Background With no lysine kinases (WNK) are regulators of transporters, channels, and paracellular proteins. They play crucial roles in ion transport processes, maintaining cellular osmotic pressure, and regulating cell volume homeostasis. Currently, no studies have conducted systematic identification of the WNK gene family in channel catfish (Ictalurus punctatus) and investigate its role in immune responses.

Objective This study aims to systematically identify the WNK gene family in channel catfish and investigate their roles during Edwardsiella ictalurid infection.

Methods Through bioinformatic approaches, the WNK gene family sequences of other species were used to blast against the genome of channel catfish to identify the WNK gene family sequences in channel catfish. The WNK gene family in channel catfish was annotated and confirmed through domain analysis and phylogenetic analysis. Quantitative real-time polymerase chain reaction (qPCR) was employed to analyze the differential expression patterns of WNK genes between E. ictaluri-susceptible (YG group) and -resistant (KX group) channel catfish populations following E. piscicida infection.

Results Six WNK genes were identified in channel catfish, namely WNK1a, WNK1b, WNK2, WNK3, WNK4a, and WNK4b. After E. ictaluri infection, except for WNK1b in the intestine of the YG48 group Enteric septicaemia of catfish (ESC)-susceptible fish that died within 24−48 hours, WNK1a/b in the liver and intestine of other YG groups and the KX group all showed a down-regulated trend; WNK2, WNK3, and WNK4a/b in the liver and intestine of both YG and KX groups mostly presented a significant up-regulated trend, with the expression levels in the YG group being significantly higher than those in the KX group.

Conclusion WNK genes in the intestinal and liver of channel catfish are involved in the pathogenesis of ESC. The results of the study provide a reference for analyzing the molecular genetic mechanism of disease-resistant traits.