Complexity, cross talk and integration of plant MAP kinase signalling

Mitogen-activated protein kinases (MAPKs) link stimuli that are activated by external sensors to cellular responses. The completed Arabidopsis genome sequence has revealed an extraordinary complexity in MAPK-signalling components in plants. Information obtained from Arabidopsis provides a framework for a unified nomenclature and for the assembly and determination of the function of MAPK-signalling pathways. Strategies and tools are evolving to connect MAPK pathways and to determine their functions. As a result, MAPK-signalling modules have emerged, one of which appears to antagonistically regulate stress- and growth-responses whereas another regulates cytokinesis.