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Genetics

Transfer, Mapping, and Cloning of Pseudomonas syringae pv. syringae Plasmid pCG131 and Assessment of Its Role in Virulence. Carlos F. Gonzalez, Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109 and Department of Plant Pathology, University of Nebraska, Lincoln 68583, Present address of senior author: Microlife Technics, P.O. Box 3917, Sarasota, FL 33578; Susan K. Layher(2), Anne K. Vidaver(3), and Ronald H. Olsen(4). (2)Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109 and Department of Plant Pathology, University of Nebraska, Lincoln 68583, Present address: Department of Microbiology, University of Texas, Austin 78712; (3)Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109 and Department of Plant Pathology, University of Nebraska, Lincoln 68583, University of Nebraska, Lincoln; (4)Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109 and Department of Plant Pathology, University of Nebraska, Lincoln 68583, University of Michigan, Ann Arbor. Phytopathology 74:1245-1250. Accepted for publication 13 May 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1245.

Pseudomonas syringae pv. syringae strain HS191 is a corn pathogen harboring plasmid pCG131. We determined that plasmid-free derivative strains still produced the phytotoxin, syringomycin. Plasmid pCG131 was cleaved with restriction endonuclease BamHI or SalI and these fragments were cloned by using the broad host range vector, pRO1614. These recombinant plasmids were transformed into PSO100, a plasmid-free, toxin-producing derivative of HS191. Plant pathogenicity tests with the collection of chimeric plasmid-containing strains in Zea mays suggested that pCG131 may contribute to the virulence of strain HS191. A selective marker for carbenicillin resistance was added to the plasmid pCG131 by the transposition of Tn1. Plasmid pCG131::Tn1 (pCG133) conjugally transferred intraspecifically to mutants of HS191 and to the SD19 strain of P. syringae pv. syringae. Toxin-negative recipients used for these tests were not converted to toxin production by the acquisition of plasmid pCG131.