DWARF14 and KARRIKIN INSENSITIVE2 mediate signaling of the apocarotenoid zaxinone in Arabidopsis

Abstract

AbstractThe natural growth regulator zaxinone increases the levels of the phytohormones strigolactone (SL) and abscisic acid in Arabidopsis (Arabidopsis thaliana) via unknown mechanisms. We demonstrate that parts of the effects of zaxinone in Arabidopsis depend on the SL receptor DWARF14 (AtD14), the karrikin receptor KARRIKIN INSENSITIVE2 (AtKAI2), and the F-Box protein MORE AXILLARY BRANCHING2 (AtMAX2) that mediates the signaling of SLs and karrikins. Binding assays and co-crystallization revealed zaxinone as an additional ligand ofAtD14 and an SL antagonist that interrupts the interaction ofAtD14 withAtMAX2. Zaxinone also bound toAtKAI2. These findings unveil a perception mechanism for zaxinone in Arabidopsis and demonstrate the capability ofAtD14 andAtKAI2 to bind signaling molecules, other than strigolactones or karrikins, and mediate their transduction.