Cloning of the Arabidopsis clock cone TOC1, an autoregulatory response regulator homolog

The toc1 mutation causes shortened circadian rhythms in Light-grown Arabido psis plants. Here, we report the same toc1 effect in the absence of tight i nput to the clock. We also show that TOC1 controls photoperiodic flowering response through clock function. The TOC1 gene was isolated and found to en code a nuclear protein containing an atypical response regulator receiver d omain and two motifs that suggest a role in transcriptional regulation: a b asic motif conserved within the CONSTANS family of transcription factors an d an acidic domain. TOC1 is itself circadianly regulated and participates i n a feedback Loop to control its own expression.