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

标题：优化蓝藻中光合作用装置的驯化反应：从生态生理学到生物物理学模型蓝藻已被广泛研究，以了解光合作用的许多细节。然而，这些生物对光和营养物质的生理反应比许多更复杂的蓝藻表现出更有限的生理反应，后者通常被认为更难研究。这一项目背后的理念是“让自然成为指南”，在有压力的现场环境中研究光合作用，并通过使用实验室模型生物体、遗传学、生物化学和生物物理学来理解那些通过机械方式确定的光合作用过程。通过更多地了解蓝藻的适应和驯化，应该有可能开发出提高作物光合作用效率的策略。最近发现的一些蓝藻利用远红光进行氧合光合作用的能力，引发了人们对这些蓝藻如何能够扩大对到达地球表面的太阳光谱的使用的疑问。该项目将使用为非模型蓝藻开发的基因系统，这些系统表现出不同的适应和驯化反应。遗传学方法以及生理、生化和生物物理方法将被用来研究这些生物的光合作用装置。这项提议提供了一个独特的机会，可以扩展有关“真实世界”光合作用的知识，并可能为智能设计符合人类需求的光合作用有机体提供新的见解，包括扩大农作物的光能利用能力。该项目将为代表不足的少数群体提供STEM研究和教育方面的培训。开发的用于课堂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。该项目的前提是陆地蓝藻已经进化出新的适应和驯化反应，以优化在强过滤(例如，远红光)、可变的氧化还原状态和高能量固氮需求的环境中的光收集和能量捕获。许多蓝藻有一个由17个基因组成的簇，编码光系统I(PSI)、PSII和藻胆体的核心亚基。结合叶绿素(Chls)f和d的合成，这些基因的产物产生一种适应反应，允许在远红光(700至800 nm)中生长，这一过程被称为FaRLiP。本项目将利用在绿球藻PCC9212中开发的遗传系统来分析FaRLiP和其他假定的驯化和适应反应，通过确定不同基因及其变体在PSI驯化反应中的作用以及它们在缺氧、固氮条件下的作用。该项目还将描述PSI和PSII复合体中的能量转移和捕获动力学，并通过执行遗传分析和操作、生化分析、质谱学/蛋白质组学、定点突变、生物物理方法(EPR光谱、时间分辨光学光谱)来研究来自经历FaRLiP和其他适应/驯化反应的细胞的长波吸收藻胆蛋白。该项目得到了生物科学局分子和细胞生物科学司分子生物物理组的支持。

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.