Molecular cloning, characterization of JunB in Schizothorax prenanti and its roles in responding to Aeromonas hydrophila infection

Abstract

The transcription factor JunB can induce physiological or pathological responses to various stimuli, including immune stimulants and bacteria, and plays an important role in the immune response process. In this study, we identified a JunB family member in Schizothorax prenanti (S. prenanti), which was designated SpJunB. The complete coding sequence (CDS) of SpJunB was 930 bp in length, which was submitted to GenBank (ID: MN215886). SpJunB encodes a putative protein of 309 amino acids, which is highly homologous to JunB of common carp. The SpJunB protein contained a conserved JunB domain, and its 3D structure was also highly similar to (77.61%) the human SpJunB protein. SpJunB was found to be extensively expressed in various tissues, with the highest expression in the spleen. The expression of SpJunB was significantly upregulated after Aeromonas hydrophila (A. hydrophila) challenge. Prokaryotic expression indicated that a 51 kDa recombinant protein was obtained after induction with 1.5 mmol/L isopropyl-beta-D-thiogalactopyranoside (IPTG) for 6 h at 37 °C. The expression levels of IL-1β, IL-6 and IL-8 were significantly upregulated (p < 0.01) after treatment of S. prenanti with the SpJunB protein. The activities of SOD, AKP and LZM were also significantly increased (p < 0.01) after the treatment of S. prenanti with the SpJunB protein. Simultaneously, the SpJunB protein reduced the infection rate of A. hydrophila in S. prenanti. In conclusion, SpJunB may improve the immune functions of S. prenanti. It will be beneficial to further study the immune mechanism of JunB in fish.