Analysis Of The Mitochondrial Genome Of Three Species Of Shrews And Discussion On The Classification Of The Genus Shrews

The species Insectivora(Soricidae)is the smallest mammal ever discovered,and is widely distributed in Asia,Africa,Europe,North and South America.Now divided into Soricinae and Crocidurinae.The Sorex belongs to the Soricinae.The Sorex is small and concealed,so it is difficult to capture.So far,there are relatively few related literatures in China.With the development of molecular biology,more and more scholars have begun to integrate traditional morphology and phylogenetic techniques and applied them to species identification,which has greatly strengthened the taxonomic research of the Soricidae.It has also received intense attention in researches such as discovering new species and re-descriptives of the Soricidae.However,due to the lack of mitochondrial genomic data,the genetic relationship and species classification status of Soricidae.Cannotbe explored at the mitochondrial genome level.Based on the Soricidae specimens accumulated since 2013,the species identification of S.roboratus,S.isodon and S.caecutiens has been completed using both traditional morphology and phylogenetic evidence.First,the morphological species identification was performed by comparing,describing,and measuring the external morphology of the specimen with the skull features.Then,the Cytb single gene in mt DNA was used to complete the phylogenetic tree reconstruction.The molecular biological species identification was performed by calculating the genetic distance between the samples.The morphological and molecular biological species identification results are consistent.After identifying the species,the mitochondrial genomes of 3 species of Sorex were amplified and sequenced.The complete sequence of the 3 species of Sorex complete mitochondrial genomes was uploaded to the NCBI-Gen Bank database,and the sequence of the other 9 known Sorex complete mitochondrial genomes was downloaded.The complete mitochondrial genes of 12 species of Sorex genes and Cytb single genes were analyzed by bioinformatics.The common and specialized features of 12 species of Sorex complete mitochondrial genomes were found and described,and the classification and system among Sorexwere systematically demonstrated.Have a relationship.In addition,the reliability of the mitochondrial single gene of Sorex in constructing phylogenetic trees was also analyzed.The findings are as follows:(1)Based on morphological measurement data analysis and Cytb gene phylogenetic tree reconstruction,a comparison of the three tested maggot samples in this study shows that the molecular biological test specimens used and the sequences of their corresponding species(Genbank download)They all clustered on a small branch,and showed obvious systematic differentiation with their related species and other species distributed in Northeast Asia.The cluster analysis results of the species are consistent with the morphological classification and identification results,and are consistent with the morphological identification results.(2)The complete mitochondrial genomes of the S.roboratus,S.isodon and S.caecutiens were amplified,which enriched the basic biological information of the Sorex.The total length of the mt DNA sequence of the S.roboratus is 17 153 bp,the crest of the S.isodon is 17 007 bp,and the crest of the S.caecutiens is 17 096 bp.The anti-codons of mitochondrial genomic t RNAs are all identical.There are minor differences in the start and stop codons encoding the protein.The mitochondrial genomes of 12 species Sorex are all circular DNA molecules,containing 13protein-coding genes,2 r RNAs and 1 D-Loop region.S.tundrensis and S.araneus have 23 t RNAs;the remaining 10 species have 22 t RNAs.The base content in the base composition follows the rules of C> A> T> G,A + T> G + C,showing a preference for AT.The nucleotide composition tends to AT coding,and the AT content of the protein coding gene is No.3.Codons are generally higher than codons 1 and 2,and the longest overlap between the ATP8 and ATP6 genes is 43 bp.(3)Phylogenetic relationships constructed based on the full sequence of 12 species of Sorex mitochondrial genomes show that all Sorex species are clustered in one branch;S.cylindricauda is the earliest differentiated species of Sorex;S.roboratus and S.unguiculatus are sisters group;S.caecutiens and S.sinalis are sisters group to each other,and S.gracillimus and S.minutissimus are sisters group to each other.The comparison of phylogenetic tree constructed with mitochondrial singlegene sequence and phylogenetic tree constructed with tandem genes found that 16 S r RNA and ND4 can restore the phylogenetic relationship of Sorex well.(4)Phylogenetic relationships constructed based on 12 Species Sorex Cytb single gene sequences indicate that support for can be divided into Otisorex and Sorex,and 12 species in Gen Bank that have been determined for the complete mt DNA sequence are vest in Sorex.