Characterization and expression analysis of heat shock protein 90β from golden pompano (Trachinotus ovatus, Linnaeus 1758) in responses to stock density stress and Cryptocaryon irritans infection

Heat shock protein 90 family, a class highly conserved protein and important molecular chaperone and its plays a role in enhancing animal adaptability to environmental stress and improving immunity. In this study, a full-length HSP90 beta cDNA (ToHSP90 beta) sequence was identified from Trachinotus ovatus. The cDNA of ToHSP90 beta was 2648 base-pairs (bp) long and contained a 5'-terminal untranslated region of 130 bp, a 3'-terminal untranslated region of 334 bp, and the open reading frame length 2184 bp, which can encode 728 amino acids. The ToHSP90 beta has a heat shock protein 90 family signature. The ToHSP90 beta amino acid sequence has high homology with other fish HSP90 beta amino acids (92.5-99.17%) and contains five conserved signal regions and a structural feature of the cytoplasmic HSP90 family. Phylogenetic tree analysis indicated that ToHSP90 beta was most closely related to Seriola dumerili HSP90 beta. Tissues expression analysis showed that the ToHSP90 beta was expressed in all nine tissues of T. ovatus, and its expression was the highest in the intestine. The stocking density significantly affected the expression of ToHSP90 beta in the kidney and brain tissues, and its expression levels increased significantly with increasing stocking densities, indicating that it plays an important regulatory role in the process of T. ovatus' chronic stress response. After Cryptocaryon irritans infection, the mRNA expression of ToHSP90 beta was significantly increased in liver and kidney tissues, indicating that ToHSP90 beta would be involved in the immune regulatory response. This study was the first to analyze the expression pattern of HSP90 beta mRNA in T. ovatus tissues and their expression responses to stocking density stress and C. irritans infection. To provide a theoretical basis for further study of the function of fish HSP90 and its physiological mechanism in environmental stress and parasite infection.