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 zap1?/? 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 zap1?/? 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 zap1?/? 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 zap1?/? 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 zap1?/? 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 zap1?/? biofilm. In addition, our results indicate that Zap1 is a positive regulator of farnesol accumulation.

SUBMITTER: Ganguly S 

PROVIDER: S-EPMC3209068 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature