Rhodocollybia butyracea by José María Barrasa

Rhodocollybia butyracea (Bull.) Lennox is a very common leaf litter decayer, and one of the most frequent agarics involved in humus formation in both coniferous and deciduous forests of boreal and temperate regions. It is characterized by its dark-brown, hygrophanous pileus, white to whitish-dirty adnate gills and concolorous, striate, spongy stipe. It belongs to Omphalotaceae, a family that includes many saprobic litter and dead wood species that play an important role in nutrient cycling of forest soil. Molecular analyses includes R. butyracea in the Marasmioid clade (Matheny et al., 2006) within the order Agaricales. Genomes of some species included in this clade are already available at JGI, such as the wood rotters Schizophyllum commune (causing a "white-rot"-type mild decay of wood) and Fistulina hepatica (causing brown-rot decay), the buried-wood decomposer Gymnopus luxurians, and the plant pathogens Armillaria mellea and Moniliophtora perniciosa. However, the only leaf litter decomposing species of this clade previously sequenced and available at JGI is Gymnopus androsaceus, a specialized decomposer of conifer fallen needles, particularly on Pinus hosts. Therefore, the genome of R. butyracea will be of interest because it will provide information on the ligninolytic machinery of one of the most representative leaf litter decay Agaricales. It will also increase our knowledge of the diversification of oxidative extracellular enzymes involved in humus formation, and will encourage comparative genome studies with the already sequenced saprobic species and plant pathogens within this clade. Finally, the genome of this leaf litter decomposing fungus will also contribute to understanding the nutritional transition between lignocellulose-degrading species involved in humus formation and ectomycorrhizal species of Agaricales (whose genomic sequences are being analyzed under the CSP entitled “Exploring the Genome Diversity of Mycorrhizal Fungi to Understand the Evolution and Functioning of Symbiosis in Wood Shrubs and Trees”).