title: Increased vitamin C content accompanied by an enhanced recycling pathway confers oxidative stress tolerance in Arabidopsis.
abstract: Vitamin C (L-ascorbic acid, AsA) has important antioxidant and metabolic functions in both plants and animals. Once used, ascorbic acid can be regenerated from its oxidized form in a reaction catalyzed by dehydroascorbate reductase (DHAR, EC 1.8.5.1). To analyze the physiological role of DHAR catalyzing the reduction of DHA to ascorbate in environmental stress adaptation, we examined whether increasing the level of AsA through enhanced AsA recycling would limit the deleterious effects of oxidative stress. A chimeric construct consisting of the double CaMV35S promoter fused to the Myc-dhar gene was introduced into Arabidopsis thaliana. Transgenic plants were biochemically characterized and tested for responses to oxidative stress. Western blot indicated that the dhar-transgene was successfully expressed. In homozygous T(4) transgenic seedlings, DHAR overexpression was increased up to 1.5 to 5.4 fold, which enhanced foliar ascorbic acid levels 2- to 4.25-fold and ratio of AsA/DHA about 3- to 16-fold relative to wild type. In addition, the level of glutathione, the reductant used by DHAR, also increased as did its redox state. When whole plants were treated with high light and high temperature stress or in vitro leaf discs were subjected to 10 muM paraquat, transgenic plants showed a larger AsA pool size, lower membrane damage, and a higher level of chlorophyll compared with controls. These data suggested that increasing the plant vitamin C content through enhanced ascorbate recycling could limit the deleterious effects of environmental oxidative stress.
authors.affiliation: State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan-SJTU-Nottingham Plant Biotechnology R&D Center, Fudan University, Shanghai 200433, China.
authors.forename: Zinan
authors.initials: Z
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiao
authors.forename: Wansheng
authors.initials: W
authors.lastname: Chen
authors.forename: Kexuan
authors.initials: K
authors.lastname: Tang
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism*; D015153:Blotting, Western; D002734:Chlorophyll / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D018384:Oxidative Stress / Q000235:genetics / Q000502:physiology*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013696:Temperature
chemical_list: D002734:Chlorophyll; D010088:Oxidoreductases; C020666:glutathione dehydrogenase (ascorbate); D001205:Ascorbic Acid