Engineering C3 Plants with Carbon Concentrating Mechanisms for Enhanced Photosynthesis

限制许多作物光合作用效率的一个主要因素是氧诱导的RuBisCO酶对CO2固定的抑制，这是光呼吸过程的第一步。 光呼吸导致CO2释放而不是固定。总的来说，光呼吸使光合作用的效率降低了30%。迄今为止，试图工程减少光呼吸在很大程度上是不成功的。包括蓝藻、真核微藻和C4植物在内的几组生物已经进化出将CO2集中在RuBisCO活性位点附近的机制，从而减少光呼吸。本项目将利用藻类生物化学和细胞生物学研究中获得的知识，对C3模式植物拟南芥进行改造，使其在RuBisCO活性位点附近聚集CO2，从而有利于CO2的固定。该项目还将在生物化学和系统水平上量化植物生产力的预期变化（同位素标记和叶片代谢通量分析）。研究策略包括：1）通过工程化拟南芥叶中碳酸氢盐转运蛋白和其他无机碳代谢酶的过表达来增强光合碳固定，以及2）开发叶同位素标记和通量分析方法以量化野生型和突变体叶中的光合代谢和呼吸。通量分析的结果将用于确定代谢瓶颈，评估整体CO2代谢，并建立一个平台，以实现进一步的代谢工程策略，提高整体光合效率。 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的个人的兴趣。这项工作将涉及本科生、中等理科学生、教师和科学家。为教师和本科生提供暑期实习机会，为教师举办专业发展讲习班，以及一个有学生和科学家伙伴参加的在线辅导方案（eScience），将使学生更好地欣赏和理解科学，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个方面。转基因株系和分子工具，沿着通量分析和计算方法，将增加叶片光合代谢和工程的信息。研究结果将通过传统期刊和会议传播，所产生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。从社会角度来看，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，而无需依赖石油方法。

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.