Institute of Chemistry, Academia Sinica, Taipei, 11529, Taiwan.
Bioinformatics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 115, Taiwan.
Sci Rep. 2018 Sep 17;8(1):13944. doi: 10.1038/s41598-018-32030-z.
In higher plants (e.g., Arabidopsis thaliana), the core structure of the circadian clock is mostly governed by a repression process with very few direct activators. With a series of simplified models, we studied the underlying mechanism and found that the Arabidopsis clock consists of type-2 incoherent feed-forward loops (IFFLs), one of them creating a pulse-like expression in PRR9/7. The double-negative feedback loop between CCA1/LHY and PRR5/TOC1 generates a bistable, hysteretic behavior in the Arabidopsis circadian clock. We found that the IFFL involving PRR9/7 breaks the bistability and moves the system forward with a rapid pulse in the daytime, and the evening complex (EC) breaks it in the evening. With this illustration, we can intuitively explain the behavior of the clock under mutant conditions. Thus, our results provide new insights into the underlying network structures of the Arabidopsis core oscillator.
在高等植物（如拟南芥）中，生物钟的核心结构主要由抑制过程控制，很少有直接的激活剂。通过一系列简化模型，我们研究了其潜在的机制，发现拟南芥生物钟由两种类型的非相干前馈环（IFFL）组成，其中一种在 PRR9/7 中产生脉冲样表达。CCA1/LHY 和 PRR5/TOC1 之间的双负反馈环在拟南芥生物钟中产生双稳态、滞后行为。我们发现，涉及 PRR9/7 的 IFFL 打破了双稳态，并在白天通过快速脉冲推动系统向前，而晚上复合物（EC）在晚上打破它。通过这个说明，我们可以直观地解释在突变条件下时钟的行为。因此，我们的结果为拟南芥核心振荡器的潜在网络结构提供了新的见解。
