Combined Effect of Temperature and Cadmium on Molecular Responses of Hsp70 and P-gp Genes in Crassostrea gigas

To evaluate the combined effect of temperature and cadmium on the molecular responses of heat shock protein 70 (hsp70) and P-glycoprotein (P-gp) in mantle, digestive gland and gills of Crassostrea gigas, oysters were exposed to combinations of five temperature levels (10, 15, 20, 25, and 30°C) and 10 µg L⁻¹ cadmium for 21 days. Oysters were sampled for mRNA quantification by qPCR, and the results showed that the P-gp gene expression changed significantly after treatment at different temperatures and different treatment times. The P-gp gene expression was the highest in the digestive gland. Compared with the control group, the P-gp gene expression in cadmium treatment groups at all the different temperatures were significantly higher than the control group. The control oysters (kept at 10° during the whole experiment without cadmium) expressed low levels of hsp70, but the groups treated with cadmium displayed somewhat higher levels. The present study demonstrated hsp70 and P-gp played an important role in the detoxification of Cd in C. gigas, and confirmed temperature should be considered for the assessment of Cd-induced toxicity in oysters.