| description |
In many organisms, the circadian clock is composed of functionally coupled morning and evening oscillators that regulate the bouts of dawn and dusk activity. In Arabidopsis, oscillator coupling relies on a core loop in which the evening oscillator component TOC1 was proposed to activate a subset of morning-expressed oscillator genes. Our systems-biological approach overturns the current view of the Arabidopsis circadian clock showing that TOC1 does not function as an activator but as a timely-controlled general repressor of morning and evening oscillator components. Repression occurs through rhythmic binding to the promoters of all oscillator genes, suggesting a previously unexpected direct connection between the morning and evening loops.Overall design: Examination of TOC1 genome-wide binding using TOC1 Minigene (TMG) seedlings expressing the genomic fragment of TOC1 fused to the Yellow Fluorescent Protein in a toc1-2 mutant background (TMG-YFP/toc1-2 seedlings) grown under LD cycles (12h light:12h dark). |