TRANSFORMATION OF PENICILLIUM-ROQUEFORTI TO PHLEOMYCIN-B-RESISTANCE AND TO HYGROMYCIN-B-RESISTANCE

A strain of Penicillium roqueforti was transformed to hygromycin B and phleomycin resistance using resistance genes under the control of A. nidulans sequences. The transformation efficiency ranged from 0.15 to 1 transformant per mu-g DNA per 10(6) viable protoplasts when transformants were selected on medium containing a high antibiotic concentration (7-10 times the minimum inhibitory concentration). Transformation resulted from either single copy or tandem integration of the phleomycin vector while the hygromycin vector was modified during integration. The transformed antibiotic-resistant phenotypes were mitotically stable with or without selective pressure.