HUNTSVILLE, Ala.– Fossil evidence suggests that coal deposits in the earth sharply decreased around the end of the Carboniferous period. Using genome sequence of fungi living now, Jeremy Schmutz from the HudsonAlpha Institute for Biotechnology and colleagues around the world say mushrooms may hold the clues to this decrease while also providing insight to spur technical progress for cellulosic biofuels production.
 

Things on Earth were moving along during the Carboniferous period, about 300 million years ago. Trees with bark made from a carbon-containing molecule called lignin had just evolved, but nothing was around to consume this new substance in tree bark. So when the trees died, they were absorbed into the ground and over time created large deposits of coal.

This period of geologic time ended with a sharp decline in the amount of coal being buried in the earth. Could something have evolved to degrade and digest lignin, preventing it from becoming coal? A group of scientists in 12 countries decided to find out by looking at the genomes of 31 fungi alive today, including 12 fungal genomes not previously sequenced.

By comparing genes present in Agaricomycetes species, including white and brown rot fungi and other mushrooms, the group saw an increase in lignin-degrading enzymes, specifically in the white rot lineage. “The rise of the white rot fungi, the only organisms that can degrade lignin, occurs in the same period as the reduction in coal deposits,” said Schmutz, a faculty investigator at HudsonAlpha. The data suggest these enzymes were present in the common ancestor of all Agaricomycetes and then lost in some descendant fungi.

Schmutz, who is also plant genomics program lead for the U.S. Department of Energy’s Joint Genome Institute, added scientists are examining the degrading mechanisms that white and brown rot fungi use to breakdown plant cell walls and convert them to useable energy.  “This research is funded by the DOE to enable us to apply the processes these fungi use to breakdown the woody material in grasses like switchgrass or trees like poplar, and convert the sugars in the woody material into alternative liquid fuels. The DOE and its scientists are applying research like this to build a sustainable and domestic fuel supply.”

Since the new fungi, which later became white rot and other mushrooms, were able to digest bark from trees, they may be responsible for reshaping the history of the earth. In applying this research to biofuels production, they could also shape the future.

The paper describing the work on fungi genomes, The Paleozoic Origin of Enzymatic Lignin Decomposition Reconstructed from 31 Fungal Genomes will be published in Science on 28 June 2012.