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Mobilization, Cloning, and Sequence Determination of a Plasmid-Encoded Polygalacturonase from a Phytopathogenic Burkholderia (Pseudomonas) cepacia

September 1997 , Volume 10 , Number  7
Pages  840 - 851

Carlos F. Gonzalez , Elizabeth A. Pettit , Victoria A. Valadez , and Ellen M. Provin

Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843-2132 U.S.A.

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Accepted 24 June 1997.

Phytopathogenic strains of Burkholderia cepacia (synonym Pseudomonas cepacia) produce endopolygalacturonase, whereas strains of clinical and soil origin do not. Growth of a phytopathogenic strain (ATCC25416) at elevated temperatures resulted in nonpectolytic derivatives that were either cured of a resident plasmid or contained a plasmid of reduced mass. The resident 200-kb plasmid (pPEC320) in strain ATCC25416 was tagged with Tn5-Mob. The pPEC320∷Tn5-Mob (pPEC321) plasmid was mobilized in B. cepacia strains of soil and clinical origin. Transconjugants containing pPEC321 expressed the endopolygalac-turonase and showed differential activity on plant tissue. No evidence for self-transfer of pPEC320 or the tagged derivative was observed. A 2.85-kb cloned fragment from pPEC320 containing the plasmid-borne pehA gene was sequenced and compared to the pehA gene from Erwinia carotovora subsp. carotovora and Ralstonia solanacearum and the polygalacturonase sequence from Lycopersicon esculentum.

Additional keywords: Pseudomonas solanacearum, virulence factor.

© 1997 The American Phytopathological Society