Abstract
In Arabidopsis thaliana, the transcripts of the APRR1 family genes start each accumulating after dawn rhythmically and one after another at intervals in the order of APRR9, APRR7, APRR5, APRR3 and APRR1 under continuous light. APRR1 is identical to TOC1 that is believed to be a component of the central oscillator. To gain further insight into the molecular function of APRR1, we screend the factors which interact with it and identified a Mic-related bHLH transcription factor. This protein named PIL1 is similar in its amino acid sequence to PIF3, which has been identified as a phytochrome-interacting transcription factor. We searched other proteins whose bHLH domains are similar to that of PIL1. In this study, we selected 6 bHLH proteins and examined their competence to interact with APRR1 and expression patterns in detail. These results will be discussed with special reference to feedback and output mechanism of circadian clock.
