Three mutations repurpose a plant karrikin receptor to a strigolactone receptor

International audience Uncovering the basis of small molecule hormone receptors evolution is paramount to a complete understanding of how protein structure drives function. In plants, hormone receptors for strigolactones are well suited to evolutionary inquires because closely related homologs have different ligand preferences. More importantly, because of facile plant transgenic systems, receptors can be swapped and quickly assessed functionally in vivo. Here, we show only three mutations are required to switch the non-strigolactone receptor, KAI2, into a strigolactone receptor. This modified receptor still perceives KAI2 ligands and does not require receptor hydrolysis for activity. Structural and molecular dynamic modeling suggest receptor pocket flexibility is important for ligand specificity and downstream signaling partner affinity. These findings indicate a few keystone mutations link strigolactone signaling to germination, which explains how parasitic plants that devastate African agriculture evolved SL receptors to sense the presence of a host plant.