The identification of mutations in Aspergillus nidulans that lead to increased levels of ADHII

Summary There are at least three alcohol dehydrogenases in Aspergillus nidulans. ADHII has been observed in polyacrylamide gels stained for ADH activity but, unlike ADHI and ADHIII, no physiological function has been attributed to it. This paper describes mutations that have been isolated from strains carrying a deletion in the structural gene for ADHI (alcA) and its adjacent positively-acting regulatory gene (alcR) that restore some ability to utilise ethanol as a carbon source. The mutations map at three loci, and all show elevated levels of the ADHII staining band. An assay for ADHII has been developed. The growth on ethanol has been shown to be dependent on the previously identified aldehyde dehydrogenase (structural gene, aldA). Two of the mutations, alcD and alcE, represent newly discovered mutations affecting ethanol utilisation while the third mutation is in amdA, a previously described trans-acting regulatory protein.