Molecular convergence of clock and photosensory pathways through PIF3–TOC1 interaction and co-occupancy of target promoters

Abstract

This study defines a molecular mechanism for how clock- and light-signaling pathways converge in Arabidopsis. The data reveal that TOC1, an essential core component of the central oscillator, binds to and represses PIF transcriptional activators, which are also the direct molecular signaling partners of the phytochrome photosensory receptors. This finding shows that TOC1 functions as a clock output-transducer, directly linking the core oscillator to a pleiotopically-acting transcriptional network, through repression of target genes. Collectively, in the plant, these components comprise a transcriptionallycentered signaling hub that provides clock-imposed gating of PIF-mediated, photosensory-regulated diurnal growth patterns. These results provide a framework for future research aimed at understanding how circadian dynamics are integrated with other plant physiological processes important for optimal plant fitness.