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Identification of a Pathogenicity Locus, rpfA, in Erwinia carotovora subsp. carotovora That Encodes a Two-Component Sensor-Regulator Protein

April 1997 , Volume 10 , Number  3
Pages  407 - 415

Reid D. Frederick , 1 , 2 Jiliang Chiu , 2 Jeffrey L. Bennetzen , 1 and Autar K. Handa 2

1Department of Biological Sciences and 2Department of Horticulture, Purdue University, West Lafayette, IN 47907 U.S.A.

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Accepted 2 January 1997.

A mutant of Erwinia carotovora subsp. carotovora, AH2552, created by a Mud1 insertion was found to be reduced in plant pathogenicity and deficient in extracellular protease and cellulase activity, although it produced normal levels of pectate lyase and polygalacturonase. A cosmid clone, pEC462, was isolated from a wild-type E. carotovora subsp. carotovora DNA library that concomitantly restored pathogenicity and protease and cellulase activities of AH2552 to wild-type levels when present in trans. The genetic locus that was disrupted in AH2552 by insertion of Mud1 has been designated rpfA, for regulator of pathogenicity factors. Sequencing of the rpfA region identified an open reading frame of 2,787 bp, and the predicted 929-amino acid polypeptide shared high identity with several two-component sensor-regulator proteins: BarA from Escherichia coli, ApdA from Pseudomonas fluorescens, PheN from P. tolaasii, RepA from P. viridiflava, LemA from P. syringae pv. syringae, and RpfC from Xanthomonas campestris pv. campestris. The RpfA locus described in this study encodes a putative sensor kinase protein that is involved in both extracellular protease and cellulase production and the pathogenicity of E. carotovora subsp. carotovora on potato tubers.

Additional keywords: histidine protein kinase, pectolytic enzymes.

© 1997 The American Phytopathological Society