Molecular characterization and functional analysis of interferon regulatory factor-4 in the Red Claw Crayfish (Cherax quadricarinatus)

Abstract

Vibrio parahaemolyticus (V. parahaemolyticus) is a primary pathogen in crustaceans and causes acute hepatopancreatic necrosis disease. Interferon regulatory factor-4 (IRF4) belongs to the regulatory factor family and plays a key role in the innate immunity of crustaceans. To better understand the IRF4 regulatory mechanism and its immunomodulatory role in response to challenge with Vibrio in crustaceans, the cDNA of Cherax quadricarinatus (C. quadricarinatus) IRF4 (CqIRF4) was isolated and the immune effect of this protein in the C. quadricarinatus response to V. parahaemolyticus was studied. The length of CqIRF4 was 2354 bp, with a 1251 bp open reading frame encoding 417 amino acids. After infection with V. parahaemolyticus, the expression levels of CqIRF4 in the hepatopancreas and hemolymph of C. quadricarinatus were significantly upregulated (P < 0.05), while no significant fluctuations were detected in muscle or gill tissues. Additionally, histopathological damage was detected in the hepatopancreas, such as loss of the stellate structure, significant vacuolization of cells, intercellular hemorrhaging, hypertrophy, and necrosis in some tissues. After injecting recombinant CqIRF4 protein in vivo, colonization of the hepatopancreas by V. parahaemolyticus decreased dramatically. The transcription levels of the interleukin-like genes IL-4, -6, -23, -12, and -15, as well as the lysozyme, AlP, ALF, SOD1, laccase, and C-type lectin genes, were significantly upregulated (P < 0.05). This study shows that the CqIRF4 as an immunomodulatory factor, was highly activated by a Vibrio challenge, and inhibited V. parahaemolyticus colonization in the hepatopancreas of C. quadricarinatus by regulating the corresponding immune genes.