Effects on short-term (6 h) and long-term (96 h) exposure to cadmium (Cd) at 0.1, 0.5 and 2.5 mg/L in microalga Dunaliella salina were assessed using both physiological end points and gene expression analysis. Different physiological responses between the short-term and long-term exposures were observed. Upon 6 h after Cd exposure, lipid peroxidation and cell ultrastructure remained unchanged, while contents of chlorophyll a, chlorophyll b, carotenoids were increased at 0.5 and 2.5 mg/L Cd. Contrarily, 96 h after Cd exposure, lipid peroxidation levels were increased, while pigments content was decreased, and damaged cell ultrastructure was apparent at 2.5 mg/L Cd. Activities of antioxidant enzymes (APX, SOD, GST, GPX, and GR) changed differently both at 6 h and 96 h after Cd exposure. Upon 6 h after Cd exposure, SOD and GST activity increased at all three doses, GR and GPX activity increased at 0.5 mg/L Cd while APX activity increased at 0.1 mg/L Cd. Contrarily, 96 h after Cd exposure, activities of all the antioxidant enzymes increased both at 0.1 and 0.5 mg/L Cd; but there was a decrease in SOD and GR activity in D. salina exposed to 2.5 mg/L Cd. RNA-seq and qRT-PCR analyses indicated that genes involved in ROS-scavenge, photosystem, and ribosome functions were differentially expressed. The most significantly enriched function was the ribosome, in which more than 30 ribosome genes were up-regulated at 6 h but down-regulated at 96 h after Cd exposure at 2.5 mg/L. Our study indicated for the first time that genes encoding ribosomal proteins are the primary target for Cd in microalgae, which allowed gaining new insights into temporal dynamics of toxicity and adaptive response pathways in microalgae exposed to metals.

使用生理终点和基因表达分析，评估了微藻杜氏盐藻对镉（Cd）的短期（6 h）和长期（96 h）暴露的影响，评估了盐藻在微藻杜氏盐藻中的浓度。在短期和长期接触之间观察到不同的生理反应。镉暴露6 h后，脂质过氧化和细胞超微结构保持不变，而叶绿素a，叶绿素b的含量，类胡萝卜素在0.5和2.5 mg / L Cd时增加。相反，在Cd暴露96 h后，在2.5 mg / L Cd下脂质过氧化水平增加，而色素含量减少，并且细胞超微结构明显受损。镉暴露后6小时和96小时，抗氧化酶（APX，SOD，GST，GPX和GR）的活性发生了不同的变化。暴露于镉后6小时，所有三种剂量的SOD和GST活性均增加，在0.5 mg / L Cd时GR和GPX活性增加，而在0.1 mg / L Cd时APX活性增加。相反，在镉暴露96小时后，在0.1和0.5 mg / L Cd时，所有抗氧化酶的活性均增加；但盐藻中的SOD和GR活性有所下降暴露于2.5 mg / L Cd。RNA-seq和qRT-PCR分析表明，参与ROS清除，光系统和核糖体功能的基因差异表达。最显着富集的功能是核糖体，其中超过30种核糖体基因在2.5 mg / L的Cd暴露后于6 h被上调，而在96 h被下调。我们的研究首次表明，编码核糖体蛋白的基因是微藻中Cd的主要靶标，这使人们对暴露于金属的微藻的毒性和适应性反应途径的时空动态有了新的认识。