Alternative Oxidase of Plant Mitochondria

植物线粒体的替代氧化酶

• 批准号: RGPIN-2014-06553
• 负责人: Vanlerberghe, Greg
• 金额: $ 2.91万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=667609
• 关键词: Alternative; Oxidase; Plant; Mitochondria

Alternative oxidase (AOX) is a non-energy conserving terminal oxidase in the plant mitochondrial electron transport chain that relaxes the coupling between respiratory carbon oxidation, electron transport, and ATP turnover. Despite key advances in our understanding of the genetic and biochemical control of AOX, the role of this auxiliary respiratory pathway in plant metabolism and mitochondrial physiology, as well as its overall impact on plant growth and performance remains poorly understood. As often highlighted in influential reviews, this represents a major gap in our understanding of plant primary metabolism. AOX gene expression is highly responsive to environmental cues and some evidence indicates that the pathway may be of particular importance under variable and stress conditions. Theoretically, AOX should negatively impact growth since it reduces ATP yield. However, it may have key roles in metabolism and mitochondrial physiology that outweigh this energy cost. **My research proposal has two broad scientific goals. The first is to establish the role of AOX in supporting leaf metabolism. An emphasis will be to elucidate the mechanisms by which AOX supports photosynthesis. Our preliminary work shows that during drought stress, photosynthesis is strongly compromised in transgenic plants lacking AOX. Gas exchange and chlorophyll fluorescence analyses indicate that this is the result of a severe biochemical (rather than stomatal) limitation in plants lacking AOX. Detailed physiological and biochemical analyses will elucidate the nature of this limitation. We will also investigate the interaction of AOX and photosynthesis in plants grown at ambient versus high CO2. High CO2 has the potential to increase photosynthetic rate but can result instead in a down-regulation of photosynthetic capacity, such that the potential for higher source activity is not met. The propensity for such down-regulation depends strongly upon the response of sinks to high CO2. While respiration is a critical sink activity, little is known regarding specifically AOX at high CO2. This is a major gap in our understanding of how photosynthesis and growth will be impacted by future high CO2 conditions.* *A second broad scientific goal of the research proposal is to establish the role of AOX in supporting mitochondrial physiology. An emphasis will be elucidating the role of AOX in supporting the signaling function of mitochondria. Mitochondria act as signaling organelles involved in stress acclimation, but the primary "signals" from mitochondria that are involved in such responses are unknown. Our proposal builds upon a major finding from our previous work, where biochemical and confocal imaging analyses established that AOX controls the ETC generation of superoxide and nitric oxide, reactive species that can act as damaging molecules or signaling molecules within the cell. These reactive species, along with downstream products (hydrogen peroxide, peroxynitrite) are lead candidates as signal molecules for stress acclimation. Our ability to manipulate the level of these molecules using plants with altered AOX amount provides a powerful strategy to test hypotheses regarding the signaling capability of specific reactive oxygen and nitrogen species emanating from a specific cell compartment, the mitochondrion. We will investigate this signaling capability in support of stress acclimation responses at both the molecular level (ie. changes in nuclear gene expression) and cell level (ie. guard cell movements). **Another important overall goal of the research proposal is the mentorship and training of three postdoctoral fellows, eight graduate students and numerous undergraduates. This will include a fostering of independence and multidisciplinary work.

替代性氧化酶（AOX）是植物线粒体电子传输链中的一种非能量保存末端氧化酶，可放松呼吸碳氧化，电子传输和ATP周转之间的耦合。尽管我们对AOX的遗传和生化控制的理解取得了重要成长，但这种辅助呼吸道途径在植物代谢和线粒体生理学中的作用，以及其对植物生长和性能的总体影响仍然很众所周知。正如在有影响力的评论中经常强调的那样，这代表了我们对植物主要代谢的理解的主要差距。 AOX基因表达对环境线索的反应很高，一些证据表明该途径在可变和应力条件下可能特别重要。从理论上讲，AOX应该对生长产生负面影响，因为它会降低ATP产量。但是，它可能在代谢和线粒体生理学中具有关键作用，使能量成本超过了。 **我的研究建议有两个广泛的科学目标。首先是确定AOX在支持叶片代谢中的作用。重点是阐明AOX支持光合作用的机制。我们的初步工作表明，在干旱压力中，光合作用在缺乏AOX的转基因植物中受到严重损害。气体交换和叶绿素荧光分析表明，这是缺乏AOX的植物中严重的生化（而不是气孔）限制的结果。详细的生理和生化分析将阐明这种限制的性质。我们还将研究在环境与高二氧化碳生长的植物中AOX和光合作用的相互作用。高二氧化碳具有提高光合速率的潜力，但可能导致光合作用能力下调，因此无法满足更高源活性的潜力。这种下调的倾向在很大程度上取决于水槽对高二氧化碳的响应。尽管呼吸是一种关键的下沉活性，但在高二氧化碳处的AOX方面鲜为人知。这是我们了解光合作用和增长将如何受到未来高二氧化碳条件影响的主要差距。 * *研究建议的第二个广泛的科学目标是确定AOX在支持线粒体生理学方面的作用。重点将是阐明AOX在支持线粒体信号传导功能中的作用。线粒体作为参与压力适应的信号细胞器的作用，但是从线粒体中涉及的主要“信号”是未知的。我们的建议基于我们以前的工作的重大发现，在该研究中，生化和共聚焦成像分析表明，AOX控制了超氧化物和一氧化氮的ETC生成，反应性物种可以充当细胞内的有害分子或信号分子。 这些反应性物种以及下游产物（过氧化氢，过氧亚硝酸盐）是铅候选物，作为用于应激适应的信号分子。我们使用具有变化AOX量的植物来操纵这些分子水平的能力为测试假设的特定活性氧和氮物质的信号传导能力测试假设，从而从特定的细胞室散发出线粒体，即线粒体。我们将研究这种信号传导能力，以支持分子水平（即核基因表达的变化）和细胞水平（即后卫细胞运动）的压力适应反应。 **研究建议的另一个重要总体目标是对三名博士后研究员，八名研究生和众多大学生进行指导和培训。这将包括促进独立性和多学科工作。