Overexpression of chloroplastic monodehydroascorbate reductase enhanced tolerance to temperature and methyl viologen-mediated oxidative stresses

Abstract

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.

Ascorbate metabolism in vegetative and reproductive organs of "cherry" tomato

“…Similar results for APX transcription were obtained by Panchuk et al (2005). In Arabidopsis, Li et al (2010a) also found minor differences in the transcripts levels of MDAHR and DAHR between young and mature leaves, as recorded in the current study as well. Thus, it could be said that different molecular mechanisms participate in controlling the transcriptional regula- tion of ASA metabolism genes in young and mature leaves.…”

Arabidopsis CSN5B Interacts with VTC1 and Modulates Ascorbic Acid Synthesis

“…Alternatively, given evidence showing that vtc1-1 is hypersensitive to ammonium and that VTC1 has functions in cell wall polysaccharide synthesis and protein N-glycosylation (Qin et al, 2008;Barth et al, 2010), it is possible that the modulation of CSN5B by VTC1 results in altered glycoprotein synthesis, which further affects the csn5b response to salt stress. In addition, one important role of AsA is to remove ROS, which are triggered by light and oxidative stress, in plants (Smirnoff, 2000;Li et al, 2010). Plants require many small molecules to maintain a steady redox state in vivo.…”

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

“…Overexpression of Arabidopsis MDHAR gene in tobacco confers enhanced tolerance to salt and polyethylene glycol stresses [217]. Tomato chloroplastic MDHAR overexpressed in transgenic Arabidopsis enhanced its tolerance to temperature and methyl viologen-mediated oxidative stresses [218].…”