title: Novel acid phosphatase in Candida glabrata suggests selective pressure and niche specialization in the phosphate signal transduction pathway.
abstract: Evolution through natural selection suggests unnecessary genes are lost. We observed that the yeast Candida glabrata lost the gene encoding a phosphate-repressible acid phosphatase (PHO5) present in many yeasts including Saccharomyces cerevisiae. However, C. glabrata still had phosphate starvation-inducible phosphatase activity. Screening a C. glabrata genomic library, we identified CgPMU2, a member of a three-gene family that contains a phosphomutase-like domain. This small-scale gene duplication event could allow for sub- or neofunctionalization. On the basis of phylogenetic and biochemical characterizations, CgPMU2 has neofunctionalized to become a broad range, phosphate starvation-regulated acid phosphatase, which functionally replaces PHO5 in this pathogenic yeast. We determined that CgPmu2, unlike ScPho5, is not able to hydrolyze phytic acid (inositol hexakisphosphate). Phytic acid is present in fruits and seeds where S. cerevisiae grows, but is not abundant in mammalian tissues where C. glabrata grows. We demonstrated that C. glabrata is limited from an environment where phytic acid is the only source of phosphate. Our work suggests that during evolutionary time, the selection for the ancestral PHO5 was lost and that C. glabrata neofunctionalized a weak phosphatase to replace PHO5. Convergent evolution of a phosphate starvation-inducible acid phosphatase in C. glabrata relative to most yeast species provides an example of how small changes in signal transduction pathways can mediate genetic isolation and uncovers a potential speciation gene.
authors.affiliation: Department of Biology, Villanova University, Villanova, Pennsylvania 19085, USA.
authors.forename: Brianne R
authors.initials: BR
authors.lastname: Orkwis
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Davies
authors.forename: Christine L
authors.initials: CL
authors.lastname: Kerwin
authors.forename: Dominique
authors.initials: D
authors.lastname: Sanglard
authors.forename: Dennis D
authors.initials: DD
authors.lastname: Wykoff
mesh_terms: D000135:Acid Phosphatase / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D041221:Candida glabrata / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D004790:Enzyme Induction / Q000187:drug effects; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D015723:Gene Library; D005800:Genes, Fungal / Q000235:genetics; D005816:Genetic Complementation Test; D006868:Hydrolysis / Q000187:drug effects; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D016366:Open Reading Frames / Q000235:genetics; D010710:Phosphates / Q000172:deficiency / Q000378:metabolism* / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012641:Selection, Genetic; D016415:Sequence Alignment; D015398:Signal Transduction / Q000187:drug effects; D013379:Substrate Specificity / Q000187:drug effects
chemical_list: D005656:Fungal Proteins; D010710:Phosphates; D011993:Recombinant Fusion Proteins; D000135:Acid Phosphatase