Recent Advances on the Genomics of Litter- and Soil-Inhabiting Agaricomycetes

Fungi, particularly the Agaricomycetes, play a pivotal role cycling nutrients in forest soils. Although these filamentous fungi are clearly responsible for lignocellulose decomposition, the underlying mechanisms remain uncertain. This article reviews current understanding of Agaricomycete physiology as it relates to lignocellulose conversions. Fresh insights into the mechanisms of plant cell wall degradation have been made possible by recently available genome sequences. For efficient lignin degradation, the repertoire of genes and expression analyses support an important role for high oxidation potential peroxidases working in conjunction with peroxide-generating oxidases. Generally associated with dead wood, some of these “white rot” fungi are also tree pathogens and litter-inhabiting saprophytes. In contrast, certain wood-decay fungi are unable to remove lignin but have adapted to rapidly depolymerize cellulose. Such decay patterns are typically classified as brown rot, and evidence suggests the involvement of small molecular oxidants such as hydroxyl radical. Uncertainty remains in part due to the dearth of experimental tools, but progress in transcriptomics, proteomics, and genetic transformation offers opportunities for rapid advances.