唐古拉山牦牛群体的母系遗传多样性及遗传结构分析

目的]从分子水平上探究青海省唐古拉山牦牛群体的母系遗传多样性、群体遗传结构及其遗传背景。方法] 对52头唐古拉山牦牛个体mtDNA D-loop区序列进行测定后，使用生物信息学软件分析确定其核苷酸变异位点和单倍型数目，计算单倍型多样度和核苷酸多样度大小，并进行系统发育分析。结果] 在619 bp唐古拉山牦牛D-loop区序列分析中，排除2处插入（缺失）后共检测到31处多态位点，包括单一多态位点5处和简约信息位点26处。根据序列间核苷酸变异共确定了13种单倍型，单倍型多样度和核苷酸多样度分别为0.821±0.043和0.007±0.004。与我国其他18个家牦牛品种和野牦牛相比，唐古拉山牦牛群体单倍型多样度和核苷酸多样度值均较低，表明该群体遗传变异较为贫乏，母系遗传多样性水平较低。以美洲野牛为外群，邻接法（即NJ法）构建的系统发育树结果显示：唐古拉山牦牛群体13种单倍型分布在A、B、C、D和E五种单倍型组中，且聚为2个大的母系分支（即I和II），支系Ⅰ占比为77%，提示唐古拉山牦牛由2个母系支系组成，拥有2个母系起源且以支系Ⅰ为主。 结论] 唐古拉山牦牛母系遗传多样性水平较低，由2个母系支系组成，以支系Ⅰ为主，推测其有2个母系起源。

Maternal genetic diversity and genetic structure of Tanggula yak population

Objective] The maternal genetic diversity, population structure and genetic background of the Tanggulashan yak population in Qinghai Province were explored at molecular level. Method] The mtDNA D-loop region of 52 Tanggulashan yaks were sequenced with polymorphic sites and bioinformatic analysis for haplotype numbers, haplotype diversity and nucleotide diversity, and phylogenetic analysis. Results] In the 619 bp D-loop region, 31 polymorphic sites were detected after excluding 2 insertions (deletions), including 5 single polymorphic sites and 26 parsimony information sites. A total of 13 haplotypes were identified based on nucleotide sequence variations with nucleotide diversity of 0.007±0.004 and haplotype diversity of 0.821±0.043. Compared with wild yak and other 18 domestic yak breeds/populations in China, the values of haplotype diversity and nucleotide diversity of Tanggulashan yak population were relatively lower, indicating poor genetic variation and lower level of maternal genetic diversity. The phylogenetic tree constructed by NJ method showed that 13 haplotypes belonging to A, B, C, D and E were clustered into two large maternal lineages (I and II) with lineage I accounted for 77%, indicating that Tanggulashan yak population is composed of two maternal lineages and has two maternal origins. Conclusion] The Tanggulashan yak population had relatively lower maternal genetic diversity, consisting of two maternal lineages dominated by lineage I, which is speculated to have two maternal origins.