Activation of expression of the lcc4 and tir genes encoding laccase and tyrosinase was observed during transition of a xylotrophic basidiomycete Lentinus edodes from the vegetative to the generative growth stages. This was especially pronounced in the brown mycelial mat (the stage preceding formation of the fruiting bodies). Development of this structure was shown to be associated with a sharp increase of laccase and tyrosinase activities, as well as with rearrangements in the phenol oxidase complex. Formation of the tissues with thickened cell walls was associated with enhanced expression of the chi and exg1 genes encoding chitinase and glucanase, respectively. Exogenous treatment of the vegetative mycelium with laccase preparation from the brown mycelial mat promoted formation of this morphological structure. Activation of the lcc4, tir, chi, and exg1 genes may be used as a marker of readiness to fruition in xylotrophic fungi.