Transformation of Penicillium roqueforti to phleomycin- and to hygromycin B-resistance

Summary 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 g DNA per 10⁶ 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.