Plant host traits mediated by foliar fungal symbionts and secondary metabolites

Fungal symbionts living inside plant leaves (“endophytes”) can vary from beneficial to parasitic, but the mechanisms by which the fungi affect the plant host phenotype remain poorly understood. Chemical interactions are likely the proximal mechanism of interaction between foliar endophytes and the plant, as individual fungal strains are often exploited for their diverse secondary metabolite production. Here, we go beyond single strains to examine commonalities in how 16 fungal endophytes shift plant phenotypic traits such as growth and physiology, and how those relate to plant metabolomics profiles. We inoculated individual fungi on switchgrass, Panicum virgatum L. This created a limited range of plant growth and physiology (2–370% of fungus-free controls on average), but effects of most fungi overlapped, indicating functional similarities in unstressed conditions. Overall plant metabolomics profiles included almost 2000 metabolites, which were broadly correlated with plant traits acros..., Switchgrass (Panicum virgatum) seedlings were inoculated individually with 16 foliar fungal endophytes at 4 weeks old and at least 4 cm tall and grown for an additional 6 weeks under well-watered conditions. Controls were fungus-free plants inoculated with water. Each treatment and control included 6 replicates, although mortality resulted in fewer at the harvest. All fungi were Ascomycetes isolated from plants in central Texas. Plants were monitored weekly for height, wilt, water loss, and survival. At the harvest, leaf-level physiology (photosynthesis and conductance) was measured, along with fresh shoot biomass and oven-dried root biomass. A subset of leaf replicates was further characterized by untargeted metabolomics profiling., All data files are .csv and analysis files are in .Rmd, which can be opened in any text editor, R, and many other programs.Â