Origin And Evolution Of Wuzhishan Pig Based On Mitochondrional Variation Analysis

The complete mitochondrial genome sequence of Wuzhishan pig, Lingao pig, Wenchang pig and Hainan Wild Boar were reported in this paper. The structural features of the Wuzhishan pig mitochndrial genome was analyzed and described. Meanwhile, combining with the mitochndrial genome of the pigs in Sus Scrofa species, based on12kinds of protein-coding gene sequences, phylogenetic tree and Network analysis diagram were constructed to explore the evolutionary status and origin of Wuzhishan pig. In addition, we sequenced and analyzed complete control region of Wuzhishan pig, Lingao pig, Wenchang pig, Hainan Wild Boar to research the structure and variation of control region, and discussed the genetic diversity and genetic differentiation in populations of Wuzhihsan pig. Phylogenetic tree and Network analysis diagram were established to deduce the origin of Wuzhishan pig. The purpose of the study about the origion and evolution of Wuzhishan pig based on mitochondrial variation is to provide scientific basis for the protection and exploitation of this endangered species.The main research results were as follows:1?PCR and TA-cloning methods were used to obtain the mitochondrial sequence of Wuzhishan pig, Lingao pig, Wenchang pig and Hainan Wild Boar. It was the first time to obtain the complete mitochndrial genome of Lingao pig and Wenchang pig. The results showed that the mitochondrial genome of Wuzhishan pig was16689bp in length with13protein-coding genes,2ribosomal RNA (rRNA) genes,22transfer RNA(tRNA) genes and1non-coding control region (D-loop region). The base composition was A-34.7%, C-26.2%, G-13.3%and T-25.8%. All the protein coding genes of the mitogenome in Wuzhishan pig started with ATG, except for ND2, ND3and ND5with ATA, ND4L with GTG. The terminate codon of ND1and ND2was TAG, Cyt b was AGA, the termination signal of COX ??COX ??ND3and ND4was the incomplete T and the rest was TAA. The comparison results of the protein-coding genes in5species of Chinese miniature pig indicated that ND2and ND5in Wuzhishan pig were diffenent with the others.All tRNA can form typical secondary structure, except tRNASer (AGY) with an absence of DHU arm. The control region contained22tandem repeat sequences-ACGTGCGTAC and its total length was1254bp.2?Phylogenetic relationship and Network analysis diagram of Sus Scrofa were constructed by using12kinds of protein-coding gene sequences. The results showed that there were two plate(Asia and Europe). The plate of Asia contained domestica pig breeds and Wild boar. Wuzhishan pig was one of the S.S.domestica in Sus Scrofa species. Compaired with other breeds, Wuzhishan pig emerged recently in pig evolutionary history.3?The length of the complete control region sequences among Wuzhishan pig was1254-1335. The tandem repeats region was composed of repeating segments-TTATAAAACAC. The repetitive sequence "TTATAAAACAC" appeared in the conservative regions of21mtDNA D-Loop sequences in56samples.The length difference of control region was caused by the different number of tandem repeat region and the variation of conservative regions. The samples of Wuzhishan pig were divided into two parts with the variation of conservative regions and it is roughly identical to the classification result of phylogenetic tree.4?13haplotypes and14variable sites were observed in56sequences. Haplotype diversity and nucleotide diversity (Hd=0.838and Pi=0.00334) indicated that Wuzhishan pig had high genetic diversity. The transitions in278,404and451site were salient and it divided the samples of Wuzhishan pig into two parts similar to the results caused by the variation of conservative regions. The variation in240,300and559site divided the samples without variation in conservative into two parts. The variation of conservative regions and the variation in6site (240,278,300,404,451and559) could be regarded as genetic marker utilizing in the classification and evolution study of Wuzhishan pig. The Tajima's D number is0.39502(P>0.10) and the result of mismatch analysis was multiple-peaked. It indicated that the population of Wuzhishan pig was stable.5?The phylogenetic tree and Network analysis diagram which were constructed based on12kinds of protein-coding gene and control region sequences showed that Asia and Europe were two independent origin centers. Wuzhishan pig had two maternal origins locating in Yangtze valley and Southern China. Wuzhishan pig, Wenchang pig and Lingao pig had different origin in inland regions of China and the dominant haplotype of Wuzhishan pig had close genetic relationship with Lantang pig. The genetic differentiation index(Fst) of the two groups which were divided in the phylogenetic tree of Wuzhishan pig was0.49492(P<0.001).There exist significantly differentiation among the Wuzhishan pig.