GSE41064
The APSES Transcription factor Efg1 regulates a novel phenotype switch in Candida parapsilosis [RNA-seq].
In Candida albicans the Efg1 transcription factor (a member of the APSES family) is an important regulator of hyphal growth, and of the white-to-opaque transition. In contrast, we show that the Efg1 ortholog in Candida parapsilosis is a major regulator of a different morphological switch at the colony level, from a concentric to smooth morphology. The rate of switching is at least 100-fold increased in an efg1 knockout relative to wild type. Deleting efg1 also reduces biofilm formation, and results in increased sensitivity to SDS, Congo red, caspofungin and calcofluor white in cells of both morphologies. Biofilm reduction is more dramatic in in vitro than in in vivo models. We use ChIP-seq to show that Efg1 binds to 502 promoter regions, including 70 potential transcription factors or regulatory proteins. Several of the transcription factors belong to networks that regulate biofilm development and white-opaque switching in C. albicans. Efg1 also binds to its own promoter. The binding site for C. parapsilosis Efg1 resembles that of orthologs in other fungi. Many Efg1 targets are probably also regulated by the Ndt80 transcription factor. We show that a paralog of Efg1 (Efh1) is restricted to Candida species. Efh1 does not regulate concentric-smooth phenotype switching, biofilm formation or stress response in C. parapsilosis. Our analysis supports the hypothesis that Efg1 has an ancient role as regulator of development in fungi, but we have identified a new role in C. parapsilosis as a regulator of colony switching that is distinct from the white-opaque switch in C. albicans. Overall design: RNA was isolated from  C. parapsilosis wild type (three biological replicates, concentric phenotype), and from efg1 deletion strains (three biological replicates from both concentric and smooth phenotype). Gene expression was determined using strand-specific RNA-seq.