The Effect of Gene on the Virulence of and the Immune Response of .

is the causative agent of "visceral white spot disease" in cultured fish and has resulted in serious economic losses. gene plays a crucial role in the uptake of nutrients from the outer membranes in Gram-negative bacteria. The previous results of our lab showed that the expression of gene of was significantly upregulated in the spleens of infected . To explore the effect of gene on the virulence of and the immune response of gene of was knocked down by RNAi; and the differences between the wild-type strain and the -RNAi strain of were investigated. The results showed that all of the four mutants of exhibited significant decreases in mRNA of gene, and the best knockdown efficiency was 94.0%; the survival rate of infected with the -RNAi strain was 20% higher than of the counterpart infected with the wild strain of . Meanwhile, the infected with the -RNAi strain of carried less pathogens in the spleen and less white spots on the surface of the spleen; compared with the wild-type strain, the motility, chemotaxis, adhesion, and biofilm formation of the -RNAi strain were significantly attenuated; the transcriptome data of infected with the -RNAi strain were different from the counterpart infected with the wild strain of ; the antigen processing and presentation pathway and the complement and coagulation cascade pathway were the most enriched immune pathways. The results indicated that was a virulence gene of ; gene was involved in the regulation of motility, chemotaxis, adhesion, and biofilm formation; gene affected the immune response of to infection.