Glutathione-induced drought stress tolerance in mung bean: coordinated roles of the antioxidant defence and methylglyoxal detoxification systems.

Md. Mahabub Alam,Masayuki Fujita,Kamrun Nahar,Mirza Hasanuzzaman

doi:10.1093/aobpla/plv069

Md. Mahabub Alam, Masayuki Fujita + Show 2 more

Open Access

https://doi.org/10.1093/aobpla/plv069

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Abstract

Drought is considered one of the most acute environmental stresses presently affecting agriculture. We studied the role of exogenous glutathione (GSH) in conferring drought stress tolerance in mung bean (Vigna radiata L. cv. Binamoog-1) seedlings by examining the antioxidant defence and methylglyoxal (MG) detoxification systems and physiological features. Six-day-old seedlings were exposed to drought stress (-0.7 MPa), induced by polyethylene glycol alone and in combination with GSH (1 mM) for 24 and 48 h. Drought stress decreased seedling dry weight and leaf area; resulted in oxidative stress as evidenced by histochemical detection of hydrogen peroxide (H2O2) and [Formula: see text] in the leaves; increased lipid peroxidation (malondialdehyde), reactive oxygen species like H2O2 content and [Formula: see text] generation rate and lipoxygenase activity; and increased the MG level. Drought decreased leaf succulence, leaf chlorophyll and relative water content (RWC); increased proline (Pro); decreased ascorbate (AsA); increased endogenous GSH and glutathione disulfide (GSSG) content; decreased the GSH/GSSG ratio; increased ascorbate peroxidase and glutathione S-transferase activities; and decreased the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and catalase. The activities of glyoxalase I (Gly I) and glyoxalase II (Gly II) increased due to drought stress. In contrast to drought stress alone, exogenous GSH enhanced most of the components of the antioxidant and glyoxalase systems in drought-affected mung bean seedlings at 24 h, but GSH did not significantly affect AsA, Pro, RWC, leaf succulence and the activities of Gly I and DHAR after 48 h of stress. Thus, exogenous GSH supplementation with drought significantly enhanced the antioxidant components and successively reduced oxidative damage, and GSH up-regulated the glyoxalase system and reduced MG toxicity, which played a significant role in improving the physiological features and drought tolerance.

Highlights

With increasing population and economic development, the agricultural, energy and industrial sectors of the world’s economy have expanded, resulting in a manifold increase in demand for water
Exogenous GSH addition could not reduce the spots of H2O2 from mung bean leaves
The results of this study showed that drought caused higher ascorbate peroxidase (APX) activity (Table 4) compared with the control, which agrees with previous findings where drought caused higher APX activity and reduced monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) activities with reduced AsA level in B. napus (Hasanuzzaman and Fujita 2011; Alam et al 2013)

Summary

Introduction

With increasing population and economic development, the agricultural, energy and industrial sectors of the world’s economy have expanded, resulting in a manifold increase in demand for water. Drought can reduce stomatal conductance; impair and reduce the membrane electron transport rate, CO2 diffusion, carboxylation efficiency, water-use efficiency, respiration, transpiration and photosynthesis; damage organelle membranes; limit growth and developmental processes; and reduce yields. These damaging effects are very common under drought stress (Lawlor 2002; Pinheiro and Chaves 2011). Constraints in stomatal movement, photosynthetic reaction centre, biochemical reactions of the Calvin cycle, electron transport system or enzyme activities during photosynthesis may result in overproduction of reactive oxygen species (ROS) like O2·−, 1O2, hydrogen peroxide (H2O2) and OH·, which cause oxidative stress and damage cells or their components by disrupting the enzymatic functions of biochemical reactions (Faize et al 2011; Sorkheh et al 2011). MG concentration increases 2- to 6-fold in response to different stresses such as salinity, drought and cold (Yadav et al 2005a, b, c), and it can create similar oxidative stress effects on plant cells like increased ROS (Wang et al 2009; Desai et al 2010)

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