Comparative analysis of the complete mitochondrial genomes of four
cordyceps fungi
Abstract
Cordyceps is a large group of entomogenous, medicinally important fungi.
In this study, we sequenced, assembled, and annotated the entire
mitochondrial genome of O. xuefengensis, in addition to comparing it
against three other complete cordyceps mitogenomes that were previously
published. Comparative analysis indicated that the four complete
mitogenomes are all composed of circular DNA molecules, although their
sizes significantly differ due to high variability in intron and
intergenic region sizes in the O. sinensis and O. xuefengensis
mitogenomes. All mitogenomes contain 14 conserved genes and two
ribosomal RNA genes, but varying numbers of tRNA introns. The Ka/Ks
ratios for all 14 PCGs and rps3 were all less than 1, indicating that
these genes have been subject to purifying selection. Phylogenetic
analysis was conducted using concatenated amino acid and nucleotide
sequences of the 14 PCGs and rps3 using two different methods (Maximum
Likelihood and Bayesian analysis), revealing highly supported
relationships between O. xuefengensis and other Ophiocordyceps species,
in addition to a close relationship with O. sinensis. Further, the
analyses indicated that cox1 and rps3 play important roles in population
differentiation. These mitogenomes will allow further study of the
population genetics, taxonomy, and evolutionary biology of medicinally
important cordyceps species.