title: Evaluation of the roles that alkyl hydroperoxide reductase and Ohr play in organic peroxide-induced gene expression and protection against organic peroxides in Xanthomonas campestris.
abstract: Alkyl hydroperoxide reductase (ahpC) and organic hydroperoxide resistance (ohr) are distinct genes, structurally and regulatory, but have similar physiological functions. In Xanthomonas campestris pv. phaseoli inactivation of either gene results in increased sensitivity to killing with organic peroxides. An ahpC1-ohr double mutant was highly sensitive to both growth inhibition and killing treatment with organic peroxides. High level expression of ahpC or ohr only partially complemented the phenotype of the double mutant, suggesting that these genes function synergistically, but through different pathways, to protect Xanthomonas from organic peroxide toxicity. Functional analyses of Ohr and AhpC abilities to degrade organic hydroperoxides revealed that both Ohr and AhpC could degrade tert-butyl hydroperoxide (tBOOH) while the former was more efficient at degrading cumene hydroperoxide (CuOOH). Expression analysis of these genes in the mutants showed no compensatory alterations in the levels of AhpC or Ohr. However, CuOOH induced expression of these genes in the mutants was affected. CuOOH induced ahpC expression was higher in the ohr mutant than in the parental strain; in contrast, the ahpC mutation has no effect on the level of induced ohr expression. These analyses reveal complex physiological roles and expression patterns of seemingly functionally similar genes.
authors.affiliation: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, 10210, Bangkok, Thailand.
authors.forename: Paiboon
authors.initials: P
authors.lastname: Vattanaviboon
authors.forename: Wirongrong
authors.initials: W
authors.lastname: Whangsuk
authors.forename: Warunya
authors.initials: W
authors.lastname: Panmanee
authors.forename: Chananat
authors.initials: C
authors.lastname: Klomsiri
authors.forename: Saovanee
authors.initials: S
authors.lastname: Dharmsthiti
authors.forename: Skorn
authors.initials: S
authors.lastname: Mongkolsuk
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001555:Benzene Derivatives / Q000378:metabolism / Q000633:toxicity; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D007700:Kinetics; D009154:Mutation; D010544:Peroxidases / Q000235:genetics / Q000502:physiology*; D010545:Peroxides / Q000633:toxicity*; D054464:Peroxiredoxins; D012329:RNA, Bacterial / Q000096:biosynthesis; D016959:Xanthomonas campestris / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D020122:tert-Butylhydroperoxide / Q000378:metabolism / Q000633:toxicity
chemical_list: D001426:Bacterial Proteins; D001555:Benzene Derivatives; D010545:Peroxides; D012329:RNA, Bacterial; C112257:organic hydroperoxide resistance protein, Xanthomonas campestris; D020122:tert-Butylhydroperoxide; D010544:Peroxidases; D054464:Peroxiredoxins; C007164:cumene hydroperoxide