Transfer, Mapping, and Cloning ofPseudomonas syringaepv.syringaePlasmid pCG131 and Assessment of Its Role in Virulence

Abstract

P. syringae pathovar [pv] syringae strain HS191 is a corn pathogen harboring plasmid pCG131. Plasmid-free derivative strains still produced the phytotoxin, syringomycin. Plasmid pCG131 was cleaved with restriction endonuclease Bam HI 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.