This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at the University of Kentucky Martin-Gatton College of Agriculture, Food and Environment (CAFE) have discovered that a fungus living inside a common Kentucky woodland grass produces a rare combination of chemicals that likely helps protect the plant from hungry insects. The study, published in Applied and Environmental Microbiology, examined bearded shorthusk, a wild grass that grows in forests across Kentucky.
Inside the grass is the fungus Epichloë brachyelytri, an "endophyte" that lives inside a plant without harming it. The fungus and the grass are symbiotic: The grass gives the fungus a home, and in return, the fungus makes chemicals that keep insects from eating the plant. The research team, led by Christopher Schardl and Padmaja Nagabhyru in the Department of Plant Pathology, found that the fungus makes three different alkaloids.
Two of them—exo-1-acetamidopyrrolizidine and chanoclavine—are usually intermediate compounds that other fungi turn into more complex chemicals. But this fungus stops the process early and keeps them as final products. "What makes it special is that it is the first fungus ever shown to do this with both chemicals at the same time," Schardl said.
The team collected grass samples from six locations across Kentucky, along a path spanning 171 kilometers (106 miles). The locations included the Kentucky River Palisades, Mammoth Cave National Park, Red River Gorge and Carter Caves State Resort Park. They also studied grass grown at The Arboretum, State Botanical Garden of Kentucky, where University of Kentucky staff members Wes Hansen and Judson Collins helped grow the plants.
Using an ultrahigh-performance liquid chromatography (UHPLC)-tandem mass spectrometry (MS/MS) instrument to measure tiny amounts of chemicals in each grass sample, the scientists compared how much of each alkaloid was in leaves, seeds and young shoots. Making these chemicals costs the fungus a lot of energy, Schardl said. "We have intriguing evidence that in young shoots, the endophyte has an internal struggle over which chemical pathways to feed, when those pathways need the same building blocks," Schardl said.
"That also explains why the endophyte has lost one or another of these chemicals in a few locations where we guess that insects aren't as much of a problem and the fungus can save energy by skipping some of the chemistry." This suggests that producing these insect-fighting chemicals is a big investment for the fungus, so they must be important for survival in most places. The team also found that the rare chemical combination discovered in this forest grass originated in other fungal species through different evolutionary paths—including gene swapping between species and hybridization when two species mix. Understanding how these grass-fungus partnerships work matters beyond forest ecology.
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