蝙蝠蛾鳞翅虫草Samsoniella hepiali模式菌株线粒体基因组系统发育分析

蝙蝠蛾鳞翅虫草Samsoniella hepiali是重要的药用虫生真菌,根据现代分类系统,隶属于虫草科Cordycipitaceae鳞翅虫草属Samsoniella。本研究对蝙蝠蛾鳞翅虫草模式菌株(ICMM 82-2)线粒体基因组进行测序、组装和注释,发现其线粒体基因组成闭合环状,大小为24 246 bp。基因区域占比为85.10%,共编码42个基因,包括15个蛋白质编码基因(PCGs)、2个rRNA基因和25个tRNA基因。15个PCGs均以ATG为起始密码子,以TAA为终止密码子,偏好密码子为UUA。各氨基酸使用频率具有较大差异,其中亮氨酸(Leu)出现频率最高。25个tRNA基因可转运全部20种氨基酸,其中19个tRNA基因二级结构为三叶草结构。本研究基于线粒体基因组中14个PCGs基因串联数据集,构建肉座菌目6科50个物种的系统发育树,进一步证实蝙蝠蛾鳞翅虫草模式菌株系统发育位置隶属于肉座菌目Hypocreales虫草科Cordycipitaceae鳞翅虫草属Samsoniella。通过虫草科线粒体基因组共线性分析,发现其中12个物种有5个同源区,3个物种存在6个同源区,同源区域A和B长度变异较大。与其他虫草科物种相比,蝙蝠蛾鳞翅虫草线粒体基因组较小,同源区域相对较短。蝙蝠蛾鳞翅虫草模式菌株线粒体基因组信息有助于鉴别其物种特异性,确定其系统发育关系,将为虫草系统发育研究提供新思路,为继续研究鳞翅虫草属物种药用价值提供系统发育依据。

Phylogenetic analysis of the mitochondrial genome of the Samsoniella hepiali holotype strain

Samsoniella hepiali is an incredibly valuable medicinal entomogenous fungus, belonging to Samsoniella of Cordycipitaceae. The mitochondrial genome of S. hepiali holotype strain ICMM 82-2 was sequenced, assembled, and annotated. It was found that the mitochondrial genome was a circular DNA molecule with 24 246 bp in length. The gene regions accounted for 85.10%, encoded 42 genes, containing 15 PCGs, 2 rRNA and 25 tRNAs. ATG was the start codon, and TAA was the end codon of 15 PCGs. The preferred codon was UUA. There were significant differences in the frequencies of amino acids in the PCGs, and Leu had the highest frequency. The 25 tRNAs coded for all 20 amino acids, and 19 tRNA genes adopted a typical cloverleaf structure. The 14 concatenated mitochondrial PCG genes’ phylogenetic trees consisting of 50 species of 6 families in Hypocreales were built for studying the systematic position of S. hepiali holotype strain. The results showed that S. hepiali holotype strain belonged to Samsoniella of Cordycipitaceae in Hypocreales. Collinearity analysis of the mitochondrial genome of Cordycipitaceae showed that the number of homologous regions in 12 species was five and that of the other 3 species was six, and the length of homologous regions A and B was different. Compared with the other species, S. hepiali mitochondrial genome has smaller and shorter homologous regions. Based on analyzing the mitochondrial genome of S. hepiali holotype strain, this study once again confirmed the phylogenetic position of S. hepiali, providing important data of phylogeny for the future studies of Samsoniella with medicinal value.