The control of specificity in guard cell ROS-based signalling

几千年来，植物进化了一种机制，使之能够适应不断变化的环境条件。这些反应的核心是一些系统，这些系统使植物能够检测到环境的变化，然后对变化的条件做出适当的反应。在单个细胞水平上，受体检测到变化，然后一个复杂的细胞内机制负责激发适当的细胞内反应。这个过程被称为刺激-反应耦合(或细胞内信号传递)。这台机器的核心是活性氧(ROS)。当细胞对外界刺激做出反应时，细胞内的ROS浓度会增加。这充当了一个中间或触发器，导致最终响应的生成。RO作为参与对过多不同刺激反应的中间体的普遍存在提出了一个重要的问题，这就是：RO的增加如何引起特定的反应？这个问题的本质可以通过考虑一个例子很容易理解。气孔是叶片表面的气孔，随着环境条件的变化而打开和关闭。气孔孔由两个保卫细胞组成。当这些毛孔收缩时，毛孔关闭，而膨胀则导致打开。气孔很重要，因为它们控制着二氧化碳的吸收和水分的流失。在保卫细胞中，导致肿胀(打开)或关闭(收缩)的刺激都使用涉及ROS增加的细胞内信号通路。这是怎么回事？如何在单个细胞中控制反应的特异性是植物细胞信号传递中尚未解决的大问题之一。以前测量细胞内的ROS一直是有问题的，然而在这个应用中，我们利用我们的一个实验室开发的阶跃变化技术来提供对单个细胞中ROS动力学的前所未有的了解。我们相信，我们在这一领域处于国际领先地位，因此，这是一个非常及时的应用，将埃克塞特的新技术和布里斯托尔的生物系统(气孔)结合在一起，为一个重大的悬而未决的问题找到答案。我们的假设得到了初步数据的支持，即不同的刺激会在细胞内产生独特的ROS模式。我们称这些为ROS签名。然后，这些信息被细胞内的细胞内机器解码，以产生特定的反应。在本应用程序中，我们将使用我们的新技术来验证这一假设。我们还将找出ROS增加的来源(S)以及不同刺激之间的差异，我们还将研究ROS增加控制气孔开放和关闭机制的哪些部分。最后，我们将研究另一种细胞内信号(钙)之间的相互作用，以揭示反应的特异性在多大程度上受ROS和钙信号通路相互作用的控制。

Over the millennia plants have evolved mechanisms that allow then to adapt to changing environmental conditions. At the heart of these responses are systems that enable plants to detect changes in their environment and then to formulate the appropriate response to the changed conditions. At the level of the single cell changes are detected by receptors and then a complex intracellular machinery is responsible for the elicitation of the appropriate intracellular response. This process is known as stimulus-response coupling (or intracellular signalling). At the heart of this machinery are Reactive Oxygen Species (ROS). When a cell reacts to an external stimulus the concentration of the ROS inside the cell increases. This acts as an intermediate, or trigger, leading to the generation of the final response. The ubiquity of ROS as intermediaries involved in the responses to a plethora of different stimuli raises an important question and this is; how can the increase in ROS elicit specific responses? This nature of the problem can be readily understood by considering one example.Stomata are pores on the surfaces of leaves that open and close in response to changing environmental conditions. The stomatal pore is formed by two guard cells. When these shrink the pore closes whereas swelling results in opening. Stomata are important because they control carbon dioxide uptake and water loss. In guard cells stimuli that bring about swelling (opening) or closure (shrinking) both use intracellular signalling pathways that involve an increase in ROS. How does this work? Unravelling how response specificity is controlled in a single cell is one of the big and unresolved questions in plant cell signalling. Previously making measurements of ROS inside cells has been problematic, however in this application we are making use of step-change advances in technology developed in one of our labs to provide an unprecedented understanding of ROS dynamics in single cells. We believe that we have an international lead in this area, accordingly this is a very timely application, bringing together the new technology from Exeter and the biological system (stomata) in Bristol to find answers to a major unresolved question. Our hypothesis, backed by our preliminary data, is that different stimuli generate unique patterns of ROS inside cells. We call these ROS signatures. These are then decoded by the intracellular machinery inside the cell to produce the specific response. In this application, we will use our new technology to test this hypothesis. We will also find out the origin(s) of the ROS increase and whether these differ between stimuli and we will also investigate what parts of the stomatal opening and closure mechanism are controlled by increases in ROS. Finally we will investigate the interaction between another intracellular signal (calcium) to reveal the extent to which response specificity is controlled by the interaction of ROS and Ca signalling pathways.