基于Cytb基因多态性研究西藏地区8个藏山羊群体遗传结构及母系起源

摘要

旨在基于Cytb基因多态性探讨藏山羊群体间遗传结构及其母系起源.对西藏8个地区157只藏山羊的细胞色素b基因(Cytb)全序列进行扩增和测序,分析群体遗传多样性,计算群体间遗传分化指数,构建系统发育邻接树等.结果显示,藏山羊Cytb全序列为1 140 bp,在8个群体中共检测到33个变异位点,定义了30种单倍型,单倍型多样性(Hd)和核苷酸多样度(Pi)分别为0.736和0.001 8,表明西藏地区藏山羊群体具有较丰富的遗传多样性.78.6％的群体间发生了显著的遗传分化(P＜0.05),组内群体间的变异极显著(FsC=0.321,P＜0.001);系统发育邻接树分为了4个单倍型组(Haplogroup A-D),提示藏山羊有4个母系起源;单倍型网络图显示,不同地理来源的藏山羊没有完全聚类在同一群簇.在历史驯养过程中,藏山羊发生过群体扩增事件.本研究表明,西藏地区藏山羊有4个母系起源,并呈现出较丰富的遗传多样性,虽然群体间有一定程度的遗传分化,但没有形成明显的地理分隔格局,遗传结构差异在缩小.本研究结果为藏山羊遗传资源的保护和利用提供了科学依据.%The aim of this study was to disclose the information of genetic structure and maternal origins of Tibetan goat populations based on the Cytb gene diversity.Mitochondrial Cytb gene of 157 individuals from 8 Tibetan goat populations in Tibet plateau areas were amplified and sequenced.The genetic diversity and genetic differentiation indexes were analyzed,and phylogenetic tree was constructed.The results showed that the length of Cytb was 1 140 bp,and 33 variation sites were detected.Thirty haplotypes were defined,and haplotype diversity (Hd) and nucleotide diversity (Pi) were 0.736 and 0.001 8,respectively,which suggested that there was rich genetic diversity in Tibetan goat populations in Tibet.There were significant genetic differentiation among the 78.6％ populations (P＜0.05) and extremely significant variation among populations within group (FsC =0.321,P＜0.001).Phylogenetic tree revealed 4 haplogroups (A-D),suggesting that Tibetan goats had 4 maternal origins.Network of haplotypes showed that Tibetan goats didn't cluster into a cluster from different Tibet plateau areas.There was at least one population expansion event occurred during the domestic history of Tibetan goats.These results demonstrate that Tibetan goats in Tibet have rich genetic diversity and 4 maternal origins.Although apparent genetic differentiation has been occurred among the populations,there is no strong phylogeographic structure.And the genetic structure difference may become weak.These results will provide a scientific basis for protecting and utilizing the genetic resources of Tibetan goats.