A Functional Genomics Approach Reveals CHE as a Component of the <i>Arabidopsis</i> Circadian Clock

TLDR

Transcriptional feedback loops form the core of the Arabidopsis circadian clock, with CCA1 and TOC1 constituting a core loop, but TOC1 lacks DNA‑binding domains and cannot directly repress CCA1. The study aimed to identify new components of the circadian clock by applying a functional genomic strategy that uncovered CHE, a TCP transcription factor binding the CCA1 promoter. The authors used a functional genomic approach to discover CHE, a TCP transcription factor that specifically binds the CCA1 promoter. CHE functions as a clock component that partially overlaps with LHY in repressing CCA1, is transcriptionally regulated by CCA1 to form a feedback loop, and interacts with TOC1, thereby linking TOC1 to CCA1 regulation.

Abstract

Transcriptional feedback loops constitute the molecular circuitry of the plant circadian clock. In Arabidopsis, a core loop is established between CCA1 and TOC1. Although CCA1 directly represses TOC1, the TOC1 protein has no DNA binding domains, which suggests that it cannot directly regulate CCA1. We established a functional genomic strategy that led to the identification of CHE, a TCP transcription factor that binds specifically to the CCA1 promoter. CHE is a clock component partially redundant with LHY in the repression of CCA1. The expression of CHE is regulated by CCA1, thus adding a CCA1/CHE feedback loop to the Arabidopsis circadian network. Because CHE and TOC1 interact, and CHE binds to the CCA1 promoter, a molecular linkage between TOC1 and CCA1 gene regulation is established.