Molecular characterization and expression analysis of interferon-gamma in the large yellow croaker Larimichthys crocea.

Abstract The large yellow croaker Larimichthys crocea is an important mariculture fish species in China, and the bacterium Vibrio harveyi ( V. harveyi ) and the ciliate protozoan Cryptocaryon irritans ( C. irritans ) are the two major pathogens in its aquaculture sector. Interferon-gamma (IFN-γ) plays important roles in regulating both innate and cell mediated immune responses as an inflammatory cytokine. In this study, we obtained the nucleotide sequence of IFN-γ from the large yellow croaker (LcIFN-γ). The phylogenetic relationship tree of 18 available IFN-γ genes was constructed based on their sequences. Expression analyses in 10 various tissues were conducted after the croaker challenged with V. harveyi and C. irritans , respectively. Real time PCR analysis showed that the expression of LcIFN-γ was observed broadly in health individuals. After injected with V. harveyi , the 10 tissues had a higher expression of IFN-γ at the first day (1 d); only spleen, muscle, intestine, heart and skin had higher expressions after infected with C. irritans at 1 d. Major immune tissues (skin, gill, head kidney and spleen) and detoxification tissue (liver) were sampled at 0 h, 6 h, 1 d, 2 d, 3 d, 4 d, 5 d and 7 d to understand the expression trends of LcIFN-γ after challenged with C. irritans . The expressions of LcIFN-γ in skin and gill (the primary immune organs) showed a clear correlative relationship with the life cycle of C. irritans .