Unravelling the characterization of hypoxia‐inducible factor‐1α ( HIF‐1α ) and antioxidant enzymes in clam Cyclina sinensis in response to hypoxia

Aquatic hypoxia has negative or detrimental effects on clams. To cope with hypoxia stress, a complex series of physiological and biochemical strategies can be employed in clams. Hypoxia-inducible factor-1α (HIF-1α) and antioxidant enzymes are commonly found in aquatic animals as an adaptation against hypoxia. In the present study, we cloned the HIF-1α sequence in clam Cyclina sinensis, and it consists of 2654 base pairs (bp) carrying a single open-reading frame that encompasses 2235 bp of the coding region. The predicted C. sinensis HIF-1α protein (744 amino acids) has the conserved HLH-PAS domain, which contained one N-terminal basic helix–loop–helix (bHLH) domain and two Per-ARNT-Sim A/B (PAS) domains, followed by PAS-associated C-terminal (PAC) domain. HIF-1α is expressed predominantly in gills. Exposed to hypoxia, the transcript level of HIF-1α was significantly up-regulated in response to hypoxia, and then, the transcript level declined continuously with the time elapsed. The antioxidant enzymes (SOD, CAT and GSH-PX) in gills were increased initially and then decreased after acute hypoxia exposure. Our study indicates that the HIF-1α gene and antioxidant enzymes may play an important role in cope with acute hypoxia exposure.