Cryptochrome 1 is involved in anti-bacterial immunity in Japanese flounder (Paralichthys olivaceus)

Cryptochrome is a pivotal protein of the core regulatory machinery in circadian clock and participates in various biological processes including immunity. In fish, the immunological functionality of Cryptochrome is unclear. In this study, we profiled the expression pattern of Japanese flounder cryptochrome 1 (named PoCry1) and inves-tigated its involvement in the immune response during bacterial infection. PoCry1 is approximately 75% iden-tical in amino acid sequence to mammalian Cryptochrome 1 and possesses the conserved DNA photolyase domain and FAD binding domain. Its transcription was detected in 10 flounder tissues and was reduced upon Vibrio harveyi challenge. The transcription of PoCry1 exhibited apparent rhythmic oscillation upon the light actuation of a day-night cycle in different tissues. The knockdown of PoCry1 resulted in significant augment of inflammatory cytokine expression. During bacterial infection, PoCry1 silencing led to increase in cytokine expression and decrease in bacterial dissemination, which could be neutralized by a specific PKA inhibitor, suggesting PoCry1 is likely able to negatively modulate the immune response to bacterial infection through PKA associated pathways.Taken together, our results revealed that PoCry1 is circadian oscillated in transcription upon rhythmic light stimulation and involved in anti-infection immunity, thus enlightening that light condition as a circadian zeit-geber could be exploited to strength fish immune system and benefit disease control in aquaculture.

Automated summary

This study investigates the involvement of PoCry1 in the immune response during bacterial infection in Japanese flounder. The results show that PoCry1 is involved in anti-infection immunity and exhibits circadian oscillation in transcription upon rhythmic light stimulation. These findings suggest that light condition can be exploited to strengthen fish immune system and benefit disease control in aquaculture.