MOLECULAR CHARACTERIZATION AND EXPRESSION ANALYSIS OF HIF-1α IN LARGE YELLOW CROAKER (LARIMICHTHYS CROCEA)

Hypoxia-inducible factor-1α (HIF-1α) is considered as the master regulator of the response to hypoxia, through activating target gene expression involved in angiogenesis, erythropoiesis and glycolysis. In recent years, HIF-1α has been found to regulate the immune response. However, very little information was available about its functions in fish immune response. In this study, the cDNA sequence of HIF-1α gene (LcHIF-1α) was cloned from large yellow croaker Larimichthys crocea. Its open reading frame (ORF) was 2256 nucleotides long, encoding a peptide of 751 amino acids. The deduced LcHIF-1α protein contained five typical motifs: a helix-loop-helix (HLH) domain, two PAS domains, a DNA binding domain (HIF-1), and a HIF-1α C-terminal transactivation domain (HIF-1a_CTAD). Phylogenetic analysis showed LcHIF-1α formed a separate clade with sequences from other fish species, far from the clades formed by avian, amphibian and mammalian HIF-1α proteins. The LcHIF-1α transcripts were constitutively expressed in all examined tissues and significantly up-regulated in the spleen and head kidney tissues by Vibrio alginolyticus, and reached the peak at 24h, with 6.8- and 2.9-fold increases, respectively. Its transcripts were also detected in neutrophils, macrophages and lymphocytes from large yellow croaker, and significantly up-regulated by lipopolysaccharide (LPS) in neutrophils and macrophages with 2.6- and 1.8-fold increases at the peak. These results indicate that LcHIF-1α may play a role in mediating the immune response of large yellow croaker.