Survival In Non-Host Plant Seeds And Function Analysis Of Type Ⅳ Pili-Related Gene In Acidovorax Citrulli

In recent years,Bacterial fruit blotch （BFB） caused by Acidovorax citrulli（Ac）, is a serious disease.In watermelon, melon and other cucurbits it will produce serious damage of leaves, causing fruit rot. Ac is one of the international regulations of quarantine plant diseases.Now people focused on the identification of biological characteristics, the occurrence of disease law and other aspects of its pathogenesis and the study of genes related to but few. So Ac disease-causing gene and its pathogenesis on research for disease prevention and treatment is crucial.The prevention and control of BFB is basically control efficiency is very low, but still there is no effective control methods. General studies suggest that Ac mainly through seed dispersal, but chemical treatment is also not achieve the desired control effect on seed treatment.it was suspected there are other routes of the primary infection source as seed dispersal.In this study, constructing the Ac fluorescent strains to study the primary infection source of weed, direct inoculation of the Ac bacteria in the weeds flowering on the stigma, collect seeds, the bacteria isolated from the seeds will be again inoculated in melon cotyledon,the incidence of wild-type is basically the same, so the preliminary experiments proved that the Ac can survive in weed seeds, and can again lead host disease, which has practical applications in the prevention and treatment of Ac.For many gram-negative bacteria, pili decomposition can lead to serious loss of virulence, indicating that the pili of pathogenic is critical.Assembly of type IV pili by the pilus subunit build a helix in the aggregate structure.Type IV pili regulate diverse cellular functions, including surface motility, micro-colonies and biofilm formation, host cell adhesion, immune evasion, cell signaling, DNA uptake and transformation as well as the phage attachment.In this study, by constructing part of the type IV pili related genes mutants,and their pathogencity was tested. Which Aave3550（pilE）, Aave₃156（pill）, Aave₄679（pilA） gene mutant virulence significantly decreased by seed soaking experiments. Related functional analysis of the mutants showd that:the mutants losed their biofilm formation, swimming molitity and pathogencity weakened. Build complementary strain allows it to function partially restored. These prove that the type Ⅳ pili genes associated with pathogencity in Ac.