A bacterial sensor of plant cell contact controls the transcriptional induction of Ralstonia solanacearum pathogenicity genes.
The hrp genes of the plant pathogen Ralstonia solanacearum are key pathogenicity determinants; they encode a type III protein secretion machinery involved in the secretion of mediators of the bacterium-plant interaction. These hrp genes are under the genetic control of the hrpB regulatory gene, expression of which is induced when bacteria are co-cultivated with plant cell suspensions. In this study, we used hrp-gfp transcriptional fusions to demonstrate that the expression of the hrpB and type III secretion genes is specifically induced in response to the bacterium-plant cell contact. This contact-dependent induction of hrpB gene expression requires the outer membrane protein PrhA, but not a functional type III secretion apparatus. Genetic evidence indicates that PrhA constitutes the first example of a bacterial receptor for a non-diffusible signal present in the plant cell wall and which triggers the transcriptional activation of bacterial virulence genes.
Aldon
D
D
Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, INRA-CNRS, BP27, 31326 Castanet-Tolosan Cedex, France.
Brito
B
B
Boucher
C
C
Genin
S
S
D017360:Arabidopsis / Q000235:genetics / Q000382:microbiology*; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins / Q000235:genetics*; D020562:Betaproteobacteria / Q000472:pathogenicity / Q000502:physiology*; D004268:DNA-Binding Proteins; D015964:Gene Expression Regulation, Bacterial; D018398:Homeodomain Proteins / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D014157:Transcription Factors; D014158:Transcription, Genetic
D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C109355:PRHA protein, Arabidopsis; D010940:Plant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C079047:hrpB protein, Ralstonia solanacearum