Phosphatase regulation inAspergillus nidulans: responses to nutritional starvation

Abstract

SUMMARYThe regulation of the syntheses of a number of phosphatases in the fungusAspergillus nidulanshas been examined. Levels of the intracellular alkaline phosphatase P11 are increased by starvation for carbon, nitrogen, phosphorus or sulphur. There is, however, no evidence that any of the wide domain regulatory genes which mediate sufficiency-triggered repression for each of these elements involved. A possible interpretation is that all four forms of starvation result in accumulation of an inducing metabolite. ThepalcA gene has been identified as a wide domain, probably positive-acting regulatory gene mediating phosphate repression. ThepalcA product controls the syntheses of alkaline phosphatase PI, acid phosphatases PIII and PV, a phosphodiesterase lacking phosphomonoesterase activity and probably also a phosphate permease. Mutations resulting in derepression of phosphate-repressible activities at acid but not alkaline growth pH define a gene designatedpacJ.pacJ mutations also confer arsenate resistance at low but not high pH. It is likely that phosphate derepression and arsenate resistance result from reduced uptake of H2PO4−. Finally, phosphatase regulation might be less complex than previously thought. Mutations designatedrand mapping at several loci apparently have no effect on phosphatase. They enhance phosphatase colony staining but this occurs even if the phosphatase substrates are omitted from the staining mixtures.rmutations appear to promote reactions converting the diazonium salts used for phosphatase staining to coloured precipitates.