Collaborative Research: Multiple Approaches to Gain Increased Capture of Carbon Dioxide

21世纪最重要的挑战之一是确保世界70多亿人口的粮食安全。植物利用光合作用的过程来利用阳光的能量，将二氧化碳转化为食物和纤维，帮助世界人口提供食物和衣服。负责这一过程的酶(Rubisco)将二氧化碳合并到糖中，但它也将氧气合并到无法被植物利用的产品(乙醇酸)中，因此必须被分解和回收；据估计，植物捕获的来自太阳的光能有多达30%因此被浪费。二氧化碳和氧气竞争Rubisco酶上的结合部位，因此提高植物生产力的一种方法是提高植物细胞中二氧化碳相对于氧气的浓度。在这个由来自美国和英国的研究团队参与的合作研究项目中，这一目标将通过设计一个由阳光驱动的生物泵来实现，该泵将把大气中的二氧化碳输送到植物细胞中，浓缩并储存在那里用于光合作用。这个项目涉及一个由植物生物学家、生物化学家、生物物理学家、蛋白质设计师、化学工程师和数学模型师组成的大型跨学科团队。该项目将为本科生、研究生和博士后研究人员提供教育和培训机会，他们都在高度合作的国际科学背景下工作。此外，还包括面向公众的出版物、公众演讲和网站。增加光合作用中可用于固定的二氧化碳的数量将通过一个光驱动的碳酸氢泵和一个保持二氧化碳的支架来实现，直到它可以被核酮糖二磷酸羧化酶/加氧酶(Rubisco)固定。这将通过向叶绿体和蓝藻中引入蛋白质卤视紫质和AE1来实现光驱动的重碳酸盐净运输，卤视紫质利用光来泵送氯离子，AE1是氯/重碳酸盐的交换器。在一个平行的策略中，卤视紫红质将被修改为直接运输碳酸氢盐，以及利用可见光光谱以外的光。碳酸酐酶在叶绿体中释放的二氧化碳需要保留足够长的时间才能与Rubisco反应。为了实现这一点，将设计用于将二氧化碳输送到Rubisco的分子支架，包括二氧化碳海绵和工程设计的反向C4途径。数学建模将在运输和脚手架工作中将理论与实验联系起来。使用光驱碳酸氢泵和二氧化碳支架/海绵的方法有可能将叶绿体内二氧化碳的分压提高高达60%，从而大幅增加由Rubisco固定的二氧化碳与氧气的比率。对植物的结果应该是在实验室和田间显著提高光合作用生产率。该奖项由分子和细胞生物科学部门的细胞动力学和功能集群以及化学、生物工程、环境和运输系统部门的生物技术、生化和生物质工程计划共同支持。

One of the foremost challenges of the 21st century is to ensure food security for the world's population of over 7 billion people. Plants use the process of photosynthesis to harness the energy of sunlight to convert carbon dioxide into food and fiber that helps feed and clothe the world's population. The enzyme responsible for this process (RuBisCO) incorporates carbon dioxide into sugars, but it also incorporates oxygen into a product (glycolate) that cannot be used by the plant and therefore must be broken down and recycled; it is estimated that up to 30% of the light energy from the sun that is captured by a plant is thereby wasted. Carbon dioxide and oxygen compete for the binding site on the enzyme RuBisCO thus one way to increase plant productivity would be to raise the concentration of carbon dioxide relative to that of oxygen in the plant cell. In this collaborative research program engaging teams of researchers from the US and the United Kingdom, this goal will be addressed by engineering a biological pump, driven by sunlight, that will transport atmospheric carbon dioxide into the plant cell, concentrating and storing it there for use in photosynthesis. This project engages a large interdisciplinary team of plant biologists, biochemists, biophysicists, protein designers, chemical engineers, and mathematical modelers. This project will provide educational and training opportunities for undergraduate students, graduate students and postdoctoral researchers, all working in a highly cooperative, international scientific context. There are also provisions for public outreach, including publications, public talks, and websites geared toward the general public.Increasing the amount of carbon dioxide available for fixation in photosynthesis will be achieved with a light-driven bicarbonate pump and a scaffold to retain the carbon dioxide until it can be fixed by ribulosebisphosphate carboxylase/oxygenase (RuBisCo). This will be accomplished by introducing into chloroplasts and cyanobacteria the proteins halorhodopsin which uses light to pump chloride ions, and AE1, a chloride/bicarbonate exchanger, to achieve net light-driven bicarbonate transport. In a parallel strategy, halorhodopsin will be modified to transport bicarbonate directly as well as to utilize light outside the visible spectrum. The carbon dioxide released in the chloroplast by carbonic anhydrase needs to be retained long enough to react with RuBisCO. To accomplish this, molecular scaffolds will be designed for the delivery of carbon dioxide to RuBisCO, including a carbon dioxide sponge and an engineered reverse C4 pathway. Mathematical modeling will link theory with experiment in both the transport and scaffolding efforts. The approach of using a light-driven bicarbonate pump and a carbon dioxide scaffold/sponge has the potential to raise the partial pressure of carbon dioxide by up to 60% inside the chloroplast, thereby allowing a large increase in the ratio of carbon dioxide to oxygen fixed by RuBisCO. The consequence to the plant should be a significantly higher photosynthetic productivity in the laboratory as well as in the field.This award is supported jointly by the Cellular Dynamics and Function Cluster in the Division of Molecular and Cellular Biosciences and by the Biotechnology, Biochemical and Biomass Engineering Program in the Division of Chemical, Bioengineering, Environmental and Transport Systems.