Molecular and Genetic Analysis of ZTL Function in the Arabidopsis Circadian Clock

生物钟既提供了对即将到来的变化的预期，也提供了对环境快速变化的缓冲。尽管生物钟很重要，但人们对植物生物钟的分子组成知之甚少，尽管许多现象学已经表明，在动植物王国中，生物钟的基本特性是相似的。这项研究的长期目标是识别植物生物钟系统的组成部分，并将其整合到一个连贯的相互作用框架中。实现这一目标的具体手段将是利用最近克隆的拟南芥ZEITLUPE(ZTL)基因座的突变体和野生型基因产物。该基因座(ZTL-1，-2)的突变以一种光依赖的方式影响开花时间，并极大地增加了生物钟的周期。这些轨迹将是用于了解输入到时钟系统的光如何与振荡器本身连接的主要工具之一。ZTL由一个推测的光敏结构域(LOV结构域)、一个F-box和6个海带基序组成，识别可能在该蛋白的功能中发挥不同作用的区域。该项目的具体目标是：1)在已知的红光和蓝光信号转导途径的背景下，完成ZTL基因座的遗传定位。2)通过酵母双杂交文库筛选和候选因子的靶向性检测，寻找ZTL蛋白的物理相互作用伙伴。3)根据ZTL-1的表型，通过抑制子和增强子的筛选，寻找ZTL的遗传互作伙伴。鉴于这些突变对开花时间的强烈影响，这些研究应该更清楚地发展生物钟、光信号和植物发育之间的联系。

The circadian clock provides for both anticipation of coming changes and for a buffering against rapid variation in the environment. Despite its importance, little is known about the molecular components of the circadian clock in plants, though much phenomenology has shown that the basic properties of clocks are similar across the plant and animal kingdoms. The long-term objective of this study is to identify and integrate components of the circadian clock system of plants into a coherent framework of interaction. The specific means towards this end will be through using the mutant and wild-type gene products of the recently cloned locus in Arabidopsis, ZEITLUPE (ZTL). Mutations at this locus (ztl-1, -2) affect flowering time and greatly increase the period of the circadian clock in a light dependent way. These loci will be one of the primary tools used to understand how light input to the clock system interfaces with the oscillator itself. ZTL is comprised of a novel combination of a putative light-sensing domain (LOV domain), an F-box and 6 kelch motifs, identifying regions that are likely to play distinct roles in function of this protein. The specific goals of this project are: 1) to complete the genetic positioning of ZTL locus within the context of the known red light and blue light signal transduction pathways. 2) To identify physical interaction partners of the ZTL protein through yeast 2-hybrid interaction library screens and through targeted testing of candidate factors. 3) To identify genetic interaction partners of ZTL through suppressor and enhancer screens based on the ztl-1 phenotype. Given the strong effects these mutations have on flowering time, these studies should more clearly develop the link between the circadian clock, light signaling and plant development.