Abstract：Erwinia amylovora causes fire blight of pear, apple, and many of the Rosaceae family. The cyclic adenosine monphosphate (cAMP) receptor protein(CRP), which is encoded by crp gene, plays a crucial role in expression of the pectinolysis genes and regulation of the pathogenicity in Erwinia chrysanthemi. In this study, the homolog of crp gene, designated Eacrp, was identified and cloned in Erwinia amylovora. A crp disruption mutant EaΔcrp was successfully generated by homologous recombination. Complement strain EaΔcrp (pME-crp) was also constructed. Then crp gene was characterized to virulence, hypersensitive response(HR), extracellular polysaccharide (EPS), motility and other phenotypes of the phytopathogens Erwinia amylovora. The results showed that the crp mutant EaΔcrp displayed the reduced virulence, EPS production and growth in vitro and motility. However, compared to wild type strain NCPPB1665(Ea1665), the induction of HR in nonhost tobacco, peroxide resistance, sedimentation, biofilm synthesis and AI-2 production of the crp mutant EaΔcrp was not affected. These findings demonstrated that crp gene in Erwinia amylovora is involved in EPS production, growth, and motility and play an important role in virulence.
