Cloning of the <i>Arabidopsis</i> Clock Gene <i>TOC1</i> , an Autoregulatory Response Regulator Homolog

TLDR

The toc1 mutation shortens circadian rhythms in light‑grown Arabidopsis plants. The TOC1 gene encodes a nuclear protein with an atypical response regulator receiver domain, a CONSTANS‑like basic motif, and an acidic domain, indicating a role in transcriptional regulation. TOC1 shortens circadian rhythms even without light input, regulates photoperiodic flowering through the clock, and its own expression is circadianly regulated as part of a feedback loop.

Abstract

The toc1 mutation causes shortened circadian rhythms in light-grown Arabidopsis plants. Here, we report the same toc1 effect in the absence of light input to the clock. We also show that TOC1 controls photoperiodic flowering response through clock function. The TOC1 gene was isolated and found to encode a nuclear protein containing an atypical response regulator receiver domain and two motifs that suggest a role in transcriptional regulation: a basic motif conserved within the CONSTANS family of transcription factors and an acidic domain. TOC1 is itself circadianly regulated and participates in a feedback loop to control its own expression.