Enhanced tolerance to ozone and drought stresses in transgenic tobacco overexpressing dehydroascorbate reductase in cytosol

Abstract

Ascorbate (vitamin C) is a potent antioxidant protecting plants against oxidative damage imposed by environmental stresses such as ozone and drought. Dehydroascorbate reductase (DHAR; EC 1.8.5.1) is one of the two important enzymes functioning in the regeneration of ascorbate (AsA). To examine the protective role of DHAR against oxidative stress, we developed transgenic tobacco plants overexpressing cytosolic DHAR gene from Arabidopsis thaliana. Incorporation of the transgene in the genome of tobacco plants was confirmed by polymerase chain reaction and Southern blot analysis, and its expression was confirmed by Northern and Western blot analyses. These transgenic plants exhibited 2.3–3.1 folds higher DHAR activity and 1.9–2.1 folds higher level of reduced AsA compared with non‐transformed control plants. The transgenic plants showed maintained redox status of AsA and exhibited an enhanced tolerance to ozone, drought, salt, and polyethylene glycol stresses in terms of higher net photosynthesis. In this study, we report for the first time that the elevation of AsA level by targeting DHAR overexpression in cytosol properly provides a significantly enhanced oxidative stress tolerance imposed by drought and salt.

Up-regulation of antioxidant and glyoxalase systems by exogenous glycinebetaine and proline in mung bean confer tolerance to cadmium stress

“…DHA undergoes irreversible hydrolysis to 2, 3-diketogulonic acid or is recycled to AsA by DHAR, thereby capturing AsA before it lost. Recent studies showed that both MDHAR and DHAR are equally important in regulating AsA levels and its redox state under oxidative stress condition (Eltayeb et al 2006(Eltayeb et al , 2007Wang et al 2010;Shalata et al 2001). Results obtained in this study showed that both MDHAR and DHAR decreased along with a decreased level of AsA (Figs.…”

Transgenic potato overexpressing Arabidopsis cytosolic AtDHAR1 showed higher tolerance to herbicide, drought and salt stresses

“…Among antioxidative enzymes, DHAR overexpression represents a reliable approach to confer enhanced tolerance to multiple environmental stresses such as ozone, drought, slat and aluminum stresses (Eltayeb et al 2006, Yin et al 2010. In the present study, we report the generation of transgenic potato overexpressing AtDHAR1, the metabolic effects of DHAR overproduction on the AsA pool, and the resulting gain in stress tolerance against the herbicide methylviologen (MV) and against drought and salt stress.…”

“…Immunodetection was performed using diluted (1 : 10 000) guinea pig antibodies against the DHAR protein (Eltayeb et al 2006) as the first antibody and a diluted (1 : 5000) horseradish peroxidase-conjugated anti-guinea pig IgG (Sigma) as the second antibody. Chemiluminescent detection was carried out using Immobilon Western Chemiluminescent HRP Substrate (Millipore, Tokyo, Japan), and the signals were visualized using the LAS-4000 Mini (Fujifilm, Tokyo, Japan).…”

“…DHAR was assayed as described previously (Eltayeb et al 2006) in a reaction mixture that contained 50 mM potassium phosphate, 5 mM GSH, 2 mM dehydroascorbate (DHA), and the crude extracts. The increase in absorbance at 290 nm due to the ascorbate was monitored and the activity was calculated using an absorbance coefficient of 2.8 mM −1 cm −1 .…”

“…In particular, few researchers have integrated genes for antioxidative enzymes into potato plants. Transgenic potato with enhanced tolerance to oxidative stress has been reported as a result of overexpressing a Cu/Zn superoxide dismutase gene (Perl et al 1993 Among antioxidative enzymes, DHAR overexpression represents a reliable approach to confer enhanced tolerance to multiple environmental stresses such as ozone, drought, slat and aluminum stresses (Eltayeb et al 2006, Yin et al 2010. In the present study, we report the generation of transgenic potato overexpressing AtDHAR1, the metabolic effects of DHAR overproduction on the AsA pool, and the resulting gain in stress tolerance against the herbicide methylviologen (MV) and against drought and salt stress.…”