ESTs from the basidiomycete Schizophyllum commune grown on nitrogen-replete and nitrogen-limited media S. Guettler, 1 E.N. Jackson, 2 S.A. Lucchese, 3 L. Honaas, A. Green, C.T. Hittinger, 4 Y. Tian, W.W. Lilly, and A.C. Gathman * Southeast Missouri State University Biology Department, 1 University Plaza, Cape Girardeau, MO 63701, USA Received 20 December 2002; accepted 12 February 2003 Abstract Lambda phage cDNA libraries were constructed using mRNAs from the basidiomycete Schizophyllum commune grown on media with high or low nitrogen concentrations. A total of 440 clones were sequenced, representing 373 distinct transcripts. Of these, 166 showed significant similarity to annotated genes in GenBank. Those that could be tentatively identified using BLAST searches were classified by function using the Gene Ontology (GO) database. Genes with products involved in cell-cycle processes were more frequent in the nitrogen-limited libraries, while genes with products involved in protein biosynthesis were more frequent in the nitrogen-replete library. Overall, clones showed much greater similarity to the one publicly available basidiomycete genome, Phanerochaete chrysosporium, than to any of the ascomycete genomes. Ó 2003 Elsevier Science (USA). All rights reserved. Keywords: Basidiomycetes; Nitrogen limitation; EST 1. Introduction Schizophyllum commune is a widely distributed wood- decaying basidiomycete. Over 50 years of cytological, physiological, biochemical, and genetic studies provide a strong basis for research using this organism. It has proven to be a tractable model system to understand mechanisms of mating (Casselton and K€ ues, 1994), fruit body formation (Wessels, 1993), signal transduction (Fowler et al., 1999), biodegradation (Haltrich et al., 1993), and nutrient recycling and translocation (Lilly et al., 1991; Olsson and Gray, 1998). In the past decade, the organism has also been demonstrated to be an opportunistic human pathogen of some importance in both immune-compromised and immune-competent in- dividuals (Lacaz et al., 1996; Sigler et al., 1999). Fungi that inhabit wood live in a substrate that is a very poor source of nutrients other than carbon (Carlile and Watkinson, 1994). Nitrogen constitutes only 0.01– 0.3% of the dry weight of wood, with a concentration estimated at 0.0075 M (Boddy and Watkinson, 1995). Furthermore, some of this nitrogen is sequestered in lignin and other aromatics and is not available to fungi lacking the ability to metabolize these molecules. Fur- thermore, few wood-decayers can utilize oxidized forms of nitrogen such as nitrate (Cooke and Rayner, 1984; n.b. S. commune does not utilize nitrate). Indeed, most data suggest that nitrogen is the limiting nutrient in fungal growth in wood (Levi and Cowling, 1969; Merrill and Cowling, 1966; Park, 1976). Thus, the mechanisms by which wood-decaying fungi respond to nitrogen limitation are crucial to an understanding of their physiology. The principal mechanism that supports sustained growth in S. commune under nitrogen-limited condi- tions is autolysis of older cells and the subsequent Fungal Genetics and Biology 39 (2003) 191–198 www.elsevier.com/locate/yfgbi * Corresponding author. Fax: 1-573-986-6433. E-mail address: agathman@biology.semo.edu (A.C. Gathman). 1 Current address: Developmental Biology Programme, European Molecular Biology Laboratory, Heidelberg, Germany. 2 Current address: Center for Cardiovascular Research, Washing- ton University School of Medicine, St. Louis, MO, USA. 3 Current address: University of Missouri Medical School, Colum- bia, MO, USA. 4 Current address: Laboratory of Genetics, University of Wiscon- sin, Madison, WI, USA. 1087-1845/03/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S1087-1845(03)00017-3