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gdhB, a gene encoding a second quinoprotein glucose dehydrogenase in Pantoea citrea, is required for pink disease of pineapple

Catherine J. Pujol

Department of Plant Pathology, University of California, Davis, CA 95616, USA

ABSTRACT

The pink disease of pineapple, caused by the bacterium Pantoea citrea, is characterized by a dark coloration on fruit slices after canning. A glucose dehydrogenase (Gdh) encoded by the gdhA gene has been implicated in the colour formation activity of P. citrea. In this paper it has been shown that P. citrea contains a second, homologous gdh gene and its product, GdhB, represents the main source of Gdh activity in this organism. Unlike gdhA, gdhB is constitutively expressed during the exponential phase of growth and is induced in stationary phase. A previously isolated chemical mutant, CMC6, which is deficient in Gdh activity and pink disease formation, failed to express gdhB during the stationary phase of growth. The CMC6 mutant can be complemented by a 54 bp DNA fragment located upstream of gdhA. This fragment, which contains an operator-like 11 bp inverted repeat, strongly enhances the expression of gdhA, probably by titrating away a negative effector of its expression. These results illustrate the complex interplay operating between the two gdh genes and emphasize the role of glucose metabolism in the pathway leading to pink disease.

Author for correspondence: Clarence I. Kado. Tel: + 1 530 752 0325. Fax: + 1 530 752 5674. e-mail: cikado@ucdavis.edu

Present address: Medical Pathology Department, UCD Medical Center, Room 3300A, 4645 2nd Avenue, Sacramento, CA 95817, USA

This article has been cited by other articles:

				C. J. Pujol and C. I. Kado Genetic and Biochemical Characterization of the Pathway in Pantoea citrea Leading to Pink Disease of Pineapple J. Bacteriol., April 15, 2000; 182(8): 2230 - 2237. [Abstract] [Full Text]