Updated project metadata. Updated publication reference for DOI(s): 10.1073/pnas.2004670118. Mitogen-activated protein kinases constitute essential signaling mechanisms linking external signal perception to gene expression in all eukaryotes. In Arabidopsis, MAPKs are found in the cytoplasmic and nuclear compartments, but no nuclear phosphoproteomic studies of mapk mutants were performed so far. In this work, we report a panel of nuclear and chromatin-associated targets by performing phosphoproteome analyses of wild-type and mpk3, mpk4, and mpk6 mutant plants. Since the three MAPKs play a role in cell division, development and innate immunity, we also analyzed the phosphoproteomes following microbe-associated molecular pattern (MAMP) treatment. A total of 165 proteins were identified to be differentially phosphorylated when compared between genotypes and in response to MAMP treatment. Using different criteria, including different biochemical and interaction assays, a number of the putative MAPK substrates were validated as true substrates for different MAPKs. Signaling networks for the three MAPKs revealed their common role in RNA transcription, RNA processing and chromatin organization, but also specific roles in development and organelle organization. Overall, this study unravels a set of chromatin-associated targets for these three MAPKs and promises novel insights into yet undiscovered domains linking MAPK signaling to a number of chromatin-related events.