AreA controls nitrogen source utilisation during both growth programs of the dimorphic fungus Penicillium marneffei

The opportunistic pathogen Penicillium marneffei displays a temperature-dependent dimorphic switching program with saprophytic hyphal growth at 25 °C and yeast growth at 37 °C. The areA gene of P. marneffei has been isolated and found to be required for the utilisation of nonpreferred nitrogen sources during both growth programs of P. marneffei, albeit to differing degrees. Based on this functional characterisation and high degree of sequence conservation with other fungal GATA factors, P. marneffei areA represents an orthologue of Aspergillus nidulans areA and Neurospora crassa NIT2. Based on this study it is proposed that AreA is likely to contribute to the pathogenicity of P. marneffei by facilitating growth in the host environment and regulating the expression of potential virulence factors such as extracellular proteases.     

Regulation by carbon and nitrogen sources of a family of cellulases in Aspergillus nidulans

The total amount of Aspergillus nidulans secreted cellulases is affected by both the carbon and nitrogen source present in the medium, and is regulated directly and/or indirectly by the carbon metabolism regulators, CreA, CreB, and CreC, and the global nitrogen metabolism regulator, AreA. We have characterized two A. nidulans genes that encode exo-cellulases, and one gene that encodes an endo-cellulase which is additional to the previously described endo-cellulase encoding gene, eglA. The putative regulatory regions 5(') of all the genes contain potential binding sites for the global carbon and nitrogen regulatory proteins, CreA and AreA. The sequences 5(') of eglA and eglB also contain potential consensus binding sites for XlnR which is involved in induction in Aspergillus niger, but none of the 5(') sequences contains an exact copy of the AceII DNA binding consensus sequence involved in induction in Trichoderma reesei, and thus it is likely that they may be induced by different pathway specific regulatory proteins.     

Studies on the role of the areA gene in the regulation of nitrogen catabolism in Aspergillus nidulans.

Mutants of Apergillus nidulans with lesions in a gene, areA (formerly called amdT), have been isolated by a variety of different selection methods. The areA mutants show a range of pleiotropic growth responses to a number of compounds as sole nitrogen sources, but are normal in utilization of carbon sources. The levels of two amidase enzymes as well as urease have been investigated in the mutants and have been shown to be affected by this gene. Most of the areA mutants have much lower amidase-specific activities when grown in ammonium-containing medium, compared with mycelium incubated in medium lacking a nitrogen source. Some of the areA mutants do not show derepression of urease upon relief of ammonium repression. The dominance relationships of areA alleles have been investigated in heterozygous diploids, and these studies lend support to the proposal that areA codes for a positively acting regulatory product. One of the new areA alleles is partially dominant to areA+ and areA102. This may be a result of negative complementation or indicate that areA has an additional negative regulatory function. Investigation of various amdR; areA double mutants has led to the conclusion that amdR and areA participate in independent regulatory circuits in the control of acetamide utilization. Studies on an amdRc; areA double mutant indicate that areA is involved in derepression of acetamidase upon relief of ammonium repression.     

The areAr mutations of Aspergillus nidulans confer low pH sensitivity in the presence of ammonium as the only nitrogen source

The utilization of nitrogen sources by the fungus Aspergillus nidulans is controlled by a mechanism mediated by areA , a wide domain regulatory gene. It has been verified that the strains carrying the mutant allele areA ^r are inhibited when growing at low pH in the presence of ammonium as the only nitrogen source. The genetic analysis of this marker showed that it apparently maps at the areA locus.