Yellowstone plant reveals secret for tolerating high temperatures

A grass in Yellowstone National Park can withstand temperatures up to 140 degrees Fahrenheit if it gets a little help from a friend. Hot springs panic grass, common in geyser basins throughout Yellowstone, would die in that environment if not for a stringy, microscopic fungus on the roots that helps the plant cope. A growup of scientists in Montana and Washington has published these research findings published in the prestigious journal Science. "Even desert plants cool off at night," said Montana State University-Bozeman plant scientist and study co-author Rich Stout. "These plants don't. That's what makes them bizarre and interesting."

Plant-fungal partnerships aren't unique and may date back 500 million years or more to when plants first began to evolve. Fungi on the roots help plants absorb water and nutrients. For their efforts, the fungi get a place to live and access to food and water.

But what's unique in this situation is the fungi don't just help gather food and water; they make the plant roots tough enough to tolerate the extreme soil temperatures typical in geyser basins. In fact, neither the plant nor the fungi could live in hot Yellowstone soils alone, a relationship scientists refer to as mutualism, a type of symbiosis.

We would have been surprised if the grass didn't have a fungal partner," said study co-author and MSU microbiologist Kathy Sheehan. "What surprised us is that it imparts thermotolerance to the plant." Added Stout: "As far as we know, this is the first report of heat tolerance conferred by fungal involvement."

Just how the fungus, called Curvularia, makes hot springs panic grass thrive in soil temperatures that would kill most other plants, isn't known. The fungus could help dissipate heat throughout the plant or it could act as a "biological trigger" that tells the plant to activate a stress response.

To find out, TBI scientists plan to analyze the plant and fungal genetic codes. First they'll see which genes are switched on when the plant and fungi live alone. They'll compare those to the genes switched on when the plant and fungus coexist as soil temperatures
start to climb.

Whatever the mechanism, the steamy partnership is an exciting one, according to Tim McDermott. McDermott, a soil microbiologist and MSU Thermal Biology Institute scientist, says there's interest in transferring this type of plant/fungal partnership to farm fields so that wheat or other crop plants could withstand higher soil temperatures during hot, dry summers.

"There's justifiable excitement about these kinds of applications," says McDermott.