Collaborative Research: PurSUiT: Phylogenomics and taxonomic revision of Rhopalodiales - diatoms with obligate cyanobacterial endosymbionts

共生现象是自然界中的一种普遍现象，是不同生物体之间的密切联系。从人类细胞内的古老细胞器，到地衣和珊瑚，来自不同背景的生命形式的整合发生在生命之树上。是什么机制促使这种整合发生？这些关系的成本和收益是什么？在一组被称为硅藻的真核微生物中（它们构成水生生态系统食物链的基础，通过光合作用产生的氧气比所有热带雨林的总和还要多），共生体通常与“固定”氮的蓝藻形成。该项目将分析这些生物是如何聚集在一起的;这种情况是发生一次还是多次;这种关联对宿主，共生体及其生活的生态系统的影响;以及共生生物如何协调其生命活动。超过40名学生将通过课程，研讨会和研究培训参与研究。该项目将在蒙大拿大学土著研究和STEM教育暑期项目提供的微生物多样性隐藏世界课程中展出。三所美国大学与中国、印度、印度尼西亚和阿根廷的七所大学、研究机构和博物馆之间的科学合作将从各种来源收集数据，包括硅藻宿主的叶绿体和线粒体的整个基因组，硅藻的细胞壁形态和蓝藻共生体的整个基因组（也称为球状体），以解决三个主要目标：1）硅藻目的Rhopalodiales的进化起源和多样化，包括当内共生体是在这个谱系的多样化过程中获得的; 2）Rhopalodiales的姐妹分类群，以及世界性Rhopalodian分类群之间的隐蔽多样性程度;（3）宿主与共生体的协同进化。该项目将整合来自美国、欧洲和南美洲植物标本馆的现存和化石分类群的信息。综合遗传学、功能基因组学和分类学修订工作将产生一个时间校准的遗传学，为该小组修订分类系统提供信息。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Symbiosis, the close association of distinct organisms living together, is a common phenomenon in nature. From the ancient organelles inside human cells, to lichens and corals, the integration of life forms from disparate backgrounds occurs across the tree of life. What are the mechanisms that drive this integration to happen? What are the costs and benefits of these relationships? In one group of eukaryotic microorganisms called diatoms (which form the base of the food chain in aquatic ecosystems and generate more oxygen by photosynthesis than all rainforests combined), symbioses are commonly formed with cyanobacteria that “fix” nitrogen. This project will analyze how these organisms came together; whether that happened once or many times; the impacts of the association on host, symbiont and the ecosystems in which they live; and how the co-occurring organisms coordinate their life activities. Over 40 students will be involved in the research through courses, workshops, and research training. The project will be featured in the Hidden World of Microbial Diversity course offered through the University of Montana’s Indigenous Research and STEM Education summer program.A scientific collaboration between three U.S. universities and seven universities, research institutes and museums in China, India, Indonesia and Argentina will gather data from a variety of sources, including entire genomes of the chloroplast and mitochondria of the diatom hosts, cell wall morphology of the diatoms, and the entire genome of the cyanobacterial symbiont (also called a spheroid body) to address three main aims: 1) the evolutionary origins and diversification of the diatom order Rhopalodiales, including when the endosymbiont was acquired during diversification of this lineage; 2) the sister taxon of the Rhopalodiales, and the extent of cryptic diversity among cosmopolitan rhopalodian taxa; 3) the coevolution of host and symbiont. The project will integrate information on the group from herbarium collections in the United States, Europe and South America for both extant and fossil taxa. Integrated phylogenetics, functional genomics and taxonomic revisionary work will produce a time-calibrated phylogeny that will inform a revised classification system for the group.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.