Desmethyl butenolides are optimal ligands for karrikin receptor proteins

Strigolactones and karrikins are butenolide molecules that regulate plant growth. They perceived by the ?/?-hydrolase DWARF14 (D14) its homologue KARRIKIN INSENSITIVE2 (KAI2), respectively. Plant-derived strigolactones have a ring with methyl group is essential for bioactivity. By contrast, abiotic in origin, nonessential. KAI2 probably receptor an endogenous butenolide, but identity of this compound remains unknown. Here we characterise specificity towards differing ligands using genetic biochemical approaches. We find proteins from multiple species most sensitive to desmethyl butenolides lack group. Desmethyl-GR24 desmethyl-CN-debranone active not D14. more potent agonists compared their methyl-substituted reference compounds both vitro plants. The preference conserved Selaginella moellendorffii Marchantia polymorpha, suggesting it ancient trait land evolution. Our findings provide insight into mechanistic basis differential ligand perception D14, support view substrates D14 distinct chemical structures biosynthetic origins.