How the luxR Gene Affects the Pathogenicity of Pseudomonas plecoglossicida and the Immune Response of Epinephelus coioides

This study aimed to investigate the effect of reduced expression of the luxR gene on the virulence of Pseudomonas plecoglossicida and the immune response of Epinephelus coioides. To achieve this, RNA interference (RNAi) was used to silence the luxR gene, and the pathogenicity of wild-type and luxR-RNAi strains of P. plecoglossicida, as well as the immune response of Epinephelus coioides 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 luxR gene in the mutant strain resulted in a significant 30% reduction in mortality rates in artificially infected Epinephelus coioides compared to the wild-type strain. Transcriptome analysis revealed that the host transcriptome, particularly in the spleens of infected Epinephelus coioides, was markedly altered by the silencing of the luxR gene in the mutant strain. Tilapia infected with the luxR-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 luxR 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 IL-1 beta 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.