Characterization of cetacean Numt and its application into cetacean phylogeny

The translocations of mitochondrial DNA into chromosomal DNA (nuclear mitochondrial DNA, Numt) are ubiquitous in eukaryotes including yeasts, plants, and animals. The features of Numt and the recent sequencing technology can facilitate an expanded application of Numt into a valuable phylogenetic marker for unresolved taxa. To date, the phylogeny of extant cetaceans has been studied by a variety of morphological and molecular data and still has long attracted attention. Here, the Numts of cattle, two baleen whale and four toothed whales were detected by BLAST-search of the mitochondrial sequences of each species against its corresponding nuclear genome and we investigated the characteristics of cetacean Numt and revisited the phylogeny and evolution of cetartiodactyl using Numts. The content and distribution of Numt length showed similar patterns among six cetacean genomes. Under-representation of D-loop region-derived Numts and different abundance of Numt across D-loop sub-domains were observed in cetacean Numts except sperm whale. Examination of Numt location in cetacean nuclear genomes showed that some of orthologous Numts were integrated into exons, introns, and pseudogenes, suggesting that cetacean Numts may contribute to cetacean biology and evolution. Our phylogenetic study with cetacean Numt based on the maximum likelihood method corresponded to the study from other phylogenetic markers.