Chinese Wolf, Canine, And Some Carnivores Mitochondrial Whole Genome Studies

The vertebrate mitochondrial DNA(MtDNA) are double-stranded circular molecules of approximately 16kb.Many features of MtDNA,such as high mutation rate than nuclear genome, maternal inheritance and lack of recombination,made it the biological material of choice widely used in phylogenetic analyses.MtDNA is the only genomie molecular mark in animal phylogenetic analyses at present.Mitochondrial genomics has great potential for resolving ancient patterns of evolutionary history and for serving as a model of genome evolution.Species diversity and genetic diversity of Carnivora were high.Most of the animals were on the top of food chain.Carnivora has an important status in ecosystems.Classification and phylogenesis of Carnivora are debatable.In present study,we determined the complete mitochondrial genome sequence of Chinese grey wolf based on the PCR from 14 primer pairs that were designed on the basis of mtDNA sequences of related species.Phylogenetic analyses were executed in order to confirm Chinese grey wolf phylogenetic relationship.Canidae,Camivora's mitoehondrial genome were compared and analyzed.1.The complete mitochondrial DNA is 16,774 nucleotides in length and contains 22 transfer RNA genes,13 protein-coding genes,two ribosomal RNA genes,and one control region.The pDRAW32 software was used for restriction enzyme mapping.Except for ND2,ND3,ND5 start with AUA,the rest(ND1,COX1,COX2,ATP8,ATP6,COX3,ND4L,ND4,ND6,Ctyb) of protein-coding genes initiate with AUG codon.Three genes end in two incomplete stop codons, UA_ND3 and U_COⅢ,ND4,which are presumably completed as UAA by posttranscriptional poly adenylation.COⅡ/gene of Canis lupus chanco ends with UAG,whereas the stop codon of the gene of Canis lupus lupus and Canis lupus familiaris is UAA.The sizes of 12S rRNA and 16S rRNA are 954 bp and 1579 bp.Control region's length due to the variable tadem repeats 5'-GTACACGTAC-3',which repeated 31 times.The molecular phylogenetic analysis was performed on the sequences of 12S rRNA gene and 16S rRNA gene,and suggested that Chinese grey wolf was more primitive than Eurasia grey wolf which were consistent with former morphological research.2.The features of mitochondrial genomes of Canidae were compared and analyzed.It was found that the genome organization and gene order which were similar to the typical vertebrate. The nucleotide compositions of the mitochondrial genome showed the bias of higher AT and lower G contents.The intergenic spacer of tRNA-Trp/tRNA-Ala,COX2/tRNA-Lys are longer than others.The overlapping sequence of ATP8/ATP6,ND5/ND6 are notable.CUA(Leu), AUU(Ile),AUA(Met) codon were the most frequency.There is a strong bias against G at the third codon position in protein-coding genes.The light-strand replication origin which was located in WANCY region were highly conservative.A large similar number of tandem repeats were presented at the 3'end of the control regions in wolf,dog and cotoye,whereas the repeats which observed in red fox were discrepant.Furthermore,constitutions and numbers of these tandem units might be regarded as special molecular markers for its conservative character and applied to the phylogenetics,taxonomic,molecular genetics and conservation of Canidae.3.The character of mt genomes of Camivora was analysed.The base compositions of mt genome also showed the bias of higher AT and lower GC contents.AUG,UAA were used the most frequency as start codon and stop codon.The abnormal phenomena which COⅢ,NADH3 and NADH4 lack stop codon in translation were found in Phocidae.The frequencies of CUA(Leu),AUU(Ile),AUC(Ile),AUA(Met) are higher than those of other codons.CUA(Leu) was most often used as codon.There is no AGG(Ter) codon.All of the tRNA genes can fold into typical cloverleaf secondary structure except the tRNA-Ser(AGY)gene,which appears to lack dihydrouridine arm.The repeats(CACGT)(only several base changed) which were also found in other mtDNA genome shows highly conserved in Carnivora.