Finessing, Extending and Developing an Overview of the Regulation of Ascorbate in plants (FEDORA)

精炼、扩展和发展植物中抗坏血酸的调控概述 (FEDORA)

• 批准号: BB/W006707/1
• 负责人: Cathie Martin
• 金额: $ 53.94万
• 依托单位: John Innes Centre
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FW006707%2F1
• 关键词: Finessing; Extending; Developing; Overview; Regulation

Ascorbate is a key metabolite for all plants, from eukaryotic algae to angiosperms. It is the most abundant water-soluble antioxidant with major roles in photosynthesis, transmembrane electron transport, cell division, growth and tolerance of biotic and abiotic stress. It performs these diverse roles by serving as a major scavenger of active oxygen species generated as by-products of photosynthesis, in the dissipation of excess photonic energy through the water-water cycle and as a co-factor in the xanthophyll cycle. It serves as a cofactor for dioxygenases, which are active in the synthesis of the phytohormones, ethylene, abscisic acid and gibberellins and in the generation of hydroxyproline, important for decorating small signalling peptides like CLAVATA3 and arabinogalactan-proteins (AGPs), which are ubiquitous cell surface proteoglycans proposed to play essential roles in plant growth and development, including cell expansion, cell division, reproductive development and somatic embryogenesis. Consequently the regulation of ascorbate levels is key to a large number of physiological processes in the growth and development of all plants.There is a vast body of literature describing the processes that influence ascorbate levels, but remarkably few papers describe the mechanisms of regulation, particularly at the molecular level. Needless to say, this lack of understanding of mechanism has limited our ability to engineer processes dependent on ascorbate through biotechnology or plant breeding for crop improvement. This limitation extends even to efforts to enhance ascorbate levels in fresh fruit and vegetables, despite the alarming reports of recent increases in the incidence of scurvy resulting from ascorbate/vitamin C deficiency. For example, in the UK between 2009 and 2014, hospital admissions related to scurvy went up by 27% due to malnutrition and obesity related to over-consumption of junk food diets. All that was changed by the publication of two landmark papers, one by Laing et al., in The Plant Cell in 2015 demonstrating a unique negative feedback regulatory mechanism controlling the translation of GDP-L-galactose phosphorylase (GGP) an enzyme active in the Smirnoff-Wheeler pathway for ascorbate synthesis, and the other by Fenech et al., in Plant Physiology (2021) showing that GGP activity is the only significant controlling step determining ascorbate levels in plant tissues and shows almost linear control of flux through the Smirnoff-Wheeler pathway.The aim of this application is to integrate our understanding of the regulation of ascorbate in plant cells. We aim to define the molecular mechanism for the negative feedback regulation of GGP translation and to understand how translational control of GGP is set within the boundaries defined by transcriptional control. We propose to understand how the control of GGP activity impacts flux to ascorbate. We propose to integrate our investigations of the mechanisms of regulation by studying primarily two plant species, Arabidopsis and tomato, to develop generic understanding of mechanisms for plants that could be broadly applicable. We propose to extend our understanding of the mechanism of negative feedback regulation of GGP to green algae through collaboration. To understand the physiological roles of ascorbate in different plant species we will investigate the phenotypic consequences of a series of GGP mutants with mis-regulated ascorbate levels, and determine whether similar or different phenotypic effects are observed in Arabidopsis.

抗坏血酸是所有植物的关键代谢物，从真核藻类到被子植物。它是最丰富的水溶性抗氧化剂，在光合作用、跨膜电子传递、细胞分裂、生长和对生物和非生物胁迫的耐受中起重要作用。它作为光合作用副产物活性氧的主要清除者，在水循环中耗散多余的光子能量，并作为叶黄素循环的辅助因子，发挥着这些不同的作用。它是双加氧酶的辅助因子，双加氧酶在植物激素、乙烯、脱落酸和赤霉素的合成以及羟脯氨酸的生成中具有活性，对修饰CLAVATA3和阿拉伯半乳糖蛋白（AGPs）等小信号肽具有重要作用，这些小信号肽是普遍存在的细胞表面蛋白聚糖，在植物的生长发育过程中起着重要作用，包括细胞扩增、细胞分裂、生殖发育和体细胞胚胎发生。因此，抗坏血酸水平的调节是所有植物生长发育过程中大量生理过程的关键。有大量的文献描述了影响抗坏血酸水平的过程，但很少有论文描述了调节机制，特别是在分子水平上。不用说，这种对机制的缺乏理解限制了我们通过生物技术或植物育种来设计依赖于抗坏血酸的过程的能力。这种限制甚至延伸到提高新鲜水果和蔬菜中抗坏血酸水平的努力，尽管最近有令人震惊的报告称，由于缺乏抗坏血酸/维生素C而导致的坏血病发病率增加。例如，在2009年至2014年间，英国因坏血病住院的人数上升了27%，原因是营养不良和过度食用垃圾食品导致的肥胖。这一切都因两篇具有里程碑意义的论文的发表而改变，一篇由Laing等人于2015年发表在《植物细胞》上，展示了一种独特的负反馈调节机制，控制着gdp - l -半乳糖磷酸化酶（GGP）的翻译，GGP是一种在smiroff - wheeler途径中活性的酶，用于抗坏血酸合成，另一篇由Fenech等人发表。植物生理学（2021）的研究表明，GGP活性是决定植物组织中抗坏血酸水平的唯一重要控制步骤，并显示通过Smirnoff-Wheeler途径几乎线性控制通量。该应用的目的是整合我们对植物细胞中抗坏血酸调节的理解。我们的目标是明确GGP翻译负反馈调控的分子机制，并了解GGP的翻译控制是如何在转录控制定义的范围内设置的。我们建议了解GGP活性的控制如何影响抗坏血酸通量。我们建议通过对拟南芥和番茄两种植物的研究来整合我们对调控机制的研究，以建立对植物机制的一般理解，这些机制可能广泛适用于植物。我们建议通过合作将我们对GGP负反馈调控机制的理解扩展到绿藻。为了了解抗坏血酸在不同植物物种中的生理作用，我们将研究一系列抗坏血酸水平失调的GGP突变体的表型后果，并确定在拟南芥中是否观察到类似或不同的表型效应。