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

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.