Molecular Genetic Analysis of Plant Circadian Rhythms

在没有环境时间线索的情况下，每隔大约24小时发生的节律性生物现象被称为昼夜节律。关于昼夜节律的两个基本问题涉及的机制：1)时间信息被用来调节被观察到有节奏的生物现象，2)时间被测量。为了解决前者，已经确定了拟南芥中表达以昼夜节律方式调节的基因。使用基因融合、凝胶阻滞和DNA保护策略，将对顺式或反式昼夜节律调节所需的元件进行表征。时间测量的机制将通过识别和表征破坏生物计时的突变来解决。探讨硝酸还原酶的昼夜节律，看看蛋白质表达和mRNA水平是否对应。如果它们确实对应，硝酸盐还原酶水平将被测量，以试图筛选昼夜节律调节突变。融合基因，其中时钟控制被赋予一个报告基因，将被用作生物时钟上的分子标签，用于识别影响时钟功能的突变。气孔的昼夜节律将用于选择昼夜节律调节改变的突变体。这些突变的特征将确定时钟本身或通过时间控制施加的调节系统的元素。* * * / /

Rhythmic biological phenomena which occur at approximately 24 h intervals in the absence of environmental time cues are termed circadian rhythms. Two basic questions about circadian rhythms concern the mechanisms by which: 1) time information is used to regulate biological phenomena observed to be rhythmic, and 2) time is measured. To address the former, genes have been identified whose expression is regulated in a circadian fashion in Arabidopsis thaliana. Elements will be characterized that are required, in cis or in trans, for this circadian regulation using gene fusion, gel retardation and DNA protection strategies. The mechanism of time measurement will be addressed through the identification and characterization of mutations which disrupt biological timekeeping. The circadian rhythm in nitrate reductase will be explored to see if the protein expression and mRNA levels correspond. If they do correspond, nitrate reductase levels will be measured in an attempt to screen for circadian regulation mutations. Fusion genes, in which clock control is conferred on a reporter gene will be used as molecular tags on the biological clock in screens designed to identify mutations which affect clock function. The circadian rhythm in stomatal apertures will be used to select mutants in which circadian regulation is altered. Characterization of these mutations will identify elements either of the clock itself or of the regulatory system by which time control is exerted. *** //