Collaborative Research: Functional and evolutionary bases of substrate-specificity in wood-decaying basidiomycetes

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Wood (lignocellulose) is one of the most abundant carbon pools in terrestrial ecosystems. Fungal decomposition of wood is a critical component of the carbon cycle, impacts soil productivity, and has the potential to be exploited in the production of biofuels and other 'green' technologies. The major wood-decaying fungi are mushroom-forming (Agaricomycetes). The physical characteristics and chemical composition of wood vary among plant species, and most wood-decaying Agaricomycetes have characteristic wood substrate ranges. However, it is not understood why individual species of wood decaying fungi tend to occur on specific plant hosts. This project will investigate the mechanisms of substrate specificity and substrate switching in wood-decaying Agaricomycetes using a combination of analyses of genes expressed during decay, and physical and chemical characterization of the decay process. Fungal enzymes that are involved in wood decay or degradation have potential applications in emerging bioprocesses, such as energy-related bioconversions, including biofuel production, and bioremediation. Enhanced understanding of the mechanisms that allow different species of fungi to exploit particular wood substrates could help guide development of genetic resources that could be used for such applied purposes. This project will support one Postdoctoral Fellow and two graduate students, and will provide training to undergraduates at three collaborating academic institutions in the US. To bring information about fungi and wood decomposition to a wide audience, this project will create interactive exhibits and develop accompanying public programs at the Worcester EcoTarium (http://www.ecotarium.org/), a science and nature museum which serves over 140,000 visitors annually including large numbers of students from regional public schools. Exhibits will illustrate fungal diversity, the decay process, and the role of fungi in the carbon cycle.The proposed research will focus on four species of Agaricomycetes (with distinct substrate preferences) with available genome sequences. The fungi will be cultured on solid wafers of four different tree species (two conifers and two hardwoods). Transcriptome profiling will be performed with the Illumina HiSeq 2000 platform, focusing on genes encoding enzymes known or suspected to be involved in wood decay, as well as co-expressed genes of unknown function. Phylogenomic analyses will make use of all available genomes of wood-decaying Agaricomycetes, focusing on gene families that are likely to play a role in decay, as informed by expression profiles. Physical and chemical characteristics of decay will be addressed using microscopy, mass spectrometry, and chemical analyses of colonized substrates. The proposed research is a collaboration between researchers with expertise in fungal systematics and molecular evolution, wood decay and forest products pathology, fungal genomics, and genetics and biochemistry of decay systems. This project will capitalize on recent advances in genomics of wood-decaying basidiomycetes. It will provide insight into the functioning and evolution of fungi in forest ecosystems, and create a framework for future studies aimed at understanding the specific plant-derived compounds that affect expression of particular fungal genes.