Figure 2.

The diurnal oscillation of tetrapyrroles contributes to the circadian control of CBF3 expression. Plants were grown in short-day conditions (9/15 h light/dark), and 3-week-old plants were sampled every 3 h starting at dawn until 3 h into the dark period. After the dark period, the plants were kept in constant light for 27 h, and then another set of samples were collected every 3 h starting 3 h after the subjective dawn. Black bars on the x axis represent the true dark period, while gray bars represent the subjective dark period during the free-running period. A, Samples were analyzed for CBF3 (At4g25480) expression normalized to ubiquitin-like protein (At4g36800), and each time point was related to the amount present in wild-type Col at ZT 6. B and C, Mg-ProtoIX (B) Mg-ProtoIX-ME (C) contents. Each data point represents the mean ± sd of at least three biological replicates. FW, Fresh weight.