H2O2 treatment induces glutathione accumulation and chilling tolerance in mung bean

Mung bean (Vigna radiata L. cv. TN5, a chilling-sensitive cultivar) was employed to evaluate the importance of glutathione in hydrogen peroxide (H2O2)-induced chilling tolerance. Seeds germinated at 25degreesC for 7 d were subjected to different periods of chilling treatment, prior to analysis of the glutathione contents of their leaves. In a comparison of acclimation temperatures from 2-12degreesC, it was found that an 8degreesC acclimation for 36 h induced a 5.7-fold increase, the highest glutathione level among the temperatures tested. Seedlings acclimated at 8degreesC for 36 h showed 97% survival after a 36-h, 4degreesC chilling stress, compared with 33% survival of non-acclimated plants. Pretreatment with 200 mM H2O2 for 12 h before a 36-h, 4degreesC chilling treatment increased glutathione levels by 30% and reduced electrolyte leakage to 43%, relative to the untreated control. Treated seedlings also showed a survival rate of 71% after the same chilling treatment. Application of 1 mM buthionine sulfoximine, a specific inhibitor of glutathione synthesis, reversed the protection against chilling stress provided to seedlings either by acclimation at 8degreesC for 36 h or H2O2 pretreatment. The role of glutathione in chilling acclimation or H2O2-pretreatment-induced chilling tolerance is thus confirmed.