Temperature-dependent regulation of gene expression in Japanese flounder Paralichthys olivaceus kidney after Edwardsiella tarda formalin-killed cells

Temperature affects the activities of the immune system and the susceptibility of fish to pathogens. To investigate the modulation of temperature on immune related gene expression in formalin-killed cells (FKC) of Edwardsiella tarda-injected Japanese flounder Paralichthys olivaceus, fish reared at 15 or 22 °C were injected with FKC of E. tarda. The up-regulation of immune related genes was detected in FKC-injected fish at both temperatures by qPCR. The mRNA expression of IFNγ was highly up-regulated at 6 h post injection (hpi) in FKC-injected fish at 15 °C, whereas at 22 °C, strong up-regulation of the gene was detected at 3 hpi The mRNA expression level of IRF1 was detected from 3 hpi to day 14 post injection in fish reared at 15 °C, but the gene was up-regulated from 3 to 6 hpi in fish reared at 22 °C. Comprehensive gene expression profiling showed that immune related genes are differentially expressed between 15 and 22 °C. Genes involved in the IFNγ signaling pathway were up-regulated at 22 °C but not at 15 °C. These results demonstrate that gene(s) involved in IFNγ signaling pathway in Japanese flounder stimulated with FKC of E. tarda are regulated by temperature.