Complete sequence of the yak ( Bos grunniens) mitochondrial genome and its evolutionary relationship with other ruminants

The yak ( Bos grunniens) is the most important domesticated species in the Qinhai-Tibetan Plateau. In present study, the complete sequence of the yak mitochondrial genome was determined. Sequence analysis revealed that there are no differences with cattle in the yak mitochondrial genome organization. Interestingly, within the D-loop, the conserved sequence blocks are less conserved than surrounding regions. Neighbor-Joining (NJ) trees based on single genes, gene sets and concatenated genes of mitochondrial genome were constructed. The analysis identified the yak as a sister group of a cattle/zebu clade. Based on substitutions in 22 tRNA genes, 12S rRNA gene and 16S rRNA gene, the dating of divergence between yak and cattle/zebu, and yak and water buffalo, was proposed to have occurred 4.38–5.32 and 10.54–13.85 million years before present, respectively. This is consistent with the paleontologyical data. Yak and sheep/goat divergent dating predicts that their divergence occurred at 13.14–27.99 million years before the present day.