Protein-protein interactions in plant mitogen-activated protein kinase cascades.

Mitogen-activated protein kinases (MAPKs) form tightly controlled signaling cascades that play essential roles in plant growth, development, and defense. However, the molecular mechanisms underlying MAPK cascades are still elusive, due largely to our poor understanding of how they relay the signals. Extensive effort has been devoted to characterization of MAPK-substrate interactions to illustrate phosphorylation-based signaling. The diverse MAPK substrates identified also shed light on how spatiotemporal-specific protein-protein interactions function in distinct MAPK cascade-mediated biological processes. This review surveys various technologies used for characterizing MAPK-substrate interactions and presents case studies of MPK4 and MPK6, highlighting the multiple functions of MAPKs. Mass spectrometry-based approaches in identifying MAPK-interacting proteins are emphasized due to their increasing utility and effectiveness. The potential for using MAPKs and their substrates in enhancing plant stress tolerance is also discussed.