The Importance of Glutathione in Defence against Cadmium-induced Toxicity of Rice Seedlings

Abstract

Cadmium (Cd)-sensitive and -tolerant rice cultivars were used to study the role of reduced glutathione (GSH) in Cd-induced toxicity. Cd toxicity of rice seedlings was evaluated by the decrease in chlorophyll content and the increase in malondialehyde content in the second leaves. On treatment with 5 μM CdCl2 for 6 days, the content of GSH decreased in the second leaves of Cd-sensitive cultivar (cv. Taichung Native 1; TN1) but not in the Cd-tolerant cultivar (cv. Tainung 67; TNG67). Moreover, Cd-reduced GSH content was prior to Cd-decreased chlorophyll content in the second leaves of TN1 seedlings. Pretreatment of TN1 seedlings with 1 mM GSH for 6 h resulted in an increase in the contents of GSH and ascorbate (AsA) and the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) in the second leaves of TN1 seedlings. Rice seedlings of TN1 pretreated with GSH were observed to reduce the subsequent Cd-induced toxicity. Exogenous application of the buthionine sulfoximine (BSO), a specific inhibitor of GSH biosynthesis, reduced the contents of GSH and AsA, the activities of GR and APX, and decreased Cd tolerance of TNG67 seedlings. BSO effects on the contents of GSH and AsA, the activities of GR and APX, and Cd toxicity were reversed by the application of GSH. Based on the data obtained in this study, it could be concluded that GSH content plays a role in regulating Cd toxicity of rice seedlings.