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DOE Pulse
  • Number 434  |
  • March 9, 2015

A study in symbiosis: Mushrooms and carbon

Mycorrhizal fungi include some of the most conspicuous forest mushrooms, such as the fly agaric (Amanita muscaria), one of the fungi sequenced for this project. (Francis Martin, INRA)

Mycorrhizal fungi include some of the most
conspicuous forest mushrooms, such as the
fly agaric (Amanita muscaria), one of the
fungi sequenced for this project.
(Francis Martin, INRA)

With apologies to the poet John Donne, it can be said that no plant is an island, entire of itself. Mycorrhizal fungi, a group that includes some of the most conspicuous forest mushrooms, live in the roots of host plants, where they exchange sugars that plants produce by photosynthesis for mineral nutrients that fungi absorb from the soil. To bioenergy researchers, these fungi are of interest because they play roles in maintaining the health of candidate feedstock crop trees. Recent studies indicate that mycorrhizal fungi also play a significant role in belowground carbon sequestration, which may mitigate the effects of anthropogenic CO2 emissions.

To understand the basis for fungal symbiotic relationships with plants, a team fromthe U.S. Department of Energy Joint Genome Institute (DOE JGI), a DOE Office of Science user facility and longtime collaborators at the French National Institute for Agricultural Research (INRA) and Clark University conducted the first broad, comparative phylogenomic analysis of mycorrhizal fungi, drawing on 49 fungal genomes, 18 of which were sequenced for this study. Published ahead online in the February 23, 2015 edition of Nature Genetics, these researchers describe how the comparative analyses of these genomes allowed them to track the evolution of mycorrhizal fungi.

DOE JGI’s Igor Grigoriev pointed out, “This first large-scale study of mycorrhizal genomics is also the first step in both broader and deeper exploration of mycorrhizal diversity, their interactions with host plants, and roles in forest ecosystems using genomics tools, which are the focus areas for the JGI Fungal Genomics Program.”

The analyses of the fungal genomes and fossils suggested that, in comparison to brown rot fungi and white rot fungi that evolved over 300 million years ago, ectomycorrhizal fungi emerged fairly recently from several species and then spread out across lineages less than 200 million years ago. The team also found that up to 40 percent of the symbiosis-induced genes were restricted to a single mycorrhizal species. Such results help researchers understand how plants and fungi developed symbiotic relationships, and how the mutualistic association provides host plants with beneficial traits for environmental adaptation. Read the full story at http://jgi.doe.gov/retracing-roots-fungal-symbioses/.

[Massie Ballon, 925.927.2541,
mlballon@lbl.gov]