A Functional Genomics Approach Reveals CHE as a Component of the Arabidopsis Circadian Clock

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.