Circadian Rhythms of Gene Expression in Cyanobacteria

蓝藻基因表达的昼夜节律

• 批准号: 9633267
• 负责人: Carl Johnson
• 金额: $ 22.9万
• 依托单位: Vanderbilt University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-04-01 至 2000-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9633267&HistoricalAwards=false
• 关键词: Circadian; Rhythms; Gene; Expression; Cyanobacteria

Abstract Johnson 9633267 Organisms at all levels of biological complexity manifest circadian (daily) rhythms which are controlled by an endogenous biochemical oscillator. Many physiological and cellular processes, including sleeping/waking, body temperature, homeostatic functions, gene expression, cell division, and enzymatic activities, are regulated by these "biological clocks". In addition, these oscillators are also the timers that measure the daylength in photoperiodic timing of reproductive processes in plants and animals. Therefore, understanding the biochemical mechanism of circadian clocks is of fundamental biological interest . The biochemical nature of these biological clocks has been elusive, but their salient properties (persistence, temperature compensation, and entrainment) are conserved in all organisms in which circadian behavior has been observed, from bacteria to mammals. This suggests that the biochemical mechanism has also been conserved--if not in exact homology, then at least in terms of the general components and composition of the clock. The approach to unveiling the mechanism of circadian oscillators described in this proposal focuses on the least-complex and most technically-approachable organism in which a biological clock has been demonstrated, the cyanobacterium, Synechococcus sp. strain PCC 7942. The technical advantages of 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. This project will use this system to address three aspects of biological rhythmicity: (1) identi fication 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. %%% Organisms at all levels of biological complexity manifest circadian (daily) rhythms which are controlled by an internal biochemical oscillator. Many physiological and cellular processes, including sleeping/waking, body temperature, homeostatic functions, gene expression, cell division, and enzymatic activities, are regulated by these "biological clocks." In addition, these clocks are also the timers that measure the daylength in photoperiodic timing of reproductive processes in plants and animals. Psychiatric and medical studies have shown that circadian rhythms are involved in some forms of depressive illness, "jet lag," drug tolerance/efficacy, sleep disorders, and other aspects of human physiology. Understanding the mechanism of these biological clocks has been elusive, but one principle which has emerged is that their major properties are conserved in all organisms in which circadian behavior has been observed, from bacteria to mammals. The approach to unveiling the mechanism of circadian oscillators described in this project focuses on using the least-complex and most technically-approachable organism in which a biological clock has been demonstrated (a cyanobacterium) to discover how the clock works at a molecular level. Information gained from this work about the mechanism of circadian clocks is of fundamental biological interest and may lead to insights which will be useful in agriculture and in the diagnosis and treatment of mental health and other human disorders. *** ??

摘要 Johnson 9633267 生物复杂性的各个层次的生物体都表现出昼夜节律，这些节律由内源性生化振荡器控制。 许多生理和细胞过程，包括睡眠/觉醒、体温、稳态功能、基因表达、细胞分裂和酶活性，都受到这些“生物钟”的调节。 此外，这些振荡器也是测量植物和动物生殖过程光周期计时中日长的计时器。 因此，了解生物钟的生化机制具有根本的生物学意义。 这些生物钟的生化性质一直难以捉摸，但它们的显着特性（持久性、温度补偿和夹带）在所有观察到昼夜节律行为的生物体（从细菌到哺乳动物）中都是保守的。这表明生化机制也是保守的——即使不是完全同源，那么至少在时钟的一般成分和组成方面是保守的。 该提案中描述的揭示昼夜节律振荡器机制的方法侧重于最不复杂且技术上最容易实现的生物体，其中已经证明了生物钟，即蓝藻，聚球藻属。 PCC 7942 菌株。该生物体的技术优势在于其基因组较小，易于遗传操作，并且已开发出一种生物发光菌株，其中昼夜节律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。 在一次实验中可以对数千个菌落进行筛选，以发现扰乱生物钟或以其他方式导致异常节律行为的突变。 因此，该蓝藻系统具有用于详细分子/遗传分析和时钟研究的优秀工具。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中获得的适应性优势。 %%% 各种生物复杂性水平的生物体都表现出昼夜节律（每日）节律，这些节律由内部生化振荡器控制。许多生理和细胞过程，包括睡眠/觉醒、体温、稳态功能、基因表达、细胞分裂和酶活性，都受到这些“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光周期计时中日长的计时器。 精神病学和医学研究表明，昼夜节律与某些形式的抑郁症、“时差反应”、药物耐受性/疗效、睡眠障碍以及人类生理学的其他方面有关。 了解这些生物钟的机制一直难以捉摸，但已经出现的一个原则是，它们的主要特性在所有观察到昼夜节律行为的生物体（从细菌到哺乳动物）中都是保守的。该项目中描述的揭示昼夜节律振荡器机制的方法侧重于使用最简单且技术上最容易实现的生物体（其中已证明生物钟（蓝细菌））来发现生物钟如何在分子水平上工作。 从这项工作中获得的有关生物钟机制的信息具有基本的生物学意义，并可能带来对农业以及心理健康和其他人类疾病的诊断和治疗有用的见解。 *** ??