Fig. 3.

PIFs are involved in directly regulating signals from sucrose to the oscillator. (a) PIF affects circadian rhythms in all light fluences in plants growing on sucrose. pifQ CCA1:LUC and wt CCA1:LUC lines were entrained on medium with 3% (90mM) sucrose before being transferred to Rc of different fluences. Luciferase activity was plotted together with the SEM. The average of 3–4 independent experiments (n ≥46). (b) Sucrose response curve for PIF regulation of the circadian oscillator. pifQ CCA1:LUC and wt CCA1:LUC lines were entrained on medium supplemented with 0, 0.1, 0.2, 0.5, 1, 2 or 3% sucrose, and transferred to 1Zmol red light luciferase activity was plotted together with the SEM. The average of 2–3 independent experiments, n ≥77. At the lowest (0.2% and below) sucrose concentrations, amplitudes of luciferase activity were very low which made it difficult to accurately measure circadian period and three biological repeats with n ≥120 plants were taken. (c–d) R.A.E. is affected by sucrose. The R.A.E. were plotted for (c) data shown in Fig. 3b and (d) data shown in Fig. 2a. (e) The effects of mannitol on PIF control of circadian rhythms. pifQ CCA1:LUC and wt CCA1:LUC lines were entrained on medium supplemented with or without 3% (90mM) sucrose or 90mM mannitol before being transferred to 1 μmol m⁻²s⁻² continuous red light (Rc) at 23°C. Luciferase activity was plotted together with the SEM. The average of 2–3 independent experiments, n≥126. (f) pifQ plants are less sensitive to sucrose pulses. Sucrose pulse experiments were performed as described in Materials and Methods. n≥43. ** p<0.01, *** p<0.001 (Student two-tailed t-test).