蛹虫草线粒体DNA的遗传多样性与线粒体遗传规律的研究

Mitochondrial DNA (mtDNA) as a genetic element independent of nuclear DNA, has been widely used in evolutionary biology thanks to its higher evolution rate than nuclear DNA. While maternal mitochondrial inheritance is the dominant pattern in animals, various mitochondrial inheritance patterns were reported among closely related species, or even different strains of the same species in the fungal world. Cordyceps militaris has a worldwide distribution and is an economically and medicinally important fungus, but its mtDNA genetic diversity and mitochondrial inheritance pattern are largely unknown. We have collected more than 70 C. militaris isolates from multiple countries. In this application, we plan to assemble mitochondrial genomes of 100 representative C. militaris isolates in order to reveal its mtDNA genetic diversity. We will also compare nucleotide variations between mtDNA and nuclear DNA, and investigate whether mtDNA and nuclear DNA reveal similar phylogenetic relationships among different C. militaris isolates. By examining mt genotypes (with intron distribution patterns as markers) of enormous progeny resulting from sexual crosses of parental isolate pairs with different mating types and different mt genotypes, we will determine the mitochondrial inheritance mechanism of C. militaris. Implementation of this project will not only reveal the mtDNA genetic diversity and mitochondrial inheritance mechanism in C. militaris, but also provide theoretical reference to protection of germplasm resources of C. militaris, and develop the fungus as am important model to study fungal mitochondrial inheritance.

线粒体DNA作为独立于细胞核外的遗传因子，具有较快的进化速率，已广泛用于进化生物学研究。动物线粒体一般遵循严格的母系遗传，但近缘真菌物种间甚至同一真菌的不同菌株都可能具有不同的线粒体遗传模式。蛹虫草在世界上广泛分布，是一种经济价值较高的食药用真菌，但其线粒体DNA的遗传多样性及遗传规律尚未明了。我们前期已收集了70余株来自多个国家的蛹虫草菌株。本项申请拟在继续收集蛹虫草菌株的基础上，通过测定100个代表性菌株的线粒体基因组揭示蛹虫草线粒体DNA的遗传多样性；比较线粒体DNA和细胞核DNA的变异水平及所揭示的不同蛹虫草菌株间的系统发育关系；以线粒体内含子分布模式为标记分析蛹虫草有性杂交后代的线粒体基因型，明确蛹虫草的线粒体遗传规律。本项目的开展不仅能够揭示蛹虫草线粒体DNA的遗传多样性和遗传规律，而且可以为蛹虫草种质资源保护提供理论依据，并有望将蛹虫草发展成研究丝状真菌线粒体遗传的重要模型。

蛹虫草在世界上广泛分布，是一种经济价值较高的食药用真菌，但其线粒体DNA的遗传多样性及遗传规律尚未明了。本项目围绕蛹虫草mtDNA的遗传多样性和线粒体遗传规律开展研究，取得如下重要研究进展：.通过对广泛采集的108个蛹虫草菌株测定完整线粒体基因组序列并进行比较分析，发现不同菌株的线粒体基因组差异较大（26-40 kb），但线粒体基因组常见基因的基因含量和排列顺序却非常保守，基因组共线性关系也很好。造成不同线粒体基因组大小差异的原因主要是内含子数目的不同和基因间区长短不一。.从这些蛹虫草菌株中获得23个细胞核DNA片段的序列（总长度达28.3 kb）。比较细胞核DNA和mtDNA的变异水平，发现蛹虫草的线粒体DNA进化速率相比核DNA进化速率慢（SNP频率2.52% vs. 5.20%）。通过构建系统发育树揭示不同菌株间的系统发育关系，发现线粒体DNA和核DNA反映的不同蛹虫草菌株间的系统发育关系虽然并不完全一致，但大部分菌株的聚类关系是相似的。.通过分析不同线粒体基因型的双亲杂交产生的大量有性后代的线粒体基因型，发现蛹虫草同时具有单亲遗传和双亲遗传。多数杂交组合子代线粒体基因是遗传自交配型MAT1-2的亲本菌株，但也有的杂交组合是遗传自交配型MAT1-1的亲本菌株。.本项目不仅揭示了蛹虫草线粒体DNA的遗传多样性和遗传规律，而且为蛹虫草种质资源保护提供了理论依据。项目共发表SCI论文3篇，中文核心期刊4篇，获省级二等奖1项。培养博士研究生1人，硕士研究生5人。

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