Many people know the button mushroom (Agaricusbisporus) as a tasty ingredient in their food. In the forest, though, this mushroom helps break down leaf litter in environments rich with humus, a mixture of soil and compost that contributes to the health of the microbial communities in, on and around the plant as well as the plant itself.
In a study published online in the Proceedingsof the National Academy of Sciences on October 8, 2012, an international team of scientists led by researchers from the DOE Joint Genome Institute and the French institute INRA reported the full genome of the button mushroom, and identified both the metabolic pathways and the genes and enzymes involved in them that allow A. bisporusto thrive in this environment.
Unlike many of the fungal species sequenced at the DOE JGI, noted Fungal Program head Igor Grigoriev, the button mushroom is neither a brown-rot nor a white-rot fungus and doesn’t do a very good job of breaking down non-degraded plant matter such as wood. However, when it comes to breaking down partially decaying plant matter such as leaf litter in humic environments such as forest floors and grassland soils, the mushroom plays a role in carbon sequestration.
The team found genes in the button mushroom that are also present in wood-decaying fungal species, but are more active in the presence of humus. They also identified higher levels of enzymes such as heme-thiolateperoxidases and etherases, which allow the mushroom to break down lignin and other polymers in humicenvironments.