Evolutionarily conserved CLE peptide signaling in plant development, symbiosis, and parasitism

•CLE-receptor-WOX pathway is common in stem cell maintenance in Arabidopsis SAM, columella stem cells, and vascular stem cells.•CLE signaling is conserved for meristem maintenance in grasses but it shows the functional redundancy.•Legumes use CLE signaling as a root-to-shoot signal for autoregulation of nodulation in rhizobial symbiosis.•Plant-parasitic nematodes hijack CLE signaling pathway of host plants for successful infection. Small polypeptides are widely used as signaling molecules in cell-to-cell communication in animals and plants. The CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) gene family is composed of numerous genes that contain conserved CLE domains in various plant species and plant-parasitic nematodes. Here, we review recent progress in our understanding of CLE signaling during stem cell maintenance in Arabidopsis and grasses. We also summarize the roles of CLE signaling in the legume-Rhizobium symbiosis and infection by plant-parasitic nematodes. CLE signaling is important for diverse aspects of cell-to-cell signaling and long-distance communication, which are critical for survival, and the basic components of the CLE signaling pathway are evolutionarily conserved in both plants and animals.