PARASITIC PLANTS. Probing strigolactone receptors in Striga hermonthica with fluorescence.

Elucidating the signaling mechanism of strigolactones has been the key to controlling the devastating problem caused by the parasitic plant Striga hermonthica. To overcome the genetic intractability that has previously interfered with identification of the strigolactone receptor, we developed a fluorescence turn-on probe, Yoshimulactone Green (YLG), which activates strigolactone signaling and illuminates signal perception by the strigolactone receptors. Here we describe how strigolactones bind to and act via ShHTLs, the diverged family of α/β hydrolase-fold proteins in Striga. Live imaging using YLGs revealed that a dynamic wavelike propagation of strigolactone perception wakes up Striga seeds. We conclude that ShHTLs function as the strigolactone receptors mediating seed germination in Striga. Our findings enable access to strigolactone receptors and observation of the regulatory dynamics for strigolactone signal transduction in Striga.