Tomás Rush began studying the mysteries of fungi in fifth grade and spent his college intern days tromping through forests, swamps and agricultural lands searching for signs of fungal plant pathogens causing disease on host plants.

Today, as a plant pathologist and mycologist at Oak Ridge National Laboratory, he’s using his knowledge to better understand the symbiosis between plants and fungi with the goal of creating hardier bioenergy and food crops.

Rush is particularly interested in the chemical signaling that affects the symbiosis between fungi and plant roots. The resulting fungal network extends far from its plant host to increase nutrient uptake and provide a warning system against disease and pests. In return, plants feed carbon to the fungus, which encourages its growth. An estimated 90% of land plants have mycorrhizal fungi associated with their roots.

While a doctoral student at the University of Wisconsin–Madison, Rush embarked on a study that found that certain signaling molecules thought to be produced by a limited number of microbes were actually transmitted by a majority of fungal species. These signals, known as lipo-chitooligosaccharides, or LCOs, likely govern the colonization of plant roots by fungus and may be involved in other important processes as well.

“We found that this signal is produced by most organisms throughout the fungal kingdom,” Rush said. “The discovery resulted in a paradigm shift in our thinking about how these organisms communicate.”

As part of the Plant Microbe Interfaces Scientific Focus Area at ORNL, Rush is exploring how LCOs influence the plant microbiome. “Just as we discovered how important gut flora is to human health, we’re working to understand how this communication between plants, fungi and bacteria affects the well-being of plants,” he said.

One of Rush’s research areas is focused on the presence of LCO receptors in many types of plants, in fungi, and even in humans. A previous study showed that endothelial cells in rat aorta assays have been shown to respond to the signal, “so there may be a larger role for LCOs in mammalian processes than we currently know,” he said.

Rush and colleagues published a paper suggesting LCOs may have a function in the growth and development of the Laccaria bicolor fungus typically associated with the poplar tree, a key bioenergy crop. Their ongoing work examines how the influence of LCOs may be changing the metabolic profile of the fungus that helps poplar grow.