Figure 3.

Rhythmic expression of GUS driven by the upstream fragment of the QH6 promoter immediately before (GB+) or after (GB−) the G-box motif. Arabidopsis thaliana plants were transformed by GB+ or GB− constructs. The steady-state level of GUS transcripts was quantified by real-time PCR, using Actin8 as a reference gene. Leaves were sampled in triplicate for two continuous days, with the first day in standard 12h/12h light/dark cycle and the second day in constant dark. ZT is Zeitgeber time and here represents time from light on at dawn. Filled and open bars indicate subjective days and nights. Data represent means ± SD. The differences of expression levels were assessed by unpaired Student's t-test. ^*p < 0.05 and ^**p < 0.01 in GB+ vs. GB− transgenic Col-0 plants.