GSE204793
The F-box cofactor UFO redirects the LEAFY floral regulator to novel cis-elements
In angiosperms, flower patterning requires the localized expression of the APETALA3 (AP3) floral homeotic gene involved in petal and stamen development. AP3 is synergistically induced by the master transcription factor LEAFY (LFY) and the F-box protein UNUSUAL FLORAL ORGANS (UFO), but the molecular mechanism underlying this synergy has remained unknown. Here we show that the connection to ubiquitination pathways suggested by the F-box domain of UFO is mostly dispensable and that UFO instead acts by forming a transcriptional complex with LFY on newly discovered regulatory elements. The cryo-electron microscopy structure of the UFO-LFY-DNA complex shows that UFO-DNA contacts allows relocating LFY to novel DNA sites. Finally, we show that this complex has a deep evolutionary origin, largely predating flowering plants. This work unravels an unsuspected role for a member of one of the largest protein families in plants as a modulator of the DNA binding specificity of a master TF. Overall design: ampDAP-seq experiments with tagged LFY, LFYK249R and UFO proteins were done on 2-weeks old Arabidopsis thaliana seedlings. LFY and UFO tagged proteins were first mixed together and then with DNA prior to affinity purification. The same strategy was applied to the mutated version of LFY (LFYK249R), with and without UFO. Three replicates were done for LFYUFO and only consensus peaks in all three were retained. Two replicates were done for LFYK249R and LFYK249RUFO and common peaks in the two were retained.