A novel improved method for Aspergillus nidulans transformation.

We systematically investigated the efficiency of Aspergillus nidulans transformation using protoplasts prepared from different stages of conidiospore germination and young mycelium. Using standard integrative plasmids, increased transformation yields were obtained with protoplasts isolated from a specific stage coincident with germ tube emergence. This increase ranged, on the average, from two- to eightfold depending on different plasmids used. Transformation efficiencies with a replicative plasmid were similar to those obtained using previously described methods. Although this observation suggests that elevated transformation efficiencies might be due to increased efficiency of recombination between plasmid and genomic sequences, we cannot exclude other factors associated with the particular developmental stage used. In the course of this study, we also examined the effect of other parameters that might enhance transformation yields. The method described is also significantly easier and faster than other current methods.