尼罗鳄MHCⅡ类B基因第二外元的序列变异分析  

Sequence Variation at Exon 2 of MHC ClassⅡB Gene in Nile Crocodile(Crocodylus niloticus)

作　　者：李恩[1] 晏鹏[1] 吴孝兵[1] 

机构地区：[1]安徽师范大学生命科学学院,安徽芜湖241000

出　　处：《激光生物学报》2010年第6期804-808,共5页Acta Laser Biology Sinica

基　　金：国家自然科学基金项目(30770312);安徽省优秀青年基金项目(04043049);重要生物资源保护与利用研究安徽省重点实验室基金项目

摘　　要：利用一对简并引物扩增了尼罗鳄MHCⅡ类分子B基因第二外元的部分片段,并对PCR产物进行了克隆和测序,结果得到8种不同的序列,序列长度为166 bp;经分析,序列中有56个变异位点,核苷酸的非同义替换多于同义替换,造成30个位点氨基酸的改变,氨基酸的替换趋于集中在假定的抗原结合位点附近。核苷酸和氨基酸序列与已报道的扬子鳄和密河鳄的MHCⅡ类B基因第二外元序列有较高的同源性,利用PAUP4.0软件构建的NJ树显示,鳄类的MHCⅡ类B基因存在跨种多态性现象。A pair of degenerate primers was used to amplify fragments of exon 2 of MHC class Ⅱ B gene from the genomic DNA of Nile crocodile （ Crocodylus niloticus）. Eight different sequences were obtained from cloning and sequencing, which were 166 bp long （except three 165 bp）. There were 56 variable sites in the nucleotide sequences, the ratio of nonsynonymous substitutions was higher than that of synonymous substitutions, which caused 30 variable sites among amino acid sequences. Substitutions of amino acid tended to be clustered around the putative antigen-binding sites （pABS） , suggesting that the variation at these sites would be responsible for recognition and presentation of different kinds of antigens. Nucleotide acid and amino acid sequences both showed high level of similarity to exon 2 of MHC class Ⅱ B gene of Alligator sinensis and Alligator mississippiensis. Phylogenetic relationships were constructed by neighbor-joining （NJ） method in PAUP4.0, suggesting trans-species polymorphism exists in MHC class ⅡB gene of Crocodilians.

关 键 词：尼罗鳄 MHCⅡ类B基因第二外元 跨种多态性 

分 类 号：Q959.64[生物学—动物学]