REGULATION OF THE GLAA GENE OF ASPERGILLUS-NIGER

The glucoamylase gene of Aspergillus niger, glaA, is expressed at high levels in the presence of starch. We have determined the nucleotide sequence of 1966 bp of the 5' flanking region of the glaA gene and have begun to identify sequences important for the control of glaA expression by deletion analysis. Constructs containing deletions extending into the glaA gene promoter were introduced into an A. niger host whose own glaA gene had been disrupted by a gene replacement event. Secreted levels of glucoamylase, expressed from each of the recombinant glaA genes, were measured by enzyme immunoassay. The effect of each deletion on the expression of glaA, when grown on differing carbon sources, was used to determine the limits of sequences upstream of glaA responsible for gene regulation. A region between -562 and -318 appears to direct high-level expression, whereas only 214 bp of 5' flanking sequence is required to initiate the start to transcription.