title: Induction of Pseudomonas syringae pv. tomato DC3000 MexAB-OprM multidrug efflux pump by flavonoids is mediated by the repressor PmeR.
abstract: In this study, we have analyzed the expression of the Pseudomonas syringae pv. tomato DC3000 mexAB-oprM efflux pump operon and of the regulatory gene pmeR, and we have investigated the role of the PmeR protein on transcription from both promoters. We demonstrate that mexAB-oprM and pmeR are expressed in vivo at a relatively high and moderate basal level, respectively, which, in both cases, increases in the presence of different flavonoids and other compounds, such as butyl and methylparaben. We show that PmeR is the local repressor of the mexAB-oprM promoter and is able to regulate its own expression. The mechanism for this regulation includes binding to a pseudopalindromic operator site which overlaps both mexAB-oprM and pmeR promoters. We have also proven that flavonoids are able to interact with PmeR and induce a conformational change that interferes with the DNA binding ability of PmeR, thereby modulating mexAB-oprM and pmeR expression. Finally, we demonstrate by in vivo experiments that the PmeR/MexAB-OprM system contributes to the colonization of tomato plants. These results provide new insight into a transcriptional regulator and a transport system that play essential roles in the ability of P. syringae pv. tomato DC3000 to resist the action of flavonoids produced by the host.
authors.affiliation: Department of Soil Microbiology and Symbiotic System, Estación Experimental del Zaidin, Granada, Spain.
authors.forename: Paola
authors.initials: P
authors.lastname: Vargas
authors.forename: Antonia
authors.initials: A
authors.lastname: Felipe
authors.forename: Carmen
authors.initials: C
authors.lastname: Michán
authors.forename: María-Trinidad
authors.initials: MT
authors.lastname: Gallegos
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D019450:Genes, MDR; D054884:Host-Pathogen Interactions / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D018551:Solanum lycopersicum / Q000382:microbiology*; D009876:Operon; D011401:Promoter Regions, Genetic; D044224:Pseudomonas syringae / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D012097:Repressor Proteins / Q000378:metabolism; D024363:Transcription Initiation Site
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005419:Flavonoids; D012097:Repressor Proteins