Liver transcriptome profiling of the largemouth bass (Micropterus salmoides) suggests host immunoregulatory mechanism in response to Edwardsiella tarda infection.

As a non-native species, largemouth bass (Micropterus salmoides) has become an important economically farmed fish in China. In recent years, although the aquaculture industry has suffered significant commercial losses due to Edwardsiella tarda infection, knowledge of the interactions between E. tarda and this fish species is still limited. This study conducted RNA sequencing in the liver of largemouth bass at 1 day post-infection with E. tarda to investigate the associated immunoregulatory mechanisms. Compared to the control group, 3198 differentially expressed genes (DEGs) were identified, including 1765 upregulated and 1433 downregulated genes, which were enriched in 874 gene ontology (GO) terms and 160 Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathways. Further annotation and enrichment analysis revealed significant changes in pattern recognition receptor (PRR)-mediated signalling pathways, pro-inflammatory cytokines, phagosomes, lysosomes, adaptive immunity-related genes and metabolism-related pathways, suggesting that largemouth bass infected with E. tarda elicited a robust innate immune response, accompanied by antigen-specific T/B cell activation and metabolic dysregulation. This research provides new insights on the immunoregulatory mechanism of largemouth bass in response to E. tarda infection, offering a valuable foundation for future research.