The genome of P. ostreatus contains 12 laccase genes clustered into three major groups (Fig. 1). Lacc2 and Lacc10 have been shown to be overexpressed in the mycelia of P. ostreatus in submerged culture when induced by wheat straw extract in a chemically defined medium [24]. However, the present study showed that expression of the two laccases was negligible in sawdust medium at all developmental stages (Fig. 2C), indicating that P. ostreatus expresses different laccase enzymes depending on the medium conditions. Lacc1 and Lacc3 were specific to the mycelial stage in solid medium (Fig. 2C). Lacc6 was highly expressed in all developmental stages whereas Lacc5 and Lacc12 were specific for fruiting bodies and primordia, respectively (Fig. 2C). Lacc6 was characterized as a blue laccase under the name POXA1b [31].