Hypoxia Actives HIF-1α and Affects Genes Expression Associated with Hypoxia and Transcriptional Regulation of PHD by HIF-1α under Hypoxia in Tegillarca granosa

Abstract

Abstract Background Hypoxia-inducible factor-1α (HIF-1α) is actived in response to hypoxia and can regulate genes expression related to hypoxia pathway. However, far less is known about how HIF-1 regulates downstream target genes to produce hypoxia adaptive responses in molluscaunder hypoxia and whether the activity of PHDs under hypoxia is controlled by HIF-1α. Methods and results. qRT-PCR was performed to determine the expression of Tg-HIF-1α ,Tg-PHD, Hb, Mb and dual-luciferase reporter analysis was used to detect the transcriptional activity. Results showed that expression level of Tg-HIF-1α and Tg-PHD were both highest in gill and lowest in adductor muscle. Additionally, a significant expression increase in Tg-HIF-1α and Tg-PHD was observed after hypoxia 8 h when DO concentrations were 0.5 mg/L and 2.0 mg/L (P<0.01), then decreased slowly after 24 h, It was still higher than that normoxia (P<0.01), after 72 h, Tg-PHD expression showed no significant change (P>0.05). After 8 h at 0.5 mg/L of DO, Hb expression decreased in hemocytes (P<0.01); at the same 0.5 mg/L of DO, in the hepatopancreas, the expression of MbI and MbII were increased (P<0.01) after hypoxia 24 h and 120 h, respectively. The dual-luciferase reporter analysis revealed that Tg-HIF-1α could transactivate the promoter of PHD but not of Hb. Conclusion Hypoxia induced significant changes in Tg-HIF-1α, Tg-PHD, Tg-Hb and Tg-Mb expressions. Tg-HIF-1α can bind to PHD’s hypoxia response elements but not Hb’s. It appears that the regulation of Tg-HIF-1α transcript levels may be a useful biomarker for hypoxia exposure in the environment.