Mitochondrial genomics of fishes : determination and analysis of complete nucleotide sequence of the mtDNA

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Genetic information encoded on the DNA provides important makers for estimating genealogy, population structure, phylogeny, and evolution of organisms. However, it has become apparent that obtaining enough genetic information from the nuclear genome is a rather difficult task because the nuclear genome is a very complex entity in which many genes are duplicated. In this context, preferable is the mitochondrial (mt) genome because of its simplicity. Mitochondrial genomes (and their genes) in "advanced" animals are homologous undoubtedly and are inherited without recombination, and thus they are attractive for phylogenetic and population genetic researches as an important information source. In this project, we determined and compared complete nucleotide sequences of the mt genomes from many fishes representing major lineages of fish, and then tried to estimate comprehensive phylogenetic framework of teleostean fishes on the basis of the resultant large DNA dataset.Thanks to further development of experimental procedures, equipments, and our research group, we have sequenced complete mt genomes from more than 200 species, which number exceeded ten times as many as what we first aimed to sequence. From the sequence data, various new types of gene arrangement deviated from that of the common vertebrate were found. Phylogenetic analysis of the sequence data also provided many new findings on the relationships among basal teleosts. One of important findings is that the Elopomorpha which includes eels is found to be much more basal in the teleostean phylogeny than assumed previously.