This research elucidates mechanisms of sustained mycelial growth of the wood-decaying fungus, Schizophyllum commune. The first phase of the project involves characterization of proteolytic enzyme systems involved in intramycelial protein turnover and recycling during nitrogen-limited growth. This problem is being addressed by purifying several proteases found in control and nitrogen-starved colonies. Subsequent classification of these enzymes is being based on biochemical characteristics, substrate and inhibitor specificity, and subcellular localization. An investigation for potential ubiquitin-mediated proteolysis also is being performed. The second phase provides initial data for studying the regulation of the nitrogen-stress response. Antibodies are being generated to specific proteases which are differentially expressed. These antibodies are to be used to assess levels of expression during nitrogen-stress and to analyze mutants for deficiencies in specific protease production. In vivo and in vitro translation products for control and nitrogen- stressed colonies are being analyzed. In addition, the potential for using heterologous cDNA probes for some specific protease messages is being investigated. This project complements other Schizophyllum research and provides a fungal system in which nutrient-stress related autolysis can be studied in the absence of sexual differentiation. Schizophyllum commune is a model system for studying biological processes in basidiomycetes and other fungi. Because it is a wood-decayer in nature, results from the proposed research should lead to a better understanding of other, more economically important wood-decaying fungi. Such fungi are of interest either because of their capability to destroy wood building materials or for their potential in biomass conversion of agricultural waste materials. It is thought that nitrogen is the limiting factor in the natural growth substrate for wood-decayers, thus our understanding of nitrogen nutrition of these organisms may lead to better methods for their control in the first instance or better methods and/or genetically engineered strains for cultivation in the latter.
