蛹虫草线粒体DNA与细胞核DNA进化关系的比较

Comparison of evolutionary relationships between mitochondrial and nuclear DNAs in Cordyceps militaris

摘要:

[目的] 分析蛹虫草是否存在核内线粒体DNA片段，比较蛹虫草线粒体DNA与细胞核DNA的碱基变异程度及所反映的菌株间的系统发育关系。[方法] 通过本地BLAST或LAST对蛹虫草线粒体基因组和核基因组进行序列相似性搜索；从10个已知线粒体基因组的蛹虫草菌株中分别扩增7个细胞核蛋白编码基因片段，并与其在14个线粒体蛋白编码基因上的碱基变异情况进行比较。[结果] 蛹虫草核基因组中存在5处较短的核内线粒体DNA片段，总长只有278 bp。蛹虫草核DNA的变异频率整体上高于线粒体DNA。核DNA和线粒体DNA所反映的蛹虫草菌株间的系统发育关系存在显著差异。[结论] 蛹虫草线粒体DNA与核DNA间不存在长片段的基因交流，二者变异频率不同，所反映的蛹虫草菌株间的系统发育关系也有差异。本研究增加了对蛹虫草线粒体与细胞核DNA进化关系的认识。

Abstract:

[Objective] To detect possible nuclear mitochondrial DNA segments (Numts) within nuclear genomes of Cordyceps militaris and to compare the degree of nucleotide variations and phylogenetic relationships between mitochondrial and nuclear DNAs by employing multiple C. militaris isolates.[Methods] Nuclear genomes of C. militaris were searched for sequence similarities by local BLAST/LAST analyses with its mitochondrial genome as the query. Seven nuclear protein-coding gene fragments were amplified from 10 C. militaris isolates that had available mitochondrial genomes. Nucleotide variations at seven nuclear fragments were compared with those at 14 mitochondrial protein-coding genes. [Results] Five short Numts with a total length of 278 bp were identified in the nuclear genomes of C. militaris. The overall nucleotide variabilities of C. militaris on nuclear fragments were generally higher than that on mitochondrial fragments. The phylogenetic relationships among different C. militaris isolates revealed by nuclear and mitochondrial DNAs were significantly different. [Conclusion] There was no detectable gene transfer of long fragments between mitochondrial and nuclear genomes of C. militaris. The nucleotide variabilities of mitochondrial and nuclear DNAs were different, and the phylogenetic relationships of different C. militaris isolates revealed by them were different either. This study enhanced our understanding of the evolutionary relationship between mitochondrial and nuclear DNAs in C. militaris.