Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA.
Nat Cell Biol. 2011 May;13(5):616-22. doi: 10.1038/ncb2219. Epub 2011 Apr 17.
The circadian clock controls many metabolic, developmental and physiological processes in a time-of-day-specific manner in both plants and animals. The photoreceptors involved in the perception of light and entrainment of the circadian clock have been well characterized in plants. 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.
生物钟以时间特异性的方式控制着动植物的许多代谢、发育和生理过程。在植物中，已经很好地描述了参与光感知和生物钟同步的光受体。然而，光信号如何从光受体传递到中央生物钟振荡器，以及由昼夜光信号产生和维持时钟基因的节律表达模式仍然不清楚。在这里，我们表明在拟南芥中，FHY3、FAR1 和 HY5，三种光敏色素 A 信号通路的正调控因子，直接结合到中央振荡器的拟议组成部分 ELF4 的启动子上，并在白天激活其表达，而昼夜节律控制的 CCA1 和 LHY 蛋白则通过与这些转录促进因子的物理相互作用，周期性地在黎明时直接抑制 ELF4 的表达。我们的发现提供了证据表明，一组光和昼夜调节的转录因子直接协调作用于 ELF4 启动子，以调节其周期性表达，并建立了一个潜在的分子联系，将环境的光暗周期与中央振荡器连接起来。
