title: CO(2) regulates white-to-opaque switching in Candida albicans.
abstract: To mate, Candida albicans must undergo homozygosis at the mating type-like locus MTL[1, 2], then switch from the white to opaque phenotype [3, 4]. Paradoxically, when opaque cells are transferred in vitro to 37 degrees C, the temperature of their animal host, they switch en masse to white [5-7], suggesting that their major niche might not be conducive to mating. It has been suggested that pheromones secreted by opaque cells of opposite mating type [8] or the hypoxic condition of host niches [9, 10] stabilize opaque cells. There is, however, an additional possibility, namely that CO(2), which achieves levels in the host 100 times higher than in air [11-13], stabilizes the opaque phenotype. CO(2) has been demonstrated to regulate the bud-hypha transition in C. albicans[14, 15], expression of virulence genes in bacteria [16], and mating events in Cryptococcus neoformans[14, 17]. We tested the possibility that CO(2) stabilizes the opaque phenotype, and found that physiological levels of CO(2) induce white-to-opaque switching and stabilize the opaque phenotype at 37 degrees C. It exerts this control equally under anaerobic and aerobic conditions. These results suggest that the high levels of CO(2) in the host induce and stabilize the opaque phenotype, thus facilitating mating.
authors.affiliation: Department of Biology, The University of Iowa, Iowa City, 52242, USA.
authors.forename: Guanghua
authors.initials: G
authors.lastname: Huang
authors.forename: Thyagarajan
authors.initials: T
authors.lastname: Srikantha
authors.forename: Nidhi
authors.initials: N
authors.lastname: Sahni
authors.forename: Song
authors.initials: S
authors.lastname: Yi
authors.forename: David R
authors.initials: DR
authors.lastname: Soll
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002176:Candida albicans / Q000166:cytology / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D049770:Genes, Mating Type, Fungal; D010641:Phenotype; D018631:ras Proteins / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D002245:Carbon Dioxide; D018631:ras Proteins; D002256:Carbonic Anhydrases; D000262:Adenylyl Cyclases