The three enzymes necessary to catabolize quinate to protocatechuate are inducible by quinic acid, and transcription of their corresponding genes is controlled by the action of a positively acting activator gene and a negatively acting repressor gene. Transformed strains of Aspergillus nidulans containing multiple copies of the activator gene (QUTA) but single copies of the other QUT genes retain normal regulation of the gene cluster and do not show any overexpression of the three quinic acid catabolic enzymes. Transformed strains containing equal multiple copies of the activator gene (QUTA) and QUTE (encoding catabolic 3-dehydroquinase), but single copies of the other QUT genes, retain normal regulation of the QUT gene cluster, but selectively overexpress the QUTE gene upon quinic acid induction. Data are presented that strongly suggested that the gene QUTG, which is physically located within the QUT gene cluster and for which no function has been identified, is not required for expression of the gene cluster and does not encode a chlorogenic acid esterase.
Selective overexpression of the QUTE gene encoding catabolic 3-dehydroquinase in multicopy transformants of Aspergillus nidulans