Fisheries Science Institute, Chonnam National University, Yeosu, 59626, South Korea.
Fisheries Science Institute, Chonnam National University, Yeosu, 59626, South Korea; Department of Ocean Integrated Science, Chonnam National University, Yeosu 59626, South Korea.
Environ Pollut. 2023 Nov 15;337:122554. doi: 10.1016/j.envpol.2023.122554. Epub 2023 Sep 15.
The brackish water clam (Corbicula japonica) is constantly exposed to stressful salinity gradients and high levels of heavy metals in the freshwater-saltwater interface of estuary environments, which are introduced from upstream regions and land. To identify the key molecular pathways involved in the response to salinity changes and heavy metal bioaccumulation, we obtained the transcriptomes of C. japonica inhabiting different salinities and heavy metal distributions in Gwangyang Bay (Korea) using RNA sequencing. Among a total of 404,486 assembled unigenes, 5534 differentially expressed genes were identified in C. japonica inhabiting different conditions, 1549 of which were significantly upregulated and 1355 were significantly downregulated. Correlation analyses revealed distinct gene expression patterns between the low and high conditions of salinity and heavy metal bioaccumulation. Functional annotation revealed significant downregulation of genes involved in "ubiquitin-dependent protein catabolic process," "tricarboxylic acid cycle," and "intracellular protein transport" in C. japonica from the high condition compared to the low condition. Transcription and translation pathways were significantly enriched in the high condition. Additionally, upon comparison of the low and high conditions by qRT-PCR and proteasome enzyme activity analyses, our findings demonstrated that environmental stress could suppress the ubiquitin-proteasome complex (UPC). Additionally, transcriptomic changes under high salinity stress conditions may be related to an increase in cellular protection by defense enzymes, which leads to more energy being required and a disruption of energy homeostasis. Ultimately, this could cause growth retardation in the clam C. japonica. In summary, this study provides the first evidence of UPC suppression induced by a combination of high salinity and heavy metal bioaccumulation stress in C. japonica, which could compromise the survival and growth of estuarine bivalves.
咸淡水蛤（Corbicula japonica）经常暴露于河口环境中淡水-海水界面处的应激盐度梯度和重金属水平，这些物质是由上游地区和陆地带来的。为了确定参与盐度变化和重金属生物积累反应的关键分子途径，我们使用 RNA 测序获得了栖息在韩国光阳湾不同盐度和重金属分布条件下的 C. japonica 的转录组。在总共 404486 个组装的 unigenes 中，鉴定出 5534 个在不同条件下栖息的 C. japonica 中差异表达的基因，其中 1549 个基因显著上调，1355 个基因显著下调。相关性分析显示，盐度和重金属生物积累的低条件和高条件之间存在明显不同的基因表达模式。功能注释显示，与低条件相比，高条件下与“泛素依赖性蛋白分解代谢过程”、“三羧酸循环”和“细胞内蛋白质运输”相关的基因显著下调。转录和翻译途径在高条件下显著富集。此外，通过 qRT-PCR 和蛋白酶体酶活性分析比较低条件和高条件，我们的研究结果表明，环境应激可以抑制泛素-蛋白酶体复合物（UPC）。此外，高盐度应激条件下的转录组变化可能与防御酶引起的细胞保护增加有关，这会导致更多的能量需求和能量平衡的破坏。最终，这可能导致咸淡水蛤 C. japonica 的生长迟缓。总之，本研究首次提供了 C. japonica 中高盐度和重金属生物积累应激诱导 UPC 抑制的证据，这可能会危及河口双壳类动物的生存和生长。
