Dual RNA-seq provides novel insight into the roles of from in pathogen-host interactions with large yellow croakers ( ).

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