Abstract
PnC401 which was isolated from Pharbitis nil cv. Violet showed specific expression during the flower inductive darkness. PnC401 and AtC401, a homologue in Arabidopsis thaliana, showed circadian regulated expression. By the reporter analyses using AtC401 promoter::luciferase transgenic Arabidopsis plants, we showed 146 bp fragment was sufficient to regulate the rhythmic expression of that AtC401. To investigate the regulation mechanism in detail, we determined the transcriptional initiation site by primer extension experiment and found 73 bp of downstream sequence in the 146 bp fragment. The AtC401 promoter fragments in which the downstream (-174/+2) from the initiation site was deleted could not drive the expression of luciferase reporter, and the fragment fused to 47 bp minimum fragment of CaMV35S promoter did not show rhythmic expression of the reporter. These results suggest that the rhythmic expression of AtC401 is regulated by the element(s) located in the downstream sequence from the transcriptional initiation site.
