ADHII in Aspergillus nidulans is induced by carbon starvation stress

in Aspergillus nidulans there are three NAD(+)-dependent alcohol dehydrogen ases (ADHs) that are capable of utilizing ethanol as a substrate. ADHI is t he physiological enzyme of ethanol catabolism and ADHIII is induced under c onditions of anaerobiosis. The physiological role of ADHII (structural gene alcB) is unknown. We have measured beta -galactosidase in a transformant w ith an alcB::lacZ fusion and have shown that alcB is maximally expressed un der conditions of carbon starvation. The behavior of the alcB::lacZ transfo rmant suggests a hierarchy of repressing carbon sources characteristic of r epression by the general carbon catabolite repressor protein, CreA, but in a creA(d)30 background the transformant shows only partial derepression of P-galactosidase on 1% glucose compared to the creA(+) strain. Our results s uggest that, in addition to carbon catabolite repression acting via CreA, a CreA-independent mechanism is involved in induction of alcB on carbon star vation. (C) 2001 Academic Press.