Active Competition in Nutritional Mutualisms: Metabolites to Symbiotic Stability

This project will identify bioactive compounds made by mutualistic fungi and how much it costs to make them. Fungi make many chemicals that they use to fight off competitors. However, for fungi that form beneficial mutualisms with trees, fighting their competitors may prevent them from helping their tree hosts. These fungi must trade nutrients with trees to survive, and producing defense chemicals uses up nutrients that could be shared instead. Loblolly Pine and its fungal partners are a widespread and economically important symbiosis in the United States. Understanding how fungi balance defending against competitors and helping their host trees is important to the bioeconomy. The project will also identify new bioactive compounds with the potential for future practical uses. This project also supports research experiences for community college students aiming to transfer to four-year degree programs. This research will use ectomycorrhizal fungi in symbiosis with the host tree Pinus taeda, focusing on fungi in the genus Suillus. To identify the metabolites involved in competition and the ecological scenarios that induce bioactive metabolite induction, host trees colonized by Suillus will be challenged with competitors representing three forms of antagonism: competition over substrate, over nutrients, and against injury. After reliable induction triggers are identified, the research team will induce metabolite expression to quantify 1) the cost of production, 2) the effect of fungal competition on the host plant, and 3) the scenarios leading to mutualistic breakdown. This will be achieved using a combination of nutrient-depletion coupled to metabolomics, transcriptomics, and isotopic tagging to track nutrient transfer. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.