Mechanisms of interspecific interactions in two model brown rot fungi, Postia placenta and Gloeophyllum trabeum

Gerald Presley 1 Jiwei Zhang 1 Ellen Panisko 2 Samuel Purvine 3 Jonathan Schilling 1
1Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, USA
2Chemical and Biological Process Development, Pacific Northwest National Laboratory, Richland, Washington , USA
3Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA

Wood degrading basidiomycetes live in complex communities of microbes and interspecific interactions are vital processes for their survival. In this study, we used model interaction microcosms to pair two model decay fungi, Postia placenta and Gloeophyllum trabeum, against one another and investigate the mechanisms of interspecific interactions using transcriptomics and proteomics. We found 20 proteins, mostly of unknown function, that were secreted from exclusively at the interaction zone, 10 from P. placenta and 10 from G. trabeum. Pectinase activity was highest at the interaction zone compared to ingle species cultures or non-interacting hyphae. Most genes 4-fold or more upregulated at the interaction zone in both fungi had no known function, but the second largest group of genes upregulated were oxidoreductases. Known lignocellulose-degrading genes such as glycoside hydrolases were mostly not upregulated at the interaction zone, suggesting greater investment in biosynthesis than decay. Several secondary metabolite-synthesizing genes in G. trabeum were upregulated during the interaction, whereas this was not seen in P. placenta, suggesting the two fungi differ in competitive tactics. This work identifies several secondary metabolites synthesizing genes that could help mediate interspecific combat and identifies G. trabeum as a useful model fungus for studying the interactions of wood degrading basidiomycetes.