Mutation of mpk6 enhances cadmium tolerance in Arabidopsis plants by alleviating oxidative stress

Cadmium (Cd) could activate activity of mitogen-activated protein kinase MPK6 in plants. In this study, we investigated the role of MPK6 in mediating Cd toxicity in plants. The wild type Arabidopsis plants (WT) and the mpk6-2 mutants were subjected either 0 (Control) or 10 mu M Cd treatment. Kinase activity of MPK6, nitric oxide (NO) level, Cd concentration, and oxidative stress were measured. In WT plants, Cd exposure rapidly stimulated kinase activity of MPK6. However, upon Cd exposure, mpk6-2 showed better growth than the WT. Although Cd-induced production of NO in roots was greater in WT than in mpk6-2, there was no difference in Cd concentration between the two plants. Nevertheless, the Cd-induced hydroperoxide burst, lipid peroxidation and loss of membrane integrity, were all more severe in the WT than in mpk6-2. Foliar applications of antioxidant ascorbic acid, vigorously improved the growth of both the WT and mpk6-2 under Cd exposure. Thereby the growth difference between these two plants was minimized. Mutation of mpk6 enhances Cd tolerance in plants by alleviating oxidative stress, but did not affect cadmium accumulation in plants.