Abstract
AtC401 is an Arabidopsis homolog of Pharbitis nil C401 (PnC401) that relates the photoperiodic induction of flowering and shows a circadian oscillation at the transcriptional level. We previously reported that the AtC401 minimal promoter does not required the canonical TATA box but required the 5' UTR sequence for circadian regulation, and suggested that the novel transcription machinery regulates the circadian transcription of AtC401. This minimal promoter contains two candidates of cis-elements; GATA motifs and CCA1 binding like motifs. Then, we constructed the promoter fragments mutated these elements, and fused a firefly luciferase reporter gene (luc+). The reporter analysis using the transgenic plants showed the CCA1 binding like motifs is required for circadian regulation. Moreover, we confirmed the binding of recombinant CCA1 protein to the motif by electrophoretic mobility shift assay. These results suggest that these CCA1 binding like motifs and CCA1 protein are required for circadian regulation of AtC401.
