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

题目：优化蓝藻光合机构的驯化反应：从生态生理学到生物物理学模型蓝藻已经被广泛研究，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更有限，后者通常被认为更难研究。这个项目背后的概念是“让自然成为向导”，在有压力的环境下研究光合作用，并通过实验室模式生物、遗传学、生物化学和生物物理学来理解那些机械地确定的光合作用过程。通过更多地了解蓝藻的适应和驯化，应该有可能制定提高作物光合效率的策略。最近发现的一些蓝细菌利用远红光进行氧光合作用的能力提出了一个问题，即这些蓝细菌如何能够扩大它们对到达地球表面的太阳光谱的利用。该项目将使用遗传系统，已开发的非模式蓝藻，表现出多样化的适应和驯化反应。遗传学的方法，连同生理学、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来扩展“现实世界”光合作用的知识，并可能为满足人类需求的智能工程光合生物提供新的见解，包括扩大作物植物的光利用能力。该项目将为未被充分代表的少数民族提供STEM研究和教育方面的培训。为教室开发的光生物反应器概念将用于让K-12级别的学生参与STEM教育。这个项目的决定性前提是，陆生蓝藻已经进化出了新的适应和驯化反应，以优化在强过滤（如远红光）光、可变氧化还原状态和氮固定的密集能量需求的环境中的光收集和能量捕获。许多蓝藻有一个由17个基因组成的集群，编码光系统I （PSI）、PSII和藻胆异构体的核心亚基。结合叶绿素f和叶绿素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到800纳米）下生长，这一过程被称为FaRLiP。本项目将利用在fritschii Chlorogloeopsis PCC 9212中开发的遗传系统，通过确定不同基因及其变异在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和其他假设的驯化和适应性反应。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、位点特异性诱变、生物物理方法（EPR光谱、时间分辨光学光谱），研究经历FaRLiP和其他适应/驯化反应的细胞中的长波吸收藻脂蛋白。该项目得到了生物科学理事会分子和细胞生物科学部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.