Enhanced resistance of triploid crucian carp to cadmium-induced oxidative and endoplasmic reticulum stresses.

Cadmium (Cd) is highly toxic to aquatic organisms. In this study, we found a new variety of triploid crucian carp with strong Cd resistance. Under Cd stress, the mortality and abnormality rates in triploid crucian carp were lower than those of diploid strains. To explore the molecular mechanisms underlying Cd stress, the liver transcriptomes of triploid crucian carp were obtained. The expression of 5,797 unigenes in Cd-treated triploid crucian carp differed significantly from those of control group. These differential expression genes mainly involved in endoplasmic reticulum (ER) associated ubiquitin-dependent proteins, membrane proteins of ER and mitochondria. Quantitative real-time PCR and enzyme activity analysis all confirmed triploid crucian carp resistance to Cd stress was regulated by both oxidative stress and ER stress responses. Underlying Cd stress, the enhanced expression of sestrin-1 gene may increase triploid crucian carp survival compared to diploid fish. This study also provides important clue that IRE-1 and PERK, but not ATF-6, were involved in enhancement of Cd resistance in triploid crucian carp. Moreover, our results showed that egg envelopes of crucian carp had strong ability to block Cd and could protect embryos from Cd stress damage.