Bacterial Controls of Endophyte Phenotypes: an Unexplored Dimension of Diverse Plant-fungal Symbioses

地球上绝大多数植物的健康叶片中都有真菌内生菌。这些内生菌增强了植物的生理机能和对病原体的防御能力，并塑造了作物和野生植物的生产力。最近发现，内生菌有自己的内共生体——生活在真菌组织内的内共生细菌（内菌丝细菌）。细菌共生体增强了真菌的抗逆性和纤维素降解等特性，这表明在构建真菌与其寄主植物之间的有益关系中起着重要但未知的作用。更广泛的影响将直接影响到高中生、本科生、研究生和公众，通过亚利桑那大学真菌学植物标本馆的旋转展示，为大型城市西班牙裔学校的学生提供一系列广泛的研讨会，为高中生提供实地体验和实验室实习，为高中教师提供培训，开发课程以达到亚利桑那州的科学标准，将项目材料整合到亚利桑那大学的本科课程中，并指导处于不同人生阶段的初级研究人员。更广泛地说，这项工作将有助于对形成植物参与的最重要但研究最少的共生关系之一的因素有新的认识，从而有助于人类健康和可持续发展。该项目提出了一种假设，即内生真菌的表型变异及其与植物的关联结果反映了菌丝内细菌的主要作用。使用可处理的模型系统，将测试这些关联及其结果的特异性和不稳定性。转录组学将用于确定细菌和真菌如何交流，并确定哪些途径在这些动态共生中被上调。总的来说，在实验室、实验植物和跨环境梯度中研究细菌对真菌的表型效应相关的多样性、可塑性、特异性和基因表达，将阐明这种三方共生的生态重要性。

The vast majority of plants on earth harbor fungal endophytes within their healthy leaves. These endophytes enhance plant physiology and defense against pathogens, and shape the productivity of crops and wild plants. It was recently discovered that endophytes harbor their own endosymbionts -- endosymbiotic bacteria that live within fungal tissues (endohyphal bacteria). Fungal traits such as stress tolerance and cellulose degradation are enhanced by bacterial symbionts, suggesting an important, yet previously unknown, role in structuring beneficial relationships between fungi and their host plants. Broader impacts will directly reach high school students, undergraduates, graduate students, and the public via a rotating display in the University of Arizona Mycological Herbarium, an extensive series of workshops for students at a large, urban, Hispanic-serving school, field experiences and laboratory internships for high school students, training for high school teachers, development of curriculum to achieve State of Arizona science standards, integration of project material into undergraduate courses at the University of Arizona, and mentoring junior researchers at multiple life stages. More broadly, the work will contribute to a new understanding of the factors shaping one of the most important, but least-studied, symbioses in which plants engage,thereby contributing to human health and sustainability.The project addresses the hypothesis that phenotypic variation in endophytic fungi, and the outcomes of their associations with plants, reflect a major role of endohyphal bacteria. Using tractable model systems, the specificity and lability of these associations and their outcomes will be tested. Transcriptomics will be used to identify how bacteria and fungi communicate, and to determine which pathways are upregulated in these dynamic symbioses. Overall, examining the diversity, plasticity, specificity, and gene expression associated with phenotypic effects of bacteria on fungi in the lab, in experimental plants, and across an environmental gradient will clarify the ecological importance of this tripartite symbiosis.