FIGURE 1.

(A) The action of FHY3 and FAR1 in regulation of ELF4 expression is light dependent. Wild-type (WT), fhy3, far1, and fhy3 far1 mutant seedlings were grown in 12 h white light:12 h dark cycles for 1 week before transfer to constant red light for a 4 days at of a range of different intensities. Mean ELF4 expression relative to IPP2 measured by RT-qPCR for two independent replicates + standard error. (B) FHY3 and FAR1 directly regulate acute light responsive ELF4 expression in the early part of the subjective night. WT and fhy3 far1 seedlings, both expressing ELF4::LUC, as well as WT seedlings expressing an ELF4::LUC construct in which the FHY3/FAR1 binding site was mutated (mFBS), were grown in 12 h white light/12 h dark cycles for 1 week prior to transfer to constant darkness at dawn (Circadian Time 0). Seedlings were then given a 30 min pulse of 100 μmol m^–2 s^–1 red light at one of four time points over a circadian cycle. Left hand axis (black labels): percentage increase in bioluminescence recorded 30 min after the pulse at the four time points indicated. Right hand axis (red labels): mean relative bioluminescence of untreated WT seedlings, shown by red circles, and measured at a number of points over the time course to show the background pattern of ELF4 expression. Dotted line represents trend line based on third order polynomial. Light and dark bars above the figure indicate the times of subjective day and night. N = at least 19 seedlings + standard error.