title: Co-expression of monodehydroascorbate reductase and dehydroascorbate reductase from Brassica rapa effectively confers tolerance to freezing-induced oxidative stress.
abstract: Plants are exposed to various environmental stresses and have therefore developed antioxidant enzymes and molecules to protect their cellular components against toxicity derived from reactive oxygen species (ROS). Ascorbate is a very important antioxidant molecule in plants, and monodehydroascorbate reductase (MDHAR; EC 1.6.5.4) and dehydroascorbate reductase (DHAR; EC 1.8.5.1) are essential to regeneration of ascorbate for maintenance of ROS scavenging ability. The MDHAR and DHAR genes from Brassica rapa were cloned, transgenic plants overexpressing either BrMDHAR and BrDHAR were established, and then, each transgenic plant was hybridized to examine the effects of co-expression of both genes conferring tolerance to freezing. Transgenic plants co-overexpressing BrMDHAR and BrDHAR showed activated expression of relative antioxidant enzymes, and enhanced levels of glutathione and phenolics under freezing condition. Then, these alteration caused by co-expression led to alleviated redox status and lipid peroxidation and consequently conferred improved tolerance against severe freezing stress compared to transgenic plants overexpressing single gene. The results of this study suggested that although each expression of BrMDHAR or BrDHAR was available to according tolerance to freezing, the simultaneous expression of two genes generated synergistic effects conferring improved tolerance more effectively even severe freezing.
authors.affiliation: Postharvest Research Team, Department of Horticultural Crop Research, National Institute of Horticultural & Herbal Science, Rural Development Administration, Suwon, 440-706, Korea.
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Shin
authors.forename: Myung-Hee
authors.initials: MH
authors.lastname: Kim
authors.forename: Yul-Ho
authors.initials: YH
authors.lastname: Kim
authors.forename: Hyang-Mi
authors.initials: HM
authors.lastname: Park
authors.forename: Ho-Sung
authors.initials: HS
authors.lastname: Yoon
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D001205:Ascorbic Acid / Q000378:metabolism; D018533:Biomass; D029741:Brassica rapa / Q000201:enzymology* / Q000235:genetics; D005615:Freezing / Q000009:adverse effects*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005978:Glutathione / Q000378:metabolism; D015227:Lipid Peroxidation / Q000235:genetics; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D017382:Reactive Oxygen Species; D010088:Oxidoreductases; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH); C020666:glutathione dehydrogenase (ascorbate); D005978:Glutathione; D001205:Ascorbic Acid