Overexpression of chloroplastic monodehydroascorbate reductase enhanced tolerance to temperature and methyl viologen-mediated oxidative stresses.
A tomato (Lycopersicon esculentum Mill.) monodehydroascorbate reductase gene (LeMDAR) was isolated. The LeMDAR-green fluorescence protein (GFP) fusion protein was targeted to chloroplast in Arabidopsis mesophyll protoplast. RNA and protein gel blot analyses confirmed that the sense- and antisense- LeMDAR were integrated into the tomato genome. The MDAR activities and the levels of reduced ascorbate (AsA) were markedly increased in sense transgenic lines and decreased in antisense transgenic lines compared with wild-type (WT) plants. Under low and high temperature stresses, the sense transgenic plants showed lower level of hydrogen peroxide (H(2)O(2)), lower thiobarbituric acid reactive substance (TBARS) content, higher net photosynthetic rate (P(n)), higher maximal photochemical efficiency of PSII (F(v)/F(m)) and fresh weight compared with WT plants. The oxidizable P700 decreased more obviously in WT and antisense plants than that in sense plants at chilling temperature under low irradiance. Furthermore, the sense transgenic plants exhibited significantly lower H(2)O(2) level, higher ascorbate peroxidase (APX) activity, greater P(n) and F(v)/F(m) under methyl viologen (MV)-mediated oxidative stresses. These results indicated that overexpression of chloroplastic MDAR played an important role in alleviating photoinhibition of PSI and PSII and enhancing the tolerance to various abiotic stresses by elevating AsA level.
State Key Laboratory of Crop Biology, College of Life Science, Shandong Agricultural University, Tai'an, Shandong 271018, P.R. China.
Feng
F
Li
Qing-Yun
QY
Wu
Yan-Li
YL
Sun
Li-Yan
LY
Wang
Xing-Hong
XH
Yang
Qing-Wei
QW
Meng
D000595:Amino Acid Sequence; D060387:Ascorbate Peroxidases; D001205:Ascorbic Acid / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010269:Paraquat / Q000494:pharmacology*; D010544:Peroxidases / Q000378:metabolism; D010788:Photosynthesis; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D016415:Sequence Alignment; D013696:Temperature; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
D018749:RNA, Plant; D017392:Thiobarbituric Acid Reactive Substances; D006861:Hydrogen Peroxide; D010544:Peroxidases; D060387:Ascorbate Peroxidases; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH); D010269:Paraquat; D001205:Ascorbic Acid