Molecular Genetic Analysis Of Plant Circadian Rhythms

增加了解植物对环境输入和内源性时间线索的反应具有农业重要性。 生物钟整合了时间信息，协调了生物学的许多方面，包括基本代谢和对生物和非生物胁迫的反应。 此外，环境线索和昼夜节律钟有助于光周期开花。 内源性计时机制与外部白天的适当协调赋予了适应性优势，昼夜节律功能受损与健身能力降低有关。 模式植物，拟南芥，提供了一个强大的和实验上易于处理的系统，在其中研究昼夜节律的分子机制。 因为植物是密切相关的，很可能来自拟南芥研究的理解将很容易转移到农学上重要的物种。 在气候变化的背景下，需要利用越来越边缘的栖息地，更充分地了解时钟机制可能会提供策略，以提高作物生产力。 突变分析表明，每一个都是重要的昼夜节律系统，虽然个人发挥不同的作用。 事实上，拟南芥中第一个真正的时钟突变体是prr 1，也被称为toc 1。 该突变体是根据叶片运动和基因表达监测的缩短的昼夜节律周期分离的。 TOC 1突变体在开花的光周期诱导中也表现出缺陷。 本项目的重点是PRR 9和PRR 7。 这些基因座的突变赋予不同于其他PRR基因座的表型-prr 9表现出滞后期，prr 7表现出长周期，而其他三个家族成员的突变，包括TOC 1，缩短了周期。 双prr 7 prr 9突变体在白色光下具有夸大的表型（非常长的周期，非常滞后的阶段），这表明PRR 7和PRR 9之间的部分功能冗余。 PRR 7和PRR 9的时钟缺陷被认为是在夹带到亮-暗周期或温度（暖-冷）周期之后。 这表明PRR 7和PRR 9在环境信号的感知或转导中起着核心作用。 这些PRR也可能在中央振荡器中起作用，类似于TOC 1（PRR 1），它被认为是拟南芥时钟的关键组成部分。 该项目采用遗传和生物化学方法来阐明PRR 7和PRR 9作为输入途径或振荡器本身的组成部分的作用。 这些包括过表达，使用双突变体和三突变体来评估遗传相互作用，以及筛选增强或抑制prr 7或prr 9突变表型的第二突变。 将测试PRR 7和PRR 9之间的物理相互作用，并寻找PRR 7和PRR 9的其他相互作用者。

Increased understanding of plant responses to environmental input and to endogenous temporal cues has agricultural importance. The clock integrates temporal information and coordinates many aspects of biology, including basic metabolism and responses to biotic and abiotic stresses. Additionally, environmental cues and the circadian clock contribute to the photoperiodic flowering. Proper coordination of the endogenous timing mechanism with the external day confers adaptive advantage, and impaired circadian function is associated with reduced fitness. The model plant, Arabidopsis thaliana, offers a powerful and experimentally tractable system in which to investigate the molecular mechanisms of circadian rhythmicity. Because plants are closely related, it is quite likely that understanding derived from Arabidopsis studies will be readily transferred to agronomically important species. In the context of climate change and the need to exploit increasingly marginal habitats, fuller understanding of clock mechanism may offer strategies to improve crop productivity.This project focuses on the Arabidopsis thaliana family of five Pseudo-Response Regulators (PRRs). Mutational analysis indicates that each is important to the circadian system, although individuals play distinct roles. Indeed, the first bona fide clock mutant in Arabidopsis was prr1, known also as toc1. This mutant was isolated on the basis of a shortened circadian period as monitored by leaf movement and by gene expression. toc1 mutants also exhibit defects in photoperiodic induction of flowering. This project focuses on PRR9 and PRR7. Mutation of these loci confers phenotypes distinct from those of the other PRR loci-prr9 exhibits lagging phase and prr7 exhibits long period, whereas mutation of the other three family members, including TOC1, shortens the period. The double prr7 prr9 mutant has an exaggerated phenotype in white light (very long period, very lagging phase), which suggests partial functional redundancy between PRR7 and PRR9. The clock defects of PRR7 and PRR9 are seen following entrainment either to light-dark cycles or to temperature (warm-cool) cycles. This argues for a central role of PRR7 and PRR9 in the perception or transduction of environmental signals. It is also possible that these PRRs may act within the central oscillator, analogously to TOC1 (PRR1), which is accepted as a crucial component of the Arabidopsis clock. This project employs genetic and biochemical approaches to elucidate the roles of PRR7 and PRR9 as components of input pathways or of the oscillator itself. These include overexpression, use of double and triple mutants to assess genetic interaction, and screens for second mutations that enhance or suppress prr7 or prr9 mutant phenotypes. Physical interaction between PRR7 and PRR9 will be tested, and other interactors with PRR7 and PRR9 will be sought.