Exploring the ecological role of fungal endophytes - a cryptic, but hyperdiverse group of plant-associated organisms

真菌内生菌是生活在植物内部而不会对宿主造成明显损害的真菌。它们在自然界中无处不在，而且极其多样，但它们的生态作用尚未得到明确界定。本研究以野生利马豆、西番莲及一组从这些植物叶片中分离的内生真菌为研究对象，以了解内生真菌作为植物共生体的生态功能。特别是，研究重点是内生菌介导的植物防御昆虫植食动物的影响。利马豆和西番莲都是成熟的模型系统，并表达了一系列特征良好的直接和间接防御。这允许解开植物来源的和内生菌介导的效应的相互作用。除了更好地理解植物-内生菌相互作用的生态学意义外，这项研究还为农业科学提供了新的见解，因为内生菌可以潜在地用于增强植物对各种生物（例如害虫和病原体）和非生物胁迫因素（例如土壤盐度，干旱，高温和重金属积累）的胁迫耐受性。探索通过利用有益微生物提高植物抗逆性来提高作物产量的新方法，可能有助于缓解人类面临的迫在眉睫的社会经济挑战。 研究生和本科生将接受化学分析和分子技术，数据分析和科学写作的培训。为K-12学校的教师和学生参与这项多学科研究的机会将通过讲座，实验室经验和夏季实地课程提供真菌内生菌是特殊的生化工程师，产生各种生态相关的化合物。这些化合物可能影响宿主植物与植物消费者和更高营养级的相互作用。除了产生真菌化合物之外，内生菌还可以通过上调或下调原生和次生植物化合物来改变防御性植物化学表型。然而，在自然生态系统中，植物、内生菌和其他植物相关生物之间的功能相互作用几乎是未知的。本研究的目的是通过整合实验室和田间研究来回答以下具体问题，从而为这些复杂的相互作用提供新的和功能性的理解：1）内生菌定殖是否影响植食性和捕食性昆虫？2)内生菌定殖如何改变植物化学表型？3)接种内生菌是否影响宿主植物的自然表现？和4）内生菌介导的性状是否可跨植物物种界限和世代转移？在比较代谢组学方法中，在植物中分析内生菌接种对复杂化合物库的影响。除了这种非靶向方法，高通量生物活性分析研究将用于寻找生物活性真菌化合物。与自然，植物相关的节肢动物的生物测定将阐明内生菌介导的化学植物表型的影响，其后果与消费者和捕食者在该领域的植物相互作用。这些研究与内生菌宿主特异性以及在自然条件下定量植物性能的测试相结合。

Fungal endophytes are fungi that live inside plants without causing apparent damage to their hosts. They are ubiquitous in nature and extremely diverse, yet their ecological roles are not well-defined. In this project, wild lima bean, passion vine and a defined set of fungal endophytes isolated from leaves of these plant species will be studied to understand ecological functions of endophytes as plant symbionts. In particular, the research focuses on endophyte-mediated effects on plant defenses against insect herbivores. Lima bean and passion vine are both well-established model systems and express a range of well-characterized direct and indirect defenses. This allows for disentangling of the interplay of plant-derived and endophyte-mediated effects. Beyond a better understanding of the ecological implications of plant-endophyte interactions, this research also provides novel insights for agricultural sciences, as endophytes can potentially be used to enhance plant stress tolerance to a broad variety of biotic (e.g. insect pests and pathogens) and abiotic stress factors (e.g. soil salinity, drought, high temperature, and heavy metal accumulation). The exploration of novel ways to enhance crop production, through the utilization of beneficial microbes that enhance plant stress tolerance, may help to alleviate the impending socio-economic challenges facing humanity.  Graduate and undergraduate students will be trained in chemical analytical and molecular techniques, data analysis and scientific writing. Opportunities for K-12 school teachers and students to participate in this multidisciplinary research will be provided through lectures, lab experiences and summer field courses.Fungal endophytes are exceptional biochemical engineers that produce a variety of ecologically relevant compounds. These compounds potentially affect the interaction of host plants with plant consumers and higher trophic levels. In addition to the production of fungal compounds, endophytes may alter the defensive plant chemical phenotype through up- or down-regulation of primary and secondary plant compounds. However, the functional interactions between plants, endophytes and other plant-associated organisms in natural ecosystems are virtually unknown. The aim of this research is to provide a new and functional understanding of these complex interactions by integrating laboratory and field studies to answer the following specific questions: 1) Does endophyte colonization affect herbivorous and predatory insects? 2) How does endophyte colonization alter the plant chemical phenotype? 3) Does inoculation with endophytes affect host plant performance in nature? and 4) Are endophyte-mediated traits transferable across plant species boundaries and generations? In a comparative metabolomics approach, effects of endophyte inoculations on complex compound pools are analyzed in planta. Beyond this non-targeted approach, high-throughput bioactivity profiling studies will be used to search for bioactive fungal compounds. Bioassays with natural, plant-associated arthropods will illuminate the effects of the endophyte-mediated chemical plant phenotype and its consequences for plant interactions with consumers and predators in the field. These studies are combined with tests on endophyte host-specificity as well as on quantitative plant performance under natural conditions.