Complete Mitochondrial Genome of Mackerel Icefish (Champsocephalus gunnari): Retention of ND6 and tRNAGlu, and a Novel Genome Organization

• Main Authors: Chu-Yin Lin, 林筑茵
• Other Authors: Hsiao-Wei Kao
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/b4m4ta

碩士 === 國立中興大學 === 生命科學系所 === 98 === It has been proposed that loss of ND6 and tRNAGlu is shared by all Antarctic notothenioid fishes, and likely occurs in their common ancestor (Papetti et al. 2007). To test this hypothesis, the complete mitochondrial (mt) DNA sequences of mackerel icefish (Champsocephalus gunnari), a member of Antarctic notothenioids, were obtained by polymerase chain reactions (PCR), cloning, and sequencing. In contrast to the proposal of Papetti et al. (2007), ND6 and tRNAGlu are present in the mt genome of mackerel icefish. Notably, ND6 and tRNAGlu are transposed to the position between tRNAThr and tRNAPro compared to the position between ND5 and cyt b in the ordinary vertebrate mt genomes. In addition, the segment from ND6 to control region (CR) tandemly duplicates once. Variations in gene content of the first duplicate were observed among different individuals. The variations include a full-length ND6 and tRNAGlu (referred as type-1), a truncated ND6 and loss of tRNAGlu (referred as type-2), and loss of both ND6 and tRNAGlu (referred as type-3). We proposed that tandem duplication-random loss model (TDRL model) (Moritz and Brown 1986; Moritz and Brown 1987) may account for the novel mt genome of mackerel icefish. Phylogenetic tree of notothenioids does not support that the loss of ND6 and tRNAGlu occurred at the common ancestor of Antarctic notothenioids unless ND6 and tRNAGlu were regained in mackerel icefish. The alternative hypothesis was that ND6 and tRNAGlu were lost independently in the different lineages of nototheniods and mackerel icefish was one of the lineages that retained ND6 and tRNAGlu.