MSB: Bacterial endosymbionts of arbuscular mycorrhizal fungi: ecology and evolution

该项目的目的是了解丛枝菌根（AM）真菌（肾小球菌门）与其菌丝和孢子中的细菌之间的相互作用。AM真菌及其内细菌是三方共生关系的组成部分，也包括大多数陆生植物，可能是地球上最常见的共生关系之一。AM真菌在陆地植物的根上定植，并协助植物吸收矿物质营养，以换取植物同化的碳。选择与美国北大西洋海岸沙丘植被相关的AM真菌的内细菌作为研究的焦点系统。对AM真菌谱系中的内细菌分布进行调查，并结合相互作用伙伴的系统发育重建，将有助于推断进化起源、关联年龄以及内细菌与其自由生活的亲戚的系统发育关系。重建内细菌的种群结构将阐明它们的繁殖和传播方式。评估内源性细菌对真菌和植物适应性的影响将揭示内源性细菌是AM真菌的寄生虫还是共生菌。本研究将加深对AM真菌生物学和丛枝菌根在陆地生态系统（包括农业生态系统）中功能的认识。它将提供对细菌与真菌一般相互作用的见解，并扩展涉及建立和维持内共生相互作用的进化过程的知识。通过关注海岸沙丘中自然发生的AM真菌，该项目将有助于保护和恢复脆弱的沙丘栖息地。在这个项目的过程中，将培训一名研究生和几名本科生和高中生。

The goal of this project is to understand the interaction between arbuscular mycorrhizal (AM) fungi (phylum Glomeromycota) and bacteria that reside in their hyphae and spores. AM fungi and their endobacteria are components of a tri-partite symbiotic association that also includes the majority of terrestrial plants, and may be one of the most common symbioses on the planet. AM fungi colonize roots of land plants and assist in the uptake of mineral nutrients to the plant in exchange for plant-assimilated carbon. Endobacteria of AM fungi associated with dune vegetation of the North Atlantic coast of the U. S. were selected as a focal system for the study. A survey of endobacteria distribution among AM fungal lineages combined with reconstruction of phylogenies of the interacting partners will enable inferences about the evolutionary origin, the age of the association, and the phylogentic relationships of endobacteria with their free-living relatives. A reconstruction of the population structure of endobacteria will clarify their reproductive and transmission mode. An assessment of the effects that harboring endobacteria has on the fungal and plant fitness will reveal whether endobacteria are parasites or mutualists of AM fungi.This study will enhance understanding of the biology of AM fungi and of the functioning of arbuscular mycorrhizae in terrestrial ecosystems, including agroecosystems. It will provide insights into the interactions of bacteria with fungi in general, and expand the knowledge of evolutionary processes involved in the establishment and maintenance of endosymbiotic interactions. By focusing on AM fungi that occur naturally in coastal dunes, this project will contribute to the efforts to conserve and restore the fragile dune habitat. A graduate student and several undergraduate and high school students will be trained in the course of the project.