Isolation of UV-induced mutations in the areA nitrogen regulatory gene of Aspergillus niger, and construction of a disruption mutant

The areA gene of filamentous fungi encodes a positive-acting transcriptiona l factor required for the expression of genes involved in the utilisation o f nitrogen sources other than ammonium and glutamine. In Aspergillus niger we have isolated three UV-induced areA mutants and constructed a well-defin ed disruption allele of the areA gene. The areA gene was genetically locali sed on Linkage Group III, 3.6 map units (m.u.) from bioA1 and 4.5 m.u. from lysA7. Analysis of the expression of the nitrate reductase encoding gene a nd of nitrate reductase activities show that the mutated areA strains behav e as loss-of-function mutants and can be classified as areA(r) type. In add ition, growth tests were performed using several nitrogen sources in combin ation with glucose. The results suggest that, unlike the case in A. nidulan s, in A. niger the AreA protein also plays a role in the presence of ammoni um. Furthermore, the spectrum of protease activities secreted by A. niger d iffers from that produced by A. nidulans, as only A. niger is able to degra de elastin.