| The genus Cricetulus belong to the subfamily Cricetinae,which is the biggest genus in Cricetinae with wide distribution and adaptable extreme environment.Previous researches of Cricetulus focused on the comparative morphology and had many hot disputed issues.Molecular biological approach was also used to research the classification and phylogenetic relationship of Cricetulus.However,previous researches couldn't discuss the classification and phylogenetic relationship of Cricetulus species using mitogenome data due to lack mitogenome data.Additively,the reported mitogenome of Cricetulus species failed to elaborate the evolutionary characteristics of mitogenome.Therefore,it was necessary to implement comparative analysis to Cricetulus species,and reanalyze the classification and phylogenetic relationship of Cricetulus species using mitogenome data to construct phylogenetic trees.In the present study,we found some common and special characteristics by comparisons with six mitogenomes of Cricetulus species.In addition,we reconstructed the phylogenetic relationships of Cricetulus which showed the history of speciation using the mitogenomes data.Finally,we analyzed the reliability of single mitochondrial genes of Cricetulus species when constructed phylogenetic trees.The present study results as followed:1.The mitogenome of C.migratorius contained 13 protein coding genes,2 ribosomal r RNA genes,22 transfer RNAs and one non-coding region without any deletion and rearrangement finding.The mitogenome of C.migratorius was 16246 bp long that was the shortest among Cricetulus species but Tscherskia triton was the longest ones(16488 bp).The mitogenomic characteristics of Cricetulus species had higher AT content in complete mitogenome as well as central domain of the control region.The AT content at the 3rd position higher than that of the 1st and 2nd position in triplet codon,and the G content at the 3rd position lower than that of the 1st and 2nd position.The t RNASer2 lost the dihydrouracil arm.The PCGs contained the incomplete codon,and the ATG was the most frequent used start codon,and the AUU(Ile)and CUA(Leu)codon werethe most frequent codon.The putative origin of replication for the light strand(OL)was approximately 45 bp long,and could fold a hairpin structure.In addition,the stem-loop of OL began with the conserved motif 5?-CTTCT-3?.The D-loop region contained three domains: the extended termination associated sequences(ETAS),the central conserved domain,and the conserved sequence blocks(CSB).The special characteristics of mitogenome of Cricetulus species showed that the Cricetulus species lost the CSB3 sub-block.The motif 5?-ACTAA-3? was the recognition sites of DNA polyase,but other mammal was 5?-GCCGG-3?.2.We found that with the increase of the GC composition caused the absolute value of GC skew increased based on the asymmetrical analysis of mitochondrial DNA,but the AT and GC content didn't effect on the AT skew value;the third position of codon of the GC content wasn't related to the skew value of P2 FD and P4 FD on PCGs sequence,and the GC content didn't reflect the saturation of protein evolution.In addition,we found that there wasn't correlation between the skew value of P2 FD and P4 FD and the evolutionary history of Cricetulus species.3.Based on the phylogenetic relationships reconstructed by the mitogenomes data,which showed that the C.kamensis was at the basal position and represent an old split.The results supported T.triton was affiliated with Cricetulus species.The C.griseus and C.longicaudatus were sister species.The C.migratorious and Allocricetulus eversmanni clustered in a subclade,and showed that the C.migratorious belonged to the subgenus Allocricetulus,in accord with the previous morphological conclusions.4.Compared with the phylogenetic trees between the single genes and concatenated genes constructed,and 16 S r RNA and ND4 genes were especially informative in topology resolution,which was different from other mammals. |
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