Function Analysis Of VASD-1and VASD-2Genes From T6SS Of Erwinia Amylovora Strain NCPPB1665

Erwinia amylovora causes fire blight of pear, apple and many of the Rosaceae family. To control this disease, lots of researches have been focused on the mechanisms of the virulence in Erwinia amylovora.In this study, the homolog of vasD gene, designated vasD-1and vasD-2, was identified and cloned in Erwinia amylovora for the first time. A vasD disruption mutant ΔvasD-1was successfully generated by homologous recombination. Complement strain ΔvasD was also constructed. Then ΔvasD-1gene was characterized to many phenotypes of the phytopathogens Erwinia amylovora. The results showed that, the vasD mutant ΔvasD-1displayed the reduced virulence which observed in pear leaves and Kuerle fragrant pear. Furthermore, the mutants grew more slowly than the wild type strain NCPPB1665in vitro, and EaΔvasD impaired clearly in motility in soft agar medium. It was also obersved that the ΔvasD-lexhibited reductive production of extracellular polysaccharide (EPS). But ΔvasD-1was not affected the induction of hypersensitive response(HR) in nonhost tobacco、peroxide resistance、sedimentation、and biofilm synthesis production compared to the wild type strain NCPPB1665.