Molecular cloning, antiserum preparation and expression analysis during head regeneration of $$\upalpha $$ α -crystallin type heat shock protein in Hydra vulgaris

Our previous study based on the transcriptome profiling indicated that a fragment of α-crystallin type heat shock protein (α-Hsp) gene was one of the numerous cDNA sequences expressed differentially at various stages of head regeneration in Hydra vulgaris. To further investigate the role that which α-Hsp plays during hydra regeneration, a full-length cDNA of α-Hsp gene of H. vulgaris was isolated by the rapid amplification of cDNA ends (RACE) technique. The full-length cDNA of α-Hsp gene was 1156 bp, containing a 765 bp open-reading frame (ORF), which encodes a polypeptide of 254 amino acid residues with a molecular weight of 29.27 kDa. Further, the ORF was subcloned into the plasmid pET-42a(+), and the recombinant plasmid pET-42a(+)-α- Hsp was transformed to Escherichia coli BL21(DE3), then the fusion protein GST-α-Hsp was expressed mainly in the form of a soluble molecule after induction by isopropyl-β-d-thiogalactopyranoside. In addition, BALB/Cmice were immunized with the fusion protein to prepare the polyclonal antiserum which was used as the primary antibody for whole-mount immunohistochemical assay. The results from the immunohistochemical assay showed that α-Hsp had expressedmainly at the wound site and nearby area of hydra after decapitation operation, and both quantitative real-time polymerase chain reaction (qPCR) analysis and immunohistochemical assay revealed that the expression level of α-Hsp increased gradually during the early period of hydra regeneration, then reached a peak at 24 h after decapitation operation, while decreased during the late regeneration period. Moreover, it indicated an important role of α-Hsp gene in hydra head regeneration that RNA interference (RNAi)-mediated α-Hsp silencing led to the obvious delay of the regeneration of head structures in H. vulgaris. In conclusion, our results gave the hint that α-Hsp could be related to wound healing and tissue remodelling at early regeneration stages, and may lay the foundation for further studies about the physiological function and role of α-Hsp during hydra regeneration.