Florigen family chromatin recruitment, competition and target genes

Abstract

Plants monitor seasonal cues, such as day-length, to optimize life history traits including onset of reproduction and inflorescence architecture 1-3. Florigen family transcriptional co-regulators TERMINAL FLOWER 1 (TFL1) and FLOWERING LOCUS T (FT) antagonistically regulate these vital processes 4-6 yet how TFL1 and FT execute their roles and what the mechanism is for their antagonism remains poorly understood. We show genome-wide, that TFL1 is recruited to the chromatin by the bZIP transcription factor FLOWERING LOCUS D (FD) in Arabidopsis. We find that seasonal cue-mediated upregulation of FT competes TFL1 from chromatin-bound FD at key target loci. We identify the master regulator of floral fate, LEAFY (LFY) as a target under dual opposite regulation by TFL1 and FT. Exonic bZIP motifs in LFY are critical for repression by TFL1, upregulation by FT and adoption of floral fate. Transcriptomic identification of target genes directly repressed by the TFL1-FD complex not only identifies key regulators of onset of reproduction and floral fate, but reveals that TFL1-FD repress sugar and hormone signalling pathways and chromatin regulators. Our data provide mechanistic insight into how florigen family member sculpt inflorescence architecture, a trait important for reproductive success and yield.