Function Analysis Of Pathogenicity-Related Genes Pyrg And Hpap In Acidovorax Citrulli

Acidovorax citrulli is the causal agent of bacterial fruit blotch (BFB), a threatening disease of watermelon, melon and other cucurbits, which have been reported in many countries and areas, and caused great economic losses. Acidovorax citrulli is a quarantine pest, until now most studies on this pathogen related to its detection and control, whereas few researches focused on its pathogenic mechanism and infextation way. Accordingly, this study aimed at cloning pathogenicity-related genes and analyzing their functions.The mutant library of Acidovorax citrulli strain xjL12 was constructed by mating Mini-Tn5 transposon into Ac xjL12. Two mutantΔxj13,Δxj48, which lost panthogenicity were screened, the transposon insertion site were identified as pyrG, hpaP by sub-clone stategy.With the help of suicide plasmid, disruption mutants ApyrG and AhpaP were constructed by a method of homologous recombination. The result showed that ApyrG, AhpaP lost pathogenicity to hami seedlings. Complement strains pyrG hb, hpaPhb generally recoverd pathogenicity; HR assays indicated strainsΔxj13,Δxj48,ΔpyrG,ΔhpaP and hpaPhb losted this ability, but strain pyrGhb regained it. Then, other phenotypes were studied, characterization of the mutants revealed that swimming motility, biofilm formation and growth in host plant demanded gene pyrG, hpaP; RT-PCR showed that the expression of hrcV gene needed hpaP gene and pyrG gene affected the expression of hisD gene; strainΔpyrG could not grow normally in the auxotrophic media (MMX) added histidine; These evidences in the stusy demonstrated that gene hpaP, pyrG is cirtical for the pathogenicity of Acidovorax citrulli, and plays an important role in the process of growth and infection.