Intraspecific variation in the rainbow trout mitochondrial DNA genome

Four complete mitochondrial DNA genomes for rainbow trout, Oncorhynchus mykiss, were sequenced and compared to the previously reported complete mitochondrial sequence. Analyses revealed 13 additional bp and 31 insertion/deletion (indels) sites between the four new sequences and the previously published sequence. Twenty-eight indels were single base pairs while the remaining were multiple base pair insertions, two in the ATPase6 gene, one of three bases and one of nine bases, and a two base insert in the control region. Indels in the new genomes were compared to a wide range of salmonid species and corresponded with sequences in closely related species, indicating that errors were likely incorporated into the previously published sequence. Although variable nucleotide positions were observed throughout the newly sequenced genomes, non-synonymous amino acid substitutions were observed in only six of seven ND genes. While there were only 14 amino acid substitutions between genomes, Ka/Ks ratios ranged between 0 and 1. A single amino acid deletion in the ND1 coding region unique to rainbow trout was also detected. Using complete mitochondrial genomes for all sequenced Salmonidae species, a phylogenetic analysis was performed to establish a salmonid mitochondrial phylogeny revealing support for Salvelinus, rather than Salmo, as the sister taxa to Oncorhynchus.