Volume 6, Issue 20 pp. 3065-3076
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Evidence that the hrpB gene encodes a positive regulator of pathogenicity genes from Pseudomonas solanacearum

Stéphane Genin

Stéphane Genin

Laboratoire de Biologie Moléculaire des Relations Plantes Microorganismes. INRA-CNRS. BR27, 31326 Castanet-Tolosan Cedex, France.

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Clare L. Gough

Clare L. Gough

Laboratoire de Biologie Moléculaire des Relations Plantes Microorganismes. INRA-CNRS. BR27, 31326 Castanet-Tolosan Cedex, France.

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Claudine Zischek

Claudine Zischek

Laboratoire de Biologie Moléculaire des Relations Plantes Microorganismes. INRA-CNRS. BR27, 31326 Castanet-Tolosan Cedex, France.

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Christian A. Boucher

Corresponding Author

Christian A. Boucher

Laboratoire de Biologie Moléculaire des Relations Plantes Microorganismes. INRA-CNRS. BR27, 31326 Castanet-Tolosan Cedex, France.

*Tel. 61 28 50 45; Fax 61 28 50 61 Email BOUCHER@ toulouse.inra.fr.Search for more papers by this author
First published: October 1992
Citations: 155

Summary

The hrp gene cluster of Pseudomonas solanacearum GMI1000 strain encodes functions that are essential for pathogenicity on tomato and for the elicitation of the hypersensitive response on tobacco. In this study, we present the nucleotide sequence of one of the hrp genes (hrpB) located at the left-hand end of the cluster and we show that hrpB encodes a positive regulator controlling the expression of hrp genes. hrpB has a coding capacity for a 477-amino-acid polypeptide, which shows significant similarity to several prokaryotic transcriptional activators including the AraC protein of Escherichia coli, the XylS protein of Pseudomonas putida and the VirF protein of Yersinia enterocolitica. The predicted hrpB gene product belongs to a family of bacterial regulators different from the previously described HrpS protein of the hrp gene cluster of Pseudomonas syringae pv. phaseolicola. Genetic evidence demonstrates that the hrpB gene product acts as a positive regulator of the expression in minimal medium of all but one of the putative transcription units of the hrp gene cluster and also controls the expression of genes located outside this cluster. We also show in this paper that the transcription of hrpB is induced in minimal medium and is partly autoregulated.

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