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，其调节各种生物体中的许多生化、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昼夜节律钟控制的。在这些方面，最近对模式植物拟南芥的深入研究已经开始阐明这些昼夜节律控制的生物事件背后的分子机制。在拟南芥中，已经确定了许多与昼夜节律相关的因子。其中，TOC 1被认为是中心振荡器的组成部分。TOC 1是一个蛋白质小家族的成员，被命名为拟南芥假反应调节因子（APRR 1/TOC 1、APRR 3、APRR 5、APRR 7和APRR 9）。尽管如此，目前还不清楚APRR家族成员是否也参与了昼夜节律的机制。为了进一步解决这个问题，在这里，我们描述了一组T-DNA插入突变体，其中每一个都被假定为在每一个五联体基因中有一个严重的病变。我们发现，一个给定的突变单独，如果不是直接的，同时影响昼夜节律相关的生物学事件：（i）开花时间在长日照光pertod条件下，和（ii）红光敏感性的幼苗在早期光形态建成，（iii）自由wnning节律的某些时钟控制的基因，包括CCA 1和APRR 1/TOC 1在恒定的白色光的时间。这些结果表明，尽管APRR 1/TOC 1以外的五联体成员可能不会直接整合到中央振荡器的框架中，但它们对于更好地理解拟南芥昼夜节律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.