CgmiR307 involved in the regulation of Nrf2-dependent oxidative response in the Pacific oyster Crassostrea gigas under high-temperature stress.

miRNA, a type of endogenous small non-coding RNA, is involved in the response to various environmental stresses through post-transcriptional regulation. In the present study, the role of CgmiR307 in the regulation of oxidative response under high-temperature stress by targeting CgNrf2 was investigated in the Pacific oyster Crassostrea gigas. The binding site of CgmiR307 were predicted at 1799-1818 bp in the 3'-UTR of CgNrf2, and the binding activity of CgmiR307 with the mRNA of CgNrf2 was further proved by the dual-luciferase reporter assay. The expression levels of CgmiR307 and CgNrf2 in gill were significantly higher than in other tissues, and exhibited significant fluctuations and variations after exposure to 28 °C. There was a significant reduction in the expression levels of CgSOD, and CgCAT in gill, as well as the activities of SOD, CAT, and T-AOC, while ROS and MDA contents significantly increased in CgNrf2-RNAi oysters. After CgmiR307 agomir injection and high-temperature stress, the expression levels of CgNrf2, CgSOD and CgCAT in gill, the activities of SOD and CAT and T-AOC decreased significantly, while ROS and MDA content significantly increased. After CgmiR307 antagomir injection and high-temperature stress, the changes in the parameters of oxidative response shown exactly the opposite trend. These results demonstrated that CgmiR307 was involved in the regulation of oxidative response by inhibiting the mRNA expression of CgNrf2 under high-temperature stress.