Mitochondrial genome nucleotide substitution pattern between domesticated silkmoth, Bombyx mori, and its wild ancestors, Chinese Bombyx mandarina and Japanese Bombyx mandarina

Abstract

Bombyx moriand Bombyx mandarinaare morphologically and physiologically similar. In this study, we compared the nucleotide variations in the complete mitochondrial (mt) genomes between the domesticated silkmoth, B. mori, and its wild ancestors, Chinese B. mandarina(Ch Bm) and Japanese B. mandarina(Ja Bm). The sequence divergence and transition mutation ratio between B. moriand Ch Bmare significantly smaller than those observed between B. moriand Ja Bm. The preference of transition by DNA strands between B. moriand Ch Bmis consistent with that between B. moriand Ja Bm, however, the regional variation in nucleotide substitution rate shows a different feature. These results suggest that the Ch Bmmt genome is not undergoing the same evolutionary process as Ja Bm, providing evidence for selection on mtDNA. Moreover, investigation of the nucleotide sequence divergence in the A+T-rich region of Bombyxmt genomes also provides evidence for the assumption that the A+T-rich region might not be the fastest evolving region of the mtDNA of insects. Copyright © 2009, Sociedade Brasileira de Genética.