High-temperature-induced FKF1 accumulation promotes flowering through the dispersion of GI and degradation of SVP.

Floral transition is influenced by photoperiod and ambient temperature, which are integrated to modulate development via a molecular mechanism that remains to be elucidated. Here we demonstrate that the F-box protein FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1) and its interacting partner GIGANTEA (GI), central regulators of photoperiodic flowering, target SHORT VEGETATIVE PHASE (SVP) for 26S-proteasome-dependent degradation to regulate the temperature-responsive developmental transition to flowering. At low temperatures, GI is sequestered in liquid-like nuclear condensates. By contrast, FKF1 accumulates at high temperatures and releases GI from condensates to form a nuclear-dispersed FKF1-GI complex, leading to SVP degradation under short-day conditions. Temperature sensitivity is significantly reduced in fkf1-t, gi-2 and fkf1-2 gi-2 mutants. We propose that the FKF1-GI complex mediates the proteolysis of a floral repressor via reversible liquid-liquid phase separation to accelerate floral transition at high temperatures.