School of Marine Sciences, Ningbo University, Ningbo 315211, PR China; Zhejiang Key Laboratory of Aquatic Germplasm Resources, Zhejiang Wanli University, Ningbo 315100, PR, PR China.
Zhejiang Key Laboratory of Aquatic Germplasm Resources, Zhejiang Wanli University, Ningbo 315100, PR, PR China.
Comp Biochem Physiol B Biochem Mol Biol. 2020 Jan;239:110367. doi: 10.1016/j.cbpb.2019.110367. Epub 2019 Oct 24.
The razor clam Sinonovacula constricta is a commercial benthic bivalve, and burrows the deeper cave than the other buried benthic bivalves. Due to the little exchange of seawater and to anoxic conditions, S. constricta is exposed to considerable amounts of sulfide during low tide, but exhibits strong sulfide tolerance. Mitochondrial sulfide oxidation is a particular defense strategy against sulfide toxicity of sulfide-tolerant organisms, for which sulfide:quinone oxidoreductase (SQR) is the first key enzyme. In order to investigate the mechanism of sulfide tolerance in S. constricta, its SQR (designated as ScSQR), was cloned and characterized. The full-length cDNA of ScSQR was 3698 bp and encoded 443 amino acids. The deduced ScSQR protein contained conserved FAD-binding domains, two cysteine residues, two histidines, and one glutamic acid, which are the essential elements for the catalytic mechanism of SQR. Subcellular localization analysis by the TargetP 1.1 prediction and the Western blot confirmed that ScSQR was only located in the mitochondria. The response of ScSQR in the gill and liver of S. constricta were investigated during sulfide exposure (50, 150, and 300 μM sulfide) for 0, 3, 6, 12, 24, 48, 72, and 96 h by qRT-PCR. Moreover, the time-course expressions of ScSQR protein in the S. constricta gill were detected when exposed to 150 μM sulfide by Western blot. The expression level of ScSQR increased significantly and showed a time-dependent pattern. In addition, under sulfide stress, the expression level of the gill was higher than that of liver. Together, our results suggest that ScSQR may perform important roles in protecting cells from sulfide stress by participating in mitochondrial sulfide detoxification and providing high sulfide tolerance to S. constricta.
光滑河蓝蛤（Sinonovacula constricta）是一种商业性底栖双壳贝类，其挖掘的洞穴比其他埋藏的底栖双壳贝类更深。由于海水交换量少和缺氧条件，光滑河蓝蛤在退潮时会暴露在相当数量的硫化物中，但表现出很强的硫化物耐受性。线粒体硫化物氧化是硫化物耐受生物抵御硫化物毒性的一种特殊防御策略，其中硫化物：醌氧化还原酶（SQR）是第一个关键酶。为了研究光滑河蓝蛤硫化物耐受的机制，克隆并表征了其 SQR（命名为 ScSQR）。ScSQR 的全长 cDNA 为 3698bp，编码 443 个氨基酸。推导的 ScSQR 蛋白含有保守的 FAD 结合结构域、两个半胱氨酸残基、两个组氨酸残基和一个谷氨酸残基，这些是 SQR 催化机制的必需元素。TargetP 1.1 预测和 Western blot 的亚细胞定位分析证实 ScSQR 仅位于线粒体中。通过 qRT-PCR 研究了硫化物暴露（50、150 和 300μM 硫化物）0、3、6、12、24、48、72 和 96 h 期间 ScSQR 在光滑河蓝蛤鳃和肝中的反应。此外，通过 Western blot 检测了 150μM 硫化物暴露时 ScSQR 蛋白在光滑河蓝蛤鳃中的时间过程表达。ScSQR 的表达水平显著增加，表现出时间依赖性模式。此外，在硫化物胁迫下，鳃中的表达水平高于肝。综上所述，我们的结果表明，ScSQR 可能通过参与线粒体硫化物解毒来保护细胞免受硫化物胁迫，从而在保护光滑河蓝蛤免受硫化物胁迫方面发挥重要作用，并为其提供高硫化物耐受性。
