Feb. 03, 2009

Ruth Dasso Marlaire 
Ames Research Center, Moffett Field, Calif. 
650.604.4709
ruth.marlaire@nasa.gov 

RELEASE: NASA Scientists

NASA SCIENTISTS DISPROVE 'LOST GENE' THEORY IN WOOD-EATING FUNGI

In Yellowstone National Park, east of the Virginia Cascade cutoff, 
NASA scientists found a site composed solely of pine trees and, for 
the next two years, proceeded to gently twist off one half of the 
pine needles at the base. By artificially defoliating the trees, the 
scientists wanted to examine the wood-degrading capability of a 
fungus that has the potential to digest toxins found in the soil. 

Scientists are working to isolate the gene that causes Ectomycorrhizal 
(EM) fungi to digest wood and its toxins, such as phenolics, which 
are contaminants similar to those found in soil and groundwater. 

A study led by Ken Cullings and Galina Ishkhanova of NASA Ames 
Research Center, Moffett Field, Calif. and Joan Henson of Montana 
State University, Bozeman, Mont. found evidence that the gene in the 
dominant EM fungal species (Suillus granulatus) produced 
wood-degrading enzymes, and that enzymatic activity increased 
significantly during defoliation. The study appeared in the July 2008 
issue of Oceologia. 

For a long time, scientists knew that a group of EM fungi was related 
to a wood-rotting fungus. Over time, EM fungi evolved into organisms 
that are dependent on their host plants for food, and no longer use 
their capability to break down wood for food. Scientists suspected 
that these fungi may have lost the genes necessary to convert wood 
into food. 

However, they found that was not the case. 

"Our study showed that not only do mycorrhizal fungi still have the 
gene, but the gene can be highly stimulated by removing some of the 
needles from the host tree, which restricts photosynthesis and the 
production of sugar at its root. It disproves the 'lost gene' 
theory," said Cullings. 

Scientists now believe that EM fungi have the potential to play a 
significant role in carbon, nitrogen and phosphate cycling in the 
Earth's forested ecosystem. They also found many above-ground factors 
that reduce photosynthetic potential, or divert fixed carbon from 
roots, and may have wide-reaching effects on the ecosystem. 

"I'm working to clone out the mycorrhizal toxin-degrading genes to get 
a purified enzyme of high activity use. For instance, it can be used 
as a toxic spill clean-up strategy," said Cullings. 

Related studies include comparing the effect of lost needles to plant 
diseases, such as dwarf mistletoes and pine beetles, which are 
killing record numbers of pines in the west. Scientists think that 
these diseases are increasing in range and scope due to global 
climate change, and that the break down of wood also releases carbon 
dioxide. Currently, Cullings is undertaking experiments that will 
allow these phenomena to be added to global climate change models for 
the first time. 

For more information about NASA and agency programs on the Internet, 
visit: 

http://www.nasa.gov/home/index.html

	
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