Circadian clocks synchronise biological processes with the day/night cycle, using molecular mechanisms that include interlocked, transcriptional feedback loops. Recent experiments identified the evening complex (EC) as a repressor that can be essential for gene expression rhythms in plants. Integrating the EC components in this role significantly alters our mechanistic, mathematical model of the clock gene circuit. Negative autoregulation of the EC genes constitutes the clock's evening loop, replacing the hypothetical component Y. The EC explains our earlier conjecture that the morning gene Pseudo-Response Regulator 9 was repressed by an evening gene, previously identified with Timing Of CAB Expression1 (TOC1). Our computational analysis suggests that TOC1 is a repressor of the morning genes Late Elongated Hypocotyl and Circadian Clock Associated1 rather than an activator as first conceived. This removes the necessity for the unknown component X (or TOC1mod) from previous clock models. As well as matching timeseries and phase-response data, the model provides a new conceptual framework for the plant clock that includes a three-component repressilator circuit in its complex structure.

中文翻译：

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拟南芥的时钟基因回路包括一个带有额外反馈回路的抑制因子。

生物钟使用包括互锁的转录反馈循环在内的分子机制使生物过程与昼夜循环同步。最近的实验将晚间复合物 (EC) 确定为对植物基因表达节律至关重要的阻遏物。在这个角色中集成 EC 组件显着改变了我们的时钟基因电路的机械、数学模型。EC 基因的负自动调节构成了时钟的晚间循环，取代了假设的组件 Y。 EC 解释了我们之前的猜想，即早间基因 Pseudo-Response Regulator 9 被晚间基因抑制，之前用 CAB 表达时间 1 (TOC1) 确定. 我们的计算分析表明，TOC1 是早间基因晚期伸长下胚轴和昼夜节律相关 1 的抑制因子，而不是最初设想的激活因子。这消除了以前时钟模型中未知组件 X（或 TOC1mod）的必要性。除了匹配时间序列和相位响应数据外，该模型还为工厂时钟提供了一个新的概念框架，该框架在其复杂的结构中包含了一个三分量抑制器电路。