The symbiosis between ectomycorrhizal fungi and trees is an essential part of forest ecology and depends entirely on the communication between the two partners for establishing and maintaining the relationship. The identification and characterization of differentially expressed genes is a step to identifying such signals and to understanding the regulation of this process. We determined the role of hydrophobins produced by Tricholoma terreum in mycorrhiza formation and hyphal development. A hydrophobin was purified from culture supernatant, and the corresponding gene was identified. The gene is expressed in aerial mycelium and in mycorrhiza. By using a heterologous antiserum directed against a hydrophobin found in the aerial mycelium of Schizophyllum commune, we detected a hydrophobin in the symbiosis between T. terreum and its native pine host Pinus sylvestris. The hydrophobin was found in aerial mycelium of the hyphal mantle and also in the Hartig net hyphae, which form the interface between both partners. Interestingly, this was not the case in the interaction of T. terreum with a host of low compatibility, the spruce Picea abies. The differential expression with respect to host was verified at the transcriptional level by competitive PCR. The differential protein accumulation pattern with respect to host compatibility seen by immunofluorescence staining can thus be attributed at least in part to transcriptional control of the hyd1 gene.

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High b-galactosidase activities could easily be detected in culture supernatants of Schizophyllum commune grown on lactose and glycerol. The addition of glucose to the growth medium resulted in lower b-galactosidase activities. Two different enzymes exhibiting b-galactosidase activity were purified by affinity adsorption and anion exchange chromatography. Enzyme Gal1 possessed high substrate specificity for b-galactosides. The native enzyme (molecular mass 140 kDa) was a homodimer of subunits with an apparent molecular mass of 66 kDa. Antibodies raised against E. coli b-galactosidase recognized Schizophyllum commune Gal1. The second enzyme, Gal2, had a lower specific activity and hydrolyzed b-glucosides as well as b-galactosides. The previously characterized b-glucosidase II of S. commune (LO et al. 1990) was shown to be identical with Gal2. Both enzymes had temperature optima of 40 °C with less than 5% remaining activity at 60 °C which would allow the use of a thermo-tolerant heterologous b-galactosidase as a reporter gene in S. commune.b-Galactosidases are well studied enzymes and widely used tools in molecular biology (BADER et al. 1988, JACOBSEN et al. 1994, STEERS and SHIFRIN 1967, STEERS et al. 1971. Especially b-galactosidase reporter gene systems have found wide application due to the easy detection of the gene product. In biological systems where no endogenous activity for b-galactosidases was found, like in the yeast Saccharomyces cerevisiae, heterologous expression of b-galactosidase is a highly convenient method to monitor gene expression. In fungi that excrete b-galactosidases, however, the endogenous gene(s) are to be disrupted before a b-galactosidase reporter gene is introduced, or the experimental conditions should be chosen to minimize the endogenous enzyme activity.The white-rot fungus Schizophyllum commune is able to use a wide spectrum of growth substrates. Like many other saprophytic fungi, it secretes many hydrolytic enzymes into the culture medium that degrade biopolymers satisfactorily for uptake and metabolization. Glycosidases play a dominant role among these exo-enzymes since they degrade cellulose, hemicellulose and other polysaccharides that are used as energy and carbon sources by the fungus (WESSELS 1987, WILLICK et al. 1984. To digest lactose, b-galactosidase activity is required which is supplied by two types of enzymes: highly specific b-galactosidases and glycosidases with broader substrate specificity. Especially the b-glucosidases of S. commune were thoroughly investigated earlier (CLARKE 1990, LO et al. 1990, MORANELLI et al. 1986, WILSON and NIEDERPRUEM 1967. To identify specific b-galactosidases and to determine the biochemical parameters of the different enzymes, the b-galactolytic enzymes of S. commune were isolated and characterized in this study.The regulation of b-galactosidase expression has been studied in detail for Escherichia coli where lacZ gene expression is induced by the natural substrate lactose or with artificial inducers like IPTG. Glucose led to the inhib...

High β‐galactosidase activities could easily be detected in culture supernatants of Schizophyllum commune grown on lactose and glycerol. The addition of glucose to the growth medium resulted in lower β‐galactosidase activities. Two different enzymes exhibiting β‐galactosidase activity were purified by affinity adsorption and anion exchange chromatography. Enzyme Gal1 possessed high substrate specificity for β‐galactosides. The native enzyme (molecular mass 140 kDa) was a homo‐dimer of subunits with an apparent molecular mass of 66 kDa. Antibodies raised against E. coli β‐galactosidase recognized Schizophyllum commune Gal1. The second enzyme, Gal2, had a lower specific activity and hydrolyzed β‐glucosides as well as β‐galactosides. The previously characterized β‐glucosidase II of S. commune (Lo et al. 1990) was shown to be identical with Gal2. Both enzymes had temperature optima of 40 °C with less than 5% remaining activity at 60 °C which would allow the use of a thermo‐tolerant heterologous β‐galactosidase as a reporter gene in S. commune.