Abstract:
The HIF (hypoxia-inducible factor) signaling pathway is an oxygen-sensing signaling pathway in animals, and plays important roles in metabolism and energy homeostasis in hypoxia environments. In this study, four key genes of HIF signaling pathway,
HIF-1
α,
HIF-1
β,
PHD2
A and
PHD2
B, were cloned using PCR from S
inonovacula constricta, and the physicochemical properties and domains of their encoded proteins were predicted, and analyzed their phylogenetic relationships. The results showed that HIF-1 contained typical HLH, PAS, PAC, and C-TAD domains, HIF-1α specific ODDD and N-TAD domains, and ScPHD2 contained zf-MYND and P4Hc domains; unlike other invertebrates, shellfish including razor clam PHD2 had two copies. Using real-time fluorescence quantitative PCR (RT-qPCR), the expression levels of
HIF-1 and
PHD2 were further analyzed at different developmental stages, in different tissues of adults and under hypoxia (0.5 mg/L and 2.0 mg/L) and air exposion (21 ℃ air exposion and 4 ℃ air exposion) stresses. The results showed that razor clam
HIF-1 and
PHD2 were expressed from the egg stage,
ScHIF-1
α was expressed at higher levels than other genes in the six tissues examined, and the highest expression was in gill, followed by hepatopancreas, while
ScPHD2
A and
ScPHD2
B were expressed at very low levels in all six tissues. Under hypoxia stress,
ScHIF-1α and
ScPHD2 expressions were significantly up-regulated, but the 0.5 mg/L group was more up-regulated than the 2 mg/L group, while
ScHIF-1
β expressions were not significantly changed. Under air exposion stress,
ScHIF-1
β expression did not change significantly, while
ScHIF-1
α and
ScPHD2 expression were significantly up-regulated, and the up-regulation was greater in the 4 ℃ air exposion group than in the 21 ℃ air exposion group. It was shown that ScHIF-1 and ScPHD2 possessed typical HIF and PHD family characteristics, respectively, and their expression was induced to be up-regulated under hypoxia, suggesting that they may be involved in the response process of razor clam after low oxygen stress. The results of the study provide a reference value for further research on the hypoxia signaling pathway and hypoxia adaptation mechanism of razor clam.