title: Dosage-dependent functions of fatty acid desaturase Ole1p in growth and morphogenesis of Candida albicans.
abstract: Conditions in the infected human host trigger virulence attributes of the fungal pathogen Candida albicans. Specific inducers and elevated temperatures lead to hyphal development or regulate chlamydospore development. To explore if these processes are affected by membrane lipids, an investigation of the functions of the Ole1 fatty acid desaturase (stearoyl-CoA desaturase) in C. albicans, which synthesizes oleic acid, was undertaken. A conditional strain expressing OLE1 from the regulatable MET3 promoter was unable to grow in repressing conditions, indicating that OLE1 is an essential gene. In contrast, a mutant lacking both alleles of OLE2, encoding a Ole1p homologue, was viable and had no apparent phenotypes. Partial repression of MET3p-OLE1 slightly lowered oleic acid levels and decreased membrane fluidity; these conditions permitted growth in the yeast form, but prevented hyphal development in aerobic conditions and blocked the formation of chlamydospores. In contrast, in hypoxic conditions, which trigger an alternative morphogenetic pathway, hyphal morphogenesis was unaffected. Because aerobic morphogenetic signalling and oleic acid biosynthesis require oxygen, it is proposed that oleic acid may function as a sensor activating specific morphogenetic pathways in normoxic conditions.
authors.affiliation: Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
authors.forename: Shankarling
authors.initials: S
authors.lastname: Krishnamurthy
authors.affiliation: Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
authors.forename: Armêl
authors.initials: A
authors.lastname: Plaine
authors.affiliation: Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
authors.forename: Juliane
authors.initials: J
authors.lastname: Albert
authors.affiliation: Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Tulika
authors.initials: T
authors.lastname: Prasad
authors.affiliation: Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Rajendra
authors.initials: R
authors.lastname: Prasad
authors.affiliation: Institut für Mikrobiologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
authors.forename: Joachim F
authors.initials: JF
authors.lastname: Ernst
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D002176:Candida albicans / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D003470:Culture Media; D005227:Fatty Acids / Q000032:analysis; D015966:Gene Expression Regulation, Fungal; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008560:Membrane Fluidity; D008969:Molecular Sequence Data; D009024:Morphogenesis; D019301:Oleic Acid / Q000378:metabolism; D013230:Stearoyl-CoA Desaturase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D003470:Culture Media; D005227:Fatty Acids; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D019301:Oleic Acid; D013230:Stearoyl-CoA Desaturase