Abstract
The circadian clock controls many metabolic, developmental and physiological processes in a time-of-day-specific manner in both plants and animals1,2. The photoreceptors involved in the perception of light and entrainment of the circadian clock have been well characterized in plants3. However, how light signals are transduced from the photoreceptors to the central circadian oscillator, and how the rhythmic expression pattern of a clock gene is generated and maintained by diurnal light signals remain unclear. Here, we show that in Arabidopsis thaliana, FHY3, FAR1 and HY5, three positive regulators of the phytochrome A signalling pathway, directly bind to the promoter of ELF4, a proposed component of the central oscillator, and activate its expression during the day, whereas the circadian-controlled CCA1 and LHY proteins directly suppress ELF4 expression periodically at dawn through physical interactions with these transcription-promoting factors. Our findings provide evidence that a set of light- and circadian-regulated transcription factors act directly and coordinately at the ELF4 promoter to regulate its cyclic expression, and establish a potential molecular link connecting the environmental light–dark cycle to the central oscillator.
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Acknowledgements
We thank S. Kay for providing the CAB2::LUC, TOC1::LUC and CCA1::GFP–CCA1 reporter lines; R. McClung for CAT3::LUC reporter lines; R. Ulm for the HY5::HY5–YFP seeds; K. Halliday for the cca1-11 lhy-21 double-mutant seeds; T. Mockler for discussion; T. Xu for technical help with IVIS Spectrum; and C. Lin and J-M. Zhou for providing the transient expression system (Dual-LUC) and LCI system. This work was supported by grants from National Science Foundation (IOS-1026630 and MCB-1004808) to H.W., the Biotechnology and Biological Sciences Research Council (BBF02116X1) to P.F.D., National Institutes of Health (GM47850) to X.W.D. and National High Technology Research and Development Program of China (2009AA101101) to J.W.
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P.F.D., X.W.D., J.W. and H.W. contributed to project design. R.L. recorded the phenotype of fhy3 mutants and generated FHY3–LUC reporter lines. X-Y.W. generated 3×Flag–3×HA transgenic lines. H.S. carried out the bioluminescence analyses of all the LUC reporter lines. Y.T. carried out the yeast assays, qRT–PCR and generated ELF4-OX transgenic lines. G.L. carried out all other experiments. G.L., P.F.D. and H.W. wrote the manuscript. All authors discussed the results and commented on the manuscript.
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Li, G., Siddiqui, H., Teng, Y. et al. Coordinated transcriptional regulation underlying the circadian clock in Arabidopsis. Nat Cell Biol 13, 616–622 (2011). https://doi.org/10.1038/ncb2219
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DOI: https://doi.org/10.1038/ncb2219
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