Genome-wide identification and functional characterization of NOD-like receptors (NLRs) in snakehead (Channa argus)

• A total of 33 NLR genes were detected in snakehead. • The altered expression patterns of NLR genes indicate their involvement in the immune response to Nocardia seriolae . • The inhibitory effect of NLRC18 on NF-κB activation reached 38%, and the expression level of NLRC18 was upregulated by 339.6-fold after stimulation with iE-DAP. NLR (NOD-like receptor) is a pattern recognition receptors (PRRs) and is crucial in the innate immune response. It identifies pathogen-associated molecular patterns (PAMPs) and modulates associated immune pathways. Snakehead ( Channa argus ) is an economically important fish with rapid growth and high meat content, but research on its NLR family is still incomplete. In this study, a total of 33 NLR genes were identified in snakehead, among which NOD1, NOD2, NLRC5 and MHC class II transactivator (CIITA) belong to the NLR-A subfamily, NLRC1-NLRC4 and NLRC6-NLRC27 belong to the NLR-C subfamily, and NLRX1, APAF1 and NWD1 belong to other subfamilies. Their biological characteristics, phylogenetic relationships, gene structure, conserved motifs, domain organization, expression profiles, and protein-protein interaction networks were characterized. In addition, the expression of NLR genes was observed in different healthy tissues of snakehead, and the expression patterns were diverse. The expression levels were the highest in the blood, intestine and gill. Nocardia seriolae is a key pathogenic bacterium that causes diseases in snakehead. The altered expression patterns of NLR genes indicate their involvement in the immune response to N.seriolae . Finally, it was also detected that the inhibitory effect of NLRC18 on NF-κB activation reached 38%, and the expression level of NLRC18 was upregulated by 339.6-fold after stimulation with iE-DAP. This study offers robust evidence that enhances our understanding of the immune regulatory mechanisms and functional roles of NLR genes in snakehead.