【摘要】 为探究三疣梭子蟹的免疫机制以及谷胱甘肽过氧化物酶(GPx)在甲壳动物响应寄生虫感染免疫过程中的作用,本研究采用RACE方法从三疣梭子蟹中克隆获得硒半胱氨酸-谷胱甘肽过氧化物酶基因的全长cDNA序列,其cDNA序列全长为696bp,5′-UTR长度为102bp,3′-UTR长度为87bp,开放阅读框长度为507bp,编码168个氨基酸,其中含有一个典型的由蛋白石终止密码子(220TGA222)编码的硒半胱氨酸(40U)。预测了该基因编码的氨基酸序列及其中的保守结构域,包括GPx家族签名序列(64LAFPCNQF71)、活性位点序列(152WNFEKF157)以及与酶催化活性相关的氨基酸位点包括谷氨酰胺(74Q)、精氨酸(90R和168R)和色氨酸(142W)。相似性比对和系统发育分析结果表明,三疣梭子蟹硒半胱氨酸-谷胱甘肽过氧化物酶(SeGPx)与甲壳动物中的SeGPxs相似性较高,其中与拟穴青蟹SeGPx相似性最高,并与其在系统发育树中聚为一支。经血卵涡鞭虫侵染后(0—192h),SeGPx基因在三疣梭子蟹的血细胞、肝胰腺和鳃组织中的转录水平均发生显著性升高。该结果表明,SeGPx在三疣梭子蟹应对血卵涡鞭虫的免疫反应中发挥重要作用,可通过调控甲壳宿主体内被病原扰乱的氧化还原状态进而起到宿主组织保护作用。更多还原

【Abstract】 Glutathione peroxidase(GPx) is an essential antioxidant enzyme that associated with the immune defense of aerobic living organisms against invading pathogens.To investigate the potential role of GPx genes in crustacean immune response against parasitic infection,we isolated and characterized a novel selenium-dependent glutathione peroxidase gene(PtSeGPx) in Portunus trituberculatus.The open reading frame(ORF) encoded 168 amino acids,with a characteristic selenocysteine residue(40 U) encoded by an opal codon(220 TGA222).The conserved domains including the GPx signature motif 2(64 LAFPCNQF71) and the active site motif(152 WNFEKF157),as well as the catalytically related amino acid residues consisting of Gln(74 Q),Arg(90 R),Trp(142 W),and Arg(168 R),were identified in the deduced PtSeGPx protein sequence.Amino acid comparison and phylogenetic analyses indicated that the PtSeGPx was closely related to and clustered with the crustacean SeGPxs.The PtSeGPx transcripts were extensively and induced significantly in multiple major tissues(e.g.hemocytes,hepatopancreas,and gills) of P.trituberculatus during its host immune response against the invasion of the parasitic dinoflagellate Hematodinium,implying its involvement in the crustacean innate immunity against parasitic infection.更多还原