title: An internal polarity landmark is important for externally induced hyphal behaviors in Candida albicans.
abstract: Directional growth is a function of polarized cells such as neurites, pollen tubes, and fungal hyphae. Correct orientation of the extending cell tip depends on signaling pathways and effectors that mediate asymmetric responses to specific environmental cues. In the hyphal form of the eukaryotic fungal pathogen Candida albicans, these responses include thigmotropism and galvanotropism (hyphal turning in response to changes in substrate topography and imposed electrical fields, respectively) and penetration into semisolid substrates. During vegetative growth in C. albicans, as in the model yeast Saccharomyces cerevisiae, the Ras-like GTPase Rsr1 mediates internal cellular cues to position new buds in a prespecified pattern on the mother cell cortex. Here, we demonstrate that Rsr1 is also important for hyphal tip orientation in response to the external environmental cues that induce thigmotropic and galvanotropic growth. In addition, Rsr1 is involved in hyphal interactions with epithelial cells in vitro and its deletion diminishes the hyphal invasion of kidney tissue during systemic infection. Thus, Rsr1, an internal polarity landmark in yeast, is also involved in polarized growth responses to asymmetric environmental signals, a paradigm that is different from that described for the homologous protein in S. cerevisiae. Rsr1 may thereby contribute to the pathogenesis of C. albicans infections by influencing hyphal tip responses triggered by interaction with host tissues.
authors.affiliation: Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Brand
authors.forename: Anjalee
authors.initials: A
authors.lastname: Vacharaksa
authors.forename: Catherine
authors.initials: C
authors.lastname: Bendel
authors.forename: Jennifer
authors.initials: J
authors.lastname: Norton
authors.forename: Paula
authors.initials: P
authors.lastname: Haynes
authors.forename: Michelle
authors.initials: M
authors.lastname: Henry-Stanley
authors.forename: Carol
authors.initials: C
authors.lastname: Wells
authors.forename: Karen
authors.initials: K
authors.lastname: Ross
authors.forename: Neil A R
authors.initials: NA
authors.lastname: Gow
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Gale
mesh_terms: D000818:Animals; D002176:Candida albicans / Q000166:cytology* / Q000378:metabolism; D002177:Candidiasis / Q000469:parasitology; D016764:Cell Polarity; D004847:Epithelial Cells / Q000469:parasitology; D005260:Female; D005656:Fungal Proteins / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D025301:Hyphae / Q000378:metabolism; D007668:Kidney / Q000469:parasitology; D051379:Mice; D009055:Mouth / Q000469:parasitology; D020691:rab GTP-Binding Proteins / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D020558:GTP Phosphohydrolases; D020691:rab GTP-Binding Proteins