Functional elements of the promoter region of the Aspergillus oryzae glaA gene encoding glucoamylase

Analysis was made of the promoter region of the Aspergillus oryzae glaA gene encoding glucoamylase. Northern blots using a glucoamylase cDNA as a probe indicated that the amount of mRNA corresponding to the glaA gene increased when expression was induced by starch or maltose. The promoter region of the glaA gene was fused to the Escherichia coli uidA gene, encoding β-glucuronidase (GUS), and the resultant plasmid was introduced into A. oryzae. Expression of GUS protein in the A. oryzae transformants was induced by maltose, indicating that the glaA-GUS gene was regulated at the level of transcription in the presence of maltose. The nucleotide sequence 1.1 kb upstream of the glaA coding region was determined. A comparison of the nucleotide sequence of the A. oryzae glaA promoter with those of A. oryzae amyB, encoding α-amylase, and A. niger glaA showed two regions with similar sequences. Deletion and site-specific mutation analysis of these homologous regions indicated that both are essential for direct high-level expression when grown on maltose.