Identification of novel genes conferring altered azole susceptibility in Aspergillus fumigatus

Abstract

Azoles are currently the mainstay of antifungal treatment both in agricultural and clinical settings. Although the target site of azole action is well studied the basis of azole resistance and the ultimate mode of action of the drug in fungi is poorly understood. In order to gain a deeper insight into these aspects of azole action restriction mediated plasmid integration (REMI) was used to create azole sensitive and resistant strains of the clinically important fungus Aspergillus fumigatus. Four azole sensitive insertions and 4 azole resistant insertions were characterised. Three phenotypes could be re-created in wild type AF210 by reintegration of rescued plasmid and a further 4 could be confirmed by complementation of the mutant phenotype with a copy of the wild type gene predicted to be disrupted by the original insertional event. Six insertions were in genes not previously associated with azole sensitivity or resistance. Two insertions occur in transporter genes that may affect drug efflux whereas others may affect transcriptional regulation of sterol biosynthesis genes and NADH metabolism in the mitochondrion. Two insertions are in genes of unknown function.