Engineering C3 Plants with Carbon Concentrating Mechanisms for Enhanced Photosynthesis

在许多作物中，限制光合作用效率的一个主要因素是氧气诱导的对Rubisco酶固定二氧化碳的抑制，这是被称为光呼吸的过程的第一步。光呼吸导致二氧化碳的释放，而不是固定。总体而言，光呼吸使光合作用效率降低多达30%。到目前为止，设计减少光呼吸的尝试基本上是不成功的。包括蓝藻、真核微藻和C4植物在内的几类生物已经进化出机制，将二氧化碳集中在Rubisco的活性部位附近，从而减少光呼吸。基于对藻类中碳浓缩机制的生物化学和细胞生物学研究所获得的知识，该项目将对C3模式植物拟南芥进行工程改造，使其在Rubisco活性部位附近浓缩二氧化碳，从而有利于二氧化碳的固定。该项目还将在生物化学和系统层面上量化植物生产力的预期变化(叶片的同位素标记和代谢通量分析)。研究策略包括：1)通过在拟南芥叶片中过表达碳酸氢盐转运蛋白和其他无机碳代谢酶来增强光合碳固定；2)建立叶片同位素标记和通量分析方法来量化野生型和突变型叶片的光合代谢和呼吸作用。通量分析的结果将被用于识别代谢瓶颈，评估整体二氧化碳新陈代谢，并建立一个平台，以支持进一步的代谢工程战略，以提高整体光合作用效率。这项研究的范围是高度跨学科的。因此，预计该项目将吸引来自不同背景和教育背景的个人的兴趣。这项工作将涉及本科生、中级理科学生、教师和科学家。为教师和本科生提供暑期实习，为教师提供专业发展研讨会，以及由学生和科学家合作伙伴参与的在线指导计划(EScience)，将导致对科学的更大欣赏和理解，并强调研究与食品生产和绿色能源的相关性，这些都是日常生活的一部分。转基因品系和分子工具，以及通量分析和计算方法，将增加有关叶片光合作用代谢和工程的越来越多的信息。结果将通过传统的期刊和会议传播，制作的软件和同位素数据将通过网络公开提供，作为研究和教学的宝贵资源。从社会背景来看，植物生物量的增加有助于满足日益增长的营养和化学原料需求，而不依赖于以石油为基础的方法。

A major factor limiting photosynthetic efficiency in many crop plants is oxygen-induced inhibition of CO2 fixation by the enzyme RuBisCO, a first step in a process known as photorespiration. Photorespiration leads to CO2 release rather than fixation. Overall, photorespiration reduces the efficiency of photosynthesis by as much as 30%. To date, attempts to engineer reduced photorespiration have largely been unsuccessful. Several groups of organisms including, cyanobacteria, eukaryotic microalgae, and C4 plants have evolved mechanisms to concentrate CO2 near the active site of RuBisCO, reducing photorespiration. Based on knowledge gained from investigations on the biochemistry and cell biology of carbon concentrating mechanisms in algae, this project will engineer the C3 model plant, Arabidopsis thaliana, to concentrate CO2 near the active site of RuBisCO so as to favor CO2 fixation. The project will additionally quantify the expected changes in plant productivity at the biochemical and systems levels (isotopic labeling and metabolic flux analysis of leaves). The research strategies include: 1) enhancing photosynthetic carbon fixation by engineering the overexpression of bicarbonate transporters and other inorganic carbon metabolizing enzymes in leaves of Arabidopsis thaliana, and 2) developing leaf isotopic labeling and flux analysis methods to quantify photosynthetic metabolism and respiration in wild-type and mutant leaves. Results from flux analyses will be used to identify metabolic bottlenecks, assess the overall CO2 metabolism, and establish a platform to enable further metabolic engineering strategies for improving overall photosynthetic efficiency.Broader Impacts. The scope of the research is highly interdisciplinary. Therefore, it is anticipated that the project will attract the interest of individuals from diverse backgrounds and education. The work will involve undergraduates, secondary science students, teachers, and scientists. The offering of summer internships to teachers and undergraduates, as well as professional development workshops for teachers, and an on-line mentoring program (eScience) involving student and scientist partners will result in a greater appreciation and understanding of science and stress the relevance of the research to food production and green energy that are aspects of everyday life. The transgenic lines and molecular tools, along with flux analyses and computational methods, will add to the growing body of information on leaf photosynthetic metabolism and engineering. Results will be disseminated through traditional journals and meetings, and the software and isotope data produced will be publicly available via the Web to serve as a valuable resource for research and teaching. From a societal context, increases in plant biomass serve to meet growing nutritional and chemical feedstock needs without a reliance on petroleum-based approaches.