Organ communication in the Arabidopsis circadian clock

生命已经在地球上进化，地球绕着它的轴旋转，因此不断经历着总共持续24小时的光明和黑暗的循环。因此，大多数生物体，也许是所有生物体，都有一个“生物钟”，它的周期约为24小时，它决定了各种生理过程发生的时间。时钟不会保持准确的时间，但每天都会根据光等信号重新设置。人类最熟悉的“昼夜节律”是我们的睡眠/清醒周期，这是时差反应和轮班相关问题的原因。其他包括啮齿动物的运动活动(例如，仓鼠在夜间而不是白天在活动轮上奔跑)和豆类植物的叶子运动。后一种节奏在近300年前首次被描述！生物钟为生物体提供了一个显著的优势，因为它允许生物体预测明/暗的变化，并相应地调整自己的行为，而不仅仅是对变化做出反应。对比动物、植物和真菌的时钟，似乎它们的设计原则基本相同，但机械原理却大相径庭。有些细菌含有另一种类型的时钟。这意味着，在地球生命的历史上，时钟至少分别进化了四次，这表明了它的作用的关键性质。重要的是要了解生物钟在植物中的作用方式，特别是在许多植物中，它与日长相互作用来控制开花时间。随着全球变暖和气候变化的到来，扩大特定作物生长的纬度是可取的。但白天的长度会随着纬度的变化而变化，所以为了种子而种植的农作物在不同的纬度可能不会有生产力，即使它们可以生长得很好。如果我们了解时钟是如何工作的，我们应该能够培育或选择能够在不同纬度高效生长的作物变种。在过去十年左右的时间里，我们对植物生物钟机制的理解取得了巨大的进步。然而，其中大部分来自对生长在含有糖的琼脂平板上的整个幼苗的实验，这些幼苗的根暴露在普遍的光/暗循环中。这样的条件显然与一种根在黑暗中没有糖的成熟植物无关！我们在更现实的情况下进行了实验，使用的是根部处于持续黑暗中的成熟植物，而它们的叶子暴露在光/暗循环中。我们有两个发现，这两个发现从根本上影响了我们认为植物时钟的工作方式。首先，时钟是器官特有的，也就是说，根中的机械与茎中的不同。其次，新梢能够向根部发送信号，每天重新设置根时钟。在我们的工作之前，这些财产都没有被怀疑过。这项拨款申请的目的是扩展我们的工作，并确定生物钟在成熟植物不同器官中的机械和功能。

Life has evolved on the planet Earth, which rotates on its axis, and therefore continuously undergoes a cycle of light and darkness lasting 24 h in total. As a result, most, perhaps all, organisms possess a 'circadian clock' that has a period of about 24 h and that determines the time at which various physiological processes occur. The clock does not keep exact time but is re-set each day by signals such as light. The 'circadian rhythm' most familiar to humans is our sleep/wake cycle, the cause of jetlag and problems associated with shiftwork. Others include locomotor activity in rodents (e.g. hamsters run on an activity wheel at night rather than in the day) and leaf movements in bean plants. The latter rhythm was first described nearly 300 years ago! The circadian clock provides organisms with a significant advantage because it allows them to anticipate light/dark changes and adjust their behaviour accordingly, not just react to the changes. Comparing the clock in animals, plants and fungi, it seems that the 'design principles' are basically the same but the machinery is quite different. Some bacteria contain another type of clock. This implies that a 'clock' has evolved separately at least four times during the history of life on earth, indicating the key nature of its role. It is important to understand the way that the circadian clock functions in plants, particularly because in many plants it interacts with daylength to control flowering time. With the advent of global warming and climate change, it is desirable to extend the latitude at which particular crops grow. But daylength changes with latitude, so crop plants grown for their seeds may not be productive at different latitudes even if they can grow well. If we understand how the clock works, we should be able to breed or select crop variants that can grow productively at different latitudes. There have been huge advances in the last ten years or so in our understanding of the mechanism of the circadian clock in plants. However most of these have come from experiments on whole seedlings grown on agar plates containing sugars, with their roots exposed to the prevailing light/dark cycle. Such conditions are clearly irrelevant to a mature plant with its roots in the dark without sugars! We have carried out experiments in a more realistic situation, using mature plants with their roots in constant darkness while their leaves are exposed to the light/dark cycle. We have made two findings that radically affect the way we think the plant clock works. First, the clock is organ-specific, i.e. the machinery in the root is not the same as in the shoot. Secondly, the shoot is able to send a signal to the root that re-sets the root clock each day. Neither of these properties had been suspected before our work. The aim of this grant application is to extend our work and define the machinery and the functions of the circadian clock in different organs of mature plants.