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

该项目的目标是了解丛枝菌根(AM)真菌(球菌门)与其菌丝和孢子中的细菌之间的相互作用。AM真菌及其内生细菌是三方共生协会的组成部分，该协会还包括大多数陆地植物，可能是地球上最常见的共生之一。AM真菌在陆地植物的根部定居，并帮助植物吸收矿物质营养，以换取植物吸收的碳。与美国北大西洋沿岸沙丘植被相关的AM真菌的内生细菌被选为研究的焦点系统。调查内生细菌在AM真菌谱系中的分布，结合相互作用伙伴的系统发育重建，将能够推断内生细菌与其自由生活的近亲的进化起源、联合的年龄以及系统学关系。重建内生细菌的种群结构将阐明它们的繁殖和传播模式。对内生细菌对真菌和植物适合性的影响的评估将揭示内生细菌是AM真菌的寄生还是互惠共生。这项研究将增进对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)中功能的了解。它将提供对细菌和真菌相互作用的一般见解，并扩大关于建立和维持内共生相互作用所涉及的进化过程的知识。通过重点研究自然出现在沿海沙丘上的AM真菌，该项目将有助于保护和恢复脆弱的沙丘栖息地。一名研究生和几名本科生和高中生将在项目过程中接受培训。

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.