Abstract：
Species in estuaries tend to undergo both cadmium (Cd) and low salinity stress. However, how low salinity affects the Cd toxicity has not been fully understood. Investigating the impacts of low salinity on the dose-response relationships between Cd and biological endpoints has potential to enhance our understanding of the combined effects of low salinity and Cd. In this work, changes in the transcriptomes of Pacific oysters were analyzed following exposure to Cd (5, 20, 80 μg/L Cd2+) under normal (31.4 psu) and low (15.7 psu) salinity conditions, and then the dose-response relationship between Cd and transcriptome was characterized in a high-throughput manner. The benchmark dose (BMD) of gene expression, as a point of departure (POD), was also calculated based on the fitted dose-response model. We found that low salinity treatment significantly influenced the dose-response relationships between Cd and transcripts in oysters indicated by altered dose-response curves. In details, a total of 219 DEGs were commonly fitted to best models under both normal and low salinity conditions. Nearly three quarters of dose-response curves varied with salinity condition. Some monotonic dose-response curves in normal salinity condition even were replaced by nonmonotonic curves in low salinity condition. Low salinity treatment decreased the PODs of differentially expressed genes induced by Cd, suggesting that gene differential expression was more prone to being triggered by Cd in low salinity condition. The changed sensitivity to Cd in low salinity condition should be taken into consideration when using oyster as an indicator to assess the ecological risk of Cd pollution in estuaries.
摘要：
河口中的物种倾向于同时遭受镉（Cd）和低盐度胁迫。然而,低盐度对Cd毒性的影响尚未完全了解。研究低盐度对Cd与生物终点之间的剂量反应关系的影响，有可能增强我们对低盐度和Cd的综合影响的理解。在这项工作中,在正常（31.4psu）和低（15.7psu）盐度条件下暴露于Cd（5、20、80μg/LCd2+）后，分析了太平洋牡蛎转录组的变化，然后以高通量方式表征Cd与转录组之间的剂量-反应关系。基因表达的基准剂量（BMD），作为出发点(POD)，也是基于拟合的剂量反应模型计算的。我们发现，低盐度处理显着影响了牡蛎中Cd与转录本之间的剂量-反应关系，这通过改变的剂量-反应曲线来表明。在细节上,在正常和低盐度条件下，通常总共有219个DEG适合最佳模型。近四分之三的剂量反应曲线随盐度条件而变化。在正常盐度条件下，一些单调的剂量反应曲线甚至被低盐度条件下的非单调曲线所取代。低盐度处理降低了Cd诱导的差异表达基因的PODs,表明在低盐度条件下，基因差异表达更容易被Cd触发。以牡蛎为指标评估河口Cd污染的生态风险时，应考虑低盐度条件下对Cd敏感性的变化。
