Analysis of the Physiological Roles and Mode of Actions of Phthalimides as GA Signal Regulator in Rice

An N-substituted phthalimide, AC94377, was reported to mimic gibberellin (GA) activity in various plants, and was demonstrated to be a selective agonist for GA receptor GID1 in Arabidopsis, suggesting its potentiality for developing novel GA signal regulators. Here, we confirmed the GA-like activity of AC94377 in rice, including promotion on 2nd leaf sheath growth and suppression on strigolactone exudates from roots. We performed chemical and genetic manipulation of interaction between rice GA receptor GID1 and phthalimides. Our results showed that modifications of carboxamide moiety of AC94377 can interchange the preference for different GID1-subtype. To summary, our findings confirmed universal roles of AC94377 as a GID1 agonist, and the potentiality of designing novel GA agonist or even antagonist based on the scaffold of AC94377 coupled with GID1 manipulations in crops, which could be used for root parasitic weed control.