中国和越南两个缢蛏种群天然免疫GST基因的特征及比较

Characterization and comparison of innate immune GST genes in two Sinonovacula constricta populations from Vietnam and China

因为遭受细菌病原体侵害,缢蛏(Sinonovacula constricta)在孵化和自然坐床过程中损失严重。谷胱甘肽S转移酶(GSTs)是一种可以在第二解毒阶段催化外源代谢的酶。它可以作为评估水生环境中有机和无机污染物指示剂或生物标记。然而,目前对双壳贝类GST基因功能的研究甚少。报告了暴露于霍乱弧菌下GST家族的一个基因的克隆和表达以及mRNA的组织分布与时序表达。首先鉴别了Sc-GST cDNA全长序列。该序列含1052 bp核苷酸序列,包括700 bp的5′端非编码区(UTR)和3′端非编码区,开放式阅读框架含678 bp核苷酸序列编码了225个氨基酸的多肽。其后,对暴露在细菌下的缢蛏中GST基因进行鉴定并分析其表达图谱。用实时定量PCR评估细菌暴露下来自中国和越南的两个缢蛏种群血淋巴中GST基因的表达,并进行了比较。揭示了GST基因主要在缢蛏的免疫组织如血细胞、外套膜、鳃和肝中表达,并对鳗弧菌感染具有高反应性。特别需要指出的是,与中国缢蛏相比,越南缢蛏中的Sc-GST mRNA的表达水平在12 h后显著升高,直至实验结束。这可能是因为注入的细菌来自中国,中国种群在一定程度上已经适应这一来源的疾病。研究表明,Sc-GST基因在缢蛏成贝免疫反应调节中发挥重要作用并可以在基因水平上对不同的种群进行比较。

Razor clams Sinonovacula constricta are seriously affected by bacterial pathogens,which causes high losses in hatcheries and in natural beds.Glutathione S-transferases(GSTs)are enzymes that catalyze xenobiotic metabolism in the phase II detoxification process,and they can be used as biomarkers to assess the presence of organic and inorganic contaminants in aquatic environments.However,very little is known about the function of GST genes in bivalves.In this study,we first cloned and expressed Sc-GST gene from S.constricta.The full-length cDNA of Sc-GST contained 1052 base pairs(bp),including 700 bp of the 5′-untranslated region(UTR),280 bp of the 3′-UTR,and a 678 bp open reading frame that encoded a 225 amino acid polypeptide.We then used real-time qPCR to examine the Sc-GST mRNA tissue distribution pattern in S.constricta from China and time-course of expression in the hemolymph of S.constricta from both China and Vietnam in response to the pathogen Vibrio anguillarum.The Sc-GST gene was predominantly expressed in the immune tissues,including hemocytes,mantle,gill,and liver.In particular,Sc-GST gene expression in S.constricta from Vietnam significantly elevated at 12 h after injection and increased compared to the values from those of China during 12-72 h of the experiment.One explanation for these different responses is that the bacteria used in the experiment were obtained from China,and the S.constricta also from China have probably already adapted to this pathogen,and thus,showed a less severe response to infection.Results of this study suggest that the Sc-GST gene might play important roles in modulating the immune response of S.constricta.