Circadian Rhythms of Gene Expression in Cyanobacteria

这个项目的总体目标是了解细胞组织24小时(昼夜节律)生物钟的基本机制。动物和真菌生物钟计时模型的核心是涉及时钟基因的反馈环，这些基因负向调节自己的表达。在原核生物昼夜节律生物学的模式生物--长聚球藻(PCC7942)中，生物钟功能需要三个基因(KaIA、KaiB和KaiC)。来自KaiA或KaiC缺陷或过度表达的突变体的数据表明，Kaia是kaiBC启动子的正激活因子，KaiC是负调节因子。然而，长链球菌的其他突变体改变了KaIA和kaiBC的相对表达，表明这个参数对产生昼夜节律并不重要。这个项目使用生物发光报告基因来跟踪长链球菌菌株的昼夜表达，在这些菌株中，KAI基因的表达被操纵，以绕过正常的反馈环。预计处于计时机制核心的分子事件的变化，如每个KAI蛋白及其信息的积累，以及KaiC蛋白的磷酸化状态，将在可以特定操纵KAI表达的突变菌株中进行监测。该项目将揭示有助于生物钟产生的分子参数。该项目将培训博士后和本科生，并将为该物种和其他蓝藻物种生成复杂的基因工具，使更广泛的生物学问题得以解决。

The overall goal of this project is to understand the fundamental mechanisms by which a cell organizes a 24 h (circadian) biological clock. Central to models for animal and fungal circadian clock timing are feedback loops involving clock genes that negatively regulate their own expression. In the cyanobacterium Synechococcus elongatus (PCC 7942), the model organism for prokaryotic circadian biology, three genes (kaiA, kaiB, and kaiC) are required for circadian clock function. Data from mutants defective for, or that over-express, KaiA or KaiC suggest that KaiA is a positive activator, and KaiC a negative regulator, of the kaiBC promoter. However, other mutants of S. elongatus that change the relative expression of kaiA and kaiBC expression suggest that this parameter is not important for generating circadian rhythms. This project uses bioluminescent reporter genes to track circadian expression from S. elongatus strains in which kai gene expression has been manipulated to circumvent normal feedback loops. Changes in molecular events that are predicted to lie at the heart of the timing mechanism, such as the accumulation of each of the Kai proteins and their messages, and the phosphorylation state of the KaiC protein, will be monitored in mutant strains in which kai expression can be specifically manipulated. The project will reveal molecular parameters that contribute to the generation of a biological clock. The project will train postdoctoral and undergraduate students, and will generate sophisticated genetic tools for this and other cyanobacterial species, allowing a broader range of biological questions to be addressed.