Abstract
Recent studies on Arabidopsis thaliana have begun to shed light on the mechanisms underlying the plant biological clock. We have been characterizing a small family of proteins, designated as APRRs, including APRR1 that is identical to TOC1, which is believed to be a component of central clock. Nevertheless, the molecular function of APRR1 remains to be fully elucidated. In this respect, we previously showed that APRR1 interacts with certain bHLH family members that include PIF3 and homologs (designated the PIL family). Among them, PIF4, PIL6, and PIL8 are particularly intriguing, because the transcription of each gene is clearly under the control of circadian rhythms. Here we constructed PIF4-overexpressing (-ox), PIL6-ox, and PIL8-ox plants. They were extensively characterized in terms of their light sensitivity, flowering time, and circadian rhythm. The functions of these novel bHLH family members will be discussed with reference to photosensory signal transduction and circadian clock.
