Polyporus arcularius fruiting body. Picture by Zaca (www.mushroomobserver.com).

Within the framework of the CSP 'Metatranscriptomics of Forest Soil Ecosystems' project, we are aiming to explore the interaction of forest trees with communities of soil fungi, including ectomycorrhizal symbionts that dramatically affect bioenergy-relevant plant growth, and saprotrophic soil fungi impacting carbon sequestration in forests. We are sequencing the genome of the most abundant fungal species harvested on studied sites to serve as the foundation for a reference database for metagenomics of fungi and for a comprehensive survey of the potential soil fungal metabolome.

Polyporus arcularius
The genus Polyporus is the type genus of the large basidiomycete order Polyporales, which includes some of the most powerful wood-degrading fungi. P. arcularius is a common species on various types of hardwoods, typically appearing on smaller fallen branches in the early phase of decomposition. P. arcularius causes a white rot, i.e. it has a powerful set of peroxidases to decompose both cellulose and lignin in the wood. A comparison of the plant cell wall degrading enzymes of this species to that of a suite of other Polyporales species will contribute to inferring a more detailed view on the evolution of wood-decay in the Basidiomycota.
In addition to wood-decay chemistry, the genome of P. arcularius will provide an excellent opportunity for investigating the evolution of hymenophore development. The hymenophore is the spore-bearing surface of mushrooms and can take several morphological manifestations, such as pored, gilled, toothed or smooth. All of these morphologies aim to increase the useful surface for spore production, which helps in the dispersal of the fungus. P. arcularius has a pored hymenophore, but the pores are wide, resembling a transitional stage between gilled and pored surfaces, where single gills are anastomosing to give a pored appearance. Indeed, P. arcularius is closely related to the gilled genus Lentinus, with which it shares the production of a pileus (cap) on a centrally attached stipe (stalk). Another group of “gilled polypores” is the genus Panus, including P. rudis, which has also had a complete genome sequence produced at the JGI. A comparison of P. arcularius with P. rudis will provide insights into the development of hymenophores and the evolution of increasing hymenophore surfaces.