Circadian Clock- and PIF4-Controlled Plant Growth: A Coincidence Mechanism Directly Integrates a Hormone Signaling Network into the Photoperiodic Control of Plant Architectures in Arabidopsis thaliana

The plant circadian clock regulates growth by controlling specific hormone-associated genes in Arabidopsis thaliana.

• The clock influences diurnal and photoperiodic growth, particularly affecting hypocotyl and petiole elongation.
• Accumulation of the PIF4 protein at night under short-day conditions is linked to the plant's internal and external cues.
• A set of hormone-associated genes, including those for auxin, brassinosteroids, gibberellic acids, ethylene, and cytokinin, were identified as specific targets of PIF4.
• Expression profiles of these hormone-associated genes are altered in phyB and circadian clock mutants.
• The findings indicate that the circadian clock may integrate various hormone signaling pathways to regulate plant growth in response to photoperiod.

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