Effect of environmental pH on morphological development of Candida albicans is mediated via the PacC-related transcription factor encoded by PRR2

The ability to respond to ambient PII is critical to the growth and virulence of the fungal pathogen Candida albicans, This response entails the differential expression of several genes affecting morphogenesis, To investigate the mechanism of pH-dependent gene expression, the C, albicans homolog of pacC, designated PRR2 (for pH response regulator), was identified and cloned. pacC encodes a zinc finger-containing transcription factor that mediates pH-dependent gene expression in Aspergillus nidulans. Mutants lacking PRR2 can no longer induce the expression of alkaline expressed genes or repress acid-expressed genes at alkaline pH. Although the mutation did not affect growth of the cells at acid or alkaline DH, the mutants exhibited medium-conditional defects in filamentation, PRR2 was itself expressed in a pH-conditional manner, and its induction at alkaline pH aas controlled by PRR1, PRR1 is homologous to palF, a regulator of pacC, Thus, PRR2 expression is controlled by a pH-dependent feedback loop. The results demonstrate that the pH response pathway of Aspergillus is conserved and that this pathway has been adapted to control dimorphism in C. albicans.