Two zinc finger transcription factors, CrzA and SltA, are involved in cation homoeostasis and detoxification in Aspergillus nidulans.
To investigate cation adaptation and homoeostasis in Aspergillus nidulans, two transcription-factor-encoding genes have been characterized. The A. nidulans orthologue crzA of the Saccharomyces cerevisiae CRZ1 gene, encoding a transcription factor mediating gene regulation by Ca(2+), has been identified and deleted. The crzA deletion phenotype includes extreme sensitivity to alkaline pH, Ca(2+) 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 (green fluorescent protein)-tagged form of the CrzA protein is apparently excluded from nuclei in the absence of added Ca(2+), but rapidly accumulates in nuclei upon exposure to Ca(2+). In addition, the previously identified sltA gene, which has no identifiable homologues in yeasts, was deleted, and the resulting phenotype includes considerably enhanced toxicity by a number of cations other than Ca(2+) and also by alkaline pH. Reduced expression of a homologue of the S. cerevisiae P-type ATPase Na(+) pump gene ENA1 might partly explain the cation sensitivity of sltA-null strains. Up-regulation of the homologue of the S. cerevisiae vacuolar Ca(2+)/H(+) exchanger gene VCX1 might explain the lack of Ca(2+) toxicity to null-sltA mutants, whereas down-regulation of this gene might be responsible for Ca(2+) toxicity to crzA-null mutants. Both crzA and sltA encode DNA-binding proteins, and the latter exerts both positive and negative gene regulation.
Spielvogel
Anja
A
Department of Microbiology and Genetics, Institute of Biotechnology, Berlin University of Technology, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany.
Findon
Helen
H
Arst
Herbert N
HN
Araújo-Bazán
Lidia
L
Hernández-Ortíz
Patricia
P
Stahl
Ulf
U
Meyer
Vera
V
Espeso
Eduardo A
EA
D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism / Q000633:toxicity; D002413:Cations, Divalent / Q000378:metabolism* / Q000633:toxicity; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005656:Fungal Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D016335:Zinc Fingers
D002413:Cations, Divalent; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D002118:Calcium