NLRs are a large family of intracellular pathogen recognition receptors (PRRs) that recognize pathogen associated molecular patterns (PAMPs). In the previous study, the identification of NLRs subfamily A (NODs) and gene expression was carried out in channel catfish (Ictalurus punctatus). However, the gene expression profiles of channel catfish NODs (NOD1, NOD2, NLRC3, NLRC5 and NLRX1) after infection with various bacteria and virus are still unclear. In this study, expression of five NODs genes was analyzed by quantitative real-time PCR method. In healthy catfish tissues, all tested NODs genes were found to be ubiquitously expressed. After infection with Edwardsiella tarda, Aeromonas hydrophila, Streptococcus iniae, or channel catfish hemorrhage reovirus (CCRV), expression of NOD1, NOD2, NLRC3, NLRC5 showed a significant up-regulation in the intestine, liver and head kidney, whereas down-regulation was observed in the spleen after infection with A. hydrophila and CCRV. Expression of NLRX1 gene was up-regulated in the intestine, liver and head kidney, while obviously decreased in the spleen after infection with four pathogens. Among four different pathogens, S. iniae largely up-regulated NODs mRNAs, while CCRV only slightly enhanced NODs gene expression. Among four immune-related tissues, the order for NODs up-regulation was liver, head kidney, intestine, and spleen after infection with various pathogens. All data suggest NODs are involved in the immune responses of channel catfish against the intracellular bacterial and virus pathogens in tissue-specific and pathogen-specific manners, and provide the evidence for exploring the precise immune-related molecular mechanism of NODs in channel catfish.
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