Adaptive Diversification in the Cellular Circadian Behavior of Arabidopsis Leaf- and Root-Derived Cells

Abstract

The plant circadian system is based on self-sustained cellular oscillations and is utilized to adapt to daily and seasonal environmental changes. The cellular circadian clocks in the above- and belowground plant organs are subjected to diverse local environments. Individual cellular clocks are affected by other cells/tissues in plants, and the intrinsic circadian properties of individual cells remain to be elucidated. In this study, we monitored bioluminescence circadian rhythms of individual protoplast-derived cells from leaves and roots of a CCA1::LUC Arabidopsis transgenic plant. We analyzed the circadian properties of the leaf- and root-derived cells and demonstrated that the cells with no physical contact with other cells harbor a genuine circadian clock with ~24 h periodicity, entrainability, and temperature compensation of the period. The stability of rhythm was dependent on the cell density. High cell density resulted in an improved circadian rhythm of leaf-derived cells while this effect was observed irrespective of the phase relation between cellular rhythms. Quantitative and statistical analyses for individual cellular bioluminescence rhythms revealed a difference in amplitude and precision of light/dark entrainment between the leaf- and root-derived cells. Circadian systems in the leaves and roots are diversified to adapt to their local environments at the cellular level.

Dissecting the complexity of local and systemic circadian communication in plants

“…Strong coupling is found in areas of high cell density, like the root tip and shoot apex 36,44 . A recent study showed that while isolated leaf-derived cells maintained rhythms that responded to light and temperature cues, rhythmic stability improved with higher cell density 49 . The circadian clock association with both the endocycle and mitotic cycle 50 opens the possibility of differential coupling strength between actively dividing and other cells.…”

Spatially specific mechanisms and functions of the plant circadian clock

“…An approach to clarify our understanding of organ-specific clock function was taken by using luciferase imaging of a CCA1::LUC reporter in individual root or leaf-derived cells in cell culture ( Nakamura and Oyama, 2021 ). This builds on previous research examining clock rhythms in cell culture and in excised parts of the plant (e.g.…”