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Unstable Phase Response Curves Shown by Spatiotemporal Patterns in the Plant Root Circadian Clock
Kosaku Masuda1,2, Hirokazu Fukuda1
1Graduate School of Engineering, Osaka Prefecture University, Osaka, Japan.
Journal of Biological Rhythms
|July 27, 2021
Summary
Plant circadian clocks are unstable. New methods reveal how temperature, individual differences, and root age affect phase response curves (PRCs), improving understanding of plant adaptation to environmental changes.
Area of Science:
- Chronobiology
- Plant Physiology
- Biophysics
Background:
- Phase response curves (PRCs) are crucial for understanding how circadian clocks entrain to environmental cycles.
- Plant circadian clock PRCs are notoriously unstable, influenced by noise, individual variation, and developmental factors.
- Existing methods average responses across many individuals, masking specific factor effects.
Purpose of the Study:
- To measure plant root circadian clock PRCs using a novel spatiotemporal 'stripe pattern' method.
- To investigate the impact of thermal stimuli, individual differences, circadian amplitude, and root age on PRCs.
- To model the influence of internal and measurement noise on PRC stability.
Main Methods:
- Utilized the plant root 'stripe pattern' spatiotemporal expression to measure PRCs for thermal stimuli in individual roots.
- Assessed PRCs under varying temperature stimulus polarities (positive/negative), stimulus strengths, circadian amplitudes, and root ages (hypocotyl vs. tip).
- Employed a phase oscillator model to simulate and analyze the effects of noise on PRC characteristics.
Main Results:
- Plant root PRCs exhibited asymmetric responses to positive and negative temperature stimuli.
- Individual differences in PRCs were significant for weak but not strong stimuli.
- PRCs varied with circadian rhythm amplitude, with younger root tissues near the hypocotyl showing higher sensitivity.
- Simulations confirmed that both internal and measurement noise contribute to PRC instability.
Conclusions:
- Plant circadian clock entrainment instability arises from multiple, distinct factors including stimulus type, individual variation, developmental stage, and amplitude.
- The spatiotemporal 'stripe pattern' method provides a powerful tool for dissecting PRC complexities in individual plants.
- Understanding these factors is key to comprehending plant circadian clock adaptation in dynamic environments and internal integration of rhythms.
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