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Mol. Cell. Biol., 02 1995, 601-613, Vol 15, No. 2
SM Saporito-Irwin, CE Birse, PS Sypherd and WA Fonzi
Candida albicans, like many fungi, exhibits morphological plasticity, a
property which may be related to its biological capacity as an
opportunistic pathogen of humans. Morphogenesis and alterations in cell
shape require integration of many cellular functions and occur in response
to environmental signals, most notably pH and temperature in the case of C.
albicans. In the course of our studies of differential gene expression
associated with dimorphism of C. albicans, we have isolated a gene,
designated PHR1, which is regulated in response to the pH of the culture
medium. PHR1 expression was repressed at pH values below 5.5 and induced at
more alkaline pH. The predicted amino acid sequence of the PHR1 protein was
56% identical to that of the Saccharomyces cerevisiae Ggp1/Gas1 protein, a
highly glycosylated cell surface protein attached to the membrane via
glycosylphosphatidylinositol. A homozygous null mutant of PHR1 was
constructed and found to exhibit a pH-conditional morphological defect. At
alkaline pH, the mutant, unlike the parental type, was unable to conduct
apical growth of either yeast or hyphal growth forms. This morphological
aberration was not associated with defective cytoskeletal polarization or
secretion. The results suggest that PHR1 defines a novel function required
for apical cell growth and morphogenesis.
Copyright © 1995, American Society for Microbiology
PHR1, a pH-regulated gene of Candida albicans, is required for morphogenesis
Department of Microbiology and Molecular Genetics, California College of Medicine, University of California, Irvine 92717.
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