Acclimation Responses that Optimize the Photosynthetic Apparatus in Cyanobacteria: from Ecophysiology to Biophysics

职务名称：蓝细菌光合机构优化的适应反应：从生理生态学到生物生态学模式蓝细菌已被广泛研究，以了解光合作用的许多细节。然而，这些生物体对光和营养物质的生理反应比许多更复杂的蓝藻更有限，这通常被认为是更难以研究。这个项目背后的概念是“让自然成为向导”，以研究光合作用在紧张的设置在现场，并了解那些光合作用过程中确定机械使用实验室模型生物，遗传学，生物化学和生物物理学。通过了解更多关于蓝藻的适应和驯化，应该有可能制定策略，以提高作物的光合效率。最近发现的一些蓝细菌利用远红光进行光合作用的能力提出了关于这些蓝细菌如何能够扩大其对到达地球表面的太阳光谱的使用的问题。该项目将使用已开发的非模式蓝藻，表现出不同的适应性和驯化反应的遗传系统。遗传学方法，以及生理学，生物化学和生物物理学的方法将被用来研究这些生物的光合机构。这一提议提供了一个独特的机会，以扩大知识的“现实世界”的光合作用，并可能提供新的见解工程光合生物智能为人类的需求，包括扩大作物的光利用能力。该项目将为STEM研究和教育中代表性不足的少数民族提供培训。为教室开发的光生物反应器概念将用于让K-12水平的学生参与STEM教育。 该项目的定义前提是，陆地蓝藻已经进化出新的适应性和驯化反应，以优化在具有强烈过滤的环境中的光捕获和能量捕获（例如，远红）光、可变的氧化还原状态以及固氮的强烈能量需求。许多蓝细菌具有编码光系统I（PSI）、PSII和藻胆体的核心亚基的17个基因簇。结合叶绿素（Chls）f和d的合成，这些基因的产物赋予了一种适应反应，允许在远红光（700至800 nm）下生长，这一过程被称为FaRLiP。本项目将利用在Chlorogloeopsis fritschii PCC 9212中开发的遗传系统，通过确定不同基因及其变体在PSI的驯化反应中的作用以及它们在缺氧、固氮条件下的作用，来剖析FaRLiP和其他假定的驯化和适应反应。该项目还将表征PSI和PSII复合物中的能量转移和捕获动力学，并通过进行遗传分析和操作，生化分析，质谱/蛋白质组学，定点诱变，生物物理方法（EPR光谱，时间分辨光谱）研究来自经历FaRLiP和其他适应/驯化反应的细胞的长波长吸收藻胆蛋白。该项目得到了生物科学理事会分子和细胞生物科学司分子生物物理学小组的支持。

Title: Acclimation responses that optimize the photosynthetic apparatus in cyanobacteria: from ecophysiology to biophysicsModel cyanobacteria have been extensively studied to learn many details of photosynthesis. However, these organisms exhibit more limited physiological responses to light and nutrients than many more complex cyanobacteria, which are often considered to be more difficult to study. The concept behind this project is "to let nature be the guide" to study photosynthesis in stressful settings in situ and to understand those photosynthetic processes identified mechanistically by using laboratory model organisms, genetics, biochemistry and biophysics. By learning more about adaptation and acclimation in cyanobacteria, it should be possible to develop strategies to improve photosynthetic efficiency in crop plants. The recently discovered capacity of some cyanobacteria to use far-red light for oxygenic photosynthesis raises questions about how those cyanobacteria are able to expand their usage of the solar spectrum reaching Earth's surface. This project will use genetic systems that have been developed for non-model cyanobacteria that exhibit diverse adaptive and acclimation responses. Genetic methods, together with physiological, biochemical and biophysical approaches will be used to study the photosynthetic apparatus in these organisms. This proposal offers a unique opportunity to expand knowledge of 'real-world' photosynthesis and is likely to provide new insights for engineering photosynthetic organisms intelligently for human needs, including expanding the light-use capabilities of crop plants. This project will provide training for underrepresented minorities in STEM research and education. The developed photobioreactor concept for the classroom will be used to involve K-12 level students in STEM education. The defining premise of this project is that terrestrial cyanobacteria have evolved novel adaptive and acclimation responses to optimize light harvesting and energy trapping in environments with strongly filtered (e.g., far-red) light, variable redox states, and the intensive energetic demands of nitrogen fixation. Many cyanobacteria have a cluster of 17 genes encoding core subunits of Photosystem I (PSI), PSII, and phycobilisomes. Combined with the synthesis of chlorophylls (Chls) f and d, the products of these genes confer an acclimation response that permits growth in far-red light (700 to 800 nm), a process known as FaRLiP. This project will use the genetic system developed in Chlorogloeopsis fritschii PCC 9212 to dissect FaRLiP and other postulated acclimation and adaptive responses by determining role of different genes and their variants in acclimation responses of PSI and their roles under anoxic, nitrogen-fixing conditions. This project will also characterize the energy transfer and trapping kinetics in PSI and PSII complexes and study long-wavelength-absorbing phycobiliproteins from cells undergoing FaRLiP and other adaptation/acclimation responses by performing genetic analyses and manipulations, biochemical analyses, mass spectrometry/proteomics, site-specific mutagenesis, biophysical methods (EPR spectroscopy, time-resolved optical spectroscopy). This project is supported by the Molecular Biophysics Cluster of the Molecular and Cellular Biosciences Division in the Directorate for Biological Sciences.