[Geysers] Brand New Science from Yellowstone...Again !!

[Robert C. Johnson]

  Gang,

   A lot has been made over the past few years about a simbiotic fungus that 
apparently allows plants to tolerate high soil temps in Yellowstone.

    Well.....*now* it turns out that that was....not all there was to 
it.....as the following story explains :

  ( Submitted to you all by Bob Johnson, a Gazer from the early 80's who is 
hoping to get back again soon ! )





   Secret Agent: Hidden helper lets fungus save plants from heat

Susan Milius  ( From Science News )

The story of a fungus that keeps plants from withering in hot soil turns out 
to have been missing a character—the virus that makes it all work.

The fungus Curvularia protuberata grows inside plant tissues without 
damaging them. In 2002, researchers working in Yellowstone National Park 
reported that grass colonized by the fungus thrived in soils that simmer at 
over 40°C (104°F) all summer.

A closer look now shows that the fungus alone doesn't protect plants from 
heat, says virologist Marilyn Roossinck of the Samuel Roberts Noble 
Foundation in Ardmore, Okla. The fungus itself has to be infected with a 
previously unknown agent, which she and her colleagues have named Curvularia 
thermal-tolerance virus, the group reports in the Jan. 26 Science.

Researchers haven't found many three-partner mutual-benefit societies, and 
this is the first plant-fungus collaboration known to have a virus as a 
third party, Roossinck says. She speculates that new ways to protect crops 
from heat might eventually result from understanding this threesome.

"I would hope that it changes people's thinking about viruses," Roossinck 
says. Scientists have primarily chosen to study viruses that cause disease, 
but she says that she suspects that most viruses don't have ill effects on 
their hosts. "There's a huge world out there that hasn't been looked at," 
she says.

Researchers discovered the original grass-fungus arrangement in a species of 
what's called panic grass, Dichanthelium lanuginosum.

While working on a different project in 2003, Roossinck looked through the 
Yellowstone Curvularia samples. She found signs of viral infection in the 
fungi in hot spot grasses but not in fungi from cooler places. Yellowstone 
soil can heat up to 50°C.

Roossinck and her colleagues isolated the virus and tested its powers in 
both the grass and tomato plants. One of the challenges that she faced was 
the failure of standard techniques to cure the fungus of its viral 
infection. However, when bringing fungal samples out of storage, Roossinck 
serendipitously discovered that freezing destroys the virus but not its 
host.

After Roossinck removed the virus by freezing the fungus, the latter no 
longer offered even limited protection to tomato plants. When she reinfected 
the fungus, its protective powers returned.

The new study "nicely demonstrates the complexity of plant-microbial 
interactions," says Stan Faeth of Arizona State University in Tempe, who 
studies grass and their live-in fungi.

The newly described three-way partnership reminds Nancy Moran of the aphids 
that she studies, which depend on resident bacteria for defense against 
parasites. Moran, who's at the University of Arizona in Tucson, showed that 
a virus in the bacteria provides the genes for toxins that could protect the 
host.

Live-in helpers "are a way for multicellular hosts, such as plants and 
animals, to acquire new ecological capabilities without actually 
incorporating foreign genes directly into their genomes," she says. "And 
viruses collectively have the greatest diversity of any genomes."