Differential activation of MAPKs by CuCl2 and CdCl2. Seedlings were treated with 100 μm CuCl2 or CdCl2. Roots were harvested at the given time points. A, Immunokinase assays were performed with M23, M11, M14, or M24 antibodies that specifically recognize SIMK, MMK2, MMK3, or SAMK, respectively. B, The same protein extracts were used for protein gel-blot analysis with M23, M11, M14, or M24 antibodies. The experiment was repeated twice revealing similar kinetics in all cases.