛾的遗传分化及对菌侵染性的影响

Cordyceps, a well-known traditional Chinese medicine endemic to Qinghai-Tibet Plateau, is the complex of the Hepialidae larva parasitized by the fungus Ophiocordyceps sinensis (Berk.). The distribution areas of O. sinensis are very special, and its natural production is extremely limited. Overexploitation driven by its high commercial value and habitat degradation has endangered the species in recent years. The objective of this study is to reveal the genetic differentiation of O. sinensis and host insects and the effect on fungal infectivity for promoting its artificial cultivation, conservation and sustainable development. Based on the achievement of research group, genetic differentiation of the fungus and its host insects from different populations will be further investigated by at the genome level. By investigating species and composition of host insects and constructing their phylogenetic relationships, the pattern and cause of genetic differentiation will be revealed, and also formation and evolutionary mechanism could be speculated. The effect of their genetic difference on fungal infectivity at the genome level will be analyzed, and try to verify the probable model of random or specificity to infect the host insects by the fungus. According to the analyses of relationship between fungus and insects, coevolutionary mechanism(s) between the fungus and its host insects will be discussed. The possible reasons for these species existing and becoming endangered will be inferred, which are fundamentally important for developing related conservation and utilization strategies.

冬虫夏草为我国青藏高原特有的传统名贵中药，是由冬虫夏草菌和寄主蝠蛾所形成的菌虫复合体。冬虫夏草分布区域特定，产量有限，加上生态环境的破坏和长期过度采挖，其自然种群已濒临枯竭。为促进冬虫夏草资源的培育、保护及可持续利用，本项目开展冬虫夏草菌与寄主蝠蛾的遗传分化及对菌侵染性影响的研究。在项目组已有研究基础上，通过基因组重测序，在基因组水平进一步明晰冬虫夏草菌种群的遗传分化。探讨我国冬虫夏草寄主蝠蛾的种类及构成，构建其系统发育关系，揭示冬虫夏草寄主蝠蛾遗传分化格局及成因，推测冬虫夏草寄主蝠蛾物种形成及演化机制。分析冬虫夏草菌和寄主蝠蛾在基因组水平上的遗传差异对冬虫夏草菌侵染性的影响，验证冬虫夏草菌可能存在随机性亦或专一性侵染寄主的模式。分析菌、虫两个类群的相互关系，探讨冬虫夏草菌与其寄主蝠蛾间的协同进化机制；推测冬虫夏草的形成历史及濒危的可能原因，提出相应的保护和利用策略。

冬虫夏草是由线虫草科冬虫夏草菌侵染蝙蝠蛾科昆虫幼虫形成的菌虫复合体，为我国青藏高原特有的传统名贵中药。本研究在冬虫夏草居群水平上探讨冬虫夏草菌与寄主蝠蛾的遗传分化及对菌侵染寄主蝠蛾的影响。结果表明冬虫夏草居群水平上冬虫夏草菌和其寄主蝠蛾均存在显著的遗传分化，呈现广泛分布和区域分布两种不同分布模式，主要共享单倍型广泛分布在整个冬虫夏草主产区，而独享单倍型仅分布在西藏林芝和青藏高原的边缘区域。与真菌侵染及致病性密切相关的冬虫夏草菌NADPH-细胞色素P450还原酶基因共享单倍型和独特单倍型基因在序列上存在变异。生物信息学分析表明这些序列差异导致其编码蛋白产生理化性质、磷酸化位点、模体和结构域等变化，进而可能影响冬虫夏草菌的侵染性。基于冬虫夏草个体菌、虫一一对应关系，推测广泛分布的共享单倍型冬虫夏草菌可能通过口腔进食的方式随机侵染大多数寄主蝠蛾，而独享单倍型的冬虫夏草菌仅能通过表皮特异性侵染少数特定单倍型的寄主蝠蛾。寄主蝠蛾在其形成冬虫夏草前后线粒体COI、COII和Cytb基因序列存在差异，某种 Cytb 基因偏向型寄主蝠蛾更易被冬虫夏草菌侵染形成冬虫夏草，而变异最小的COII基因可为冬虫夏草寄主蝠蛾物种鉴定的可靠分子标记。不同冬虫夏草居群的冬虫夏草菌和寄主蝠蛾的系统发育关系存在一致性，两者的遗传距离也呈极显著相关，存在协同进化关系。除了西藏林芝和青藏高原的边缘区域的冬虫夏草资源之外，环青海湖区域的冬虫夏草及其寄主的起源较早也需重点保护。本研究结果为青藏高原的虫生真菌冬虫夏草与其寄主的系统发育和侵染模式提供扎实的基础，并有助于促进冬虫夏草和其寄主的人工培育、保护和可持续利用。