Modeling the crosstalk between the circadian clock and ROS in Neurospora crassa.

The circadian clock regulates the expression of clock-controlled genes and adapts to environmental changes. Reactive oxygen species (ROS) also undergo circadian rhythms and have a role in circadian timekeeping. To elucidate crosstalk between ROS and the circadian clock in Neurospora crassa, we build an integrative network model, characterizing the circadian oscillator, ROS system and their interactions. Notably, the (de)phosphorylation and nuclear-cytoplasmic shuttling of clock proteins are modeled in detail. Simulation results quantitatively reproduce the essential features of circadian rhythm (both in constant darkness and under light/dark cycles) and the changes in period length and phase when ROS levels are altered under diverse conditions. This work clarifies the effects of three interactions between ROS and the clock on the circadian rhythm, suggesting that the regulation of WCC activity by protein phosphatase 2A in an O-dependent manner plays a predominant role. The functional significance of such modulations is also discussed.