COTRANSFORMATION IN THE PHYTOPATHOGENIC FUNGUS SEPTORIA-NODORUM

Septoria nodorum has been cotransformed with a number of DNA species. Transformants were selected for resistance to hygromycin B conferred by plasmid pAN7-1. When a second vector (pBT6, pAN5-41B or λ) was included in the transformation experiments, approximately 50% of the hygromycin-resistant transformants had expressed and/or integrated this unselected DNA. Plasmid pBT6 cotransformed Septoria to MBC-resistance by expression of a benomyl-resistant allele of the Neurospora crassa β-tubulin gene (tub-2). Endogenous β-galactosidase in S. nodorum was found to be repressed by growth on sucrose and this allowed the detection of cotransformants expressing a translational fusion between the Aspergillus nidulans gpd gene and the Escherichia coli lazZ gene, carried by the plasmid pAN5-41B. Unlike the presence of the two unselected vectors mentioned above, the presence of wild-type λ-DNA in cotransformation experiments lowered the frequency with which hygromycin-resistant transformants appeared. However, 50% of these were still found to have been cotransformed following Southern hybridization analysis. These high cotransformation frequencies are consistent with previous reports for Septoria and other fungal species and are suggestive of the presence of a small subpopulation of competent protoplasts. © 1990, British Mycological Society. All rights reserved.