Functional characterization of four metallothionein genes in Daphnia pulex exposed to environmental stressors.
Functional characterization of four metallothionein genes in Daphnia pulex exposed to environmental stressors.
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DOI：
10.1016/j.aquatox.2011.12.010
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发表时间：
2012-04
期刊：
影响因子：
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通讯作者：
De Schamphelaere KA
中科院分区：
文献类型：
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作者：
Asselman J;Glaholt SP;Smith Z;Smagghe G;Janssen CR;Colbourne JK;Shaw JR;De Schamphelaere KA
本研究从分子水平和生态毒理学水平研究了兴安水蚤的金属硫蛋白基因(MT1、MT2、MT3和MT4)。因此，我们对基因位置和预测的蛋白质序列进行了生物信息学分析，并筛选了上游侧翼区域的调控元件。这些元件的数量及其相对于起始密码子的位置在四个基因之间甚至在两个重复基因(Mt1A和Mt1B)之间差异很大，这表明这四种蛋白质在生物体对胁迫的反应中发挥了不同的作用。随后，我们进行了长达16天的不同环境应激源(亚致死性水平，导致繁殖减少约50%)的慢性暴露。基于先验知识，我们将它们暴露在金属镉、铜和镍、蜕皮激素羟基蜕皮激素(20E)以及氧化应激源蓝藻(铜绿微囊藻)和百草枯(PQ)中。然后，我们比较了这四个mt基因在这些胁迫条件下和对照条件下的mt基因的表达水平，并对其全基因组进行了测序和注释。综上所述，不同胁迫条件下mt基因的表达结果表明，不同的mt基因可能在杜鹃对胁迫的响应中发挥不同的作用，这四个基因之间的部分(但不是全部)差异可能与其上游侧翼区域的调控元件模式有关。
We characterized the metallothionein genes (Mt1, Mt2, Mt3, and Mt4) in Daphnia pulex on both molecular and ecotoxicological level. We therefore conducted a bioinformatical analysis of the gene location and predicted protein sequence, and screened the upstream flanking region for regulatory elements. The number of these elements and their positions relative to the start codon varied strongly among the four genes and even among two gene duplicates (Mt1A and Mt1B), suggesting different roles of the four proteins in the organisms’ response to stress. We subsequently conducted a chronic 16-day exposure of D. pulex to different environmental stressors (at sublethal levels causing approximately 50% reduction in reproduction). Based on prior knowledge, we exposed them to the metals Cd, Cu, and Ni, the moulting hormone hydroxyecdysone (20E), and the oxidative stressors cyanobacteria (Microcystis aeruginosa), and paraquat (Pq). We then compared mRNA expression levels of the four Mt genes under these stress conditions with control conditions in “The Chosen One” clone (TCO), for which the full genome was sequenced and annotated. All together, the mRNA expression results under the different stress regimes indicate that different Mt genes may play different and various roles in the response of D. pulex to stress and that some (but not all) of the differences among the four genes could be related to the pattern of regulatory elements in their upstream flanking region.