title: Effects of osmotic stress on antioxidant enzymes activities in leaf discs of PSAG12-IPT modified Gerbera.
abstract: Leaf senescence is often caused by water deficit and the chimeric gene P(SAG12)-IPT is an auto-regulated gene delaying leaf senescence. Using in vitro leaf discs culture system, the changes of contents of chlorophylls, carotenoids, soluble protein and thiobarbituric acid reactive substance (TBARS) and antioxidant enzymes activities were investigated during leaf senescence of P(SAGl2)-IPT modified gerbera induced by osmotic stress compared with the control plant (wild type). Leaf discs were incubated in 20%, 40% (w/v) polyethylene glycol (PEG) 6000 nutrient solution for 20 h under continuous light [130 micromol/(m(2) x s)]. The results showed that the contents of chlorophylls, carotenoids and soluble protein were decreased by osmotic stress with the decrease being more pronounced at 40% PEG, but that, at the same PEG concentration the decrease in the transgenic plants was significantly lower than that in the control plant. The activities of superoxide dismutase (SOD), catalases (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and dehydroascorbate reductase (DHAR) were stimulated by PEG treatment. However, the increases were higher in P(SAG12)-IPT transgenic plants than in the control plants, particularly at 40% PEG treatment. Lipid peroxidation (TBARS content) was increased by PEG treatment with the increase being much lower in transgenic plant than in the control plant. It could be concluded that the increases in the activities of antioxidant enzymes including SOD, CAT, APX, GPX and DHAR were responsible for the delay of leaf senescence induced by osmotic stress.
authors.affiliation: Key Laboratory of Horticultural Plant Development and Biotechnology, Department of Horticulture, Zhejiang University, Hangzhou 310029, China.
authors.forename: Qi-xian
authors.initials: QX
authors.lastname: Lai
authors.forename: Zhi-yi
authors.initials: ZY
authors.lastname: Bao
authors.forename: Zhu-jun
authors.initials: ZJ
authors.lastname: Zhu
authors.forename: Qiong-qiu
authors.initials: QQ
authors.lastname: Qian
authors.forename: Bi-zeng
authors.initials: BZ
authors.lastname: Mao
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics; D000975:Antioxidants / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics; D060387:Ascorbate Peroxidases; D019659:Asteraceae / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000235:genetics; D005798:Genes, Bacterial; D017343:Genes, Plant; D015227:Lipid Peroxidation; D009997:Osmotic Pressure; D010088:Oxidoreductases / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D012995:Solubility; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D029681:Arabidopsis Proteins; D010940:Plant Proteins; D002734:Chlorophyll; D002338:Carotenoids; D010088:Oxidoreductases; D010544:Peroxidases; C121048:guaiacol peroxidase; D060387:Ascorbate Peroxidases; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase; C020666:glutathione dehydrogenase (ascorbate); D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase; C402082:SAG12 protein, Arabidopsis; D003546:Cysteine Endopeptidases