兴国红鲤MHCⅡ类基因多态性、表达及其与鱼体抗病力关系的分析

THE ANALYSIS OF THE POLYMORPHISM AND EXPRESSION OF MHC CLASS Ⅱ GENE AND ITS ASSOCIATION WITH RESISTANCE/SUSCEPTIBILITY TO AEROMONAS HYDROPHILA IN XINGGUO RED COMMON CARP

  • 摘要: 对41尾感病和22尾抗病兴国红鲤的308个有效克隆进行测序,获得171条不同的MHC Ⅱ类基因编码序列,分属26个不同的等位基因,其中Cyca-DXA24Cyca-DXA36为新发现的13个等位基因。MHCⅡ类基因片段的长度为624 bp,包括第14个外显子,分别编码信号肽、1和2结构域及连接肽/跨膜区。1结构域的变异明显大于2结构域,表现在1结构域中核苷酸和氨基酸变异位点比例(55.16%和79.76%)明显高于2结构域的变异位点比例(45.96%和68.42%)。1结构域的PBR区的非同义碱基替换率(dN)与同义碱基替换率(dS)的比值 (=dN/dS)为5.742,远远高于非抗原结合位点(non-PBR)及2结构域的0.755、0.592,揭示兴国红鲤MHC Ⅱ类基因的1结构域在进化过程中受到正向选择作用。等位基因Cyca-DXA24 (P0.01)与兴国红鲤对嗜水气单胞菌的抗性相关,等位基因Cyca-DXA3 (P0.05)、Cyca-DXA4 (P0.01)、Cyca-DXA6 (P0.05)、Cyca-DXA33 (P0.05)与兴国红鲤对嗜水气单胞菌的易感性相关。荧光定量PCR结果表明,MHCⅡ类基因在健康兴国红鲤的肾、肝、鳃等10个组织均能普遍表达。人工感染嗜水气单胞菌后,肾、肝、脾3个组织中的MHCⅡ类基因的表达量均发生了不同程度的变化,表明MHCⅡ类分子在兴国红鲤的免疫反应中起到重要作用。

     

    Abstract: We cloned 171 sequences of MHC class Ⅱ gene were determined from 41 susceptible and 22 resistant individuals of Cyprinus carpio var. singguoensis. These sequences belonged to 26 alleles, thirteen of which were novel (Cyca-DXA24-Cyca-DXA36). The total length of the sequence was 624 bp, consisting of a 33 bp exon1, a 252 bp exon2, a 285 bp exon3, and a 54 bp exon4. These exons encoded a partial signal peptide, a 1 domain, a 2 domain and a connecting peptide (CP)/partial transmembrane (TM), respectively. The mutation-Prone positions of nucleotide or amino acid sites in 1 domain (55.16%, 79.76%) significantly out number than those in 2 domain (45.96%, 68.42%). The values (= dN/dS) were 5.742 for peptide-binding region (PBR), 0.755 for non-PBR in the 1 domain and 0.592 for the 2 domain, implying that the positive selection pressure probably had occurred in the PBR region of the 1 domain. Cyca-DXA24 (P0.01) was significantly correlated with the carp's resistance to Aeromonas hydrophila, while Cyca-DXA3 (P0.05), Cyca-DXA4 (P0.01), Cyca-DXA6 (P0.05) and Cyca-DXA33 (P0.05) alleles were significantly associated with the fish's susceptibility to the disease. Real-time quantitative PCR demonstrated that MHC II genes were ubiquitously expressed in ten tissues. The expression was up-regulated in kidney, down-regulated in liver and spleen during infection. Our results indicated that the MHC class II gene might play an important role in the immune reactions of C. carpio var. singguoensis.

     

/

返回文章
返回