TOS9 Regulates White-Opaque Switching in Candida albicans
Ontology highlight
ABSTRACT:
ORGANISM(S): Candida albicans
PROVIDER: GSE5493 | GEO | 2006/09/19
SECONDARY ACCESSION(S): PRJNA96131
REPOSITORIES: GEO
Similar Datasets
Project description:The human fungal pathogen Candida albicans can switch between two cell types, “white” and “opaque,” each of which is heritable through many cell divisions. Switching between these two cell types is regulated by six transcriptional regulators which form a highly interconnected circuit with multiple feedback loops. Here, we identify a seventh regulator of white-opaque switching, which we have named Wor4. We show that ectopic expression of Wor4 is sufficient to drive switching from the white to the opaque cell type and that deletion of Wor4 blocks switching from the white to the opaque cell type. A combination of ectopic expression and deletion experiments indicates that Wor4 is positioned upstream of Wor1 and that it is formally an activator of the opaque cell type. The combination of ectopic expression and deletion phenotypes for Wor4 is unique; none of the other six white-opaque regulators show this pattern. We determined the pattern of Wor4 binding across the genome by ChIP-seq and found it is highly correlated with that of Wor1 and Wor2, indicating that Wor4 is tightly integrated into the existing white-opaque regulatory circuit. We previously proposed that white-to-opaque switching relies on the activation of a complex circuit of feedback loops that remains excited through many cell divisions. The identification of a new, central regulator of white-opaque switching supports this idea by indicating that the white-opaque switching mechanism is considerably more complex than those controlling conventional, non-heritable patterns of gene expression.
2016-01-11 | GSE75124 | GEO
Project description:The human fungal pathogen Candida albicans can switch between two cell types, âwhiteâ and âopaque,â each of which is heritable through many cell divisions. Switching between these two cell types is regulated by six transcriptional regulators which form a highly interconnected circuit with multiple feedback loops. Here, we identify a seventh regulator of white-opaque switching, which we have named Wor4. We show that ectopic expression of Wor4 is sufficient to drive switching from the white to the opaque cell type and that deletion of Wor4 blocks switching from the white to the opaque cell type. A combination of ectopic expression and deletion experiments indicates that Wor4 is positioned upstream of Wor1 and that it is formally an activator of the opaque cell type. The combination of ectopic expression and deletion phenotypes for Wor4 is unique; none of the other six white-opaque regulators show this pattern. We determined the pattern of Wor4 binding across the genome by ChIP-seq and found it is highly correlated with that of Wor1 and Wor2, indicating that Wor4 is tightly integrated into the existing white-opaque regulatory circuit. We previously proposed that white-to-opaque switching relies on the activation of a complex circuit of feedback loops that remains excited through many cell divisions. The identification of a new, central regulator of white-opaque switching supports this idea by indicating that the white-opaque switching mechanism is considerably more complex than those controlling conventional, non-heritable patterns of gene expression. C. albicans Wor4-GFP versus untagged control in both white and opaque cell types. Cells grown in SD+aa+Uri at 25°C with three technical replicates of each strain/cell type (12 total).
2016-01-11 | E-GEOD-75124 | biostudies-arrayexpress
Project description:The human commensal and opportunistic pathogen Candida albicans can switch between two distinct, heritable cell types, named “white” and “opaque,” which differ in morphology, mating abilities, metabolic preferences, and in their interactions with the host immune system. Previous studies revealed a highly interconnected group of transcriptional regulators that control switching between the two cell types. Here, we identify Ssn6, the C. albicans functional homolog of the Saccharomyces cerevisiae transcriptional co-repressor Cyc8, as a new regulator of white-opaque switching. In a or α mating type strains, deletion of SSN6 results in mass switching from the white to the opaque cell type. Transcriptional profiling of ssn6 deletion mutant strains reveals that Ssn6 represses part of the opaque cell transcriptional program in white cells and the majority of the white cell transcriptional program in opaque cells. Genome-wide chromatin immunoprecipitation experiments demonstrate that Ssn6 is tightly integrated into the opaque cell regulatory circuit and that the positions to which it is bound across the genome strongly overlap with those bound by Wor1 and Wor2, previously identified regulators of white-opaque switching. This work reveals the next layer in the white-opaque transcriptional circuitry by integrating a transcriptional regulator that does not bind DNA directly but instead associates with specific combinations of DNA-bound transcriptional regulators.
2015-12-28 | GSE74011 | GEO
Project description:The human pathogen Candida albicans can assume either of two distinct cell types, designated ‘‘white’’ and ‘‘opaque.’’ Each cell type is maintained for many generations; switching between them is rare and stochastic, and occurs without any known changes in the nucleotide sequence of the genome. The two cell types differ dramatically in cell shape, colony appearance, mating competence, and virulence properties. In this work, we investigate the transcriptional circuitry that specifies the two cell types and controls the switching between them. First, we identify two new transcriptional regulators of white-opaque switching, Czf1 and white-opaque regulator 2 (Wor2). Analysis of a large set of double mutants and ectopic expression strains revealed genetic relationships between CZF1, WOR2, and two previously identified regulators of white-opaque switching, WOR1 and EFG1. Using chromatin immunoprecipitation, we show that Wor1 binds the intergenic regions upstream of the genes encoding three additional transcriptional regulators of white-opaque switching (CZF1, EFG1, and WOR2), and also occupies the promoters of numerous white- and opaque-enriched genes. Based on these interactions, we have placed these four genes in a circuit controlling white-opaque switching whose topology is a network of positive feedback loops, with the master regulator gene WOR1 occupying a central position. Our observations indicate that a key role of the interlocking feedback loop network is to stably maintain each epigenetic state through many cell divisions. Keywords: ChIP-chip
2007-10-01 | GSE8709 | GEO
Project description:In Candida albicans the Efg1 transcription factor (a member of the APSES family) is an important regulator of hyphal growth, and of the white-to-opaque transition. In contrast, we show that the Efg1 ortholog in Candida parapsilosis is a major regulator of a different morphological switch at the colony level, from a concentric to smooth morphology. The rate of switching is at least 100-fold increased in an efg1 knockout relative to wild type. Deleting efg1 also reduces biofilm formation, and results in increased sensitivity to SDS, Congo red, caspofungin and calcofluor white in cells of both morphologies. Biofilm reduction is more dramatic in in vitro than in in vivo models. We use ChIP-seq to show that Efg1 binds to 502 promoter regions, including 70 potential transcription factors or regulatory proteins. Several of the transcription factors belong to networks that regulate biofilm development and white-opaque switching in C. albicans. Efg1 also binds to its own promoter. The binding site for C. parapsilosis Efg1 resembles that of orthologs in other fungi. Many Efg1 targets are probably also regulated by the Ndt80 transcription factor. We show that a paralog of Efg1 (Efh1) is restricted to Candida species. Efh1 does not regulate concentric-smooth phenotype switching, biofilm formation or stress response in C. parapsilosis. Our analysis supports the hypothesis that Efg1 has an ancient role as regulator of development in fungi, but we have identified a new role in C. parapsilosis as a regulator of colony switching that is distinct from the white-opaque switch in C. albicans. RNA was isolated from C. parapsilosis wild type (three biological replicates, concentric phenotype), and from efg1 deletion strains (three biological replicates from both concentric and smooth phenotype). Gene expression was determined using strand-specific RNA-seq.
2013-06-20 | E-GEOD-41064 | biostudies-arrayexpress
Project description:Torulaspora microellipsoides is a unicellular budding yeast of the Saccharomycetaceae family and is primarily associated with viticulture, however it has not been studied with regards to growth morphology or phenotypic switching. We discovered that T. microellipsoides undergoes a low-frequency morphological switch from small budding haploid (white) yeast to larger, higher ploidy (opaque) yeast. Genome sequencing of both cell types did not reveal any conspicuous differences, but comparison of transcriptomes by mRNA-seq revealed 511 differentially regulated genes, with white cells having greater expression of genes involved in stress resistance and complex carbohydrate utilization, and opaque cells up-regulating genes involved in ribosome biogenesis. Growth experiments showed that white cells are in general physiologically more resistant to stationary phase conditions and oxidative stress than opaque cells, but the latter performed better under some conditions and are more tolerant to cold temperatures. Opaque cells are also phenotypically more unstable than white cells and give rise to derivatives with diverse phenotypes and different total DNA content. We propose that ability of T. microellipsoides to switch phenotype is an ecological adaptation to specific niches, as has been suggested for similar morphological switching phenomena in distantly related species such as C. albicans, and suggest switching of this nature may be a more a more broadly utilized biological strategy among yeasts than previously thought.
2020-01-10 | GSE136991 | GEO
Project description:In Candida albicans the Efg1 transcription factor (a member of the APSES family) is an important regulator of hyphal growth, and of the white-to-opaque transition. In contrast, we show that the Efg1 ortholog in Candida parapsilosis is a major regulator of a different morphological switch at the colony level, from a concentric to smooth morphology. The rate of switching is at least 100-fold increased in an efg1 knockout relative to wild type. Deleting efg1 also reduces biofilm formation, and results in increased sensitivity to SDS, Congo red, caspofungin and calcofluor white in cells of both morphologies. Biofilm reduction is more dramatic in in vitro than in in vivo models. We use ChIP-seq to show that Efg1 binds to 502 promoter regions, including 70 potential transcription factors or regulatory proteins. Several of the transcription factors belong to networks that regulate biofilm development and white-opaque switching in C. albicans. Efg1 also binds to its own promoter. The binding site for C. parapsilosis Efg1 resembles that of orthologs in other fungi. Many Efg1 targets are probably also regulated by the Ndt80 transcription factor. We show that a paralog of Efg1 (Efh1) is restricted to Candida species. Efh1 does not regulate concentric-smooth phenotype switching, biofilm formation or stress response in C. parapsilosis. Our analysis supports the hypothesis that Efg1 has an ancient role as regulator of development in fungi, but we have identified a new role in C. parapsilosis as a regulator of colony switching that is distinct from the white-opaque switch in C. albicans.
2013-06-20 | GSE41064 | GEO
Project description:The human fungal pathogen Candida albicans can switch between two phenotypic cell types, termed “white” and “opaque.” Both cell types are heritable for many generations, and the switch between the two types occurs epigenetically, that is, without a change in the DNA sequence of the genome. Previous work identified six key transcriptional regulators important for white-opaque switching: Wor1, Wor2, Wor3, Czf1, Efg1, and Ahr1. In this work, we use a combination of genetic and genome-wide approaches to explore the topology of the transcriptional network that specifies each of the two cell types, and governs the ability to switch between them. In particular, we use a combination of genome-wide chromatin immunoprecipitation and gene expression profiling to determine the direct and indirect regulatory interactions that form the switch network. The six regulators are arranged together in a complex transcriptional network, and we propose that the topology of this network is responsible for both the epigenetic maintenance of the white and opaque states and for the switching between them. Chromatin IP's were performed using the protocol described by Hernday et al (Methods Enzymol. 2010;470:737-58. ). Briefly, log phase cultures were crosslinked with formaldehyde prior to cell lysis, chromatin shearing, and transcription-factor immunoprecipitation. Recovered DNA was amplified, dye-coupled, and competitively hybridized to a 244k-probe tiling array with a non-enriched genomic DNA reference. Immunoprecipitated chromatin was hybridized against a non-enriched genomic DNA reference to identify transcription-factor binding sites
2013-05-01 | E-GEOD-42837 | biostudies-arrayexpress
Project description:The human fungal pathogen Candida albicans can switch between two phenotypic cell types, termed “white” and “opaque.” Both cell types are heritable for many generations, and the switch between the two types occurs epigenetically, that is, without a change in the DNA sequence of the genome. Previous work identified six key transcriptional regulators important for white-opaque switching: Wor1, Wor2, Wor3, Czf1, Efg1, and Ahr1. In this work, we use a combination of genetic and genome-wide approaches to explore the topology of the transcriptional network that specifies each of the two cell types, and governs the ability to switch between them. In particular, we use a combination of genome-wide chromatin immunoprecipitation and gene expression profiling to determine the direct and indirect regulatory interactions that form the switch network. The six regulators are arranged together in a complex transcriptional network, and we propose that the topology of this network is responsible for both the epigenetic maintenance of the white and opaque states and for the switching between them. Chromatin IP's were performed using the protocol described by Hernday et al (Methods Enzymol. 2010;470:737-58. ). Briefly, log phase cultures were crosslinked with formaldehyde prior to cell lysis, chromatin shearing, and transcription-factor immunoprecipitation. Recovered DNA was amplified, dye-coupled, and competitively hybridized to a 244k-probe tiling array with a non-enriched genomic DNA reference.
2013-05-01 | GSE42837 | GEO
Project description:As a successful commensal and pathogen of humans, Candida albicans encounters a wide range of environmental changes. Among them, ambient pH is an important factor, which changes frequently and affects many biological processes in this species. The ability to adapt to pH changes is tightly linked with pathogenesis and morphogenesis. In this study, we report that pH has a profound effect on white-opaque switching and sexual mating in C. albicans. Acidic pHs promote white-to-opaque switching but repress sexual mating of opaque cells. The cAMP signaling and Rim101-mediated pH sensing pathways are involved in the regulation of pH-regulated white-opaque switching. Interestingly, white and opaque cells of the cyr1/cyr1 mutant, which is defective in producing cAMP, show distinct growth defects under acidic and alkaline conditions. Phr2 could play a major role in acidic pHs-induced opaque cell formation. We further discover that acidic pH conditions repress sexual mating due to the failure of activation of the Ste2-mediated a-pheromone response pathway. The effects of pH changes on phenotypic switching and sexual mating could be a balance behavior between host adaptation and sexual reproduction.
2015-12-30 | GSE67101 | GEO