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

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 thus suggesting it cannot directly regulate CCA1. Here, 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.

Abiotic stress and the plant circadian clock

“…As a consequence, TOC1 mRNA reaches its maximum around dusk, and by an unknown mechanism, TOC1 protein activates the transcription of CCA1 and LHY, 12,13 and it has been proposed that this is direct. 14,15 The role of CCA1/LHY and TOC1 as core elements has been confirmed by genetic experiments. 16 Though these three elements have been considered the core of the plant clock, this model cannot fully explain all experimental data.…”

“…An element acting after TOC1 was identified and termed CCA1 HIKING EXPEDITION (CHE). 15 This factor cannot be X, as its protein only binds the promoter of CCA1 and not that of LHY. Furthermore CHE binding to CCA1 promoter represses CCA1 transcription.…”

TheArabidopsis thalianaTCP transcription factors: A broadening horizon beyond development

“…61 This TCP protein interacts with TIMING OF CAB EXPRESSION 1 (TOC1) and suppresses the transcription of CIRCADIAN AND CLOCK ASSOCIATED1 (CCA1) via associating with the CCA1 promoter, thus establishing a molecular link between the 2 core elements of the clock oscillator. 61 The circadian clock cross-talks with a diverse range of plant physiological processes, including stress acclimatization, hormone signaling, photomorphogenesis and defense signaling, 80 suggestive of the functional diversity of TCP proteins. Genetic dissection of the tcp14 single mutant unravels the involvement of TCP14 in the activation of embryonic growth potential during seed germination.…”

“…1). TCP proteins from various species throughout the plant kingdom have been demonstrated to regulate a large variety of biological processes, such as floral asymmetry, 23-34 plant architectures including branching, [35][36][37][38][39] lateral organ development, 40-55 seed germination, 56,57 gametophyte development, 58,59 leaf senescence, 44,60 circadian rhythms, 61,62 and defense responses. [63][64][65] Noteworthily, several aspects of these plant processes involve a regulatory role for TCPs in the biosynthetic pathways of bioactive compounds.…”

SND1 Transcription Factor-Directed Quantitative Functional Hierarchical Genetic Regulatory Network in Wood Formation in Populus trichocarpa

“…The regulatory effects of some of these interactions were demonstrated through perturbation or induction of the specific TF in transgenics or mutants (Pruneda-Paz et al, 2009;Zheng et al, 2009;Bassel et al, 2012;Huang et al, 2012;Kumar et al, 2012). Knowledge of the TF-DNA interactions in species other than Arabidopsis is limited.…”