Transformation of Aspergillus oryzae using the A. niger pyrG gene.

A transformation system for Aspergillus oryzae based on the orotidine-5'-phosphate decarboxylase gene (pyrG) was developed. Transformation frequencies of up to 16 transformants per microgram of DNA were obtained with the vector pAB4-1, which carries the pyrG gene of A. niger. Southern blotting analysis showed that vector DNA sequences were integrated into the chromosomal DNA, in various copy numbers and presumably at different sites. Efficient cotransformation of an unselectable gene was also shown. Under the conditions used no transformants were obtained with the equivalent pyr4 gene of Neurospora crassa.