title: Increased Rate of NAD Metabolism Shortens Plant Longevity by Accelerating Developmental Senescence in Arabidopsis.
abstract: NAD is a well-known co-enzyme that mediates hundreds of redox reactions and is the basis of various processes regulating cell responses to different environmental and developmental cues. The regulatory mechanism that determines the amount of cellular NAD and the rate of NAD metabolism remains unclear. We created Arabidopsis thaliana plants overexpressing the NAD synthase (NADS) gene that participates in the final step of NAD biosynthesis. NADS overexpression enhanced the activity of NAD biosynthesis but not the amounts of NAD+, NADH, NADP+or NADPH. However, the amounts of some intermediates were elevated, suggesting that NAD metabolism increased. The NAD redox state was greatly facilitated by an imbalance between NAD generation and degradation in response to bolting. Metabolite profiling and transcriptional analysis revealed that the drastic modulation of NAD redox homeostasis increased tricarboxylic acid flux, causing the ectopic generation of reactive oxygen species. Vascular bundles suffered from oxidative stress, leading to a malfunction in amino acid and organic acid transportation that caused early wilting of the flower stalk and shortened plant longevity, probably due to malnutrition. We concluded that the mechanism regulating the balance between NAD synthesis and degradation is important in the systemic plant response to developmental cues during the growth-phase transition.
authors: Institute of Molecular and Cellular Biosciences (IMCB), The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan shashida@criepi.denken.or.jp.|Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
authors: Shin-Nosuke
authors: SN
authors: Hashida
authors: Institute of Molecular and Cellular Biosciences (IMCB), The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
authors: Taketo
authors: T
authors: Itami
authors: Institute of Molecular and Cellular Biosciences (IMCB), The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
authors: Kentaro
authors: K
authors: Takahara
authors: Institute of Molecular and Cellular Biosciences (IMCB), The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
authors: Takayuki
authors: T
authors: Hirabayashi
authors: Institute for Environmental Science and Technology (IEST), Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan.
authors: Hirofumi
authors: H
authors: Uchimiya
authors: Department of Environmental Science and Human Engineering, Saitama University, Sakura-ku, Saitama 338-0825, Japan.
authors: Maki
authors: M
authors: Kawai-Yamada
mesh_terms: D019732:Amide Synthases / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D053898:Biosynthetic Pathways; D003067:Coenzymes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis; D006861:Hydrogen Peroxide / Q000378:metabolism; D008136:Longevity; D055432:Metabolomics; D008954:Models, Biological; D009243:NAD / Q000378:metabolism*; D010084:Oxidation-Reduction; D063245:Plant Development; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified; D012098:Reproduction
chemical_list: D029681:Arabidopsis Proteins; D003067:Coenzymes; D009243:NAD; D006861:Hydrogen Peroxide; D019732:Amide Synthases; C038479:NAD+ synthase
keywords: Arabidopsis; Biosynthesis; NAD; Plant longevity; Senescence; Synthase