Fig. 3.

Regulators of the photoperiodic flowering pathway: Flowering under inductive long days requires a peak of FT expression in the late afternoon. CO transcription, CO protein stability, and FT transcription are critical to the photoperiodic flowering response. Blue light promotes flowering through FKF1 dependent degradation of CDFs and stabilization of CO protein, direct activation of FT through CIB transcription factors, and stabilization of the COP1/SPA1 complex by CRY2, which normally destabilizes CO protein in the dark. Red light inhibits flowering through destabilization of CO protein by PHYB. Far-red light promotes flowering through increased stability of CO protein by PHYA. Low temperature destabilizes CO protein through HOS1. The promotion or inhibition of each respective component can affect the flowering output, and thus serves to integrate multiple environmental signals such as day length, light quality, and temperature.