Abstract: Phytohormones, as signaling molecules, play critical roles in regulating cell-to-cell and cell-to-environment communications. The mechanisms plant cells use to perceive phytohormones remain hot research topics in plant biology. Previous studies indicated that most plant hormones are perceived by non-covalent physical interactions with their corresponding receptors. After signaling pathways are initiated, the ligands usually dissociate with their binding receptors, which can interact with other receptor molecules or go through a degradation pathway. Therefore, ligand-receptor interaction is distinct from substrate-enzyme association. Recently, Xie and colleagues resolved a 3D structure of a strigolactone-induced AtD14-D3-ASK1 receptor complex. Strigolactones could be cleaved into a covalent-linked intermediate molecule in the reaction center of AtD14, the receptor of strigolactones. Further analyses revealed detailed molecular mechanisms of strigolactone-induced ligand-receptor complex formation and subsequent signaling initiation. Such a mechanism has never been reported in plants. These results provide significant insights into our better understanding of cellular signaling in plants.