IS1327, a new insertion-like element in the pathogenicity-associated plasmid of Erwinia herbicola pv. gypsophilae

The pathogenicity-associated plasmid (pPATH) of Erwinia herbicola pv. gypsophilae was previously shown to be exclusively present in pathogenic strains and to contain a gene cluster encoding phytohormone biosynthesis. Sequence analysis of the DNA region located downstream from the cytokinin biosynthetic gene (etz) revealed homology to insertion sequences (IS) of the IS6 family. Southern blot analysis performed on plasmid DNA of E. herbicola pv. gypsophilae revealed the presence of six copies of this insertion-like element, which was designated as IS1327. Only pathogenic strains contained IS1327 and restriction fragment length polymorphism was observed among gypsophilae and beet pathovars of E. herbicola. Nonpathogenic deletion derivatives of pPATH contained fewer copies of IS1327, suggesting its presence in the deleted region. One copy of IS1327 (IS1327-R) was located 2.8 kb downstream from the IS element adjacent to the etz (IS1327-L) in a direct repeat.