title: ohrR and ohr are the primary sensor/regulator and protective genes against organic hydroperoxide stress in Agrobacterium tumefaciens.
abstract: The genes involved in organic hydroperoxide protection in Agrobacterium tumefaciens were functionally evaluated. Gene inactivation studies and functional analyses have identified ohr, encoding a thiol peroxidase, as the gene primarily responsible for organic hydroperoxide protection in A. tumefaciens. An ohr mutant was sensitive to organic hydroperoxide killing and had a reduced capacity to metabolize organic hydroperoxides. ohr is located next to, and is divergently transcribed from, ohrR, encoding a sensor and transcription regulator of organic hydroperoxide stress. Transcription of both ohr and ohrR was induced by exposure to organic hydroperoxides but not by exposure to other oxidants. This induction required functional ohrR. The results of gel mobility shift and DNase I footprinting assays with purified OhrR, combined with in vivo promoter deletion analyses, confirmed that OhrR regulated both ohrR and ohr by binding to a single OhrR binding box that overlapped the ohrR and ohr promoters. ohrR and ohr are both required for the establishment of a novel cumene hydroperoxide-induced adaptive response. Inactivation or overexpression of other Prx family genes (prx1, prx2, prx3, bcp1, and bcp2) did not affect either the resistance to, or the ability to degrade, organic hydroperoxide. Taken together, the results of biochemical, gene regulation and physiological studies support the role of ohrR and ohr as the primary system in sensing and protecting A. tumefaciens from organic hydroperoxide stress.
authors.affiliation: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand.
authors.forename: Tatsanee
authors.initials: T
authors.lastname: Chuchue
authors.forename: Weerachai
authors.initials: W
authors.lastname: Tanboon
authors.forename: Benjaphorn
authors.initials: B
authors.lastname: Prapagdee
authors.forename: James M
authors.initials: JM
authors.lastname: Dubbs
authors.forename: Paiboon
authors.initials: P
authors.lastname: Vattanaviboon
authors.forename: Skorn
authors.initials: S
authors.lastname: Mongkolsuk
mesh_terms: D016960:Agrobacterium tumefaciens / Q000187:drug effects / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics / Q000502:physiology*; D018869:Heat-Shock Response; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D018384:Oxidative Stress / Q000502:physiology*; D012097:Repressor Proteins / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C122138:peroxide repressor proteins; D006861:Hydrogen Peroxide