Genetics of Resistance to Itraconazole in Aspergillus amstelodami

Abstract

A sample of 24 spontaneous mutants resistant to the antifungal itraconazole were isolated in the brown strain A76 (18 mutants) and the white strain AZG131 (6 mutants) of the fungus Aspergillus amstelodami . Dominance tests, in heterokaryons, have shown that all mutants are recessive to their respective wild type alleles. Complementation tests, also in heterokaryons, among the mutants indicated that all mutantions belong to a single gene given the gene symbol itzA as it was the first gene of its kind to be identified in this fungus. There are nine (1-IX) linkage groups so far recognized in this fungus and haploidization analyses of diploids between one of the mutants and suitable master stains put the gene itzA outside groups I-VII, but its relationship to groups VIII and IX was not determined as no master strains carrying markers on these two groups were available at the time. Also, the biochemical function of itzA in relation to the three genes cyp51A, cyp51B and MDR, recognized to confer resistance to itraconazole in Aspergillus could not be determined.