To investigate cation adaptation and homeostasis in Aspergillus nidulans, two transcription factor-encoding genes have been characterised. The A. nidulans orthologue crzA of the Saccharomyces cerevisiae CRZ1 gene, encoding a transcription factor mediating gene regulation by Ca2+, has been identified and deleted. The crzA deletion phenotype includes extreme sensitivity to alkaline pH, Ca2+ toxicity and aberrant morphology connected with alterations of cell wall-related phenotypes such as reduced expression of a chitin synthase gene, chsB. A fully functional C-terminally GFP-tagged form of the CrzA protein is apparently excluded from nuclei in the absence of added Ca2+ but rapidly accumulates in nuclei upon exposure to Ca2+. In addition, the previously identified sltA gene, having no identifiable homologues in yeasts, was deleted and the resulting phenotype includes considerably enhanced toxicity by a number of cations other than Ca2+ and also by alkaline pH. Reduced expression of a homologue of the S. cerevisiae P-type ATPase Na+ pump gene ENA1 might partly explain cation sensitivity of null sltA strains. Up-regulation of the homologue of the S. cerevisiae vacuolar Ca2+/H+ exchanger gene VCX1 might explain the lack of Ca2+ toxicity to null sltA mutants whereas down-regulation of this gene might be responsible for Ca2+ toxicity to null crzA mutants. Both crzA and sltA encode DNA-binding proteins and the latter exerts both positive and negative gene regulation.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|