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。原绿球藻属蓝藻是最丰富的海洋光合原核生物之一，在开阔海域的初级生产中占很大比例，在全球碳和能量循环中起着关键作用。最近对几种原绿球藻和密切相关的海洋聚球菌菌株的全基因组测序显示，在原绿球藻谱系中，由于海洋环境中存在的选择压力，进化出了惊人的基因组差异。值得注意的是，最近进化的原绿球藻MED4菌株具有所有氧性光养菌中最小的基因组，并且缺少几个编码关键光合装置和应激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，高光适应进化支系的原绿球藻和低光适应进化支系的原绿球藻之间的基因组水平差异如何转化为光合能力的选择优势。虽然光和温度是限制原绿球藻全球分布的两个关键因素，但这些因素如何改变原绿球藻的光合过程尚不清楚。最先进的技术将用于表征温度和光胁迫诱导原绿球藻(1)光合能力(2)光合膜和脂质组成，以及(3)关键光合器官多肽变化的分子机制。这个项目将推进我们对光合作用的基本理解，光合作用是这个星球上最丰富和生态最重要的初级生产者之一。因此，它将有助于提高我们准确模拟海洋生态系统初级生产的能力。这项研究也将有助于我们对光合机构的结构、功能和进化的基本理解。更广泛的影响：在调查过程中，将有许多本科生参与这项研究，该项目将成为一种有效的教育工具。通过他们的参与，学生将接触到一个令人兴奋的研究领域的最新技术，并将有机会参加国家科学会议。与这个项目相关的思想和技术也将直接丰富课程设置，从而使更多的本科生认识到科学研究的重要性。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。这将有助于当地鼓励学生从事高等科学事业和提高社会科学意识的努力。

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.