Nitrite toxicity inAspergillus nidulans: a new locus in aproA1 pabaA6 yA2strain

Abstract

SUMMARY: This report describes the existence of a mutation in aproA1 pabaA6 yA2strain ofAspergillus nidulans, which prevents it growing on elevated concentrations of nitrite. The nitrite toxicity marker (nihA) resulted from a mutation in a single gene representing a new locus in linkage group I, and behaved as a recessive character. The observed recombination frequencies betweennihAandproA1and betweennihAandpabaA6were about 1 and 11%, respectively. Nitrite toxicity was not due to a defect in nitrite reductase, because the mutant grew well on nitrate. Furthermore, ammonium protected bothnis-5andniiA⁻strains against nitrite toxicity, which was not observed for thenihAstrain. Since growth of the mutant was inhibited more by a mixture of ammonium and nitrite, compared to nitrite alone, it is proposed that theproA1 pabaA6 yA2strain has a mutation leading to increased efficiency in nitrite uptake, which is not repressed by ammonium.