CLE pathways in plant development: recent advances and future perspectives

The evolution of land plants was driven by novel genes that enabled adaptation to water and nutrient deficiency and development of a three-dimensional body. The appearance of genes encoding small peptides that move from cell to cell and activate membrane-localized receptors represented an important innovation in early land plants. Among these gene families, the CLAVATA3/EMBRYO-SURROUNDING REGION-RELATED (CLE) genes were particularly crucial for plant developmental control, presumably due to their initial involvement in cell division regulation. Recent advances in understanding the role of CLE signalling in bryophytes and ferns, along with major achievements in identifying the full repertoire of CLE genes in plant genomes and unravelling their functions, have provided deeper insights into these conserved signalling pathways. Here, we provide an update on CLE pathways and their fundamental role in plant development. We also discuss emerging questions in the CLE signalling field that could open exciting research directions and offer a way to manipulate plant morphology and adaptability that will be instrumental for improving crops in the future.