Abstract：Bacteria's twin-arginine translocation system(Tat) can affect its pathogenicity seriously. In order to explore the relationship between Tat and pathogenicity of Acidovorax citrulli, a tatB disruption mutantstrain ΔtatB and its complementary strain CtatB were constructed by homologous recombination, and 6 factors (virulence, motility, growth ability, extracellular polysaccharide and cellulase producing ability and biofilm formation) were tested to illustrate Tat system's influence on Acidovorax citrulli. Comparing the expression of TrbC, hrcN, Aave_1810, Aave_0034 and hrpE genes by Real-time fluorescent quantitative PCR, to explore the relationship between tatB gene and type Ⅲ secretion system, Tat system related genes and cell toxicity related genes. ΔtatB could trigger the hypersensitive response in non-host plant tobacco(Nicotiana tabacum). The deficiency of tatB weakened Acidovorax citrulli's virulence, motility and growth ability, while had no effect on the production of extracellular polysaccharide (EPS)，extracellular cellulase and biofilm formation. Real-time fluorescent quantitative PCR analysis showed that the deficiency of tatB made the expressions of TrbC and hrcN genes in mutant strain significantly increased, while the expressions of other 3 genes notably decreased. Consequently, the deficiency of functional gene tatB in Tat system affected some biological characteristics of Acidovorax citrulli, and resulted in the decrease of pathogenic ability. These results supply basic information for pathogenicity and protein secretion research apart from secretion systemⅢ.
