Gene regulation in the white–opaque transition ofCandida albicans

Most strains of Candida albicans switch frequently and reversibly among a number of different phenotypes distinguishable by colony morphology. Previous experiments indicated that switching involved differential gene expression. Using the white–opaque transition as a model switching system, we have cloned two opaque-specific genes, PEP1 and OP4, and one white specific gene, WH11. Differential transcription of these genes suggested that switching involves the coordinate regulation of batteries of unlinked phase-specific genes. It has been demonstrated that the frequency of integration at phase specific loci is a function of the transcriptional state of the phase-specific genes. In addition, a functional dissection of the 5′-upstream region of the WH11 gene has identified two major domains containing cis-acting regulatory sequences that are involved in phase-specific transcription. Gel retardation experiments provide evidence for white phase-specific trans-acting factors which form complexes with both domains. The regulation of the switching event is discussed.