RIM101 -Dependent and -Independent Pathways Govern pH Responses in Candida albicans

Abstract

ABSTRACT Growth and differentiation of Candida albicans over a broad pH range underlie its ability to infect an array of tissues in susceptible hosts. We identified C. albicans RIM101 , RIM20 , and RIM8 based on their homology to components of the one known fungal pH response pathway. PCR product-disruption mutations in each gene cause defects in three responses to alkaline pH: filamentation, induction of PRA1 and PHR1 , and repression of PHR2 . We find that RIM101 itself is an alkaline-induced gene that also depends on Rim20p and Rim8p for induction. Two observations indicate that a novel pH response pathway also exists. First, PHR2 becomes an alkaline-induced gene in the absence of Rim101p, Rim20p, or Rim8p. Second, we created strains in which Rim101p activity is independent of Rim20p and Rim8p; in these strains, filamentation remains pH dependent. Thus, pH governs gene expression and cellular differentiation in C. albicans through both RIM101 -dependent and RIM101 -independent pathways.