9个地方鸡种MHC B-G座位多态性及其分子系统进化分析

以我国9个地方鸡为研究对象,对其MHC B-G座位全基因序列进行测序,以揭示这9个地方鸡种MHC B-G基因的遗传多样性,并构建其系统进化树.结果表明,9个地方鸡种MHC B-G基因序列具有较高的遗传多样性,在9个地方鸡种中共存在666个突变位点,其中单一位点突变554个,简约信息112个,共缺失782 bp.核苷酸多样度(Pi)为0.030 79±0.004 39,平均核苷酸差异(K)为182.639.9个地方鸡品种为9个单倍型,单倍型多样度为1.00±0.052.9个鸡种MHC B-G基因Kiumura双参数遗传距离范围为0.010～0.070,鹿苑鸡与新狼山鸡的遗传距离最小,为0.010;茶花鸡与东乡绿壳蛋鸡遗传距离最大,为0.070.根据9个鸡品种MHC B-G基因全序列构建的NJ树和ME树,茶花鸡单独聚为1类,其他8个品种被聚为2大类.Tajima's D值为-1.554 6,且差异不显著(0.10>P>0.05),说明MHC B-G基因为负向选择,不遵循中性进化理论,MHC B-G基因多态性不是遗传漂变的结果,而是自然选择和人工选择的结果.

Polymorphism and molecular phylogenetic analysis of MHC B -G locus in 9 indigenous chicken breeds

The MHC B-G locus in nine indigenous chicken breeds was sequenced to explore genetic diversity in these nine chicken breeds and to construct their phylogenetic tree.The study revealed that the genetic diversity of the MHC B-G locus in these breeds was relatively high,where there were 666 polymophic sites,among of which singleton variable sites were 554,parsimony informative sites were 112.Sites with alignment gaps or missing data were 782 bp.Nucleotide diversity(Pi)was 0.030 79±0.004 39.Average number of nucleotide differences(K) was 182.639.There was nine haplotypes in nine chicken breeds.The haplotype diversity was 1.00±0.052.Kimura 2-parameter distance between nine chicken breeds was 0.010-0.070,where the minimum was 0.010 between Luyuan and Newlangshan,while the maximum was0.070 between Chahua and Dongxiang blue.Neighbor-Joining(NJ) tree and Minimum-Evolution(ME) tree based on MHC B-G DNA sequences in nine chicken breeds were constructed.Chahua was grouped seperately while the other chicken breeds were divided into two groups.Tajima’s D was-1.554 6,and was not statistically significant(0.10>P>0.05),which showed that MHC B-G gene was minus direction selection and was not following natural therory of molecular evolution.Also,the genetic diversity of MHC B-G gene was not the result of genetic drift,but one of natural and artificial selection.