title: Enhanced dihydroflavonol-4-reductase activity and NAD homeostasis leading to cell death tolerance in transgenic rice.
abstract: The maize Hm1 gene encoding the NADPH-dependent HC-toxin reductase is capable of detoxifying HC-toxin of fungus Cochliobolus carbonum. Here, we conducted the metabolic and biochemical analysis in transgenic rice plants overexpressing an HC-toxin reductase-like gene in rice (YK1 gene). Methods employing NADPH oxidation and capillary electrophoresis mass spectrometry analysis confirmed that YK1 possessed dihydroflavonol-4-reductase activity in vitro and in vivo. The overexpression of YK1 in both suspension-cultured cells and rice plants increased NAD(H) and NADP(H) levels by causing an increase in NAD synthetase and NAD kinase activities. Activity changes in enzymes that require NAD(P) as coenzymes were also noted in rice cells ectopically expressing YK1, where the cell death caused by hydrogen peroxide and bacterial disease was down-regulated. Thus, a strategy was proposed that the combination of dihydroflavonol-4-reductase activity and the elevated level of NAD(P)H pool may confer the prevention of induced cell death in planta.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Hayashi
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Katsunori
authors.initials: K
authors.lastname: Tamura
authors.forename: Jirong
authors.initials: J
authors.lastname: Huang
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Yu
authors.forename: Maki
authors.initials: M
authors.lastname: Kawai-Yamada
authors.forename: Takafumi
authors.initials: T
authors.lastname: Tezuka
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Uchimiya
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D019732:Amide Synthases / Q000378:metabolism; D016923:Cell Death; D004396:Coloring Agents / Q000494:pharmacology; D019075:Electrophoresis, Capillary; D005070:Evans Blue / Q000494:pharmacology; D005982:Glutathione Transferase / Q000378:metabolism; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007477:Ions; D013058:Mass Spectrometry; D008954:Models, Biological; D009243:NAD / Q000737:chemistry / Q000378:metabolism*; D009249:NADP / Q000737:chemistry; D009536:Niacinamide / Q000737:chemistry; D012275:Oryza / Q000235:genetics*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified; D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D003313:Zea mays
chemical_list: D004396:Coloring Agents; D007477:Ions; D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins; D009243:NAD; D009536:Niacinamide; D005070:Evans Blue; D009249:NADP; D000429:Alcohol Oxidoreductases; C056570:dihydroflavanol 4-reductase; D005982:Glutathione Transferase; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase; D019732:Amide Synthases; C038479:NAD+ synthase