<i>Panax</i> -derived Zingibroside R1 exerts allelopathic effects on root architecture by modulating the auxin transport pathway and oxidative stress responses

Abstract The triterpenoid-rich Panax spp. possess notable allelopathic capabilities, yet current knowledge lacks comprehensive understanding of the biological mechanisms underlying these inhibitory effects. Here, we show that Zingibroside R1 (ZR1), a newly identified allelochemical from Panax spp., inhibits the adventitious root growth in ginseng and primary root elongation in Arabidopsis. Mechanistic analyses revealed that ZR1 disrupts auxin transport, as evidenced by monitoring DR5::GFP and PINs markers. The effect of ZR1 on auxin transport was further elucidated through synergistic effects observed with the auxin transport inhibitor NPA and in the auxin transport mutants aux1 and pin2. Additionally, ZR1 downregulates key root development regulators, including stem cell maintenance regulators PLT1/2, WOX5, SHR and SCR. Transcriptomic and biochemical data indicate that ZR1 triggers a ROS response in plants, which disrupts ROS scavenging—via altered peroxidase activities and GSH/GSSG balance—thereby impairing detoxification function and resulting in root shortening by regulation of auxin distribution and stem cell gene expression. Our results establish a mechanistic framework for understanding how ginsenosides mediate allelopathic effects on root development.