LAUSR

ABSTRACT RNase1 is an enzyme important in host defense in vertebrates where it degrades the RNA of bacteria and viruses. We evaluated the effect of RNase1 on the resistance to Aeromonas hydrophila infection in Megalobrama amblycephala. The fish were randomly divided into four groups: a blank group (none‐treated M. amblycephala), a control group (injected PBS), a challenge group (A. hydrophila‐injected) and a treatment group (pre‐treated with RNase1 24 h before the A. hydrophila injection), and we collected five tissues of each group. Then we recorded changes in the levels of glutathione (GSH), oxidized glutathione (GSSG), hepatic catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA) and lysozyme; and the relative mRNA expression of catalase (CAT), selenium‐dependent glutathione peroxidase (GPx), Cu/Superoxide dismutase (Cu/Zn‐SOD), glutamate‐cysteine ligase (GCLC), glutathione reductase (GR) and nuclear factor erythroid 2‐related factor 2 (Nrf2) for four groups. The expression of six genes was highest in liver and blood of the blank group. It was significantly higher in the gut of the treatment group (compared to control and challenge groups) 12 h after the infection. The treatment group exhibited a significant increase in GSH, SOD and CAT activity, and a decrease in GSSG, MDA and lysozyme content (compared to the control and challenge groups) 6 and 12 h after infection. These results suggest that supplementation with RNase1 protein can enhance resistance against A. hydrophila infections in M. amblycephala. HighlightsCAT, GPx, Cu/Zn‐SOD, GCLC, Nrf2 and GR genes in fish and mammals were analyzed.These genes were highly expressed in liver and blood of healthy M.amblycephala.Pre‐treatment with RNase1 increase GSH, CAT and SOD activity after A.hydrophila infection.Pre‐treatment with RNase1 decrease GSSG, MDA and lysozyme content after A.hydrophila infection.RNase1 protein play a protective role in M. amblycephala after A. hydrophila infection.