Two HSP90 genes in mandarin fish Siniperca chuatsi: identification, characterization and their specific expression profiles during embryogenesis and under stresses.

HSP90 plays important roles in multiple cellular stress responses. Here, two cytoplasmic HSP90 isoforms, ScHSP90α and ScHSP90β, were identified from Siniperca chuatsi. Their cDNA and gDNA structures, amino acid sequence features, and sequence identities and phylogenetic analysis with other species were described. Their expression profiles during embryonic development in different tissues and under stressful conditions were analyzed using real-time quantitative PCR. During embryogenesis, transcripts of both genes were detected at low levels during the early developmental stages and were up-regulated from appearance of myomere for ScHSP90a and closure of blastopore for ScHSP90β. ScHSP90α showed a tissue-specific variation with high expression in ovary and brain under non-stressed conditions, while ScHSP90β was ubiquitously highly expressed in different tissues. Acute heat shock resulted in a strong up-regulation of ScHSP90α in heart, liver, and head kidney, while it only weakly induced ScHSP90β in these tissues. ScHSP90α was also markedly induced in liver in a time-dependent manner under hypoxia, while the expression of ScHSP90β was not affected by hypoxia. Additionally, Aeromonas hydrophila infection markedly augmented ScHSP90α in head kidney and spleen and mildly up-regulated ScHSP90β in spleen, while suppressing ScHSP90β in head kidney. These results suggest that ScHSP90α and ScHSP90β are differently involved in embryogenesis and under different environmental conditions including high temperature, hypoxia, and bacterial infection. This study will benefit to further clarify the roles of fish HSP90 isoforms in embryogenesis and under stressful conditions and contribute to further study on enhancing stress tolerance and disease resistance of mandarin fish.