title: Untargeted metabolite profiling reveals that nitric oxide bioynthesis is an endogenous modulator of carotenoid biosynthesis in Deinococcus radiodurans and is required for extreme ionizing radiation resistance.
abstract: Deinococcus radiodurans (Drad) is the most radioresistant organism known. Although mechanisms that underlie the extreme radioresistance of Drad are incompletely defined, resistance to UV irradiation-induced killing was found to be greatly attenuated in an NO synthase (NOS) knockout strain of Drad (Δnos). We now show that endogenous NO production is also critical for protection of Drad against γ-irradiation (3000 Gy), a result of accelerated growth recovery, not protection against killing. NO-donor treatment rescued radiosensitization in Δnos Drad but did not influence radiosensitivity in wild type Drad. To discover molecular mechanisms by which endogenous NO confers radioresistance, metabolite profiling studies were performed. Untargeted LC-MS-based metabolite profiling in Drad quantified relative abundances of 1425 molecules and levels of 294 of these were altered by >5-fold (p < 0.01). Unexpectedly, these studies identified a dramatic perturbation in carotenoid biosynthetic intermediates in Δnos Drad, including a reciprocal switch in the pathway end-products from deoxydeinoxanthin to deinoxanthin. NO supplementation rescued these nos deletion-associated changes in carotenoid biosynthesis, and fully-restored radioresistance to wildtype levels. Because carotenoids were shown to be important contributors to radioprotection in Drad, our findings suggest that endogenously-produced NO serves to maintain a spectrum of carotenoids critical for Drad's ability to withstand radiation insult.
authors.affiliation: Department of Pharmacology, Weill Cornell Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Hansler
authors.affiliation: Department of Pharmacology, Weill Cornell Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
authors.forename: Qiuying
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, Weill Cornell Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Department of Pharmacology, Weill Cornell Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA. Electronic address: ssgross@med.cornell.edu.
authors.forename: Steven S
authors.initials: SS
authors.lastname: Gross
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D002338:Carotenoids / Q000096:biosynthesis* / Q000737:chemistry; D034301:Deinococcus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000528:radiation effects; D055786:Gene Knockout Techniques; D055432:Metabolomics; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000172:deficiency / Q000235:genetics; D011836:Radiation Tolerance / Q000187:drug effects
chemical_list: D000975:Antioxidants; D009569:Nitric Oxide; D002338:Carotenoids; D019001:Nitric Oxide Synthase
keywords: Knockout; Mass spectrometry; Metabolomics; Oxidative damage; Radioprtection