基于线粒体DNA D-loop区序列分析中国及新西兰奶山羊遗传进化关系

目的]分析我国地方培育奶山羊品种与国外引进品种的遗传进化关系。方法]以4个国内奶山羊品种（文登奶山羊、关中奶山羊、崂山奶山羊、雅安奶山羊）和3个新西兰引进奶山羊品种（阿尔卑斯奶山羊、吐根堡奶山羊、萨能奶山羊）为研究对象,采集33只个体的外周血样本,提取血液基因组DNA,利用PCR法扩增线粒体DNA（mitochondrial DNA,mtDNA）D-loop区全长序列,对测序获得的序列进行生物信息学分析,探究不同奶山羊品种的遗传多样性及进化关系。结果]7个品种奶山羊的mtDNA D-loop区中A、T碱基含量高于G、C碱基含量。共检测到82个多态位点,25个单一多态位点,55个简约信息位点。各品种单倍型多样度（Hd）范围为0.905~1.000,核苷酸多样度（Pi）范围为0.001 51~0.013 32;共存在26种单倍型,文登奶山羊和萨能奶山羊各有5个单倍型,阿尔卑斯奶山羊有4个单倍型,崂山奶山羊、吐根堡奶山羊、关中奶山羊、雅安奶山羊各有3个单倍型;各品种核苷酸平均差异数（K_XY）范围为6.400 00~38.450 00,核苷酸歧异度（D_XY）范围为0.005 79~0.034 76,遗传分化系数（G_ST）范围为0.000 00~0.186 05,遗传分化指数（F_ST）范围为0.231 56~0.971 52。品种间系统发育树表明,文登奶山羊和崂山奶山羊聚为一支;关中奶山羊与3种新西兰奶山羊遗传距离较近,从遗传学角度证实了关中奶山羊由国外奶山羊与地方品种经杂交选育而成;雅安奶山羊与其他品种遗传距离最远。结论]中国奶山羊存在2个支系起源且未发现群体扩张;中国培育奶山羊品种含有较多的国外奶山羊血统;文登奶山羊与崂山奶山羊亲缘关系较近,雅安奶山羊在遗传进化中可能存在地域隔离。

Analysis of Genetic and Evolutionary Relationships Between Chinese and New Zealand Dairy Goats Based on Mitochondrial DNA D-loop Region

Objective] To assess the genetic and evolutionary relationships between locally bred dairy goat varieties in China and those introduced abroad. Method] Four domestic dairy goat breeds （Wendeng dairy goat, Guanzhong dairy goat, Laoshan dairy goat, and Ya′an dairy goat） in China and three introduced breeds （Alpine dairy goat, Toggenburg dairy goat, and Saanen dairy goat） from New Zealand were used as research subjects. Peripheral blood samples were collected from 33 individuals and the genomic DNA was extracted. The full-length of D-loop region of mitochondrial DNA （mtDNA） were amplified by PCR assay and then sequenced. The obtained sequences were subjected to bioinformatic analysis to uncover the genetic diversity and evolutionary relationship of various dairy goat breeds.Result] The contents of A/T in the mtDNA D-loop region of 7 dairy goat breeds were higher than those of G/C. A total of 82 variable sites, 25 singleton variable sites, and 55 parsimony informative sites were found. The haplotype diversity （Hd） of the studied dairy goat breeds ranged from 0.905 to 1.000, and the nucleotide diversity （Pi） ranged from 0.001 51 to 0.013 32. There were 26 haplotypes in total, including 5 haplotypes each in Wendeng dairy goat and Saanen dairy goat, 4 haplotypes in Alpine dairy goat, 3 haplotypes each in Laoshan dairy goat, Toggenburg dairy goat, Guanzhong dairy goat, and Ya′an dairy goat. The ranges of average nucleotide diversity （K_XY）, nucleotide variation （D_XY）, genetic differentiation index （G_ST）, and genetic differentiation index （F_ST） were 6.400 00-38.450 00, 0.005 79-0.034 76, 0.000 00-0.186 05, and 0.231 56-0.971 52, respectively. According to the phylogenetic tree among different breeds, Wendeng dairy goat and Laoshan dairy goat were genetically clustered together into one branch. The genetic relation between Guanzhong dairy goat and three New Zealand dairy goat breeds was closer, proving that Guanzhong dairy goat was bred by hybridization of local breeds with foreign dairy goats. Ya′an dairy goat had the greatest genetic distance from the other breeds. Conclusion] In Chinese dairy goats, there are two lineage origins with no evidence of population expansion. The locally bred dairy goats in China are highly genetically linked with foreign dairy goats. Wendeng dairy goat has closely genetic relationship with Laoshan dairy goat, and Ya′an dairy goat may have experienced regional isolation during the genetic evolution.