Pseudomonas plecoglossicida is a rod-shaped, gram-negative bacterium with flagella. It causes visceral white spot disease and high mortality in
Larimichthys crocea during culture, resulting in serious economic loss. Analysis of transcriptome and quantitative real-time polymerase chain reaction (PCR) data showed that
dksA gene expression was significantly up-regulated after 48 h of infection with
Epinephelus coioides
(log
2FC=3.12,
P<0.001). RNAi of five shRNAs significantly reduced the expression of
dksA in
P. plecoglossicida, and the optimal silencing efficiency was 96.23%. Compared with wild-type strains, the symptoms of visceral white spot disease in
L. crocea infected with RNAi strains were reduced, with time of death delayed by 48 h and mortality reduced by 25%. The
dksA silencing led to a substantial down-regulation in cellular component-, flagellum-, and ribosome assembly-related genes in
P. plecoglossicida, and the significant up-regulation of
fliC may be a way in which virulence is maintained in
P. plecoglossicida. The GO and KEGG results showed that RNAi strain infection in
L. crocea led to the down-regulation of inflammatory factor genes in immune-related pathways, which were associated with multiple immune response processes. Results also showed that
dksA was a virulence gene in
P. plecoglossicida. Compared with the wild-type strains, RNAi strain infection induced a weaker immune response in
L. crocea.
