CREam of cytokinin signalling: receptor identified.

Cytokinins play a central role in the regulation of plant cell division and numerous developmental processes. Pleiotropic effects have made studies of this hormone difficult, and cytokinin signalling pathways have long remained elusive. The recent identification of CRE1 (a histidine kinase identical to AHK4 and WOL) as the cytokinin receptor of Arabidopsis thaliana is a landmark in cytokinin research. Mutations have been identified in CRE1, and the phenotype of loss-of-function mutations sheds new light on the role of cytokinins in plant development. This article describes the experimental paths leading to receptor identification and the current interpretation of its function.