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

虽然有相当大的保守的时钟组件和机制之间的不同类群，它同样清楚，有多样性的分子基础的昼夜节律。 因此，在多个系统中的昼夜节律性的调查是重要的，在昼夜节律计时的共同主题的阐明，以及新的时钟分子的定义和机制的信息输入和时间输出的时钟。 在多细胞生物体中的昼夜节律系统的最近研究中的主导主题之一是调节不同器官（例如，心脏、肝脏、骨骼肌、视网膜）。 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，以同步一系列器官特异性的“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发挥作用。 许多实验结果表明，植物也有多个时钟。 这些数据中的大多数是基于对植物内具有不同周期的节律的观察。 虽然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通过监测光脉冲或温度对时钟相位的影响。 如果两种节律对具有不同相移的相同脉冲作出响应，则这两种节律很可能对不同的时钟作出响应。 最近在拟南芥中的实验已经确定，在子叶中存在两个时钟，一个驱动CAB2转录，另一个驱动CAT3转录。 此外，驱动CAT3的时钟对温度敏感得多，所提出的工作旨在更详细地区分这两个时钟。 有两个具体目标。 首先是更彻底地表征调节CAT 3的昼夜节律振荡器的温度敏感性。 温度信号被感知并传输到时钟的机制还不清楚。 由于一般的温度传感还没有得到很好的理解，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。 生物钟系统是否被改变细胞膜特性的突变所干扰？ 温度循环的效力是由冷暖温差决定的，还是由冷温度的绝对值决定的？ 实验提出了更充分的文件从分层释放的影响，一个寒冷和黑暗的治疗水合种子。 目标是确定温度或光起始信号是否单独足以重置时钟。 最后，将进行遗传筛选，以确定适当输入温度信号到时钟所需的基因座。 第二个目的是鉴定差异地影响CAB2时钟或CAT3时钟的突变。 目前尚不清楚这两个时钟是由相同或重叠的组件组装而成的，这一目标提供了一个基因测试来解决这个关键难题。 这些结果可能对所有昼夜节律系统的知识产生广泛的影响。

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.