Cloning and characterization of heat shock transcription factor 1 and its functional role for Hsp70 production in the sea slug Onchidium reevesii

To investigate the regulatory role of heat shock transcription factor 1 of sea slug Onchidium reevesii (OrHSF1) on Hsp70 expression in the sea slug under stress , the OrHSF1 gene was cloned and bioinformatics analysis was performed, then the gene and protein expressions by RNA interference (RNAi) mediated knockdown of OrHSF1 expression were measured to clarify the regulatory relationship between OrHSF1 and Hsp70 under low-frequency noise (LFN) stress. Our study was the first to clone a 1572 bp sequence of the OrHSF1 gene, with the sequence coding for amino acids (CDS) being 729 bp, encoding 243 amino acids. O. reevesii shared a close evolutionary relationship with mollusks such as the Aplysia californica. OrHSF1 gene is widely expressed in different tissues of sea slugs, with the highest expression in the intestine and the lowest in the reproductive glands. Furthermore, we used RNA interference (RNAi) as a tool to silence the OrHSF1 gene in the central nervous system (CNS) and the results indicated that gene silencing was occurring systematically in the CNS and the suppression of OrHSF1 expression by RNAi-mediated gene silencing altered the expression of Hsp70; besides, the expression trends of OrHSF1 gene and Hsp70 were consistent in the 3 and 5-day RNAi experiment. Moreover, in sea slugs injected with siHSF1 and exposed to LFN, the mRNA expression and protein expression of Hsp70 in the CNS were significantly decreased compared to the low-frequency noise group (P < 0.05). This study demonstrated that OrHSF1 regulates Hsp70 expression in marine mollusks under low-frequency noise, and HSF1-Hsp70 axis plays a key role in stress response.