The genetics of paradoxes: CLE peptide signaling in the Arabidopsis root tip

Signaling of secreted CLAVATA3/EMBRYO SURROUNDING REGION (CLE) peptides via CLV1-type receptor kinases is a central mechanism regulating stem cell pool size. Originally characterized in the context of shoot meristem maintenance, this network has been increasingly scrutinized in recent years for its role in Arabidopsis thaliana (Arabidopsis) root meristem maintenance and organization. These analyses revealed unique, often seemingly paradoxical facets, which can be understood from the rewiring of CLE signaling networks in the root compared with the shoot. Here, we review the intricate interplay between distinct and antagonistic CLE signaling pathways in the primary root meristem, which suggests that the core function of CLE signaling in roots is to dynamically buffer antagonism between positive and negative signaling inputs, thereby enhancing developmental robustness.