sRNA113 regulates the motility of Pseudomonas plecoglossicida to affect the immune response against infection in pearl gentian grouper

Small RNAs (sRNAs) are a class of molecules capable of perceiving alterations in environment and exert post-transcriptional regulatory over target gene expression, thus participating in the modulation of bacterial virulence and host immune response. Pseudomonas plecoglossicida is a pathogen that poses a significant threat to the health of aquatic animals. However, the regulatory roles and mechanisms of sRNAs in P. plecoglossicida remain unclear. The previously identified sRNA113 is believed to have a regulatory role on the fliP gene, a key component of the lateral flagella type III secretion system. The effects of sRNA113 on the virulence of P. plecoglossicida, as well as its role in regulating the pathogenic process and modulating host immune response, were investigated through generating the sRNA113 mutant strains. In vitro experiments, the deletion of sRNA113 led to the up-regulation of the lateral flagella type III secretion system-related genes in P. plecoglossicida, thereby enhancing bacterial swarming motility, biofilm formation, and chemotaxic ability. Moreover, the in vivo infection experiments revealed that the deletion of sRNA113 augmented the pathogenicity of P. plecoglossicida by up-regulating the expression of genes associated to lateral flagella type III secretion system. As a result, there was an escalation in bacterial load, exacerbating pathological damage and disrupting immune responses within pearl gentian grouper tissues, consequently, resulting in the inability of the host to eliminate pathogenic bacteria and ultimately leading to mortality. These findings establish a theoretical framework for further elucidating the mechanism of virulence regulation in P. plecoglossicida and the host's immune response against bacterial infection.