Catalase Expression to Study Information Flow to and From the Circadian Clock

过氧化氢酶表达研究昼夜节律钟的信息流

• 批准号: 0316056
• 负责人: C. Robertson McClung
• 金额: $ 19万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-15 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0316056&HistoricalAwards=false
• 关键词: Catalase; Expression; Study; Information; Flow

Although there is considerable conservation of clock components and mechanisms among diverse taxa, it is equally clear that there is diversity in the molecular basis of circadian rhythmicity. Thus, investigation of circadian rhythmicity in multiple systems is important for the elucidation of common themes in circadian timekeeping as well as the definition of novel clock molecules and mechanisms of information input to and temporal output from clocks. One of the dominant themes in recent studies of circadian systems among multicellular organisms is the spatial separation of distinct clocks that regulate circadian behavior of distinct organs (e.g., heart, liver, skeletal muscle, retina). In vertebrates, the major circadian oscillator resides in the brain and is thought to provide coordinating temporal information to synchronize a series of organ specific "peripheral" oscillators. However, recent results suggest that the peripheral oscillators may function more autonomously than previously thought. A number of experimental results suggest that plants, too, have multiple clocks. The majority of these data are based on the observation of rhythms with distinct periods within a plant. Although is suggestive of two distinct clocks, it is by no means conclusive. One of the most effective means to study the circadian clock is by monitoring the effect of pulses of light or temperature on clock phase. If two rhythms respond to the same pulse with different phase shifts, it is quite likely that the two rhythms are responding to distinct clocks. Recent experiments in Arabidopsis have established that there are two clocks in the cotyledon, one driving CAB2 transcription and the other driving CAT3 transcription. Moreover, the clock driving CAT3 is considerably more sensitive to temperature.The proposed work is designed to distinguish between these two clocks in greater detail. There are two specific aims. The first is to more thoroughly characterize the temperature sensitivity of the circadian oscillator regulating CAT3. The mechanism by which temperature signals are perceived and transmitted to the clock is not well understood. Because thermosensing in general is not well understood, investigations in this area are likely to have influence well beyond the study of circadian biology. This work asks a number of specific questions. Is the circadian system perturbed by mutations that alter membrane properties? Is the potency of a temperature cycle determined by the temperature differential between warm and cold or, instead, by the absolute value of the cold temperature? Experiments are proposed to more fully document the effects of release from stratification, a cold and dark treatment of hydrated seeds. The goal is to determine if the temperature or light onset signals are individually sufficient to reset the clock. Finally, genetic screens to identify loci required for appropriate input of temperature signals to the clock will be carried out. The second aim is to identify mutantations that differentially affect either the CAB2 clock or the CAT3 clock. It is not clear if the two clocks are assembled from identical or overlapping sets of components, and this aim provides a genetic test to address this critical puzzle. These results are likely to have broad influence on knowledge of all circadian systems.

尽管在不同的分类群中存在相当大的时钟组成和机制的保守性，但同样清楚的是，昼夜节律的分子基础存在多样性。因此，研究多系统中的昼夜节律对于阐明昼夜节律计时的共同主题，以及定义新的时钟分子和时钟信息输入和时间输出机制非常重要。最近多细胞生物昼夜节律系统研究的主要主题之一是调节不同器官（如心脏、肝脏、骨骼肌、视网膜）昼夜节律行为的不同时钟的空间分离。在脊椎动物中，主要的昼夜节律振荡器位于大脑中，并被认为提供协调的时间信息，以同步一系列特定器官的“外围”振荡器。然而，最近的结果表明，外围振荡器可能比以前认为的更自主地起作用。许多实验结果表明，植物也有多个时钟。这些数据大多是基于对植物内部不同时期的节律的观察。虽然它暗示了两个不同的时钟，但这绝不是决定性的。研究生物钟最有效的方法之一是监测光脉冲或温度脉冲对生物钟相位的影响。如果两种节律以不同的相移对同一脉冲作出反应，则很可能这两种节律对不同的时钟作出反应。最近在拟南芥实验中发现，子叶中有两个时钟，一个驱动CAB2转录，另一个驱动CAT3转录。此外，驱动CAT3的时钟对温度相当敏感。拟议的工作旨在更详细地区分这两种时钟。有两个具体目标。首先是更彻底地表征调节CAT3的昼夜节律振荡器的温度敏感性。温度信号被感知并传递给生物钟的机制尚不清楚。由于一般的热感测还没有被很好地理解，这一领域的研究可能会产生远远超出昼夜节律生物学研究的影响。这项工作提出了一些具体的问题。昼夜节律系统是否受到改变膜特性的突变的干扰？温度循环的效力是由冷暖温差决定的，还是由冷暖温度的绝对值决定的？实验建议更充分地记录从分层，冷和暗处理水合种子释放的影响。目的是确定温度或光照信号是否足以单独重置时钟。最后，将进行基因筛选，以确定将温度信号适当输入时钟所需的位点。第二个目标是确定对CAB2时钟或CAT3时钟有不同影响的突变。目前尚不清楚这两个时钟是由相同的或重叠的组件组合而成的，这一目标提供了一种基因测试来解决这个关键的难题。这些结果可能对所有昼夜节律系统的知识有广泛的影响。