Molecular basis of signaling network involved in biological clock and circadian rhythms in higher plants

昼夜节律是由内源性生物钟驱动的，它调节着多种生物体内的许多生化、生理和行为过程。在高等植物中，也有广泛的生物过程是通过生物钟控制的。在这些方面，最近对模式植物拟南芥的深入研究已经开始揭示这些生物钟控制的生物事件的分子机制。在拟南芥中，已经确定了许多与昼夜节律相关的因素。其中，TOC1被认为是中心振荡器的一个组成部分。TOC1是拟南芥伪响应调控蛋白（APRR1/TOC1、APRR3、APRR5、APRR7和APRR9）小家族的成员。尽管如此，目前尚不清楚APRR1（TOC1）以外的APRR1家族成员是否也与昼夜节律的机制有关。为了进一步解决这个问题，这里我们描述了一组T-DNA插入突变体，每个突变体都被认为在五种基因中的每一种都有严重的病变。我们发现，一个特定的突变，如果不是直接的，会同时影响与昼夜节律相关的生物学事件：(i)在长日照条件下的开花时间，（ii）幼苗在光形态发生早期的红灯敏感性，（iii）某些时钟控制基因（包括CCA1和APRR1/TOC1）在恒定白光下的自由拥有节律期。这些结果表明，尽管APRR1/TOC1以外的五个成员可能不会直接整合到中心振荡器的框架中，但它们对于更好地理解拟南芥生物钟的分子机制至关重要。

Circadian rhythms are driven by an endogenous biological clock(s) that regulates many biochemical, physiological and behavioral processes in a wide variety of organisms. In higher plants too, there are a wide range of biological processes that are controlled through the circadian clock In these respects, recent intensive studies on the model plant Arabidopsis thaliana have begun to shed light on the molecular mechanisms underlying these circadian-controlled biological events. In Arabidopsis thaliana, a number of circadian-associated factors have been identified. Among those, TOC1 is believed to be a component of the central oscillator. TOC1 is a member of a small family of proteins, designated as ARABIDOPSIS PSEUDO-RESPONSE REGULATORS (APRR1/TOC1, APRR3, APRR5, APRR7, and APRR9). Nonetheless, it is not very clear whether or not the APRR family members other than APRR1(TOC1 are also implicated in the mechanisms underlying the circadian rhythm. To address this issue further, here we characterized a set of T-DNA insertion mutants, each of which is assumed to have a severe lesion in each one of the quintet genes. We found that a given mutation singly, if not directly, affects the circadian-associated biological events simultaneously : (i) the flowering time in the long-day photopertod conditions, and (ii) the red light sensitivity of seedlings during the early photomorphogenesis, (iii) the period of free-wnning rhythms of certain clock-controlled genes including CCA1 and APRR1/TOC1 in constant white light. These results suggest that, although the quintet members other than APRR1/TOC1 may not be directly integrated into the framework of the central oscillator, they are crucial for a better understanding of the molecular mechanisms underlying the Arabidopsis circadian clock.