title: Knockout of crtB or crtI gene blocks the carotenoid biosynthetic pathway in Deinococcus radiodurans R1 and influences its resistance to oxidative DNA-damaging agents due to change of free radicals scavenging ability.
abstract: Deinococcus radiodurans R1, a red-pigmented strain of the extremely radioresistant genus Deinococcus, contains a major carotenoid namely deinoxanthin. The high resistance of this organism against the lethal actions of DNA-damaging agents including ionizing radiation and ultraviolet light (UV) has been widely reported. However, the possible antioxidant role of carotenoids in this strain has not been completely elucidated. In this study, we constructed two colorless mutants by knockout of crtB and crtI genes, respectively. Comparative analysis of the two colorless mutants and the wild type showed that the two colorless mutants were more sensitive to ionizing radiation, UV, and hydrogen peroxide, but not to mitomycin-C (MMC). With electron spin resonance (ESR) and spin trapping techniques, we observed that hydroxyl radical signals occurred in the suspensions of UV irradiated Deinococcus radiodurans cells and the intensity of signals was influenced by carotenoids levels. We further showed that the carotenoid extract from the wild type could obviously scavenge superoxide anions generated by the irradiated riboflavin/EDTA system. These results suggest that carotenoids in D. radiodurans R1 function as free radical scavengers to protect this organism against the deleterious effects of oxidative DNA-damaging agents.
authors.affiliation: College of Life Sciences, Wuhan University, Wuhan 430072, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Qiao
authors.initials: Q
authors.lastname: Yang
authors.forename: Xuesong
authors.initials: X
authors.lastname: Luo
authors.forename: Chengxiang
authors.initials: C
authors.lastname: Fang
authors.forename: Qiuju
authors.initials: Q
authors.lastname: Zhang
authors.forename: Yali
authors.initials: Y
authors.lastname: Tang
mesh_terms: D000975:Antioxidants / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics*; D053898:Biosynthetic Pathways / Q000235:genetics; D002338:Carotenoids / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology*; D003600:Cytosol / Q000737:chemistry; D004249:DNA Damage; D004269:DNA, Bacterial / Q000378:metabolism*; D034301:Deinococcus / Q000737:chemistry / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000378:metabolism; D005609:Free Radicals / Q000032:analysis / Q000494:pharmacology*; D017353:Gene Deletion; D006861:Hydrogen Peroxide / Q000494:pharmacology; D016685:Mitomycin / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D016166:Free Radical Scavengers; D005609:Free Radicals; D002338:Carotenoids; D016685:Mitomycin; D006861:Hydrogen Peroxide