MIP: Bacterial Endosymbionts of Phyllosphere Fungi:resolving the Endophyte/Saprophyte/Pathogen continuum on the Navajo Nation

真菌内生菌是一种生活在植物组织（如叶子）内而不会引起疾病的真菌，从北极到热带，从农田到原始森林，都存在于健康的植物中。虽然长期被生物学家所忽视，但内生菌的多样性、分布在陆地植物的所有谱系中，以及在介导植物胁迫和抗病原体防御方面的生态作用，现在已被认识到。从8000多种以前未知的内生菌中，该实验室表明，这些无害的共生体是复杂进化连续体的一部分，其特征是频繁和重复的进化过渡(1)在病原和内生生活方式之间，(2)从内生生活方式到腐养生活方式。这些观察结果提出了一个问题：是什么遗传、生态和进化因素允许真菌在不同的生态模式之间如此频繁和重复地转换？这项研究将验证一个普遍的假设，即新发现的植物相关真菌中的细菌内共生体在驱动真菌宿主的“切换”中起着重要的作用，这在以前被忽视了，因此是理解它们所栖息的真菌的生态模式的关键。本研究将结合实地调查、系统发育分析和实验来研究Chuska山脉中与真菌内生菌、腐养菌和病原体相关的细菌内共生体的发生率、多样性、宿主亲和力、进化关系和生态重要性。Chuska山脉是亚利桑那州东北部一个生物丰富但研究不足的地区。这项工作的大部分将在纳瓦霍民族进行，并为Dine学院的纳瓦霍本科生提供保留地研究培训。这项工作的智力价值在于确定哪些隐细菌内共生体驱动各种真菌的表型，这反过来对它们所栖息的植物的生态学和进化都很重要。更广泛的影响包括(1)一所印第安部落学院的课程开发，(2)支持多达30名本科生的指导研究，其中包括18名纳瓦霍族学生，(3)支持两名真菌和细菌生态学、进化和分类学的女博士生。

Fungal endophytes, fungi that live within plant tissues such as leaves without causing disease, occur in healthy plants from the Arctic to the tropics, and from agricultural fields to primary forests. Although long overlooked by biologists, endophytes are now being recognized for their tremendous diversity, their distribution across all lineages of land plants, and their ecological roles in mediating plant stress and antipathogen defense. Drawing from a collection of over 8000 previously unknown endophytes, this laboratory is showing that these harmless symbionts are part of a complex evolutionary continuum that features frequent and repeated evolutionary transitions (1) between pathogenic and endophytic lifestyles, and (2) from endophytic to saprotrophic lifestyles. These observations raise the question: what are the genetic, ecological, and evolutionary factors that permit such frequent and repeated switching among distinctive ecological modes in fungi? The proposed study will test the general hypothesis that newly discovered bacterial endosymbionts living within plant-associated fungi play a significant and previously overlooked role in driving the "switching" of their fungal hosts, and thus are key to understanding the ecological modes of the fungi they inhabit. This study will combine field surveys, phylogenetic analyses, and experiments to examine the incidence, diversity, host affinity, evolutionary relationships, and ecological importance of bacterial endosymbionts associated with fungal endophytes, saprotrophs, and pathogens in the Chuska Mountains, a biotically rich but understudied area in northeastern Arizona. Much of this work will be carried out on the Navajo Nation with on-reservation research training for Navajo undergraduates at Dine College. The intellectual merit of this work lies in determining which cryptic bacterial endosymbionts drive the phenotypes of diverse fungi, which in turn are important in both the ecology and evolution of the plants they inhabit. Broader impacts include (1) curriculum development at a Native American tribal college, (2) support for mentored research by up to 30 undergraduates, including 18 Navajo students and (3) support for two female Ph.D. students in fungal and bacterial ecology, evolution, and taxonomy.