Photo by: Tom Kuster, Forest Products Laboratory, USDA Forest Service.

The Genome Sequence of the Brown Rot Fungus Postia placenta

The brown rot fungi, a group of filamentous basidiomycetes, rapidly depolymerize the cellulose in wood without significant lignin removal.  This type of decay differs sharply from white rot fungi such as Phanerochaete chrysosporiu m which simultaneously degrade lignin and cellulose.  Both white and brown rot fungi are common inhabitants of forest litter where they play an important role in carbon cycling.   Beyond this, brown rot fungi are most commonly responsible for the destructive decay of wood in buildings and other structures, and it has estimated that 10% of the U.S. timber harvest decays in service each year.  Irrespective of their economic importance, the mechanism of brown rot wood decay is poorly understood.  To better understand the biology of this type of wood degradation, the Department of Energy’s Joint Genome Institute has sequenced the entire 33Mb genome of the model brown rot, Postia placenta.  Using total genomic DNA from dikaryotic strain MAD-698, the JGI generated 571,000 reads that assembled into 1243 haplotype scaffolds, with 85 of these scaffolds covering half of the genome sequence.  Our investigation into the genome will provide an invaluable mechanistic perspective on cellulose depolymerization, and the unique haplotype assembly will allow us to gain insights into the complexities of genome evolution.