Acclimation of leaves to long-term changes in temperature: does it alter the efficiency of respiratory energy production?

在未来变暖的世界中，温度介导的植物呼吸变化对于确定大气中二氧化碳被生物圈吸收的程度至关重要。这是因为，在全球范围内，植物呼吸释放的二氧化碳（导致全球变暖的温室气体之一）几乎是燃烧化石燃料等的十倍。在单个植物的水平上，植物的呼吸作用向大气中释放了25-80%之前由光合作用固定的二氧化碳。然而，这种二氧化碳的释放并不完全是浪费，因为与呼吸二氧化碳的释放相结合的是植物生长和生存所必需的能量的产生。决定呼吸能量产生效率（即每单位二氧化碳释放产生的能量量）的关键是，线粒体中的呼吸是通过细胞色素氧化酶（Cox）途径产生能量还是通过能量浪费、替代氧化酶（Aox）途径发生的。了解环境变化如何影响完整组织中这两种途径的活性，对于确定呼吸CO2释放的气候依赖性变化是否与ATP产生的变化相耦合至关重要。如果ATP合成的效率确实随气候而变化，这可能对植物在自然环境中生长的生长速度和竞争能力产生深远的影响。在这个项目中，我们将确定温度的变化是否会改变完整叶片中Cox与Aox活性的比例。虽然我们知道Aox和Cox通路都对温度敏感，但我们对温度的短期和长期变化对完整叶片中Aox和Cox通路活性的影响的理解仍然有限。了解Aox和Cox途径活性随温度变化的程度对于预测气候依赖性变化、呼吸二氧化碳释放与植物生长/生存所需的呼吸能产生变化的耦合程度至关重要。我们将在实验中使用耐寒植物（拟南芥），因为我们知道这个物种能够在广泛的生长温度挑战下调节呼吸速率。拟南芥的使用还将使完整组织中呼吸速率的研究与基因表达和蛋白质合成的研究联系起来。该项目将由约克大学和澳大利亚研究委员会植物能源生物学卓越中心（CoE）合作开展；CoE拥有世界上为数不多的能够测量完整叶片中Aox和Cox途径速率的质谱仪系统之一。鉴于CoE将涵盖所有植物生长/消耗品成本，因此该提案对NERC来说是物超所值的，并且有机会实现在英国不可能实现的结果。

Temperature-mediated changes in plant respiration will be critical in determining the extent to which atmospheric carbon dioxide will be sequestered by the biosphere in a future, warmer world. This is because, on a global scale, plant respiration releases nearly ten times more carbon dioxide (one of the greenhouse gases responsible for global warming) than does the burning of fossil fuels etc. At the individual plant level, plant respiration releases into the atmosphere between 25-80% of the carbon dioxide previously fixed by photosynthesis. This release of carbon dioxide is not all wasteful, however, as coupled to the release of respiratory carbon dioxide is the production of energy necessary for the growth and survival of plants. Critical in determining the efficiency of respiratory energy production (i.e. the amount of energy produced per unit carbon dioxide released) is whether respiration in the mitochondria take place via the energy-producing how cytochrome oxidase (Cox) pathway or the energy-wasting, alternative oxidase (Aox) pathway. Understanding how environmental change impacts on the activity of these two pathways in intact tissues is critical to ascertaining whether climate-dependent alterations in respiratory CO2 release are coupled to changes in the production of ATP. If the efficiency of ATP synthesis does vary with climate, this could have profound implications for the growth rate and competitive ability of plants growing in natural environments. In this project, we will establish whether changes in temperature alter the ratio of Cox to Aox activity in intact leaves. Although we know that both the Aox and Cox pathways are temperature-sensitive, our understanding of how short- and long-term changes in temperature impact on activity of the Aox and Cox pathways in intact leaves remains limited. Understanding the extent to which Aox and Cox pathway activity vary with temperature is essential if we are predict the extent to which climate-dependent changes respiratory carbon dioxide release are coupled to changes in the production of respiratory energy necessary for plant growth/survival. We will use a cold-tolerant forb (Arabibopsis thaliana) in our experiments, as we know that this species is capable of adjusting respiration rates when challenged with a wide range of growth temperatures. Use of Arabidopsis will also enable studies of respiration rates in intact tissues to be linked to studies of gene-expression and protein synthesis. The project will be a collaboration between the University of York and the Australian Research Council Centre of Excellence (CoE) in Plant Energy Biology; the CoE has one of a few mass spectrometer systems in the world capable of measuring rates of Aox and Cox pathway in intact leaves. Given that the CoE will cover all plant growth/consumable costs, the proposal therefore represents excellent value for money for NERC and an opportunity to achieve an outcome that is not possible within the UK.