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Hymenopellis radicata by José María Barrasa

Hymenopellis radicata (Relhan) R.H. Petersen is a representative saprobic species that degrades buried wood in deciduous boreal forests (mainly from beech and oak trees) of temperate regions. It is characterize by its gelatinized rugose pileus and long stipe with a radicant part growing under the soil surface, forming mycelial cords to degrade dead and buried wood of stumps and roots. Based on molecular analysis (Matheny et al., 2006), this fungus is included in the Marasmioid clade and Physalacriaceae family. The latter family includes not only wood decomposers, such as Oudemansiella mucida (to be sequenced in JGI CSP-1609), but other buried-wood degraders such as the widespread edible species Flammulina velutipes (called “enoki mushrooms”) and Strobilurus esculentus, which typically degrade buried cones of Picea sp. (also to be sequenced in JGI CSP-1609). Other members of the Marasmioid clade, such as Gymnopus luxurians (Omphalotaceae family) whose genome is available at JGI, also grows on partially-degraded and buried wood. Species growing on this particular lignocellulosic substrate that is buried in soil, have been reported to cause a nonspecific type of rot (Dix and Webster, 1995). Furthermore, differences in fungal diversity between aerial and buried parts of wood were reported (Carruthers and Rayner, 1979). Colonization of aerial parts of fallen wood is mainly initiated by airborne spores of wood-decomposing Polyporales, whilst buried wood parts (that are in contact with soil), are usually colonized by mycelial cords or rhizhomorphs, more frequently found in Agaricales. A classification of different wood colonization strategies by fungi was reported (Coates and Rayner, 1985) in which a specific group was recognized including cord-forming basidiomycetes that colonize buried wood. Interestingly, differences in lignin degradation and oxidoreductases secretion patterns were reported between wood (including buried wood) and leaf litter decomposers (Liers et al., 2011). In a similar way, different oxidoreductase secretion patterns have been observed in plate cultures, which were suggested to correlate with colonization strategies of different ecophysiological groups of white rot fungi (Barrasa et al., 2014). The sequencing of H. radicata genome will improve our knowledge on the enzymatic machinery used by the ecophysiological group of fungi (Agaricales) growing on buried and partially-decayed wood, which could be useful for transformation of different types of plant biomass in lignocellulose biorefineries.

References

Barrasa, J.M., Blanco, M.N., Esteve-Raventós, F., Altés, A., Checa, J., Martínez, A.T. and Ruiz-Dueñas, F.J. (2014). Wood and humus decay strategies by white-rot basidiomycetes correlate with two different dye decolorization and enzyme secretion patterns on agar plates. Fungal Genetics and Biology 72, 106-114.

Carruthers, S.M. and Rayner, A.D.M., 1979. Fungal communities in decaying hardwoods branches. Trans. Brit. Mycol. Soc., 72, 283-289. Coates, D. and Rayner, A.D.M., 1985. Fungal population and community development in cut beech logs. III: Spatial dynamics, interactions and strategies. New Phytologist 101,183-198.

Dix, N.J., Webster, J., 1995. Fungal ecology. Chapman and Hall, London.

Liers, C., Arnstadt, T., Ulrich, R., Hofrichter, M. 2011. Patterns of lignin degradation and oxidative enzyme secretion by different wood- and litter-colonizing basidiomycetes and ascomycetes grown on beech-wood. FEMS Microbiol. Ecol. 78, 91-102.

Matheny, P.B., Curtis, J.M., Hofstetter, V., Aime, M.C., Moncalvo, J.M., Ge, Z.W., Yang, Z.L., Slot, J.C., Ammirati, J.F., Baroni, T.J., Bougher, N.L., Hughes, K.W., Lodge, D.J., Kerrigan, R.W., Seidl, M.T., Aanen, D.K., DeNitis, M., Daniele, G.M., Desjardin, D.E., Kropp, B.R., Norvell, L.L., Parker, A., Vellinga, E.C., Vilgalys, R., Hibbett, D.S., 2006. Major clades of Agaricales: a multilocus phylogenetic overview. Mycologia 98, 982-995.