Reciprocal Regulation Between <i>TOC1</i> and <i>LHY</i> / <i>CCA1</i> Within the <i>Arabidopsis</i> Circadian Clock

TLDR

The interactive regulation between clock genes is central for oscillator function. The study investigates interactions among LHY, CCA1, and TOC1 in Arabidopsis. The authors examined protein–DNA interactions among LHY, CCA1, and TOC1. LHY and CCA1 repress TOC1 by binding its promoter, while TOC1 promotes LHY and CCA1 expression, forming a regulatory loop essential for Arabidopsis circadian function.

Abstract

The interactive regulation between clock genes is central for oscillator function. Here, we show interactions between the Arabidopsis clock genes LATE ELONGATED HYPOCOTYL (LHY), CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), and TIMING OF CAB EXPRESSION 1 (TOC1). The MYB transcription factors LHY and CCA1 negatively regulate TOC1 expression. We show that both proteins bind to a region in the TOC1 promoter that is critical for its clock regulation. Conversely, TOC1 appears to participate in the positive regulation of LHY and CCA1 expression. Our results indicate that these interactions form a loop critical for clock function in Arabidopsis.