Stable and transient transformation, and a promoter assay in the selective lignin-degrading fungus, Ceriporiopsis subvermispora.

A genetic transformation system was developed for the selective white rot basidiomycete Ceriporiopsis subvermispora using a modified protocol with polyethylene glycol and CaCl treatment of the protoplasts and plasmids harboring recombinant hygromycin phosphotransferase (hph) driven by a homologous promoter. During repeated transfer on fresh potato dextrose agar plates containing 100 µg/ml hygromycin B, most transformants lost drug resistance, while the remaining isolates showed stable resistance over five transfers. No drug-resistant colonies appeared in control experiments without DNA or using a promoter-less derivative of the plasmid, indicating that a transient expression of the recombinant hph was driven by the promoter sequence in these unstable drug-resistant transformants.