title: Overexpression of monodehydroascorbate reductase in transgenic tobacco confers enhanced tolerance to ozone, salt and polyethylene glycol stresses.
abstract: Ascorbate (AsA) is a major antioxidant and free-radical scavenger in plants. Monodehydroascorbate reductase (MDAR; EC 1.6.5.4) is crucial for AsA regeneration and essential for maintaining a reduced pool of AsA. To examine whether an overexpressed level of MDAR could minimize the deleterious effects of environmental stresses, we developed transgenic tobacco plants overexpressing Arabidopsis thaliana MDAR gene (AtMDAR1) in the cytosol. Incorporation of the transgene in the genome of tobacco plants was confirmed by PCR and Southern-blot analysis and its expression was confirmed by Northern- and Western-blot analyses. These transgenic plants exhibited up to 2.1-fold higher MDAR activity and 2.2-fold higher level of reduced AsA compared to non-transformed control plants. The transgenic plants showed enhanced stress tolerance in term of significantly higher net photosynthesis rates under ozone, salt and polyethylene glycol (PEG) stresses and greater PSII effective quantum yield under ozone and salt stresses. Furthermore, these transgenic plants exhibited significantly lower hydrogen peroxide level when tested under salt stress. These results demonstrate that an overexpressed level of MDAR properly confers enhanced tolerance against ozone, salt and PEG stress.
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Agriculture, Tottori University, Koyama, Tottori 680-8553, Japan.
authors.forename: Amin Elsadig
authors.initials: AE
authors.lastname: Eltayeb
authors.forename: Naoyoshi
authors.initials: N
authors.lastname: Kawano
authors.forename: Ghazi Hamid
authors.initials: GH
authors.lastname: Badawi
authors.forename: Hironori
authors.initials: H
authors.lastname: Kaminaka
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sanekata
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shibahara
authors.forename: Shinobu
authors.initials: S
authors.lastname: Inanaga
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000235:genetics; D004361:Drug Tolerance; D006861:Hydrogen Peroxide / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D018384:Oxidative Stress; D010126:Ozone / Q000494:pharmacology*; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000502:physiology*; D011092:Polyethylene Glycols / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology*; D014026:Nicotiana / Q000187:drug effects / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D011092:Polyethylene Glycols; D012965:Sodium Chloride; D010126:Ozone; D006861:Hydrogen Peroxide; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH)