Robust and flexible response of Ostreococcus tauri circadian clock to light/dark cycles of varying photoperiod

TL;DR

This study investigates how the circadian clock of Ostreococcus tauri adapts to varying light/dark cycles, revealing a simple model that explains its flexible yet robust response to changing photoperiods.

Contribution

It demonstrates that a minimal two-gene transcriptional model can accurately reproduce complex clock gene dynamics across different photoperiods, highlighting the clock's adaptability.

Findings

Clock gene profiles vary with photoperiods

A simple model captures complex dynamics

Clock combines flexibility and robustness

Abstract

The green microscopic alga Ostreococcus tauri has recently emerged as a promising model for understanding how circadian clocks, which drive the daily biological rythms of many organisms, synchronize to the day/night cycle in changing weather and seasons. Here, we analyze translational reporter time series data of its central clock genes CCA1 and TOC1 for a wide range of daylight durations (photoperiods). The variation of temporal profiles with day duration is complex, with the two actors tracking different moments of the day. Nevertheless, all profiles are accurately reproduced by a simple two-gene transcriptional loop model whose parameters are affected by light only through the photoperiod value. We show that this non-intuitive behavior allows the circadian clock to combine flexibility and robustness to daylight fluctuations.