Comprehensive analysis of protein-protein interactions between Arabidopsis MAPKs and MAPK kinases helps define potential MAPK signalling modules.

The Arabidopsis genome encodes a 20-member gene family of mitogen-activated protein kinases (MPKs) but biological roles have only been identified for a small subset of these crucial signalling components. In particular, it is unclear how the MPKs may be organized into functional modules within the cell. To gain insight into their potential relationships, we used the yeast two-hybrid system to conduct a directed protein-protein interaction screen between all the Arabidopsis MPKs and their upstream activators (MAPK kinases; MKK). Novel interactions were also tested in vitro for enzyme-substrate functionality, using recombinant proteins. The resulting data confirm a number of earlier reported MKK-MPK relationships, but also reveal a more extensive pattern of interactions that should help to guide future analyses of MAPK signalling in plants.