Circadian Rhythms of Gene Expression in Cyanobacteria

95-13367戈尔登 在这个项目中，揭示昼夜节律振荡器机制的方法集中在最不复杂和最技术上接近的生物体上，其中已经证明了生物钟，即蓝细菌，聚球藻属菌株PCC 7942。使用这种生物体的技术优势在于它具有易于遗传操纵的小基因组，并且已经开发出生物发光菌株，其中昼夜基因表达的监测是目前可用的任何系统中最灵活和最容易的。在一次实验中就可以筛选出数千个菌落中是否存在破坏生物钟或导致异常节律行为的突变。因此，这个蓝藻系统有很好的工具，详细的分子遗传分析和时钟调查。该项目将使用该系统来解决生物节律性的三个方面： (1)识别和表征参与产生昼夜节律的基因，（2）表征振荡器控制节律输出的机制，以及（3）评估生物体从其昼夜节律振荡器获得的适应性优势。 生物复杂性的各个层次的生物体都表现出由内部“时钟”控制的昼夜节律。“这些生物钟的生化性质一直难以捉摸，但已经出现的一个原则是，它们的基本特性在所有观察到昼夜节律行为的生物体中是保守的，从细菌到哺乳动物。这一原理鼓励了人们的希望，即生物化学机制也被保存下来，至少在生物钟的一般组成部分和组成方面。该项目通过使用已知显示昼夜节律的最简单生物体来研究生物钟的组成：蓝细菌。人类的许多过程，包括睡眠/觉醒，体温，基因表达，细胞分裂和酶活性，都受到生物钟的调节。此外，这些时钟也是测量植物和动物生殖过程计时中日长的计时器。因此，了解生物钟的生化机制是基本的生物学兴趣，并可能导致的见解，这将是有用的，例如，在农业。 ***

95-13367 Golden The approach to unveiling the mechanism of circadian oscillators in this project focuses on the least-complex and most technically-approachable organism in which a biological clock has been demonstrated, namely the cyanobacterium, Synechococcus sp. strain PCC 7942. The technical advantages that accrue from using this organism are that it has a small genome which is easily manipulated genetically, and that a bioluminescent strain has been developed in which the monitoring of circadian gene expression is the most flexible and facile of any system presently available. Screening of thousands of colonies for mutations that disrupt the clock or otherwise cause aberrant rhythmic behavior is possible within a single experiment. Therefore, this cyanobacterial system has excellent tools for detailed molecular genetic analyses and for clock investigations. The project will use this system to address three aspects of biological rhythmicity: (1) identification and characterization of genes that are involved in generating circadian rhythms, (2) characterization of the mechanism by which the oscillator controls rhythmic outputs, and (3) assessment of the fitness advantage that organisms derive from their circadian oscillators. Living organisms at all levels of biological complexity manifest circadian (daily) rhythms which are controlled by an internal "clock." The biochemical nature of these biological clocks has been elusive, but one principle which has emerged is that their fundamental properties are conserved in all organisms in which circadian behavior has been observed, from bacteria to mammals. This principle has encouraged the hope that the biochemical mechanism has also been conserved, at least in terms of the general components and composition of the clock. This project investigates the composition of the biological clock by using the simplest organism known to show circadian rhythms: a cyanobacterium. Many processes in humans, including sleeping/waking, body temperature , gene expression, cell division, and enzymatic activities, are regulated by the biological clock.. In addition, these clocks are also the timers that measure the day length in timing of reproductive processes in plants and animals. Therefore, understanding the biochemical mechanism of- circadian clocks is of fundamental biological interest and may lead to insights which will be useful for example, in agriculture. ***