Mitochondrial DNA-like sequences in the nuclear genome of the opossum genus Didelphis (Marsupialia : Didelphidae)

This study reports the occurrence of mtDNA-like sequences in the nuclear ge nome of the opossum genus Didelphis (Didelphidae, Marsupialia). A specific primer pair designed to amplify a region encompassing a 3' terminal 118 bp region of the cytochrome b gene, the Thr and Pro tRNA genes, and a 489 bp r egion of the D-loop of the D. virginiana mtDNA, was used in highly stringen t PCR reactions. These PCR reactions resulted in several fragments per indi vidual varying in size from 259 bp to 1 kb, The sequencing of some of these fragments showed the occurrence of paralogous mtDNA-like sequences among t he PCR amplified fragments. Analyses of qualitative aspects of these sequen ces, their transition/transversion ratios, and phylogenetic relationships w ere conclusive in showing the occurrence of mtDNA-like sequences in the nuc lear genome of the genus Didelphis. Comparisons and phylogenetic analysis o f orthologous mtDNA from the four Didelphis species and paralogous nuclear sequences suggested that mtDNA migration to the nuclear genome occurred mor e than once in Didelphis evolution.