Originally published as Genetics Published Articles Ahead of Print on March 30, 2009.

Genetics, Vol. 182, 471-479, June 2009, Copyright © 2009
doi:10.1534/genetics.109.101063

Candida glabrata PHO4 Is Necessary and Sufficient for Pho2-Independent Transcription of Phosphate Starvation Genes

Christine L. Kerwin and Dennis D. Wykoff1

Department of Biology, Villanova University, Villanova, Pennsylvania 19085

1 Corresponding author: Department of Biology, Villanova University, 800 Lancaster Ave., Villanova, PA 19085.
E-mail: dennis.wykoff{at}villanova.edu

Comparative genomic analyses of Candida glabrata and Saccharomyces cerevisiae suggest many signal transduction pathways are highly conserved. Focusing on the phosphate signal transduction (PHO) pathway of C. glabrata, we demonstrate that components of the pathway are conserved and confirm the role of CgPHO81, CgPHO80, CgPHO4, and CgMSN5 in the PHO pathway through deletion analysis. Unlike S. cerevisiae, C. glabrata shows little dependence on the transcription factor, Pho2, for induction of phosphate-regulated genes during phosphate limitation. We show that the CgPho4 protein is necessary and sufficient for Pho2-independent gene expression; CgPho4 is capable of driving expression of PHO promoters in S. cerevisiae in the absence of ScPHO2. On the basis of the sequences of PHO4 in the hemiascomycetes and complementation analysis, we suggest that Pho2 dependence is a trait only observed in species closely related to S. cerevisiae. Our data are consistent with trans-regulatory changes in the PHO pathway via the transcription factor Pho4 as opposed to cis-regulatory changes (the promoter).