To get an idea of the importance of mutualistic relationships between plants and fungi, consider that a third of the carbon sequestered in the soil of boreal forests are composed of the wood residues after the fungi break down the cellulose.
Maintaining the interface between the fungi and their hosts is the job of small fungal proteins known as MiSSPs. This group involves hydrophobins, hydrophobic fungal proteins produced in response to changes in environmental conditions and which are believed to be involved in plant-fungal interactions, particularly in the free space outside plant cell walls at the roots. To learn more about these proteins, a team of researchers including DOE JGI Fungal Program head Igor Grigorievconducted a genome-wide inventory of hydrophobinsin two strains of the symbiotic fungus Laccaria bicolor, sequenced at the DOE JGI in 2008.
In their report published online January 26, 2012 in Fungal Genetics and Biology, the team proposes that the numbers of hydrophobinspresent may be related to their ability to maintain a mutualistic relationship with a host plant. “We would suggest… that hydrophobinsare expressed at higher levels in less receptive hosts to provide a thicker layer around the fungal hyphae to protect it from plant based defenses,” the team wrote. “It would be attractive to broadly conclude that hydrophobinexpression varies inversely with the ease of host colonization. It is likely that the story is far more complicated, however, and this may not always be the case. ”