Figure 2.

Mathematical Models Describing the Circadian Clock and the Photoperiod Pathway in Arabidopsis.

The CCA1/LHY-TOC1 feedback loop (Model I) was extended to include a delay between TOC1 and CCA1/LHY mRNA (X) and a light input independent of CCA1/LHY (Y) (Model II). Y was identified to be GI (Model III) and X as the EC (Model IV). The circadian clock model has also been extended to include the photoperiod pathway, which described the dual roles of CDF1 and FKF1 in regulating CO and FT mRNA (Model IV). PIF4 regulates FT mRNA in a temperature-dependent manner (red); this is not considered in the mathematical model (dotted lines). Orange, circadian clock; green, photoperiod pathway.