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

Portland State University, Portland OR

Investigators

Abstract

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.