Circadian Rhythms of Gene Expression in Cyanobacteria

该项目的总体目标是了解细胞组织24小时（昼夜）生物钟的基本机制。动物和真菌生物钟定时模型的核心是涉及负调节其自身表达的时钟基因的反馈回路。在蓝细菌细长聚球藻（PCC 7942），原核生物昼夜节律生物学的模式生物，三个基因（kaiA，kaiB和kaiC）所需的生物钟功能。来自KaiA或KaiC缺陷或过度表达KaiA或KaiC的突变体的数据表明KaiA是kaiBC启动子的正激活剂，KaiC是负调节剂。然而，S. elongatus中，改变了kaiA和kaiBC表达的相对表达，表明该参数对于产生昼夜节律并不重要。本项目利用生物发光报告基因来追踪S.其中KAI基因表达已被操纵以避开正常的反馈环。预测位于定时机制核心的分子事件的变化，例如每种Kai蛋白及其信息的积累，以及KaiC蛋白的磷酸化状态，将在其中可以特异性操纵Kai表达的突变株中进行监测。该项目将揭示有助于产生生物钟的分子参数。该项目将培训博士后和本科生，并将为这种和其他蓝藻物种生成复杂的遗传工具，从而解决更广泛的生物学问题。

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.