Cytokinin and CLE signaling are highly intertwined developmental regulators across tissues and species

The control of cell identity and differentiation is critical for proper development. In plants, cell identity is largely determined by a cell's spatial context, which is communicated in the form of varying abundances of hormones. Two classes of hormones, the classical phytohormone cytokinin and the small CLE peptide hormones, are potent regulators of cell division and cell differentiation. While a relationship between these two classes of hormones is well-established at developing shoot tips, recent evidence suggests that CLE and cytokinin signaling converge on the same developmental processes across many different contexts and in widely divergent species. Here, we review evidence predominately from Arabidopsis thaliana and the moss Physcomitrella patens that supports a general model where CLE and cytokinin signaling are highly intertwined developmental regulators with antagonistic functions in shoots and synergistic functions in roots.