摘要
根据牙鲆(Paralichthys olivaceus)主要组织相容性复合体(MHC)DAB基因序列设计特异性引物,在日本牙鲆基因组中扩增了包括DAB基因完整外显子2和内含子1在内的长度为408bp的DNA片段。对该片段克隆测序后,发现了37个MHC-DAB等位基因,各等位基因的频次以及各主型中亚型数目分布都不平衡。在第二外显子273bp核苷酸序列中有50个位点发生变异,核苷酸多样性PI值为0.0618,在编码的氨基酸序列中存在多态变异位点30个,其中简约信息位点29个,单变异位点1个。非同义替代与同义替代的比率在抗原结合区(PBR)和非PBR编码区分别为10.0和1.62,分析表明正向选择机制可能是产生牙鲆MHC-DAB多态性的主要因素。估计的核苷酸的转换和颠换数随着遗传距离的增加而增加。各等位基因间的系统发生关系表明,19个主型分为两个群。对氨基酸组分和密码子的偏倚性以及分布频率的分析表明各同义密码子的使用频率不均衡。本研究为牙鲆MHC-DAB基因的遗传进化和分子标记辅助育种的研究提供了理论基础。
Polymorphism of the major histocompatibility complex （MHC） DAB gene in Japanese flounder Paralichthys olivaceus was investigated using sequences analysis. In this study, 24 individuals were selected to amplify partial exonl and intron2, complete intronl and exon2 of DAB gene. 131 sequences were subsequently used to analyze genetic variation and revealed 31 different sequences, which presented 31 novel alleles belonging to 19 allele major types according to accepted nomenclature rules. Frequency of alleles and numbers of subtype were not distributed equally. There were 50 variable sites in exon2, the average number of nucleotide diversity PI value of the whole sequences was 0.0618. The nucleotide sequence was corresponded with putative 91 amino acids peptide, 32.97 % （30 out of 91 ） of the amino acid were variable, of which 29 parsimony informative sites were observed. The rates of non-synonymous substitution （du） were 10.00 times and 1.62 times higher than the rate of synonymous substitution （ds） in the peptidc-binding regions （PBR） and non-PBR, respectively. The rate of dx occurred at a significantly higher frequency than that of ds in PBR, dx in PBR was higher than that in non-PBR, but ds in PBR was significantly lower than in non-PBR. In this study, the high ratio of dN/ds value and high allelic diversity observed in flounder suggested a balancing selection in the MHC-DAB gene, which explained the high polymorphism of MHC-DAB gene in Japanese flounder. The number of transitions and tranversions gradually increased with genetic distances, indicating that the MHC-DAB gene might discuss the genetic evolution. Phylogenetic tree was based using NJ method revealed a preliminary phylogeny among 19 MHC-DAB major type of alleles. Frequency of synonym codons were not distributed equally. These results provide molecular date for the study on genetic variation and marker-assisted selective breeding in Japanese flounder
出处
《动物学报》
SCIE
CAS
CSCD
北大核心
2008年第5期909-917,共9页
ACTA ZOOLOGICA SINICA
基金
国家973计划项目(No.2004CB117403)
国家自然科学基金项目(No.30671623)
863计划项目(No.2006AA10A402)
山东省泰山学者建设工程专项经费资助~~
关键词
牙鲆
主要组织相容性复合体
等位基因
多态性
Japanese flounder, Paralichthys olivaceus, Maior histocompatibilitv complex. Allele. Polymophism
