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

• Effect of exogenous GSH in mitigating high temperature stress was studied in Vigna radiata seedlings.
• High temperature increases oxidative stress, methylglyoxal content and alters the physiology.
• Exogenous GSH reduces oxidative damages by improving antioxidant defense system.
• Glutathione detoxifies methylglyoxal by improving glyoxalase system.
• Glutathione improves the tolerance of V. radiata plants to high temperature stress.

The present study investigates the role of exogenous glutathione (GSH) in conferring high temperature stress (HT, 42 °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 h as 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 O2− 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, O2− 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.