Exogenous glutathione confers high temperature stress tolerance in mung bean (Vigna radiata L.) by modulating antioxidant defense and methylglyoxal detoxification system

The present study investigates the role of exogenous glutathione (GSH) in conferring high temperature stress (HT, 42 degrees C) tolerance in mung bean (Vigna radiata L. cv. Binamoog-1) seedlings by modulating the antioxidant defense and methylglyoxal (MG) detoxification systems. Six-day-old seedlings were exposed to HT stress with or without exogenous GSH (0.5 mM for 24 has pretreatment) for 24 and 48 h. Heat stress at any duration significantly increased lipid peroxidation (MDA), H2O2, MG, and Proline (Pro) content, generation rate of O-2(center dot-) and lipoxygenase (LOX) activity; decreased leaf chlorophyll (chl) and leaf relative water content (RWC), and the level of ascorbate (AsA); increased endogenous GSH and GSSG (glutathione disulfide); decreased the GSH/GSSG ratio. For both treatment durations, activities of ascorbate peroxidase (APX), glutathione reductase (GR), glutathione-S-transferase (GST) increased; the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione peroxidase (GPX), catalase (CAT) and glyoxalase I (Gly I) decreased; the activity of glyoxalase II (Gly II) increased at 48 h. Mung bean seedlings pretreated with exogenous GSH under HT improved chl and leaf RWC; increased APX (only after 24 h), MDHAR, DHAR, GR, GPX, GST (increased only after 24 h), CAT, Gly I and Gly II activities; improved endogenous GSH content and the GSH/GSSG ratio; lowered GSSG content. Glutathione supplementation with drought stress significantly decreased MDA, H2O2 and MG content, O-2(center dot-) generation rate and LOX activity. Pretreatment with GSH resulted in better physiological performance, improved antioxidant and glyoxalase systems, and reduced MG and oxidative stress under 24 h of HT stress, compared with that of 48 h. The results suggest that exogenous GSH enhances mung bean seedling tolerance of short-term HT stress by modulating the antioxidant and glyoxalase systems and by improving physiological adaptation. (C) 2014 Elsevier B.V. All rights reserved.