Dynamic involvement of PIFs in regulating circadian clock and diurnal growth in Arabidopsis.
PIFs have been shown to participate in both the input and output pathways of circadian clock. (Left) DET1 forms a complex with CCA1/LHY to repress TOC1 expression in the morning. DET1 also directly interacts with and stabilizes PIFs in the dark. PIFs might form a complex with DET1-CCA1-LHY to form a transcription complex as indicated by a dotted line. (Middle) PIF1, PIF3, PIF4 and PIF5 are necessary to mediate metabolic signaling to the clock by directly binding to the CCA1/LHY promoters in response to sugar. X, indicates an unknown factor or sugar-induced modification necessary for enhanced PIF binding to the CCA1/LHY promoters. (Right) Sequential expression of PRR5 and TOC1 gates the growth by inhibiting PIF functions, while ELF3-ELF4-LUX forms an evening complex (EC) that represses PIF4/PIF5 expression to repress growth during early evening.