Involvement of glutathione in heat shock- and hydrogen peroxide-induced cadmium tolerance of rice (Oryza sativa L.) seedlings

The role of reduced glutathione (GSH) in heat shock (HS)- and H2O2-induced protection of rice (Oryza sativa L., cv. Taichung 1) seedlings from Cd stress was investigated. HS- and H2O2-pretreatment resulted in an increase in GSH content in leaves of rice seedlings. Addition of exogenous GSH under non-HS conditions, which resulted in an increase in GSH in leaves, enhanced subsequent Cd tolerance of rice seedlings. Pretreatment with buthionine sulfoximine (BSO), a specific inhibitor of GSH synthesis, which effectively inhibited GSH content induced by HS and H2O2, reduced subsequent Cd tolerance. Furthermore, the effect of BSO on HS- and H2O2-induced GSH accumulation and toxicity by subsequent Cd stress can be reversed by the addition of GSH. The time-course analyses of HS in rice seedlings demonstrated that the accumulation of H2O2 preceded the increase in GSH. Based on the data obtained in this study, it could be concluded that the early accumulation of H2O2 during HS signals the increase in GSH content, which in turn protects rice seedlings from oxidative damage caused by Cd.