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The Presence of Diverse IS Elements and an avrPphD Homologue That Acts as a Virulence Factor on the Pathogenicity Plasmid of Erwinia herbicola pv. gypsophilae

July 2002 , Volume 15 , Number  7
Pages  709 - 716

Ming Guo , 1 Shulamit Manulis , 2 Henia Mor , 1 and Isaac Barash 1

1Department of Plant Sciences, Faculty of Life Sciences, Tel Aviv University, 69978 Israel, and 2Department of Plant Pathology, ARO, the Volcani Center, Bet Dagan 50250, Israel

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Accepted 18 March 2002.

The pathogenicity of Erwinia herbicola pv. gypsophilae (Ehg) and Erwinia herbicola pv. betae (Ehb) is dependent on a native plasmid (pPATHEhg or pPATHEhb) that harbors the hrp gene cluster, genes encoding type III effectors, phytohormones, biosynthetic genes, and several copies of IS1327. Sequence analysis of the hrp-flanking region in pPATHEhg (cosmid pLA150) revealed a cluster of four additional IS elements designated as ISEhe1, ISEhe2, ISEhe3, and ISEhe4. Two copies of another IS element (ISEhe5) were identified on the upstream region of the indole-3-acetic acid operon located on the same cosmid. Based on homology of amino acids and genetic organization, ISEhe1 belongs to the IS630 family, ISEhe2 to the IS5 family, ISEhe3 and ISEhe4 to different groups of the IS3 family, and ISEhe5 to the IS1 family. With the exception of ISEhe4, one to three copies of all the other IS elements were identified only in pathogenic strains of Erwinia herbicola pv. gypsophilae and Erwinia herbicola pv. betae whereas ISEhe4 was present in both pathogenic and nonpathogenic strains. An open reading frame that exhibited high identity (89% in amino acids) to AvrPphD of Pseudomonas syringae pv. phaseolicola was present within the cluster of IS elements. An insertional mutation in the AvrPphD Ehg reduced gall size in gypsophila by approximately 85%. In addition, remnants of known genes from four different bacteria were detected on the same cosmid.

Additional keywords: cytokinins , Pantoea agglomerans .

© 2002 The American Phytopathological Society