Figure 4.

MAP kinase activation by genotoxic stress treatment in Arabidopsis seedlings and AtMKP1-dependent activation level. (A) Immunoblot analysis with a p44/42 MAP kinase antibody (top) and a phospho-p44/42 MAP kinase antibody (bottom) detects phosphorylated MAP kinase orthologs after UV-C treatment (5 min after treatment with 3 kJ/m²). (B,C) Five-day-old seedlings of wild type (Ws), mkp1 mutant, and complemented line 6 were subjected to UV-C (B) or MMS (C) treatment and dose-dependent activation of a 49-kD kinase was detected in MBP in-gel kinase assays. Samples were taken after 5 min in the case of UV-C treatment and after 90 min in the case of MMS. On lower panels, protein loading controls are shown on 10% SDS-PAGE stained with Coomassie blue.