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

真菌内生菌，即生活在植物组织内的真菌，如不会引起疾病的叶子，存在于从北极到热带以及从农田到原始森林的健康植物中。尽管生物学家长期忽视内生菌，但内生菌因其巨大的多样性、在陆地植物所有谱系中的分布以及在调节植物胁迫和抗病原防御方面的生态作用而得到认可。该实验室从8000多种以前未知的内生植物中发现，这些无害的共生体是一个复杂的进化连续体的一部分，其特征是频繁和重复的进化转变(1)病原性和内生性生活方式之间，以及(2)从内生性生活方式到腐生性生活方式。这些观察提出了一个问题：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进行如此频繁和重复的切换？这项拟议的研究将检验一个普遍的假设，即新发现的生活在植物相关真菌中的细菌内共生体在推动其真菌宿主的“转换”方面发挥着以前被忽视的重要作用，因此是理解它们所栖息的真菌的生态模式的关键。这项研究将结合实地调查、系统发育分析和实验来研究朱斯卡山脉细菌内共生菌的发生率、多样性、宿主亲和力、进化关系和生态重要性。朱斯卡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，与真菌内生菌、腐殖体和病原体有关。这项工作的大部分将在纳瓦霍民族进行，并在Dine学院为纳瓦霍本科生进行保留研究培训。这项工作的智力价值在于确定哪些隐蔽的细菌内共生体决定了不同真菌的表型，而这些表型又对它们所居住的植物的生态和进化都很重要。更广泛的影响包括(1)一所美洲原住民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名纳瓦霍学生，以及(3)支持两名真菌和细菌生态学、进化论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.