Compariative Study Of Mitochondrial TRNA Genes And Control Region Sequence Among Birds

Mitochondrial DNA as a genetic marker has been successfully applied to the study of molecular evolution of birds. The apparently maternal inheritance of mitochondrial DNA and its fast evolution in primary sequence has made it attractive in population and evolutionary genetics. Three major clusters of mitochondrial tRNA genes (tRNAIle-tRNAGln-tRNAMet, tRNATrp-tRNAAla-tRNAAsn-tRNACys-tRNATyr and tRNAHis-tRNASer(AGY)-tRNALeu(CUN)) were amplified and sequenced from 15 species within Fringillidae and 13 species of Predatory birds. Most of the variable sites were involved in the loop regions. The stem regions were relatively conserved, and the variable base pairs were under the restriction of compensatory changes or G-U wobble pairing which could be regarded as mechanisms for maintaining a stable secondary structure. Maximum-parsimony (MP) and Neighbor-joining (NJ) phylogenetic trees were constructed using all the tRNA gene sequences or stem-forming nucleotides, respectively. We found that the bootstrap values for branches of trees using the tRNA sequences were commonly higher than the others, therefore the phylogenetic relationship reflected by these data may be closer to the truth. By comparing the secondary structure among taxa we found that the characters of nucleotide insertions and deletions in some tRNA genes have synapomorphies, suggesting that these characters may be useful for resolving the phylogenetic relationship of different families in Predatory birds with higher phylogenetic performance. Moreover, we we sequenced the entire mitochondrial DNA control region from 17 charadriiform species, and found that the base composition and distribution of the variable nucleotide sites within the control region were similar to other avian species, but a series of short tandem repeated motifs in the 3' end of domain III made A nucleotides and length increased significantly. Phylogenetic analysis showed that these sequences could not well resolve the relationship among genus in Charadriiformes, but within genera maybe has some valuable phylogenetic information.