Regulation of the expression of the isocitrate lyase gene (acuD) of Aspergillus nidulans

Analysis of the promoter region of the acetate-induced isocitrate lyase gene (acuD) of Aspergillus nidulans is described. Transcription start sites were detected at positions -163, -170 and approximately -281 upstream of the ATG. Transcription analysis showed that the acuD gene is transcribed during growth on acetate but not on hexoses or glycerol. Expression of the acuD gene was studied under inducing and repressing conditions in cre+, creA, creB and creC mutant strains, showing that the creA(d)-1 mutation led to slight derepression of isocitrate lyase. Regulation of expression of the acuD gene was also studied using an in-frame fusion with the lacZ gene of Escherichia coli. Several deletions were made in order to identify the regions responsible for acetate induction and repression. A deletion of the -412 to -200 bp upstream region resulted in loss of all promoter activity and a smaller deletion within this region abolished most of the acetate inducibility.