Collaborative Research: Improving plant productivity and models of carbon exchange by resolving mechanisms of excess carbon release in photorespiration

在光合作用过程中，植物利用来自阳光的能量将大气中的二氧化碳转化为生物质。这些生物质包括人类和地球上其他生命所需的食物、纤维和燃料。在这种转化过程中，光合作用的初始步骤可以与大气中的氧气而不是二氧化碳反应，从而产生必须回收的化合物。这种循环过程称为光呼吸，需要植物能量储备的很大比例，并释放二氧化碳，从而降低植物生长和生产力。光呼吸受环境条件的影响，随着温度的升高，相对于光合作用而增加。该研究项目探讨了光呼吸的温度响应，以确定它在未来气候下的反应，并寻求提高其效率的策略。这项建议的结果将纳入教育活动并广泛传播。不同的学生将通过与一个为代表性不足的学生服务的主要本科院校进行研究合作。此外，这项工作在提高作物产量方面的潜力以及模型在植物生物学中的重要性将通过持续的科学之声表演传播。科学之声是一个独特的合作，作曲家根据植物科学家提供的研究数据创作音乐。研究人员将与当地公共媒体合作录制研究概述和合成物的演示文稿，并有可能达到约500，000密歇根州居民的公众观众。光呼吸是受照叶片中第二大碳代谢通量，当碳固定的初始酶rubisco，与氧气而不是二氧化碳结合并产生必须回收的分子。光呼吸作用以大量碳为代价将该分子转化为卡尔文-本森循环中间体。了解光呼吸过程中二氧化碳释放的机制对于预测植物对气候变化的反应和潜在的工程植物具有改善的碳同化和生产力至关重要。当温度升高时，光呼吸释放更多的二氧化碳，但这种增加的机制是未知的。该提案的目的是解决这种过量的二氧化碳释放在高温下使用代谢建模，体内气体交换和同位素标记方法的创新组合的机制。该提议的中心假设是，当过氧化物酶体中的中间体与光呼吸产生的过氧化氢发生非酶促反应时，在升高的温度下光呼吸释放过量的二氧化碳。该假设假定在环境温度下过氧化氢被过氧化氢酶有效地解毒，但是在升高的温度下过氧化氢酶不能足够快地去除过氧化氢以使非酶促脱羧反应最小化。该项目的成果将跨越学科界限，具有改善地球系统碳循环模型的强大潜力，并确定使光合作用适应现实世界生长条件的关键特征。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

During photosynthesis, plants use energy from sunlight to convert carbon dioxide from the atmosphere into biomass. This biomass includes the food, fiber and fuel required by humans and other life on this planet. During this conversion, the initial step of photosynthesis can react with atmospheric oxygen instead of carbon dioxide, which produces compounds that must be recycled. This recycling process, called photorespiration, requires large percentages of the plant’s energy reserves and releases carbon dioxide, thereby reducing plant growth and productivity. Photorespiration is affected by environmental conditions, increasing relative to photosynthesis as temperature rises. This research project explores the temperature response of photorespiration to determine how it will respond under future climates and seeking strategies to improve its efficiency. Findings from this proposal will be integrated into education activities and disseminated widely. Diverse students will be engaged via a research collaboration with a primary undergraduate institution serving under-represented students. Additionally, the potential for this work to improve crop productivity and the importance of models in plant biology will be disseminated by continuing Sounds of Science performances. The Sounds of Science is a unique collaboration where composers create music from research data provided by a plant scientist. Presentations where the investigators present an overview of the research and the compositions are performed will be recorded in partnership with local public media and have the potential to reach a public audience of ~500,000 Michigan residents.Photorespiration is the second largest metabolic flux of carbon in an illuminated leaf and occurs when rubisco, the initial enzyme of carbon fixation, binds with oxygen instead of carbon dioxide and produces a molecule that must be recycled. Photorespiration recycles this molecule into Calvin-Benson cycle intermediates at the great cost of carbon. Understanding the mechanisms of carbon dioxide release during photorespiration is critical for predicting plant responses to climate change and potentially engineering plants with improved carbon assimilation and productivity. When temperature increases, photorespiration releases even more carbon dioxide per rubisco oxygenation, but the mechanism of this increase is unknown. The objective of this proposal is to resolve the mechanisms of this excess carbon dioxide release at high temperatures using an innovative combination of metabolic modeling, in vivo gas exchange, and isotopic labeling approaches. The central hypothesis of this proposal is that excess carbon dioxide release occurs from photorespiration at elevated temperatures when intermediates react non-enzymatically in the peroxisome with hydrogen peroxide produced from photorespiration. This hypothesis assumes that under ambient temperatures hydrogen peroxide is efficiently detoxified by the enzyme catalase, but under elevated temperatures catalase is unable to remove hydrogen peroxide quickly enough to minimize non-enzymatic decarboxylation reactions. The results of this project will reach across disciplinary boundaries with the strong potential to improve earth-system models of carbon cycling and to identify key traits for adapting photosynthesis to real-world growing conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.