Data-driven mathematical modelling explains altered timing of EARLY FLOWERING 3 in the wheat circadian oscillator.

Circadian rhythms are endogenous 24 h cycles that allow organisms to anticipate daily environmental changes. In plants, circadian timing is maintained by a network of transcriptional regulators operating within each cell. Wheat provides an opportunity to investigate how this network functions in an important agricultural species. We recently found that a single oscillator component, EARLY FLOWERING 3 (ELF3), is expressed at a different time in wheat than in the model plant Arabidopsis. This was unexpected, given the striking conservation of timing of oscillator components across species, even when animals switch from nocturnal to diurnal activity. We examined how this shift in ELF3 transcriptional timing arose and its implications for circadian oscillator function. Using experimental data and promoter structure information, we developed an optimized computational model of circadian regulation in wheat. Our simulations suggest that the dawn-phased expression of ELF3 in wheat is driven by TOC1-mediated repression of the ELF3 promoter. Despite this shift, the peak expression times of other circadian components remain unchanged. These results demonstrate that plant circadian systems have flexible architectures, allowing different oscillator structures to originate robust rhythmic behaviour.