卵形鲳鲹MHCⅡβ基因的克隆与表达分析

为探究卵形鲳鲹(Trachinotus ovatus)主要组织相容性复合体(major histocompatibility complex,MHC)的结构和作用,利用RACE技术克隆获得MHCⅡβ基因的全序列,其长度为1 472 bp,开放阅读框(ORF)747 bp,编码248个氨基酸,分为信号肽区、肽结合区、Ig样区、跨膜区、胞质区。通过NJ法构建的系统进化树分析显示卵形鲳鲹独立聚为一支,与其他鱼类亲缘关系较近,与两栖类和哺乳类的亲缘关系较远。利用同源性比对发现其与大口黑鲈(Micropterus salmoides)亲缘关系较近,同源性达到79%。qRT-PCR分析表明MHCⅡβmRNA在卵形鲳鲹13个组织中均有表达,在脾和头肾中表达量较高,在鳍中表达量最低。感染美人鱼发光杆菌(Photobacterium damselae)3 h后,卵形鲳鯵MHCⅡβmRNA在肠中显著上调表达;感染12 h后在肝中上调表达;感染24 h后在脾和头肾中显著上调表达,以上研究表明MHCⅡβ基因参与了卵形鲳鲹的免疫反应。

Cloning and expression analysis of MHCⅡβ gene in Trachinotus ovatus

To study the structure and function of MHC (major histocompatibility complex) in Trachinotus ovatus,we obtained the full-length cDNA of ToMHCⅡβ MHCⅡβ (major histoeompatibility complexⅡβ) gene from T.ovatus] by RACE-PCR (rapid amplification of cDNA ends polymerase chain reaction) technology.This sequence was 1 472 bp,including an ORF (open reading frame) region of 747 bp.The peptide encoded MHCⅡβ gene could be divided into five parts,including signal peptide,peptide binding region,IGc1 domain,transmembrane region and cytoplasm area.A neighbor-joining tree shows that the MHCⅡβ gene from T.ovatus clustered into one cluster independently.It had close genetic-relationship with other fishes and farther genetic-relationship with amphibians and mammals.Homology analysis reveals that the ToMHCⅡβ shared 79% identity with Micropterus salmoides.In all 13 tissues,the highest expression level of MHCⅡβ gene was observered in spleen and kidne,while the minimum level existed in fin using qRT-PCR.Meanwhile, MHCⅡβ gene mRNA expression levels were significantly up-regulated in intestine (at 3rd hour),liver (at 12th hour),spleen and kideny (at 24th hour) after being infected with Photobacterium damselae,which indicates that this gene has important effects on immune response.