RUI: Photosynthetic Response to Abiotic Stress in Prochlorococcus, A Globally Important Marine Cyanobacterium

地球上大约一半的光合作用发生在海洋中。原氯球藻属的蓝藻是最丰富的海洋光合原核生物之一，在开放的海洋水域中贡献了相当大的初级生产量，在全球碳循环和能量循环中发挥着关键作用。最近对几个原氯球菌和密切相关的海洋聚球藻菌株的全基因组测序显示，在海洋环境中存在的选择压力下，原氯球菌谱系内进化出了显着的基因组差异。值得注意的是，最近进化的原氯球菌MED4菌株拥有所有含氧光生生物中最小的基因组，并且缺少几个编码关键光合作用装置和胁迫反应相关蛋白的基因。该项目的总体目标是确定在特定环境条件下，属于较新进化的高光适应支系的原氯球菌和属于低光适应支系的原氯球菌之间的基因组水平差异如何转化为光合作用能力的选择性优势。虽然光和温度是限制原氯球菌全球分布的两个关键因素，但这些因素如何改变原氯球菌的光合作用过程尚不清楚。最先进的技术将被用来表征温度和光胁迫引起的原氯球菌变化的分子机制(1)光合作用能力(2)光合膜和脂组成，以及(3)关键的光合作用装置多肽。这个项目将促进我们对地球上最丰富和最重要的初级生产者之一的光合作用的基本理解。因此，它将有助于努力提高我们准确模拟海洋生态系统初级生产力的能力。这项研究也将有助于我们对光合作用装置的结构、功能和进化的基本了解。更广泛的影响：在调查过程中，许多本科生将参与这项研究，该项目将成为一种有效的教育工具。通过他们的参与，学生们将接触到令人兴奋的研究领域的最先进技术，并将有机会参加国家科学会议。与这个项目相关的想法和技术也将直接丰富课程内容，从而使更多的本科生了解科学研究的重要性。此外，项目参与者将继续参与正在进行的外展计划，并将让农村公立学校的学生参与主流科学研究。这将有助于促进旨在鼓励学生从事中学后科学事业的当地努力，并提高社会的科学意识。

Approximately one-half of the photosynthesis on Earth occurs in the oceans. Cyanobacteria of the genus Prochlorococcus are among the most abundant marine photosynthetic prokaryotes, contributing a significant fraction of the primary production in open ocean waters and playing a key role in global carbon and energy cycles. Recent sequencing of the complete genomes of several Prochlorococcus and closely related marine Synechococcus strains has revealed that striking genomic differences have evolved within the Prochlorococcus lineage in response to selection pressures present in the ocean environment. Notably, the more recently evolved Prochlorococcus MED4 strain possesses the smallest genome of any oxygenic phototroph and is missing several genes encoding key photosynthetic apparatus and stress response-related proteins. The overarching goal of this project is to establish how genome level differences between Prochlorococcus belonging to the more recently evolved, high light-adapted clade and Prochlorococcus belonging to the low light-adapted clade translate into selective advantages in photosynthetic capacity under specific environmental conditions. Although light and temperature are two critical factors limiting the global distribution of Prochlorococcus, it is unknown how these factors alter photosynthetic processes in Prochlorococcus. State-of-the-art techniques will be used in characterizing the molecular mechanisms underlying temperature and light stress-induced changes in Prochlorococcus (1) photosynthetic capacity (2) photosynthetic membrane and lipid composition, and (3) key photosynthetic apparatus polypeptides. This project will advance our fundamental understanding of photosynthesis in one of the most abundant and ecologically important primary producers on this planet. As a result, it will contribute to efforts aimed at improving our ability to model accurately primary production in ocean ecosystems. This research will also contribute to our basic understanding of the structure, function, and evolution of the photosynthetic apparatus. Broader Impacts: Numerous undergraduate students will participate in this research over the course of the investigation and this project will serve as an effective educational tool. Through their involvement, students will be exposed to state-of-the-art technology in an exciting field of study and will have the opportunity to participate in national scientific meetings. The ideas and techniques associated with this project will also directly enrich course offerings, and will thus expose a larger group of undergraduates to the importance of scientific research. Moreover, the project participants will continue to participate in ongoing outreach programs and will engage students from rural public schools in mainstream scientific research. This will contribute to local efforts aimed at encouraging students to pursue postsecondary science careers and raising the community's scientific awareness.