| Summary: | This study aimed to investigate the effect of reduced expression of the <i>luxR</i> gene on the virulence of <i>Pseudomonas plecoglossicida</i> and the immune response of <i>Epinephelus coioides</i>. To achieve this, RNA interference (RNAi) was used to silence the <i>luxR</i> gene, and the pathogenicity of wild-type and <i>luxR</i>-RNAi strains of <i>P. plecoglossicida</i>, as well as the immune response of <i>Epinephelus coioides</i> to the infection of these two strains, were compared. The mutant strain with the highest silencing efficiency of 70.1% was selected for subsequent analysis. Silencing the <i>luxR</i> gene in the mutant strain resulted in a significant 30% reduction in mortality rates in artificially infected <i>Epinephelus coioides</i> compared to the wild-type strain. Transcriptome analysis revealed that the host transcriptome, particularly in the spleens of infected <i>Epinephelus coioides</i>, was markedly altered by the silencing of the <i>luxR</i> gene in the mutant strain. Tilapia infected with the <i>luxR</i>-RNAi strain exhibited altered immune defenses, with changes in gene expression primarily in the NOD-like receptor (NLR) signaling pathway. These results suggest that the <i>luxR</i> gene plays a crucial role in the host’s resistance to pathogen invasion, and reducing its expression could decrease quorum sensing (QS) signals while increasing the expression of the <i>IL-1β</i> gene in the host’s NLR pathway. This effect may lead to a pro-inflammatory response that enhances the immune response to infection. Further investigation of these mechanisms may lead to innovative approaches to treating bacterial infections.
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