title: Discordant influence of Blastomyces dermatitidis yeast-phase-specific gene BYS1 on morphogenesis and virulence.
abstract: Blastomyces dermatitidis is a thermally induced dimorphic fungus capable of causing lung and systemic infections in immunocompetent animal hosts. With the publication of genomic sequences from three different strains of B. dermatitidis and the development of RNA interference as a gene-silencing tool, it has become possible to easily ascertain the virulence and morphological effects of knocking down the expression of candidate genes of interest. BYS1 (Blastomyces yeast-phase-specific 1), first identified by Burg and Smith, is expressed at high levels in yeast cells and is undetectable in mold. The deduced protein sequence of BYS1 has a putative signal sequence at its N terminus, opening the possibility that the BYS1-encoded protein is associated with the yeast cell wall. Herein, strains of B. dermatitidis with silenced expression of BYS1 were engineered and tested for morphology and virulence. The silenced strains produced rough-surfaced cultures on agar medium and demonstrated a propensity to form pseudohyphal cells on prolonged culture in vitro and in vivo, as measured in the mouse lung. Tests using a mouse model of blastomycosis with either yeast or spore inocula showed that the bys1-silenced strains were as virulent as control strains. Thus, although silencing of BYS1 alters morphology at 37 degrees C, it does not appear to impair the pathogenicity of B. dermatitidis.
authors.affiliation: Departments of Pediatrics, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Theerapong
authors.initials: T
authors.lastname: Krajaejun
authors.forename: Marcel
authors.initials: M
authors.lastname: Wüthrich
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Gauthier
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Warner
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Sullivan
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Klein
mesh_terms: D000818:Animals; D001758:Blastomyces / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity*; D015169:Colony Count, Microbial; D005656:Fungal Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D020868:Gene Silencing; D005800:Genes, Fungal; D025301:Hyphae / Q000254:growth & development; D008168:Lung / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D014774:Virulence
chemical_list: D005656:Fungal Proteins