Regulation of phase-specific genes in the more general switching system of Candida albicans strain 3153A.

It was previously demonstrated that the genes PEP1 and Op4 are selectively transcribed in the opaque phase of the white-opaque transition in Candida albicans strain WO-1, and that the gene Wh11 is selectively transcribed in the white phase. However, the white-opaque transition occurs in only a minority of C. albicans strains and the opaque cell phenotype is highly specialized. To test whether these genes are regulated in more mainstream switching systems in C. albicans, their expression was analysed in the switching system of the laboratory strain 3153A. Both PEP1 and Op4 are not expressed in the basic smooth phenotype of 3153A, but they are expressed in switch phenotypes. However, expression is dissociated. Op4 is expressed in irregular wrinkle, star and revertant-smooth cells, while PEP1 is expressed only in star cells. Wh11 is expressed in the basic smooth and three tested variant phenotypes and is again associated with growth in a round budding form. The results support the general conclusion that PEP1 and Op4 are under the strict regulation of switching in C. albicans.