Cloning an Aspergillus nidulans developmental gene by transformation.

We have developed a transformation system for Aspergillus nidulans giving a frequency of transformation high enough to screen a gene bank from which we were able to isolate and clone the A. nidulans developmental gene brlA by visual selection. The vector contains the selective marker argB+, and with it a frequency of transformation of 500 stable transformants/micrograms plasmid DNA can regularly be achieved. The evidence suggests that transformation is by integration but spontaneous excision of integrated plasmids is apparently frequent enough to allow the recovery of transforming plasmids in Escherichia coli.