辽东湾斑海豹MHC-DQB基因的遗传多样性分析

The genetic diversity of MHC-DQB locus of the spotted seal (Phoca largha) in Liaodong Bay,China

本文从25份斑海豹样本中获得141bp片段,发现21个变异位点,定义了12个MHC-DQB等位基因,氨基酸变异率为25.5%。等位基因之间的遗传距离范围是0.0071～0.1064,平均值为0.0577,不同等位基因之间的碱基差异是1～15bp,平均差异数为8bp。与其他鳍足类动物对比后发现,斑海豹MHC-DQB表现出较丰富的多态性。非同义替换率明显高于同义替换率,由此造成的氨基酸替换集中在肽结合位点PBR附近,表明DQB基因受到强烈的平衡选择作用。11个样本出现多于两条等位基因的情况,推测存在基因重复现象。

Sequence variation at the second exon of the MHC-DQB locus was investigated on 25 spotted seals（Phoca largha） in Liaodong Bay,China.Of the 141 nucleotides scored,21 variable sites were detected,defining 12 haplotypes,differing by 25.5% at the amino acid level.The nucleotide diversity was from 0.0071 to 0.1064（average 0.0577）,and the base difference was from 1bp to 15 bp（average 8bp）.These results showed relatively high genetic diversity in this population compared to other pinniped species.The high rate of non-synonymous versus synonymous substitution especially in the peptide-binding region（PBR） suggested strong balancing selection for maintaining high MHC diversity at the MHC-DQB locus.Eleven individuals holding more than two alleles per individual indicated the duplication of DQB gene.