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

Judit Soy, Pablo Leivar, Nahuel González-Schain, Guiomar Martín, Céline Diaz, Maria Sentandreu, Bassem Al-Sady, Peter H. Quail, Elena Monte

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Resum

A mechanism for integrating light perception and the endogenous circadian clock is central to a plant's capacity to coordinate its growth and development with the prevailing daily light/dark cycles. Under short-day (SD) photocycles, hypocotyl elongation is maximal at dawn, being promoted by the collective activity of a quartet of transcription factors, called PIF1, PIF3, PIF4, and PIF5 (phytochromeinteracting factors). PIF protein abundance in SDs oscillates as a balance between synthesis and photoactivated-phytochrome-imposed degradation, with maximum levels accumulating at the end of the long night. Previous evidence shows that elongation under diurnal conditions (as well as in shade) is also subjected to circadian gating. However, the mechanism underlying these phenomena is incompletely understood. Here we show that the PIFs and the core clock component Timing of CAB expression 1 (TOC1) display coincident cobinding to the promoters of predawn-phased, growthrelated genes under SD conditions. TOC1 interacts with the PIFs and represses their transcriptional activation activity, antagonizing PIF-induced growth. Given the dynamics of TOC1 abundance (displaying high postdusk levels that progressively decline during the long night), our data suggest that TOC1 functions to provide a direct output from the core clock that transiently constrains the growth-promoting activity of the accumulating PIFs early postdusk, thereby gating growth to predawn, when conditions for cell elongation are optimal. These findings unveil a previously unrecognized mechanism whereby a core circadian clock output signal converges immediately with the phytochrome photosensory pathway to coregulate directly the activity of the PIF transcription factors positioned at the apex of a transcriptional network that regulates a diversity of downstream morphogenic responses.

Idioma originalAnglès
Pàgines (de-a)4870-4875
Nombre de pàgines6
RevistaProceedings of the National Academy of Sciences of the United States of America
Volum113
Número17
DOIs
Estat de la publicacióPublicada - 26 d’abr. 2016

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