Transformation of the mycoparasite Parasitella simplex to neomycin resistance.

The facultatively parasitic zygomycete Parasitella simplex was transformed to neomycin resistance by a vector, which had been developed primarily for transformation of its host Absidia glauca. This plasmid, pAmNEF21, contained the bacterial resistance gene for neomycin (NPTII) under the control of the promoter region from the gene for elongation factor 1 (tef) isolated from A. glauca. Both flanking regions of the marker gene contain parts of the structural tef gene. DNA isolated from two Parasitella transformants was re-transformed in E. coli and the resulting plasmids, pAt21 and pAt35, were analyzed. The restriction map and Southern blot analysis show that both plasmids are rearranged. They had lost the structural tef information and were found to contain new DNA fragments, which were identical in both cases. Southern blot analysis of the transformants indicates that the rearranged plasmids are present in the fungal transformants and that the changes are not the result of re-transformation in E. coli. Plasmids were only recovered after growth under selective conditions. Southern blot analysis and re-transformation with undigested transformant DNA shows that the plasmids are replicated autonomously.