An insulator of CLE-signaling boosts cell-differentiation in protophloem formation

Waddington’s epigenetic landscape, a famous metaphor in developmental biology, depicts how a stem cell progresses from an undifferentiated state to a differentiated one. To some degree this metaphor can also be applied to root cell differentiation. It’s well-known that the CLE-45 peptide and its receptor BAM3 are essential for protophloem formation in Arabidopsis, but the regulation of the process of root meristem fate transition from proliferation into differentiation is unknown. Here Breda et al. found a novel mechanism in protophloem sieve element differentiation, in which a protein named OPS antagonizes CLE-45 perception by direct interference with CLE signaling in a dosage-dependent manner. The discovery reveals antagonism in the cell fate control of root meristem, which may help explain the phenotypic plasticity of plants. (Summary by Nanxun Qin) Curr. Biol. 10.1016/j.cub.2019.06.037