Molecular Genetics Analysis of Plant Circadian Rhythms

麦克朗 9723482将在模式植物拟南芥中研究植物中产生时间信息的分子基础。分子钟调节着气体交换、叶片运动和基因表达的明显节律。利用气孔孔径和气体交换的昼夜节律，研究了拟南芥对SO2暴露的抗性/敏感性的昼夜节律，分离出受时钟功能影响的突变体。65个突变体中，有3个开花显著早于野生型，30个开花显著晚于野生型。 21个测试中的6个也显示出长下胚轴表型。努力将集中在一个突变体，昼夜节律定时缺陷1（ctd 1），花晚于野生型，但保留光周期敏感性。该突变以隐性核基因遗传。ctd 1显示了一个短时期的振荡在mRNA丰度的四个基因，这意味着ctd 1影响一个过程共同表达的所有四个基因，从而定义了一个共同的振荡器或一个共同的输入或输出途径的组成部分。ctd 1将在表型和遗传学上进行表征，然后进行基因克隆和表征。其他具有改变的生物钟特性的ctd突变体将继续被鉴定，并且寻找新的突变体也将继续。 在没有环境时间线索的情况下，以大约24小时的间隔重复出现的节律性生物现象被称为昼夜节律。它们的时间是由内源性生物钟调节的。这样的节奏是普遍存在的，并已在现象学层面上进行了详细的描述。植物为昼夜节律的研究提供了很好的系统，因为植物具有强烈的节律性和对环境输入的敏感性，这可能反映了它们的固着生长形式和它们对营养和能量的直接环境的依赖。增加对植物对环境输入和内源时间线索的响应的理解具有农业重要性，特别是因为环境线索和昼夜节律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.