Molecular Genetics Analysis of Plant Circadian Rhythms

McClung 9723482 将在模型植物拟南芥中研究植物中产生时间信息的分子基础。分子钟调节气体交换、叶子运动和基因表达的明显节律。生物钟功能受到影响的拟南芥突变体已利用昼夜节律对 SO2 暴露的抵抗/敏感性进行了分离，而 SO2 暴露是由气孔孔径和气体交换的昼夜节律引起的。如果有65个突变体，其中3个开花明显早于野生型，30个开花明显晚于野生型。 21 个测试中的 6 个也显示出长下胚轴表型。工作重点将集中在一种突变体上，即昼夜节律缺陷1 (ctd1)，该突变体比野生型开花晚，但保留了光周期敏感性。该突变作为隐性核基因遗传。 Ctd1 显示四个基因的 mRNA 丰度振荡的短周期，这意味着 ctd1 影响所有四个基因表达的共同过程，因此定义了共同振荡器或共同输入或输出途径的组成部分。 Ctd1 将在表型和遗传学上进行表征，然后进行基因的克隆和表征。其他具有改变时钟特性的 ctd 突变体将继续进行表征，并且还将继续寻找新的突变体。 在没有环境时间线索的情况下以大约 24 小时间隔重复发生的节律生物现象被称为昼夜节律。它们的时间由内源性生物钟调节。这种节奏无处不在，并且已经在现象学层面上得到了详细的描述。植物为研究昼夜节律提供了优秀的系统，因为植物具有很强的节律性并且对环境输入极其敏感，这可能反映了它们的固着生长形式以及它们对直接环境的营养和能量的依赖。增加对植物对环境输入和内源时间线索的反应的了解具有农业重要性，特别是因为环境线索和生物钟都有助于光周期决定开花。将在模式植物拟南芥中对通过新型筛选鉴定的突变体进行遗传和分子生​​物学分析。

McClung 9723482 The molecular basis by which time information is generated in plants will be investigated in the model plant, Arabidopsis thaliana. The molecular clock regulates overt rhythms in gas exchange, leaf movement and gene expression. Arabidopsis mutants affected in clock function have been isolated using the circadian rhythm in resistance/sensitivity to SO2 exposure that results from the circadian rhythms in stomatal aperture and gas exchange. If 65 mutants, 3 flower significantly earlier than wild type and 30 flower significantly later. Six of 21 tested also display a long hypocotyl phenotype. Efforts will be concentrated on one mutant, Circadian Timing Defective 1 (ctd1), which flowers later than wild type, but retains photoperiod sensitivity. The mutation is inherited as recessive nuclear gene. Ctd1 shows a short period in oscillations in mRNA abundance for four genes, the implication being that ctd1 affects a process common to expression of all four genes and thus defines a component of a common oscillator or of a common input or output pathway. Ctd1 will be characterized both phenotypically and genetically followed by cloning and characterization of the gene. Other ctd mutants with altered clock properties will continue to be characterized and the search for new mutants will also be continued. Rhythmic biological phenomena which recur at approximately 24 hour intervals in the absence of environmental time cues are termed circadian rhythms. Their timing is regulated by an endogenous biological clock. Such rhythms are ubiquitous and have been described in great detail at a phenomenological level. Plants provide excellent systems for study of circadian rhythmicity because plants are robustly rhythmic and exquisitely sensitive to environmental input, probably reflecting both their sessile growth form and their dependence on their immediate environment for nutrition and energy. Increased understanding of plant responses to environmental input and to endogenous temporal cues ha s agricultural importance, in particular, because both environmental cues and the circadian clock contribute to the photoperiodic decision to flower. A genetic and molecular biological analysis of mutants identified by a novel screen will be done in Arabidopsis thaliana, the model plant.