Abstract
CLV1, which encodes a leucine-rich-repeat receptor kinase, and CLV3, which encodes a secreted peptide, function in the same genetic pathway to maintain stem cell populations in the Arabidopsis shoot apical meristem. Here, we show biochemical evidence, by ligand binding assay and photoaffinity labeling, that CLV3 peptide directly binds the CLV1 ectodomain with a dissociation constant of 17.5 nM. The CLV1 ectodomain also interacts with the structurally related CLE peptides, with distinct affinities depending on the specific amino acid sequence. Our results provide direct evidence that CLV3 and CLV1 function as a ligand-receptor pair involved in stem cell maintenance. Our results also suggest that arrays of ectodomains derived from LRR-RKs phylogenetically related to CLV1 may be able to bind CLE peptides in a sequence-specific manner in vitro. Such a biochemical approach could help clarify highly redundant and pleiotropic CLE signaling by identifying the individual ligand-receptor interactions.
