Light at the heart of time: How photoreceptors entrain the circadian clock.

As the primary driver of photosynthesis, light also serves as a crucial environmental cue that directs plant growth and developmental programs. The circadian clock functions as an intrinsic timing mechanism that synchronizes physiological and metabolic rhythms with daily environmental light-dark cycles. Sunlight acts as a major zeitgeber, resetting the clock and activating photoreceptors that modulate the transcription and activity of core oscillator components. This review provides a comprehensive overview of the interactions between distinct photoreceptors and major signaling components of the circadian clock in Arabidopsis thaliana. We emphasize how light perception pathways influence circadian rhythm regulation and how the clock, in turn, feeds back to shape light-dependent responses. We further highlight the pivotal role of light in fine-tuning plant-environment interactions, illustrating how specific wavelengths regulate the circadian system through photoreceptors and downstream signaling factors.