Motility is an important determinant for pathogenesis of Erwinia carotovora subsp. carotovora

To clarify the functions of flagella for pathogenesis of Erwinia carotovora subsp. carotovora EC1, non-polar in-frame deletion mutants of fliC and motA homologues were constructed. Both the Δ fliC and the Δ motA mutants were confirmed to be non-motile on semisolid agar medium. The Δ motA mutant was peritrichously flagellated like its parental strain under electron microscope, whereas the Δ fliC mutant was defective in flagellin production and aflagellated. We demonstrated that both the Δ fliC and the Δ motA mutants reduced their ability to elicit the soft-rot symptoms on Chinese cabbage without any deleterious effect on the production of major extracellular enzymes. They retained their ability to induce hypersensitive reaction (HR) upon inoculation into tobacco leaves. These results suggest that motility but not flagellar component (s) is (are) involved in pathogenesis of E. carotovora subsp. carotovora.