Comparative analysis of the mitochondrial genomes in Drosophila virilis species group (Diptera: Drosophilidae)

Abstract

We present comparative analysis of mitogenomics data of the Drosophila virilis group based on newly obtained complete mt-genome sequence of Drosophila littoralis, previously published mt-genome sequence of D. virilis and fragments of mt-genomes of other Drosophila species belonging to the virilis group. Drosophila of the virilis group shared most recent common ancestry 40 MYA with D. melanogaster. Therefore, presented data help to overview the evolution of the genus. The mt-genome of D. littoralis is a circular molecule of 16,017 bp with a total A+T content of 76.2%. The gene order is consistent with other Drosophila genomes. All tRNAs can be folded in the form of a typical clover-leaf structure except for tRNASer(AGN). In the control region of D. littoralis we found four conserved sequence elements: 275 bp highly conserved sequence element, two thymidylate stretches and a G-island. The most variable genes in Drosophila of the virilis group are nad6, nad3 and nad4L. The most conservative is cox1. We revealed long intergenic sequences’ (TA)n separating atp6 and cox3 genes in the mitochondrial genomes of Drosophila of the virilis group. In other insect species these genes have no or few separating nucleotides. We detected fragments of mitochondrial genes atp6 and cox3 in the nuclear genome of D. virilis. These mitochondrial pseudogenes are marked by site-specific insertions of Tv1 retrotransposon in the (TA)n intergenic spacer sequences.