title: Zap1 control of cell-cell signaling in Candida albicans biofilms.
abstract: Biofilms of Candida albicans include both yeast cells and hyphae. Prior studies indicated that a zap1Δ/Δ mutant, defective in zinc regulator Zap1, has increased accumulation of yeast cells in biofilms. This altered yeast-hypha balance may arise from internal regulatory alterations or from an effect on the production of diffusible quorum-sensing (QS) molecules. Here, we develop biosensor reporter strains that express yeast-specific YWP1-RFP or hypha-specific HWP1-RFP, along with a constitutive TDH3-GFP normalization standard. Seeding these biosensor strains into biofilms allows a biological activity assay of the surrounding biofilm milieu. A zap1Δ/Δ biofilm induces the yeast-specific YWP1-RFP reporter in a wild-type biosensor strain, as determined by both quantitative reverse transcription-PCR (qRT-PCR) gene expression measurements and confocal microscopy. Remediation of the zap1Δ/Δ zinc uptake defect through zinc transporter gene ZRT2 overexpression reverses induction of the yeast-specific YWP1-RFP reporter. Gas chromatography-mass spectrometry (GC-MS) measurements of known organic QS molecules show that the zap1Δ/Δ mutant accumulates significantly less farnesol than wild-type or complemented strains and that ZRT2 overexpression does not affect farnesol accumulation. Farnesol is a well-characterized inhibitor of hypha formation; hence, a reduction in farnesol levels in zap1Δ/Δ biofilms is unexpected. Our findings argue that a Zap1- and zinc-dependent signal affects the yeast-hypha balance and that it is operative in the low-farnesol environment of the zap1Δ/Δ biofilm. In addition, our results indicate that Zap1 is a positive regulator of farnesol accumulation.
authors: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
authors: Shantanu
authors: S
authors: Ganguly
authors: Andrew C
authors: AC
authors: Bishop
authors: Wenjie
authors: W
authors: Xu
authors: Suman
authors: S
authors: Ghosh
authors: Kenneth W
authors: KW
authors: Nickerson
authors: Frederick
authors: F
authors: Lanni
authors: Jana
authors: J
authors: Patton-Vogt
authors: Aaron P
authors: AP
authors: Mitchell
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D002176:Candida albicans / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D027682:Cation Transport Proteins / Q000096:biosynthesis; D005204:Farnesol / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D025301:Hyphae / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D053038:Quorum Sensing / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction
chemical_list: D027682:Cation Transport Proteins; D005656:Fungal Proteins; C118102:HWP1 protein, Candida albicans; D008562:Membrane Glycoproteins; D005204:Farnesol