DEFECTS IN ASSEMBLY OF THE EXTRACELLULAR-MATRIX ARE RESPONSIBLE FOR ALTERED MORPHOGENESIS OF A CANDIDA-ALBICANS PHR1 MUTANT

Analysis of Candida albicans cells using antibodies directed against G as1p/Ggp1p, Saccharomyces cerevisiae homolog of Phr1p, revealed that P hr1p is a glycoprotein of about 88 kDa whose accumulation increases wi th the rise of external pH, This polypeptide is present both in the ye ast form and during germ tube induction, In the Phr1(-) cells at pH 8 the solubility of glucans in alkali is greatly affected. In the parent al strain the alkali-soluble/-insoluble glucan ratio shows a 50% decre ase at pH 8 with respect to pH 4.5, whereas in the null mutant it is u nchanged, indicating the lack of a polymer cross-linker activity induc ed by the rise of pH, The mutant has a sixfold increase in chitin leve l and is hypersensitive to calcofluor. Consistently with a role of chi tin in strengthening the cell wall, Phr1(-) cells are more sensitive t o nikkomycin Z than the parental strain.