Genetic Basis for Dimorphism and Pathogenicity in Candida Albicans

Abstract

Our research is aimed at understanding how genetic information is differentially used in the yeast-hyphal morphogenesis of C. albicans, and the biochemical role such gene products play in the process. Toward this end, we have focused on genetic elements that are activated by pH and by temperature, two conditions that regulate the decision to produce yeast or hyphae. One gene, called PHR1, is actively transcribed only at pH's near neutrality. The inferred amino acid sequence of this gene is 56\% identical to a protein of S. cerevisiae that is anchored to the membrane by GPI (glycosylphosphatidylinositol). When PHR1 is deleted on both chromosomes, the double mutant is unable to form hyphal cells. A temperature regulated genetic element was found to have the characteristics of a retrotransposon and to be moderately repeated in the genome, with copies on several chromosomes. The distribution of this element was also found to be strain specific. We have speculated on a role such an element could play in the pathogenesis of C. albicans.