The Complete Mitochondrial Genomes Of Chinemys Reevesii And Cuora Aurocapitata

In animals, mtDNA is generally a 15~20 kb circular genome containing 37 genes: 13 protein-coding genes, two rRNA genes, and 22 tRNA genes, as well as a control region. In recent years, mitochondrial DNA (mtDNA) has been widely used as a useful marker system in numerous phylogenetic analyses of vertebrate relationships because of its maternal mode of inheritance and relative lack of recombination.The phylogenetic relationship of turtles to other vertebrate groups remains to be open. To date, complete mt genomes have been determined for only 16 species, including 15 cryptodiran turtles and a side-necked turtle. In order to provide molecular evidence for this issue, we analyzed the complete mitochondrial (mt) genome of the turtle Chinemys reevesii. DNA sequencing was based on the PCR fragments from 16 primer pairs that were designed on the basis of mtDNA sequences of three related turtle species. The genome is 16, 576 base pairs in length, contains 37 genes (two ribosomal RNA, 22 transfer RNA and 13 protein-coding genes) and a putative control region, a situation that is similar to that found in other vertebrates. The gene order is identical to that of the four other turtle species so far reported. Those genes are arranged compactly with no introns and few intergenic nucleotides. Twenty-two tRNA genes include 2 tRNASer, 2 tRNALeu and 18 different species of other tRNA genes each. The tRNAGln, tRNAAla, tRNAAsn, tRNACys, tRNATyr, tRNASer (the second one) , tRNAGlu and tRNAPro genes are encoded on the light strand, and the remainder is on the heavy strand. The length of the tRNA genes ranges from 66 bp (tRNASer and L-strand) to 77 bp (tRNATrp). All protein-coding genes begin with ATG as initiation codons except CO1 that uses GTG. Most protein-coding genes, including CO2, ATP8, CO3, ND4L, ND4, ND5 and Cytb, have a TAA termination codon, while the others have incomplete termination codons. Among the 13 protein-coding genes, only ND6 is located on the light strand, the others are on the heavy strand. The order of the 13 protein-coding genes is the same as in mammals, amphibians and crocodiles. The total length of the 13...