Transformations of Penicillium islandicum and Penicillium frequentans that produce anthraquinone-related compounds

Wild-type strains of Penicillium islandicum and Penicillium frequentans, which produce anthraquinone and related compounds, were transformed to benomyl and hygromycin B resistance. Plasmids pSV50 and pBT6, with benomyl-resistant -tublin genes, and plasmids pAN7-1 and pDH25, with a bacterial hygromycin phosphotransferase gene under the control of Aspergillus nidulans sequences, were used respectively. Transformation frequencies with these plasmids were 10–20 transformants per g of DNA per 4-8×10⁷ viable protoplasts. Intergration of plasmid DNAs into chromosomal DNAs was confirmed by Southern-blot analysis. Copy numbers and sites of integration varied among transformants. The integrated plasmid DNAs conferring a drug-resistant phenotype were mitotically stable with or without selection. The demonstration of such transformation systems is the essential first step in the application of recombinant DNA technology to study the biosynthetic genes of anthraquinone and related compounds in P. islandicum and P. frequentans.