Data-driven mathematical modelling explains altered timing ofEARLY FLOWERING 3in the wheat circadian oscillator

Circadian rhythms, daily oscillations with a free-running period of approximately 24 hours, have evolved in organisms across the kingdoms of life, enabling organisms to anticipate and adapt to environmental cycles. Circadian timing in plants is governed by an oscillator gene network of transcriptional regulators that exists in each cell. Wheat provides an opportunity to investigate the mechanisms of the plant circadian oscillator in an important agricultural species. We recently found that a single oscillator componentEARLY FLOWERING 3is expressed at a different time in wheat compared to the model plant Arabidopsis. This was unexpected since there is remarkable conservation of timing of activity of the different oscillator components within a kingdom, for example, even when animals switch from nocturnal to diurnal activity. We have examined how the change in timing ofELF3transcription between Arabidopsis and wheat has occurred and its implications for circadian oscillator function. We describe an optimised computational model of the wheat circadian oscillator that is informed by experimental data and the structure of the promoter elements driving oscillator gene expression. Our optimised computational models suggest that the dawn-expression of the key oscillator geneELF3in wheat occurs due to repression of theELF3promoter by TOC1. Our simulations predict that plant circadian oscillators are robust against changes inELF3timing. Our work demonstrates that plant circadian oscillators can have a flexible architecture such that different oscillator structures can originate circadian rhythms.