The seasons within: a theoretical perspective on photoperiodic entrainment and encoding

Area of Science:

• Chronobiology
• Physiology
• Systems Biology

Background:

• Circadian clocks are endogenous biological timekeepers synchronized with environmental light-dark cycles.
• These internal clocks exhibit photoperiod-dependent properties, crucial for seasonal adaptation.
• The circadian system generates an internal representation of season through plastic re-arrangements.

Purpose of the Study:

• To review seasonal entrainment and photoperiodic encoding by circadian clocks.
• To introduce conceptual phase oscillator models for analyzing entrainment principles.
• To contextualize model findings within more complex biological frameworks.

Main Methods:

• Review of existing literature on circadian rhythms and seasonal adaptation.
• Introduction and application of conceptual phase oscillator models.
• Discussion of findings in relation to amplitude-phase and molecular models.

Main Results:

• Seasonal variations in the phase of entrainment are systematically observed.
• Circadian clock outputs mediate photoperiodic responses like flowering and hibernation.
• Phase oscillator models provide intuitive insights into entrainment characteristics.

Conclusions:

• Circadian clocks play a vital role in seasonal adaptation and photoperiodic responses.
• Conceptual models offer valuable frameworks for understanding circadian system dynamics.
• Further integration of conceptual and molecular models is essential for a comprehensive understanding.