title: PRR1, a homolog of Aspergillus nidulans palF, controls pH-dependent gene expression and filamentation in Candida albicans.
abstract: The pH of the environment has been implicated in controlling the yeast-hypha transition and pathogenesis of Candida albicans. Several C. albicans genes, including PHR1 and PHR2, are pH dependent in their expression. To investigate the mechanism of pH-dependent expression, we have cloned and characterized PRR1 (for pH response regulator). PRR1 is homologous to palF, a component of the pH response pathway in Aspergillus nidulans. Expression of PRR1 was itself pH dependent, being maximal at acid pH but reduced severalfold at alkaline pH. In a prr1 null mutant the alkaline-induced expression of PHR1 was completely abolished. Conversely, expression of PHR2 was no longer repressed at alkaline pH. A prr1 null mutant exhibited no morphological abnormalities at either pH; however, it lost the ability to form hyphae on medium 199 and on 10% serum plates. The ability to filament on serum was not restored by forced expression of PHR1, indicating that additional PRR1-dependent genes are required for hyphal development. These developmental genes appear to be distinct from those controlled by the developmental regulator EFG1, since the EFG1-dependent gene HWP1 was expressed normally in the prr1 null mutant. We conclude that PRR1 encodes a component of the pH-dependent response pathway in C. albicans and that this pathway regulates the expression of multiple components of hyphal development.
authors.affiliation: Department of Microbiology and Immunology, Georgetown University, Washington, D.C. 20007-2197, USA.
authors.forename: A
authors.initials: A
authors.lastname: Porta
authors.forename: A M
authors.initials: AM
authors.lastname: Ramon
authors.forename: W A
authors.initials: WA
authors.lastname: Fonzi
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000235:genetics*; D002176:Candida albicans / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016415:Sequence Alignment; D014157:Transcription Factors; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; C121438:EFG1 protein, Candida albicans; D005656:Fungal Proteins; C107929:PALF protein, Emericella nidulans; D014157:Transcription Factors