Correct biological timing in Arabidopsis requires multiple light signaling pathways

Circadian oscillators provide rhythmic temporal cues for a range of biological processes in plants and animals, enabling anticipation of the day/night cycle and enhancing fitness associated traits. We have used engineering models to understand the control principles of a plant’s response to seasonal variation. We show that the seasonal changes in the timing of circadian outputs requires light regulation via feed-forward loops, combining rapid light signaling pathways with entrained circadian oscillators. Linear time-invariant models of circadian rhythms were computed for 3503 circadian-regulated genes and for the concentration of cytosolic-free calcium in order to quantify the magnitude and timing of regulation by circadian oscillators and light signaling pathways. Bioinformatic and experimental analysis demonstrate that rapid light-induced regulation of circadian outputs is associated with seasonal re-phasing of the output rhythm. We identify that external coincidence is required for re-phasing of multiple output rhythms, and is therefore important in general phase control in addition to specific photoperiod-dependent processes such as flowering and hypocotyl elongation. Our results uncover a new design principle of circadian regulation, and identify the importance of rapid light signaling pathways in temporal control.


Publisher  Proceedings of the National Academy of Sciences
Copyright 2010 Proceedings of the National Academy of Sciences.


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