Defining the role of SUMO in regulating chloroplast biogenesis and functions

定义 SUMO 在调节叶绿体生物发生和功能中的作用

• 批准号: BB/W015021/1
• 负责人: Paul Jarvis
• 金额: $ 81.76万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FW015021%2F1
• 关键词: Defining; role; SUMO; regulating; chloroplast

The human population is set to exceed 9bn by 2050, presenting significant challenges to food security and placing ever increasing pressure on natural resources. Thus, the need for increased crop yields with resilience to sub-optimal growing conditions is stronger than ever. To meet these demands it will be essential to develop improved varieties of our staple crops. Through research on the model plant thale cress, it is well established that the extent of protein modification by "SUMO" (which stands for "small ubiquitin-like modifier") increases in response to different abiotic stresses, including high salinity, high temperature, freezing, drought, and oxidative and heavy metal stresses; and that such "SUMOylation" is a vital aspect of plant stress responses. Previous studies identified over a thousand SUMO targets in thale cress, most of which are located in a central cellular structure called the nucleus. However, our latest results show that SUMO also acts on different parts of the plant cell called chloroplasts. In this project, we will define how and why SUMO acts on chloroplasts, and in so doing understand how it may be used to deliver more resilient crops.Chloroplasts are the cellular constituents (or organelles) that define plants. They contain the green pigment chlorophyll, and are the site of photosynthesis - the process which harnesses sunlight energy to power the activities of the cell and the growth of the plant. As photosynthesis is the only significant mechanism of energy-input into the living world, chloroplasts are of huge importance, not just to plants but to all life on Earth. Moreover, chloroplasts have critical roles in plant responses to stress, and so they are ideal targets for crop improvement.Chloroplasts are composed of thousands of different proteins, most of which are encoded by genes in the cell nucleus and, therefore, are made outside of the organelle in the cellular matrix known as the cytosol. As chloroplasts are surrounded by a double-membrane "envelope", sophisticated machinery is needed to import these proteins into the organelle; this comprises molecular machines in both membranes, called TOC (for "Translocon at the Outer membrane of Chloroplasts") and TIC. Each machine is composed of several proteins that work cooperatively to drive the import process.We recently made some significant breakthroughs in this area: We discovered that the constituent proteins of the TOC machinery are broken-down by a novel regulatory process named "CHLORAD" (which stands for "chloroplast-associated protein degradation"). In CHLORAD, unwanted TOC proteins are tagged with a protein modifier named ubiquitin, which targets them for removal and break-down. Thus, CHLORAD regulates the import of other proteins into the organelle, which in turn influences the development and operation of the organelle. Significantly, modifying CHLORAD activity makes plants more tolerant of stress.Now, we have new results revealing that the SUMO system also acts on chloroplasts. We believe that such SUMOylation destabilizes the TOC machinery to regulate protein import. In this project, we will study the mechanisms of SUMO-dependent chloroplast regulation in detail. We will define the SUMO pathway that acts on TOC proteins, and elucidate its physiological significance. Furthermore, inspired by our latest data suggesting that SUMO actually acts on a large number of chloroplast proteins, we will systematically identify the full range of SUMOylated chloroplast proteins, and study the effects of such SUMOylation. Lastly, we will investigate whether there is crosstalk between the SUMO and CHLORAD systems in TOC regulation.Together, our experiments will shed unprecedented new light on the mechanisms and significance of SUMO-dependent control of chloroplast functions and, in turn, plant development. This knowledge will be invaluable for the development of crops with improved chloroplast performance and stress resilience.

到 2050 年，人口将超过 90 亿，这对粮食安全提出了重大挑战，并对自然资源造成越来越大的压力。因此，对提高作物产量并适应次优生长条件的需求比以往任何时候都更加强烈。为了满足这些需求，开发主要农作物的改良品种至关重要。通过对模型植物拟南芥的研究，已经明确“SUMO”（代表“小泛素样修饰剂”）对蛋白质的修饰程度会随着不同的非生物胁迫而增加，包括高盐度、高温、冰冻、干旱、氧化和重金属胁迫；这种“SUMO化”是植物应激反应的一个重要方面。之前的研究在拟南芥中发现了超过一千个 SUMO 目标，其中大部分位于称为细胞核的中央细胞结构中。然而，我们的最新结果表明，SUMO 还作用于植物细胞的不同部分（称为叶绿体）。在这个项目中，我们将定义 SUMO 如何以及为何作用于叶绿体，并在此过程中了解如何使用它来提供更具弹性的作物。叶绿体是定义植物的细胞成分（或细胞器）。它们含有绿色色素叶绿素，是光合作用的场所——利用阳光能量为细胞活动和植物生长提供动力的过程。由于光合作用是向生命世界输入能量的唯一重要机制，叶绿体不仅对植物而且对地球上的所有生命都非常重要。此外，叶绿体在植物对胁迫的反应中发挥着关键作用，因此它们是作物改良的理想目标。叶绿体由数千种不同的蛋白质组成，其中大部分由细胞核中的基因编码，因此是在细胞核之外产生的。细胞基质中的细胞器称为胞质溶胶。由于叶绿体被双膜“包膜”包围，因此需要复杂的机器将这些蛋白质导入细胞器；这包括两个膜中的分子机器，称为 TOC（“叶绿体外膜的转运蛋白”）和 TIC。每台机器都由多种蛋白质组成，这些蛋白质协同工作来驱动导入过程。我们最近在这一领域取得了一些重大突破：我们发现TOC机器的组成蛋白质被一种名为“CHLORAD”的新型调节过程分解（代表“叶绿体相关蛋白降解”）。在 CHLORAD 中，不需要的 TOC 蛋白被一种名为泛素的蛋白修饰剂标记，该修饰剂针对这些蛋白进行去除和分解。因此，CHLORAD 调节其他蛋白质进入细胞器，进而影响细胞器的发育和运作。值得注意的是，改变 CHLORAD 活性使植物更能耐受胁迫。现在，我们的新结果表明 SUMO 系统也作用于叶绿体。我们认为这种 SUMO 化会破坏调节蛋白质输入的 TOC 机制的稳定性。在本项目中，我们将详细研究 SUMO 依赖性叶绿体调节机制。我们将定义作用于 TOC 蛋白的 SUMO 途径，并阐明其生理意义。此外，受我们最新数据的启发，SUMO 实际上作用于大量叶绿体蛋白，我们将系统地识别全系列 SUMO 化叶绿体蛋白，并研究这种 SUMO 化的影响。最后，我们将研究 SUMO 和 CHLORAD 系统在 TOC 调节中是否存在串扰。我们的实验将共同揭示 SUMO 依赖性叶绿体功能控制的机制和意义，进而揭示植物发育的机制和意义。这些知识对于开发具有改善叶绿体性能和抗逆能力的作物具有无价的价值。