Enhanced sensitivity to oxidative stress in transgenic tobacco plants with decreased glutathione reductase activity leads to a decrease in ascorbate pool and ascorbate redox state

Abstract

To investigate the possible mechanisms of glutathione reductase (GR) in protecting against oxidative stress, we obtained transgenic tobacco (Nicotiana tabacum) plants with 30-70% decreased GR activity by using a gene encoding tobacco chloroplastic GR for the RNAi construct. We investigated the responses of wild type and transgenic plants to oxidative stress induced by application of methyl viologen in vivo. Analyses of CO(2) assimilation, maximal efficiency of photosystem II photochemistry, leaf bleaching, and oxidative damage to lipids demonstrated that transgenic plants exhibited enhanced sensitivity to oxidative stress. Under oxidative stress, there was a greater decrease in reduced to oxidized glutathione ratio but a greater increase in reduced glutathione in transgenic plants than in wild type plants. In addition, transgenic plants showed a greater decrease in reduced ascorbate and reduced to oxidized ascorbate ratio than wild type plants. However, there were neither differences in the levels of NADP and NADPH and in the total foliar activities of monodehydroascorbate reductase and dehydroascorbate reductase between wild type and transgenic plant. MV treatment induced an increase in the activities of GR, ascorbate peroxidase, superoxide dismutase, and catalase. Furthermore, accumulation of H(2)O(2) in chloroplasts was observed in transgenic plants but not in wild type plants. Our results suggest that capacity for regeneration of glutathione by GR plays an important role in protecting against oxidative stress by maintaining ascorbate pool and ascorbate redox state.

Gene knockout of glutathione reductase 3 results in increased sensitivity to salt stress in rice

“…In Arabidopsis, chloroplast and mitochondrial dual-targeted GR2 knockout caused lethality in embryos (Tzafrir et al 2004). As well, chloroplastic GR knocked-down tobacco (Ding et al 2009) and tomato (Shu et al 2011) showed susceptibility to MV and chilling, respectively. These results indicate that chloroplast or mitochondrial GR plays a key role in stress tolerance and plant development.…”

“…Altered chloroplastic GR affects the glutathione redox state and pool size. For example, reduced expression of chloroplastic GR led to decreased GSH content and GSH/GSSG ratio in tobacco (Ding et al 2009) and tomato (Shu et al 2011) after MV and chilling treatment, respectively. Conversely, overexpression Fig.…”

“…Several studies have shown that GR is involved in stress tolerance (Ding et al 2009;Noctor et al 2012). Silencing of GR by RNA interference attenuated GR activity in tobacco and tomato to increase the sensitivity to oxidative and/or chilling stresses (Aono et al 1995;Ding et al 2009Ding et al , 2012Shu et al 2011).…”

“…Silencing of GR by RNA interference attenuated GR activity in tobacco and tomato to increase the sensitivity to oxidative and/or chilling stresses (Aono et al 1995;Ding et al 2009Ding et al , 2012Shu et al 2011). In contrast, overexpression of GR in tobacco by chloroplast transformation significantly improved tolerance to methyl viologen (MV), salt and cold stresses (Le Martret et al 2011).…”

Arabidopsis GLUTATHIONE REDUCTASE1 Plays a Crucial Role in Leaf Responses to Intracellular Hydrogen Peroxide and in Ensuring Appropriate Gene Expression through Both Salicylic Acid and Jasmonic Acid Signaling Pathways

“…In pea, cytosolic GR has been well characterized at the biochemical level (Edwards et al, 1990;Stevens et al, 2000), but the functional significance of the enzyme remains unclear. Underexpression or overexpression studies in tobacco and poplar (Populus species) have reported significant effects of modifying chloroplast GR capacity (Aono et al, 1993;Broadbent et al, 1995;Foyer et al, 1995;Ding et al, 2009). Less evidence is available supporting an important role for cytosolic GR.…”