1
|
Böttcher B, Kienast SD, Leufken J, Eggers C, Sharma P, Leufken CM, Morgner B, Drexler HCA, Schulz D, Allert S, Jacobsen ID, Vylkova S, Leidel SA, Brunke S. A highly conserved tRNA modification contributes to C. albicans filamentation and virulence. Microbiol Spectr 2024; 12:e0425522. [PMID: 38587411 PMCID: PMC11064501 DOI: 10.1128/spectrum.04255-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 01/18/2024] [Indexed: 04/09/2024] Open
Abstract
tRNA modifications play important roles in maintaining translation accuracy in all domains of life. Disruptions in the tRNA modification machinery, especially of the anticodon stem loop, can be lethal for many bacteria and lead to a broad range of phenotypes in baker's yeast. Very little is known about the function of tRNA modifications in host-pathogen interactions, where rapidly changing environments and stresses require fast adaptations. We found that two closely related fungal pathogens of humans, the highly pathogenic Candida albicans and its much less pathogenic sister species, Candida dubliniensis, differ in the function of a tRNA-modifying enzyme. This enzyme, Hma1, exhibits species-specific effects on the ability of the two fungi to grow in the hypha morphology, which is central to their virulence potential. We show that Hma1 has tRNA-threonylcarbamoyladenosine dehydratase activity, and its deletion alters ribosome occupancy, especially at 37°C-the body temperature of the human host. A C. albicans HMA1 deletion mutant also shows defects in adhesion to and invasion into human epithelial cells and shows reduced virulence in a fungal infection model. This links tRNA modifications to host-induced filamentation and virulence of one of the most important fungal pathogens of humans.IMPORTANCEFungal infections are on the rise worldwide, and their global burden on human life and health is frequently underestimated. Among them, the human commensal and opportunistic pathogen, Candida albicans, is one of the major causative agents of severe infections. Its virulence is closely linked to its ability to change morphologies from yeasts to hyphae. Here, this ability is linked-to our knowledge for the first time-to modifications of tRNA and translational efficiency. One tRNA-modifying enzyme, Hma1, plays a specific role in C. albicans and its ability to invade the host. This adds a so-far unknown layer of regulation to the fungal virulence program and offers new potential therapeutic targets to fight fungal infections.
Collapse
Affiliation(s)
- Bettina Böttcher
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
- Septomics Research Center, Friedrich Schiller University and Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
| | - Sandra D. Kienast
- Max Planck Research Group for RNA Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Research Group for Cellular RNA Biochemistry, Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Johannes Leufken
- Max Planck Research Group for RNA Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Research Group for Cellular RNA Biochemistry, Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Cristian Eggers
- Max Planck Research Group for RNA Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Research Group for Cellular RNA Biochemistry, Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Puneet Sharma
- Max Planck Research Group for RNA Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Research Group for Cellular RNA Biochemistry, Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Christine M. Leufken
- Max Planck Research Group for RNA Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
| | - Bianka Morgner
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
| | - Hannes C. A. Drexler
- Bioanalytical Mass Spectrometry Unit, Max Planck Institute for Molecular Biomedicine, Münster, Germany
| | - Daniela Schulz
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
| | - Stefanie Allert
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
| | - Ilse D. Jacobsen
- Research Group Microbial Immunology, Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
- Institute of Microbiology, Friedrich Schiller University, Jena, Germany
| | - Slavena Vylkova
- Septomics Research Center, Friedrich Schiller University and Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
| | - Sebastian A. Leidel
- Max Planck Research Group for RNA Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Research Group for Cellular RNA Biochemistry, Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Sascha Brunke
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
| |
Collapse
|
2
|
Fletcher J, O’Connor-Moneley J, Frawley D, Flanagan PR, Alaalm L, Menendez-Manjon P, Estevez SV, Hendricks S, Woodruff AL, Buscaino A, Anderson MZ, Sullivan DJ, Moran GP. Deletion of the Candida albicans TLO gene family using CRISPR-Cas9 mutagenesis allows characterisation of functional differences in α-, β- and γ- TLO gene function. PLoS Genet 2023; 19:e1011082. [PMID: 38048294 PMCID: PMC10721199 DOI: 10.1371/journal.pgen.1011082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 12/14/2023] [Accepted: 11/22/2023] [Indexed: 12/06/2023] Open
Abstract
The Candida albicans genome contains between ten and fifteen distinct TLO genes that all encode a Med2 subunit of Mediator. In order to investigate the biological role of Med2/Tlo in C. albicans we deleted all fourteen TLO genes using CRISPR-Cas9 mutagenesis. ChIP-seq analysis showed that RNAP II localized to 55% fewer genes in the tloΔ mutant strain compared to the parent, while RNA-seq analysis showed that the tloΔ mutant exhibited differential expression of genes required for carbohydrate metabolism, stress responses, white-opaque switching and filamentous growth. Consequently, the tloΔ mutant grows poorly in glucose- and galactose-containing media, is unable to grow as true hyphae, is more sensitive to oxidative stress and is less virulent in the wax worm infection model. Reintegration of genes representative of the α-, β- and γ-TLO clades resulted in the complementation of the mutant phenotypes, but to different degrees. TLOα1 could restore phenotypes and gene expression patterns similar to wild-type and was the strongest activator of glycolytic and Tye7-regulated gene expression. In contrast, the two γ-TLO genes examined (i.e., TLOγ5 and TLOγ11) had a far lower impact on complementing phenotypic and transcriptomic changes. Uniquely, expression of TLOβ2 in the tloΔ mutant stimulated filamentous growth in YEPD medium and this phenotype was enhanced when Tloβ2 expression was increased to levels far in excess of Med3. In contrast, expression of reintegrated TLO genes in a tloΔ/med3Δ double mutant background failed to restore any of the phenotypes tested, suggesting that complementation of these Tlo-regulated processes requires a functional Mediator tail module. Together, these data confirm the importance of Med2/Tlo in a wide range of C. albicans cellular activities and demonstrate functional diversity within the gene family which may contribute to the success of this yeast as a coloniser and pathogen of humans.
Collapse
Affiliation(s)
- Jessica Fletcher
- Division of Oral Biosciences, Dublin Dental University Hospital, & University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - James O’Connor-Moneley
- Division of Oral Biosciences, Dublin Dental University Hospital, & University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - Dean Frawley
- Division of Oral Biosciences, Dublin Dental University Hospital, & University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - Peter R. Flanagan
- Division of Oral Biosciences, Dublin Dental University Hospital, & University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - Leenah Alaalm
- Division of Oral Biosciences, Dublin Dental University Hospital, & University of Dublin, Trinity College Dublin, Dublin, Ireland
| | | | | | - Shane Hendricks
- Department of Microbiology, The Ohio State University, Columbus, Ohio, United States of America
| | - Andrew L. Woodruff
- Department of Microbiology, The Ohio State University, Columbus, Ohio, United States of America
| | - Alessia Buscaino
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Matthew Z. Anderson
- Department of Microbiology, The Ohio State University, Columbus, Ohio, United States of America
| | - Derek J. Sullivan
- Division of Oral Biosciences, Dublin Dental University Hospital, & University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - Gary P. Moran
- Division of Oral Biosciences, Dublin Dental University Hospital, & University of Dublin, Trinity College Dublin, Dublin, Ireland
| |
Collapse
|
3
|
Differences in fungal immune recognition by monocytes and macrophages: N-mannan can be a shield or activator of immune recognition. ACTA ACUST UNITED AC 2020; 6:100042. [PMID: 33364531 PMCID: PMC7750734 DOI: 10.1016/j.tcsw.2020.100042] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/08/2020] [Accepted: 07/08/2020] [Indexed: 02/08/2023]
Abstract
Cytokine response to N-mannan mutants was dependent on the immune cell type used. N-mannan mutants stimulated less cytokines from monocytes but more from macrophages. N-mannan can therefore act as both an immune agonist or an immune shield.
We designed experiments to assess whether fungal cell wall mannans function as an immune shield or an immune agonist. Fungal cell wall β-(1,3)-glucan normally plays a major and dominant role in immune activation. The outer mannan layer has been variously described as an immune shield, because it has the potential to mask the underlying β-(1,3)-glucan, or an immune activator, as it also has the potential to engage with a wide range of mannose detecting PRRs. To resolve this conundrum we examined species-specific differences in host immune recognition in the och1Δ N-mannosylation-deficient mutant background in four species of yeast-like fungi. Irrespective of the fungal species, the cytokine response (TNFα and IL-6) induced by the och1Δ mutants in human monocytes was reduced compared to that of the wild type. In contrast, TNFα production induced by och1Δ was increased, relative to wild type, due to increased β-glucan exposure, when mouse or human macrophages were used. These observations suggest that N-mannan is not a major PAMP for macrophages and that in these cells mannan does shield the fungus from recognition of the inner cell wall β-glucan. However, N-mannan is a significant inducer of cytokine for monocytes. Therefore the metaphor of the fungal “mannan shield” can only be applied to some, but not all, myeloid cells used in immune profiling experiments of fungal species.
Collapse
|
4
|
Mancera E, Frazer C, Porman AM, Ruiz-Castro S, Johnson AD, Bennett RJ. Genetic Modification of Closely Related Candida Species. Front Microbiol 2019; 10:357. [PMID: 30941104 PMCID: PMC6433835 DOI: 10.3389/fmicb.2019.00357] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 02/11/2019] [Indexed: 11/25/2022] Open
Abstract
Species from the genus Candida are among the most important human fungal pathogens. Several of them are frequent commensals of the human microbiota but are also able to cause a variety of opportunistic infections, especially when the human host becomes immunocompromised. By far, most of the research to understand the molecular underpinnings of the pathogenesis of these species has focused on Candida albicans, the most virulent member of the genus. However, epidemiological data indicates that related Candida species are also clinically important. Here, we describe the generation of a set of strains and plasmids to genetically modify C. dubliniensis and C. tropicalis, the two pathogenic species most closely related to C. albicans. C. dubliniensis is an ideal model to understand C. albicans pathogenesis since it is the closest species to C. albicans but considerably less virulent. On the other hand, C. tropicalis is ranked among the four most common causes of infections by Candida species. Given that C. dubliniensis and C. tropicalis are obligate diploids with no known conventional sexual cycle, we generated strains that are auxotrophic for at least two amino acids which allows the tandem deletion of both alleles of a gene by complementing the two auxotrophies. The strains were generated in two different genetic backgrounds for each species — one for which the genomic sequence is available and a second clinically important one. In addition, we have adapted plasmids developed to delete genes and epitope/fluorophore tag proteins in C. albicans so that they can be employed in C. tropicalis. The tools generated here allow for efficient genetic modification of C. dubliniensis and C. tropicalis, and thus facilitate the study of the molecular basis of pathogenesis in these medically relevant fungi.
Collapse
Affiliation(s)
- Eugenio Mancera
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Irapuato, Irapuato, Mexico.,Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, United States
| | - Corey Frazer
- Department of Molecular Microbiology and Immunology, Brown University, Providence, RI, United States
| | - Allison M Porman
- Department of Molecular Microbiology and Immunology, Brown University, Providence, RI, United States
| | - Susana Ruiz-Castro
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Irapuato, Irapuato, Mexico
| | - Alexander D Johnson
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, United States
| | - Richard J Bennett
- Department of Molecular Microbiology and Immunology, Brown University, Providence, RI, United States
| |
Collapse
|
5
|
Flanagan PR, Fletcher J, Boyle H, Sulea R, Moran GP, Sullivan DJ. Expansion of the TLO gene family enhances the virulence of Candida species. PLoS One 2018; 13:e0200852. [PMID: 30028853 PMCID: PMC6054389 DOI: 10.1371/journal.pone.0200852] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 06/11/2018] [Indexed: 12/12/2022] Open
Abstract
The TLO genes are a family of subtelomeric ORFs in the fungal pathogens Candida albicans and C. dubliniensis encoding a subunit of the Mediator complex homologous to Med2. The more virulent pathogen C. albicans has 15 copies of the gene whereas the less pathogenic species C. dubliniensis has only two. To investigate if expansion of the TLO repertoire in C. dubliniensis has an effect on phenotype and virulence we expressed three representative C. albicans TLO genes (TLOβ2, TLOγ11 and TLOα12) in a wild type C. dubliniensis background, under the control of either their native or the ACT1 promoter. Expression of TLOβ2 resulted in a hyperfilamentous phenotype, while overexpression of TLOγ11 and TLOα12 resulted in enhanced resistance to oxidative stress. Expression of all three TLO genes from the ACT1 promoter resulted in increased virulence in the Galleria infection model. In order to further investigate if individual TLO genes exhibit differences in function we expressed six representative C. albicans TLO genes in a C. dubliniensis Δtlo1/Δtlo2 double mutant. Differences were observed in the ability of the expressed CaTLOs to complement the various phenotypes of the mutant. All TLO genes with the exception of TLOγ7 could restore filamentation, however only TLOα9, γ11 and α12 could restore chlamydospore formation. Differences in the ability of CaTLO genes to restore growth in the presence of H2O2, calcofluor white, Congo red and at 42°C were observed. Only TLOα3 restored wild-type levels of virulence in the Galleria infection model. These data show that expansion of the TLO gene family in C. dubliniensis results in gain of function and that there is functional diversity amongst members of the gene family. We propose that this expansion of the TLO family contributes to the success of C. albicans as a commensal and opportunistic pathogen.
Collapse
Affiliation(s)
- Peter R. Flanagan
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental University Hospital, Dublin, Ireland
- University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - Jessica Fletcher
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental University Hospital, Dublin, Ireland
- University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - Hannah Boyle
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental University Hospital, Dublin, Ireland
- University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - Razvan Sulea
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental University Hospital, Dublin, Ireland
- University of Dublin, Trinity College Dublin, Dublin, Ireland
| | - Gary P. Moran
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental University Hospital, Dublin, Ireland
- University of Dublin, Trinity College Dublin, Dublin, Ireland
- * E-mail: (DJS); (GPM)
| | - Derek J. Sullivan
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental University Hospital, Dublin, Ireland
- * E-mail: (DJS); (GPM)
| |
Collapse
|
6
|
A stable hybrid containing haploid genomes of two obligate diploid Candida species. EUKARYOTIC CELL 2013; 12:1061-71. [PMID: 23709179 DOI: 10.1128/ec.00002-13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Candida albicans and Candida dubliniensis are diploid, predominantly asexual human-pathogenic yeasts. In this study, we constructed tetraploid (4n) strains of C. albicans of the same or different lineages by spheroplast fusion. Induction of chromosome loss in the tetraploid C. albicans generated diploid or near-diploid progeny strains but did not produce any haploid progeny. We also constructed stable heterotetraploid somatic hybrid strains (2n + 2n) of C. albicans and C. dubliniensis by spheroplast fusion. Heterodiploid (n + n) progeny hybrids were obtained after inducing chromosome loss in a stable heterotetraploid hybrid. To identify a subset of hybrid heterodiploid progeny strains carrying at least one copy of all chromosomes of both species, unique centromere sequences of various chromosomes of each species were used as markers in PCR analysis. The reduction of chromosome content was confirmed by a comparative genome hybridization (CGH) assay. The hybrid strains were found to be stably propagated. Chromatin immunoprecipitation (ChIP) assays with antibodies against centromere-specific histones (C. albicans Cse4/C. dubliniensis Cse4) revealed that the centromere identity of chromosomes of each species is maintained in the hybrid genomes of the heterotetraploid and heterodiploid strains. Thus, our results suggest that the diploid genome content is not obligatory for the survival of either C. albicans or C. dubliniensis. In keeping with the recent discovery of the existence of haploid C. albicans strains, the heterodiploid strains of our study can be excellent tools for further species-specific genome elimination, yielding true haploid progeny of C. albicans or C. dubliniensis in future.
Collapse
|
7
|
Cottier F, Leewattanapasuk W, Kemp LR, Murphy M, Supuran CT, Kurzai O, Mühlschlegel FA. Carbonic anhydrase regulation and CO2 sensing in the fungal pathogen Candida glabrata involves a novel Rca1p ortholog. Bioorg Med Chem 2013; 21:1549-54. [DOI: 10.1016/j.bmc.2012.05.053] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Accepted: 05/23/2012] [Indexed: 11/28/2022]
|
8
|
Thakur J, Sanyal K. Efficient neocentromere formation is suppressed by gene conversion to maintain centromere function at native physical chromosomal loci in Candida albicans. Genome Res 2013; 23:638-52. [PMID: 23439889 PMCID: PMC3613581 DOI: 10.1101/gr.141614.112] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
CENPA/Cse4 assembles centromeric chromatin on diverse DNA. CENPA chromatin is epigenetically propagated on unique and different centromere DNA sequences in a pathogenic yeast Candida albicans. Formation of neocentromeres on DNA, nonhomologous to native centromeres, indicates a role of non-DNA sequence determinants in CENPA deposition. Neocentromeres have been shown to form at multiple loci in C. albicans when a native centromere was deleted. However, the process of site selection for CENPA deposition on native or neocentromeres in the absence of defined DNA sequences remains elusive. By systematic deletion of CENPA chromatin-containing regions of variable length of different chromosomes, followed by mapping of neocentromere loci in C. albicans and its related species Candida dubliniensis, which share similar centromere properties, we demonstrate that the chromosomal location is an evolutionarily conserved primary determinant of CENPA deposition. Neocentromeres on the altered chromosome are always formed close to the site which was once occupied by the native centromere. Interestingly, repositioning of CENPA chromatin from the neocentromere to the native centromere occurs by gene conversion in C. albicans.
Collapse
Affiliation(s)
- Jitendra Thakur
- Molecular Mycology Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India
| | | |
Collapse
|
9
|
Papon N, Courdavault V, Clastre M, Simkin AJ, Crèche J, Giglioli-Guivarc’h N. Deus ex Candida genetics: overcoming the hurdles for the development of a molecular toolbox in the CTG clade. Microbiology (Reading) 2012; 158:585-600. [DOI: 10.1099/mic.0.055244-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Nicolas Papon
- EA2106, Biomolécules et Biotechnologies Végétales, Université François-Rabelais de Tours, France
| | - Vincent Courdavault
- EA2106, Biomolécules et Biotechnologies Végétales, Université François-Rabelais de Tours, France
| | - Marc Clastre
- EA2106, Biomolécules et Biotechnologies Végétales, Université François-Rabelais de Tours, France
| | - Andrew J. Simkin
- EA2106, Biomolécules et Biotechnologies Végétales, Université François-Rabelais de Tours, France
| | - Joël Crèche
- EA2106, Biomolécules et Biotechnologies Végétales, Université François-Rabelais de Tours, France
| | | |
Collapse
|
10
|
A Ser29Leu substitution in the cytosine deaminase Fca1p is responsible for clade-specific flucytosine resistance in Candida dubliniensis. Antimicrob Agents Chemother 2009; 53:4678-85. [PMID: 19704126 DOI: 10.1128/aac.00607-09] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The population structure of the opportunistic yeast pathogen Candida dubliniensis is composed of three main multilocus sequence typing clades (clades C1 to C3), and clade C3 predominantly consists of isolates from the Middle East that exhibit high-level resistance (MIC(50) > or = 128 microg/ml) to the fungicidal agent flucytosine (5FC). The close relative of C. dubliniensis, C. albicans, also exhibits clade-specific resistance to 5FC, and resistance is most commonly mediated by an Arg101Cys substitution in the FUR1 gene encoding uracil phosphoribosyltransferase. Broth microdilution assays with fluorouracil (5FU), the toxic deaminated form of 5FC, showed that both 5FC-resistant and 5FC-susceptible C. dubliniensis isolates exhibited similar 5FU MICs, suggesting that the C. dubliniensis cytosine deaminase (Fca1p) encoded by C. dubliniensis FCA1 (CdFCA1) may play a role in mediating C. dubliniensis clade-specific 5FC resistance. Amino acid sequence analysis of the CdFCA1 open reading frame (ORF) identified a homozygous Ser29Leu substitution in all 12 5FC-resistant isolates investigated which was not present in any of the 9 5FC-susceptible isolates examined. The tetracycline-inducible expression of the CdFCA1 ORF from a 5FC-susceptible C. dubliniensis isolate in two separate 5FC-resistant clade C3 isolates restored susceptibility to 5FC, demonstrating that the Ser29Leu substitution was responsible for the clade-specific 5FC resistance and that the 5FC resistance encoded by FCA1 genes with the Ser29Leu transition is recessive. Quantitative real-time PCR analysis showed no significant difference in CdFCA1 expression between 5FC-susceptible and 5FC-resistant isolates in either the presence or the absence of subinhibitory concentrations of 5FC, suggesting that the Ser29Leu substitution in the CdFCA1 ORF is the sole cause of 5FC resistance in clade C3 C. dubliniensis isolates.
Collapse
|
11
|
Enjalbert B, Moran GP, Vaughan C, Yeomans T, Maccallum DM, Quinn J, Coleman DC, Brown AJP, Sullivan DJ. Genome-wide gene expression profiling and a forward genetic screen show that differential expression of the sodium ion transporter Ena21 contributes to the differential tolerance of Candida albicans and Candida dubliniensis to osmotic stress. Mol Microbiol 2009; 72:216-28. [PMID: 19239621 DOI: 10.1111/j.1365-2958.2009.06640.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Candida albicans is more pathogenic than Candida dubliniensis. However, this disparity in virulence is surprising given the high level of sequence conservation and the wide range of phenotypic traits shared by these two species. Increased sensitivity to environmental stresses has been suggested to be a possible contributory factor to the lower virulence of C. dubliniensis. In this study, we investigated, in the first comparison of C. albicans and C. dubliniensis by transcriptional profiling, global gene expression in each species when grown under conditions in which the two species exhibit differential stress tolerance. The profiles revealed similar core responses to stresses in both species, but differences in the amplitude of the general transcriptional responses to thermal, salt and oxidative stress. Differences in the regulation of specific stress genes were observed between the two species. In particular, ENA21, encoding a sodium ion transporter, was strongly induced in C. albicans but not in C. dubliniensis. In addition, ENA21 was identified in a forward genetic screen for C. albicans genomic sequences that increase salt tolerance in C. dubliniensis. Introduction of a single copy of CaENA21 was subsequently shown to be sufficient to confer salt tolerance upon C. dubliniensis.
Collapse
Affiliation(s)
- Brice Enjalbert
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Abstract
Reporter systems are used in Candida albicans in three major experimental areas. These include gene expression, promoter analysis, and protein expression/localization. Heterologous expression in C. albicans is either not effective or inefficient due to the alternative codon usage in Candida, particularly CTG. Consequently, several reporter genes have been constructed by optimizing codons for expression in Candida. The reporter systems include lacZ, luciferase, and GFP. Generally, PCR site directed mutagenesis has been used to construct the modified reporter. Reporter gene vectors are not commercially available for Candida, but they can normally be requested from the laboratories that developed the constructs.
Collapse
Affiliation(s)
- Joy Sturtevant
- Department of Microbiology, Immunology and Parasitology, Louisiana State University School of Medicine, New Orleans, LA, USA
| |
Collapse
|
13
|
Khlif M, Sellami A, Sellami H, Makni F, Ayadi A. [Candida dubliniensis: Identification methods and epidemiologic implication]. ACTA ACUST UNITED AC 2008; 59:166-72. [PMID: 19046828 DOI: 10.1016/j.patbio.2008.09.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Accepted: 09/18/2008] [Indexed: 10/21/2022]
Abstract
Candida dubliniensis was recently described (1995) associated with oral candidiasis in HIV-positive patients. This organism is very closely related to the pathogenic human yeast, Candida albicans, and share a great number of phenotypic and genotypic characters. This great similarity limits the discrimination between these two species. Several phenotypic and molecular methods were developed. The phenotypic methods are simply used in routine discrimination between these two species and depend on the growth at high temperature, sugar assimilation, growth on special mediums and chlamydospore production…; but these methods are insensitive in discrimination between these two species. The molecular biology methods are highly reliable and able to confirm rapidly the identification of this species. In this article, we will review the various studies run out concerning the methods deployed for the identification of C. dubliniensis as well as the epidemiological implication of this new pathogen.
Collapse
Affiliation(s)
- M Khlif
- Laboratoire de biologie moléculaire, parasitaire et fongique, faculté de médecine de Sfax, avenue Magida-Boulila, 3029 Sfax, Tunisie
| | | | | | | | | |
Collapse
|
14
|
Gain-of-function mutations in the transcription factor MRR1 are responsible for overexpression of the MDR1 efflux pump in fluconazole-resistant Candida dubliniensis strains. Antimicrob Agents Chemother 2008; 52:4274-80. [PMID: 18809934 DOI: 10.1128/aac.00740-08] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Candida dubliniensis, a yeast that is closely related to Candida albicans, can rapidly develop resistance to the commonly used antifungal agent fluconazole in vitro and in vivo during antimycotic therapy. Fluconazole resistance in C. dubliniensis is usually caused by constitutive overexpression of the MDR1 gene, which encodes a multidrug efflux pump of the major facilitator superfamily. The zinc cluster transcription factor Mrr1p has recently been shown to control MDR1 expression in C. albicans in response to inducing stimuli, and gain-of-function mutations in the MRR1 gene result in constitutive upregulation of the MDR1 efflux pump. We identified a gene with a high degree of similarity to C. albicans MRR1 (CaMRR1) in the C. dubliniensis genome sequence. When C. dubliniensis MRR1 (CdMRR1) was expressed in C. albicans mrr1Delta mutants, it restored benomyl-inducible MDR1 expression, demonstrating that CdMRR1 is the ortholog of CaMRR1. To investigate whether MDR1 overexpression in C. dubliniensis is caused by mutations in MRR1, we sequenced the MRR1 alleles from a fluconazole-resistant, clinical C. dubliniensis isolate and a matched, fluconazole-susceptible isolate from the same patient as well as those from four in vitro-generated, fluconazole-resistant C. dubliniensis strains derived from two different C. dubliniensis isolates. We found that all five resistant strains contained single nucleotide substitutions or small in-frame deletions that resulted in amino acid changes in Mrr1p. Expression of these mutated alleles in C. albicans resulted in the constitutive activation of the MDR1 promoter and multidrug resistance. Therefore, mutations in MRR1 are the major cause of MDR1 upregulation in both C. albicans and C. dubliniensis, demonstrating that the transcription factor Mrr1p plays a central role in the development of drug resistance in these human fungal pathogens.
Collapse
|
15
|
Morschhäuser J, Barker KS, Liu TT, BlaB-Warmuth J, Homayouni R, Rogers PD. The transcription factor Mrr1p controls expression of the MDR1 efflux pump and mediates multidrug resistance in Candida albicans. PLoS Pathog 2008; 3:e164. [PMID: 17983269 PMCID: PMC2048531 DOI: 10.1371/journal.ppat.0030164] [Citation(s) in RCA: 239] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Accepted: 09/20/2007] [Indexed: 11/18/2022] Open
Abstract
Constitutive overexpression of the MDR1 (multidrug resistance) gene, which encodes a multidrug efflux pump of the major facilitator superfamily, is a frequent cause of resistance to fluconazole and other toxic compounds in clinical Candida albicans strains, but the mechanism of MDR1 upregulation has not been resolved. By genome-wide gene expression analysis we have identified a zinc cluster transcription factor, designated as MRR1 (multidrug resistance regulator), that was coordinately upregulated with MDR1 in drug-resistant, clinical C. albicans isolates. Inactivation of MRR1 in two such drug-resistant isolates abolished both MDR1 expression and multidrug resistance. Sequence analysis of the MRR1 alleles of two matched drug-sensitive and drug-resistant C. albicans isolate pairs showed that the resistant isolates had become homozygous for MRR1 alleles that contained single nucleotide substitutions, resulting in a P683S exchange in one isolate and a G997V substitution in the other isolate. Introduction of these mutated alleles into a drug-susceptible C. albicans strain resulted in constitutive MDR1 overexpression and multidrug resistance. By comparing the transcriptional profiles of drug-resistant C. albicans isolates and mrr1Δ mutants derived from them and of C. albicans strains carrying wild-type and mutated MRR1 alleles, we defined the target genes that are controlled by Mrr1p. Many of the Mrr1p target genes encode oxidoreductases, whose upregulation in fluconazole-resistant isolates may help to prevent cell damage resulting from the generation of toxic molecules in the presence of fluconazole and thereby contribute to drug resistance. The identification of MRR1 as the central regulator of the MDR1 efflux pump and the elucidation of the mutations that have occurred in fluconazole-resistant, clinical C. albicans isolates and result in constitutive activity of this trancription factor provide detailed insights into the molecular basis of multidrug resistance in this important human fungal pathogen. The Candida albicans MDR1 (multidrug resistance) gene encodes a multidrug efflux pump of the major facilitator superfamily that is constitutively overexpressed in many fluconazole-resistant strains. Although MDR1 overexpression is a major cause of resistance to this widely used antifungal agent and other metabolic inhibitors, so far the molecular basis of MDR1 upregulation in resistant strains has remained elusive. By comparing the transcription profiles of MDR1 overexpressing, clinical C. albicans isolates and matched, drug-susceptible isolates from the same patients, we identified a transcription factor, termed multidrug resistance regulator 1 (MRR1), which was upregulated in all resistant isolates and turned out to be a central regulator of MDR1 expression. Resistant isolates contained point mutations in MRR1, which rendered the transcription factor constitutively active. Introduction of these mutated alleles into a susceptible strain caused MDR1 overexpression und multidrug resistance. Inactivation of MRR1 in clinical isolates abolished MDR1 expression and affected fluconazole resistance even more strongly than deletion of the MDR1 efflux pump itself, indicating that additional Mrr1p target genes, which were identified by genome-wide gene expression analysis, contribute to fluconazole resistance. These findings provide detailed insights into the molecular basis of multidrug resistance in one of the most important human fungal pathogens.
Collapse
Affiliation(s)
- Joachim Morschhäuser
- Institut für Molekulare Infektionsbiologie, Universität Würzburg, Würzburg, Germany.
| | | | | | | | | | | |
Collapse
|
16
|
Paugam A, Baixench MT, Viguié C. [An update on Candida dubliniensis]. Med Mal Infect 2007; 38:1-7. [PMID: 18065177 DOI: 10.1016/j.medmal.2007.10.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Accepted: 10/07/2007] [Indexed: 11/17/2022]
Abstract
Eleven years ago, Irish authors, using molecular biology, demonstrated the existence of Candida dubliniensis, a new species of Candida close to Candida albicans. Initially isolated from AIDS patients with oral candidiasis, this species was detected, even in immunocompetent patients. Recently, with new, easy to implement identification tests (latex, immunochromatography), numerous epidemiological studies were undertaken. In most studies, C. dubliniensis was most often identified in the oral cavity. In the absence of HIV infection, the proportion C. dubliniensis/C. albicans ranged from 1 to 5% but it increased to 15-20% in case of HIV infection. It should be stressed that, from an experimental point of view, the acquisition of a secondary resistance to fluconazole is more quickly obtained with C. dubliniensis that with C. albicans, this resistance remains exceptionally observed in clinical observations.
Collapse
Affiliation(s)
- A Paugam
- Laboratoire de parasitologie-mycologie, groupe hospitalier Cochin-Saint-Vincent-de-Paul, Assistance publique-Hôpitaux de Paris, université Paris-Descartes, Paris, France.
| | | | | |
Collapse
|
17
|
Moran GP, MacCallum DM, Spiering MJ, Coleman DC, Sullivan DJ. Differential regulation of the transcriptional repressor NRG1 accounts for altered host-cell interactions in Candida albicans and Candida dubliniensis. Mol Microbiol 2007; 66:915-29. [PMID: 17927699 DOI: 10.1111/j.1365-2958.2007.05965.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Candida dubliniensis is genetically closely related to Candida albicans, but causes fewer infections in humans and exhibits reduced virulence and filamentation in animal models of infection. We investigated the role of the C. dubliniensis transcriptional repressor-encoding gene CdNRG1 in regulating this phenotype. Deletion of both copies of CdNRG1 increased the formation of true hyphae by C. dubliniensis in response to serum, exogenous cAMP and CO2. In addition, deletion of CdNRG1 greatly enhanced filamentation and survival of C. dubliniensis in co-culture with murine macrophages. In the reconstituted human oral epithelium infection model, the nrg1Delta mutant caused increased tissue damage relative to the wild-type strain. However, deletion of CdNRG1 did not change the virulence of C. dubliniensis in the systemic mouse model of infection. The increased rate of hypha formation in C. albicans relative to C. dubliniensis in response to phagocytosis by macrophages and serum was associated with rapid downregulation of NRG1 expression in C. albicans. This study demonstrates that the reduced virulence and host cell damage elicited by C. dubliniensis may in part be due to the inability of this species to modulate NRG1 expression in response to the same environmental signals that promote filamentation in C. albicans.
Collapse
Affiliation(s)
- Gary P Moran
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental School and Hospital, Trinity College Dublin, University of Dublin, Dublin 2, Republic of Ireland.
| | | | | | | | | |
Collapse
|
18
|
Stokes C, Moran GP, Spiering MJ, Cole GT, Coleman DC, Sullivan DJ. Lower filamentation rates of Candida dubliniensis contribute to its lower virulence in comparison with Candida albicans. Fungal Genet Biol 2007; 44:920-31. [PMID: 17251042 DOI: 10.1016/j.fgb.2006.11.014] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Revised: 11/22/2006] [Accepted: 11/28/2006] [Indexed: 11/19/2022]
Abstract
Candida albicans and C. dubliniensis are very closely related yeast species. In this study, we have conducted a thorough comparison of the ability of the two species to produce hyphae and their virulence in two infection models. Under all induction conditions tested C. albicans consistently produced hyphae more efficiently than C. dubliniensis. In the oral reconstituted human epithelial model, C. dubliniensis isolates grew exclusively in the yeast form, while the C. albicans strains produced abundant hyphae that invaded and caused significant damage to the epithelial tissue. In the oral-intragastric infant mouse infection model, C. dubliniensis strains were more rapidly cleared from the gastrointestinal tract than C. albicans. Immunosuppression of Candida-infected mice caused dissemination to internal organs by both species, but C. albicans was found to be far more effective at dissemination than C. dubliniensis. These data suggest that a major reason for the comparatively low virulence of C. dubliniensis is its lower capacity to produce hyphae.
Collapse
Affiliation(s)
- C Stokes
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental School and Hospital, Trinity College Dublin, Dublin 2, Ireland
| | | | | | | | | | | |
Collapse
|
19
|
Eckert SE, Heinz WJ, Zakikhany K, Thewes S, Haynes K, Hube B, Mühlschlegel FA. PGA4, a GAS homologue from Candida albicans, is up-regulated early in infection processes. Fungal Genet Biol 2006; 44:368-77. [PMID: 17257864 DOI: 10.1016/j.fgb.2006.12.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 12/05/2006] [Accepted: 12/06/2006] [Indexed: 02/06/2023]
Abstract
Transglucosidases play a significant role in fungal cell wall biosynthesis. We identified three as yet undescribed genes encoding beta-glucan transglucosidases, homologues of the pH-regulated PHR1 and PHR2, in the genome of the pathogenic yeast Candida albicans. Transcript levels of the gene PGA4 encoding a putative GPI-anchored protein were elevated in C. albicans wild-type cells during infection of reconstituted human epithelial and mouse liver tissue, and transiently increased after induction of hyphal formation with serum. The serum-specific increase in PGA4 transcript was found to be dependent on the transcription factors Ras1p, Cyr1p, and Tec1p. The remaining C. albicans Phr homologues, PHR3 and PGA5, showed low expression levels. Unlike PHR1 and PHR2, the expression of PHR3, PGA4, and PGA5 was not dependent on the pH of the growth medium. Neither PHR3 deletion nor PGA4 disruption resulted in a distinct growth or morphology phenotype. A PGA4 disruption strain was found to have wild-type capacity of infecting reconstituted oral epithelial tissue. Our data suggest that PGA4, and potentially PHR3 and PGA5, are expressed under distinct conditions, which differ from those of PHR1 and PHR2.
Collapse
Affiliation(s)
- Sabine E Eckert
- Department of Biosciences, University of Kent, Canterbury CT2 7NY, UK
| | | | | | | | | | | | | |
Collapse
|
20
|
Hiller D, Stahl S, Morschhäuser J. Multiple cis-acting sequences mediate upregulation of the MDR1 efflux pump in a fluconazole-resistant clinical Candida albicans isolate. Antimicrob Agents Chemother 2006; 50:2300-8. [PMID: 16801405 PMCID: PMC1489804 DOI: 10.1128/aac.00196-06] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Overexpression of the MDR1 gene, which encodes a multidrug efflux pump of the major facilitator superfamily, is a frequent cause of resistance to the antimycotic agent fluconazole and other metabolic inhibitors in clinical Candida albicans strains. Constitutive MDR1 overexpression in such strains is caused by mutations in as yet unknown trans-regulatory factors. In order to identify the cis-acting sequences in the MDR1 regulatory region that mediate constitutive MDR1 upregulation, we performed a promoter deletion analysis in the genetic background of an MDR1-overexpressing clinical C. albicans isolate. We found that several different regions in the MDR1 promoter can mediate MDR1 overexpression in this isolate. In contrast, deletion of one of these regions abolished benomyl-induced MDR1 expression in a C. albicans laboratory strain. These results suggest that multiple transcription factors control expression of the MDR1 efflux pump in C. albicans and that the mutation(s) that causes constitutive MDR1 overexpression and drug resistance in clinical C. albicans isolates affects the activities of several of these transcription factors.
Collapse
Affiliation(s)
- Davina Hiller
- Institut für Molekulare Infektionsbiologie, Universität Würzburg, Röntgenring 11, D-97070 Würzburg, Germany
| | | | | |
Collapse
|
21
|
Bader T, Schröppel K, Bentink S, Agabian N, Köhler G, Morschhäuser J. Role of calcineurin in stress resistance, morphogenesis, and virulence of a Candida albicans wild-type strain. Infect Immun 2006; 74:4366-9. [PMID: 16790813 PMCID: PMC1489686 DOI: 10.1128/iai.00142-06] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
By generating a calcineurin mutant of the Candida albicans wild-type strain SC5314 with the help of a new recyclable dominant selection marker, we confirmed that calcineurin mediates tolerance to a variety of stress conditions but is not required for the ability of C. albicans to switch to filamentous growth in response to hypha-inducing environmental signals. While calcineurin was essential for virulence of C. albicans in a mouse model of disseminated candidiasis, deletion of CMP1 did not significantly affect virulence during vaginal or pulmonary infection, demonstrating that the requirement for calcineurin for a successful infection depends on the host niche.
Collapse
Affiliation(s)
- Teresa Bader
- Institut für Molekulare Infektionsbiologie, Universität Würzburg, Röntgenring 11, D-97070 Würzburg, Germany
| | | | | | | | | | | |
Collapse
|
22
|
Hiller D, Sanglard D, Morschhäuser J. Overexpression of the MDR1 gene is sufficient to confer increased resistance to toxic compounds in Candida albicans. Antimicrob Agents Chemother 2006; 50:1365-71. [PMID: 16569853 PMCID: PMC1426927 DOI: 10.1128/aac.50.4.1365-1371.2006] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Overexpression of MDR1, which encodes a membrane transport protein of the major facilitator superfamily, is one mechanism by which the human fungal pathogen Candida albicans can develop increased resistance to the antifungal drug fluconazole and other toxic compounds. In clinical C. albicans isolates, constitutive MDR1 overexpression is accompanied by the upregulation of other genes, but it is not known if these additional alterations are required for Mdr1p function and drug resistance. To investigate whether MDR1 overexpression is sufficient to confer a drug-resistant phenotype in C. albicans, we expressed the MDR1 gene from the strong ADH1 promoter in C. albicans laboratory strains that did not express the endogenous MDR1 gene as well as in a fluconazole-resistant clinical C. albicans isolate in which the endogenous MDR1 alleles had been deleted and in a matched fluconazole-susceptible isolate from the same patient. Forced MDR1 overexpression resulted in increased resistance to the putative Mdr1p substrates cerulenin and brefeldin A, and this resistance did not depend on the additional alterations which occurred during drug resistance development in the clinical isolates. In contrast, artificial expression of the MDR1 gene from the ADH1 promoter did not enhance or only slightly enhanced fluconazole resistance, presumably because Mdr1p expression levels in the transformants were considerably lower than those observed in the fluconazole-resistant clinical isolate. These results demonstrate that MDR1 overexpression in C. albicans is sufficient to confer resistance to some toxic compounds that are substrates of this efflux pump but that the degree of resistance depends on the Mdr1p expression level.
Collapse
Affiliation(s)
- Davina Hiller
- Institut für Molekulare Infektionsbiologie, Universität Würzburg, Röntgenring 11, D-97070 Würzburg, Germany, and Institute of Microbiology, University Hospital Lausanne, Switzerland
| | | | | |
Collapse
|
23
|
Sullivan DJ, Moran GP, Coleman DC. Candida dubliniensis: ten years on. FEMS Microbiol Lett 2005; 253:9-17. [PMID: 16213674 DOI: 10.1016/j.femsle.2005.09.015] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 09/09/2005] [Accepted: 09/09/2005] [Indexed: 11/17/2022] Open
Abstract
Candida dubliniensis was first described as a novel species in 1995. This organism is very closely related to the important human yeast pathogen, Candida albicans. However, despite the very close phylogenetic relationship between C. albicans and C. dubliniensis and the fact that they share a large number of phenotypic traits, epidemiological and virulence model data indicate that the former is a far more successful pathogen. In order to investigate the molecular basis of the lower virulence of C. dubliniensis recent comparative genomic hybridisation studies have revealed the absence and divergence of specific genes implicated in candidal virulence. Data from the C. dubliniensis genome sequencing project will allow a complete comparison between the genomes of the two species to be performed and thus enhance our understanding of candidal virulence and how virulence has evolved in Candida species.
Collapse
Affiliation(s)
- Derek J Sullivan
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental School and Hospital, University of Dublin, Trinity College, Dublin 2, Ireland.
| | | | | |
Collapse
|
24
|
Staib P, Morschhäuser J. Differential expression of the NRG1 repressor controls species-specific regulation of chlamydospore development in Candida albicans and Candida dubliniensis. Mol Microbiol 2005; 55:637-52. [PMID: 15659176 DOI: 10.1111/j.1365-2958.2004.04414.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Candida albicans and Candida dubliniensis are opportunistic fungal pathogens that are closely related but differ in their epidemiology and in some phenotypic characteristics, including certain virulence-related traits. A comparison of these two species at the molecular level could therefore provide new insights into the biology and pathogenicity of Candida. Both species share the ability to produce chlamydospores, but only C. dubliniensis forms pseudohyphae with abundant chlamydospores on Staib agar (syn. Guizotia abyssinica creatinine agar), on which C. albicans grows as a budding yeast. To understand the basis of this species-specific, differential regulation of morphogenetic development, we set out to identify C. albicans genes that repress chlamydospore formation under these conditions. A C. albicans genomic library was integrated into the C. dubliniensis genome and transformants were screened for clones in which filamentation and/or chlamydospore production on Staib agar was suppressed. This screen identified two genes, CaNRG1 and CaPDE2, encoding a general transcriptional repressor and a high affinity cAMP phosphodiesterase, respectively. Expression of CaNRG1 in C. dubliniensis repressed pseudohyphae and chlamydospore formation, whereas expression of CaPDE2 only reduced the extent of filamentous growth but did not affect chlamydospore formation. We found that C. dubliniensis, but not C. albicans, specifically downregulates NRG1 expression on Staib medium to allow chlamydospore development. Artificial overexpression of CdNRG1 suppressed pseudohyphal growth and production of chlamydospores in C. dubliniensis. Conversely, deletion of CaNRG1 in C. albicans resulted in chlamydospore formation on Staib agar, confirming its central role in the regulation of this morphogenetic process. Our results demonstrate that differential regulation of a single gene, NRG1, in C. albicans and C. dubliniensis is responsible for their species-specific response to environmental signals that induce chlamydospore development.
Collapse
Affiliation(s)
- Peter Staib
- Institut für Molekulare Infektionsbiologie, Universität Würzburg, Röntgenring 11, D-97070 Würzburg, Germany
| | | |
Collapse
|
25
|
Reuss O, Vik A, Kolter R, Morschhäuser J. The SAT1 flipper, an optimized tool for gene disruption in Candida albicans. Gene 2005; 341:119-27. [PMID: 15474295 DOI: 10.1016/j.gene.2004.06.021] [Citation(s) in RCA: 580] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Revised: 04/19/2004] [Accepted: 06/10/2004] [Indexed: 10/26/2022]
Abstract
The construction of Candida albicans mutants by targeted gene disruption usually depends on the use of nutritional markers for the selection of prototrophic transformants from auxotrophic host strains, but it is becoming increasingly evident that this strategy may cause difficulties in the interpretation of mutant phenotypes. Here, we describe a new method for inactivating both alleles of a target gene in C. albicans wild-type strains to obtain homozygous null mutants. The SAT1 flipping method relies on the use of a cassette that contains a dominant nourseothricin resistance marker (caSAT1) for the selection of integrative transformants and a C. albicans-adapted FLP gene that allows the subsequent excision of the cassette, which is flanked by FLP target sequences, from the genome. Two rounds of integration/excision generate homozygous mutants that differ from the wild-type parent strain only by the absence of the target gene, and reintegration of an intact gene copy for complementation of mutant phenotypes is performed in the same way. Transformants are obtained after only 1 day of growth on a selective medium, and integration into the target locus occurs with high specificity after adding homologous flanking sequences on both sides of the cassette. FLP-mediated excision of the SAT1 flipper cassette is achieved by simply growing the transformants for a few hours in medium without selective pressure, and nourseothricin-sensitive (NouS) derivatives can easily be identified by their slower growth on indicator plates containing a low concentration of nourseothricin. We demonstrate the use of the system by deleting the OPT1 gene, which encodes an oligopeptide transporter, in the C. albicans model strain SC5314. The null mutants became resistant to the toxic peptide KLLEth, and reintroduction of an intact OPT1 copy restored susceptibility. The SAT1 flipping method provides a highly efficient method for gene disruption in C. albicans wild-type strains, which eliminates currently encountered problems in the genetic analysis of this important human fungal pathogen.
Collapse
Affiliation(s)
- Oliver Reuss
- Institut für Molekulare Infektionsbiologie, Universität Würzburg, Röntgenring 11, D-97070 Würzburg, Germany
| | | | | | | |
Collapse
|
26
|
Abstract
Staib liquid medium (syn. Guizotia abyssinica creatinine medium) was evaluated for the induction of chlamydospores in the yeast species Candida dubliniensis. During growth in this liquid medium C. dubliniensis produced abundant chlamydospores at the tips of pseudohyphal elements, whereas C. albicans produced only round to oval blastospores. Chlamydospore formation could be induced with the same efficiency by use of a liquid growth medium in which Helianthus annuus (sunflower) seeds, another plant of the family Compositae, were substituted for Guizotia abyssinica plant seeds. Liquid growth culture conditions for rapid and abundant formation of chlamydospores in C. dubliniensis should facilitate their enrichment and their biochemical and genetic analysis.
Collapse
Affiliation(s)
- Peter Staib
- Institut für Molekulare Infektionsbiologie, Universität Würzburg, Röntgenring, Würzburg, Germany
| | | |
Collapse
|
27
|
Kelly MT, MacCallum DM, Clancy SD, Odds FC, Brown AJP, Butler G. The Candida albicans CaACE2 gene affects morphogenesis, adherence and virulence. Mol Microbiol 2004; 53:969-83. [PMID: 15255906 DOI: 10.1111/j.1365-2958.2004.04185.x] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Morphogenesis between yeast and hyphal growth is a characteristic associated with virulence in Candida albicans and involves changes in the cell wall. In Saccharomyces cerevisiae, the transcription factor pair Ace2p and Swi5p are key regulators of cell wall metabolism. Here, we have characterized the CaACE2 gene, which encodes the only C. albicans homologue of S. cerevisiae ACE2 and SWI5. Deleting CaACE2 results in a defect in cell separation, increased invasion of solid agar medium and inappropriate pseudohyphal growth, even in the absence of external inducers. The mutant cells have reduced adherence to plastic surfaces and generate biofilms with distinctly different morphology from wild-type cells. They are also avirulent in a mouse model. Deleting CaACE2 has no effect on expression of the chitinase gene CHT2, but expression of CHT3 and the putative cell wall genes CaDSE1 and CaSCW11 is reduced in both yeast and hyphal forms. The CaAce2 protein is localized to the daughter nucleus of large budded cells at the end of mitosis. C. albicans Ace2p therefore plays a major role in morphogenesis and adherence and resembles S. cerevisiae Ace2p in function.
Collapse
Affiliation(s)
- Mary T Kelly
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | | | | | | | | | | |
Collapse
|
28
|
Klinner U, Schäfer B. Genetic aspects of targeted insertion mutagenesis in yeasts. FEMS Microbiol Rev 2004; 28:201-23. [PMID: 15109785 DOI: 10.1016/j.femsre.2003.10.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2003] [Revised: 08/20/2003] [Accepted: 10/02/2003] [Indexed: 11/16/2022] Open
Abstract
Targeted insertion mutagenesis is a main molecular tool of yeast science initially applied in Saccharomyces cerevisiae. The method was extended to fission yeast Schizosaccharomyces pombe and to "non-conventional" yeast species, which show specific properties of special interest to both basic and applied research. Consequently, the behaviour of such non-Saccharomyces yeasts is reviewed against the background of the knowledge of targeted insertion mutagenesis in S. cerevisiae. Data of homologous integration efficiencies obtained with circular, ends-in or ends-out vectors in several yeasts are compared. We follow details of targeted insertion mutagenesis in order to recognize possible rate-limiting steps. The route of the vector to the target and possible mechanisms of its integration into chromosomal genes are considered. Specific features of some yeast species are discussed. In addition, similar approaches based on homologous recombination that have been established for the mitochondrial genome of S. cerevisiae are described.
Collapse
Affiliation(s)
- U Klinner
- RWTH Aachen, Institut für Biologie IV (Mikrobiologie und Genetik), Worringer Weg, D-52056 Aachen, Germany.
| | | |
Collapse
|
29
|
Magee PT, Gale C, Berman J, Davis D. Molecular genetic and genomic approaches to the study of medically important fungi. Infect Immun 2003; 71:2299-309. [PMID: 12704098 PMCID: PMC153231 DOI: 10.1128/iai.71.5.2299-2309.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- P T Magee
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota 55455, USA.
| | | | | | | |
Collapse
|
30
|
Abstract
Subcutaneous mycoses include a heterogeneous group of fungal infections that develop at the site of transcutaneous trauma. Infection slowly evolves as the etiologic agent survives and adapts to the adverse host tissue environment. Diagnosis rests on clinical presentation, histopathology, and culture of the etiologic agents. This article considers sporotrichosis, chromoblastomycosis, and mycetoma.
Collapse
|
31
|
Alonso-Monge R, Navarro-García F, Román E, Eisman B, Nombela C, Pla J. Strategies for the identification of virulence determinants in human pathogenic fungi. Curr Genet 2003; 42:301-12. [PMID: 12612803 DOI: 10.1007/s00294-002-0364-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2002] [Revised: 12/05/2002] [Accepted: 12/05/2002] [Indexed: 10/26/2022]
Abstract
The incidence of fungal infections is increasing in different countries. The current available therapy of these infections does not satisfy all requirements in terms of specificity and therapeutic index, a fact that has stimulated the scientific community to identify fungal virulence determinants. Several pathogenic fungi are opportunistic and, therefore, identification of virulence genes is difficult, given their close relationship with host cells. In recent years, the development of genetic tools in several pathogenic fungi has enabled the development of genetic strategies for their identification. These include several strategies based on the phenotypic analysis of strains or environmental conditions in which the expression of the putative gene(s) is either altered or deleted; and this is accomplished through the development of in vitro or in vivo systems. In the near future, this research will produce a better picture of fungal pathogenesis and therefore define novel promising targets in antifungal therapy.
Collapse
Affiliation(s)
- R Alonso-Monge
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, 28040, Madrid, Spain
| | | | | | | | | | | |
Collapse
|
32
|
Moran G, Sullivan D, Morschhäuser J, Coleman D. The Candida dubliniensis CdCDR1 gene is not essential for fluconazole resistance. Antimicrob Agents Chemother 2002; 46:2829-41. [PMID: 12183235 PMCID: PMC127416 DOI: 10.1128/aac.46.9.2829-2841.2002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The present study investigated the role of the Candida dubliniensis CdCDR1 and CdCDR2 genes in the development of fluconazole resistance. The C. dubliniensis CdCDR1 gene was 92% identical at the nucleotide sequence level to the corresponding C. albicans gene. However, 58% (14 of 24) of C. dubliniensis genotype 1 isolates tested harbored a nonsense mutation in the CdCDR1 open reading frame that converted codon 756 (TAT) to a TAG translational stop codon. Analysis of five of these C. dubliniensis isolates by Western immunoblotting showed that they expressed a truncated 85-kDa CdCdr1p compared to the full-length 170-kDa CdCdr1p. Expression of CdCDR1 alleles from six C. dubliniensis isolates in a pdr5 Saccharomyces cerevisiae strain revealed that CdCDR1 alleles from three isolates that encoded truncated proteins were unable to confer resistance to drugs and antifungals. However, reassignment of the TAG sequence at codon 756 to TAT (encoding tyrosine) in an allele from strain CD36 conferred the ability to mediate resistance to multiple drugs. Fluconazole-resistant isolates of C. dubliniensis harboring functional alleles of CdCDR1 were found to exhibit two- to ninefold-higher levels of CdCDR1 mRNA than did matched fluconazole-susceptible isolates. By comparison, levels of CdMDR1 expression ranged from approximately 50- to 100-fold greater in resistant isolates. Fluconazole resistance was also identified in isolates harboring nonfunctional CdCDR1 alleles, but resistance in these isolates was only associated with increased CdMDR1 expression. Targeted disruption of two functional alleles of CdCDR1 in a fluconazole-resistant derivative of C. dubliniensis that overexpressed both CdCDR1 and CdMDR1 revealed that although CdCDR1 was important for mediating reduced susceptibility to itraconazole and ketoconazole, there was no affect on fluconazole susceptibility in the double mutant. Evidence presented in this study reveals that CdCDR1 is not essential for the development of fluconazole resistance in C. dubliniensis.
Collapse
Affiliation(s)
- Gary Moran
- Microbiology Research Unit, Department of Oral Surgery, Oral Medicine and Pathology, School of Dental Science, Trinity College, University of Dublin, Republic of Ireland
| | | | | | | |
Collapse
|
33
|
Theiss S, Kretschmar M, Nichterlein T, Hof H, Agabian N, Hacker J, Köhler GA. Functional analysis of a vacuolar ABC transporter in wild-type Candida albicans reveals its involvement in virulence. Mol Microbiol 2002; 43:571-84. [PMID: 11929516 DOI: 10.1046/j.1365-2958.2002.02769.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
ATP-driven transport proteins belonging to the ATP-binding cassette (ABC) superfamily perform important functions in cell metabolism and detoxification. Compounds can be actively transported across membranes, including the plasma membrane or organellar membranes. The vacuole is an important organelle in fungal cells required for compartmentalization of metabolites as well as toxic substances. Sequestration into the vacuole is often energy-dependent. We present the first isolation and molecular analysis of a vacuolar ABC transporter gene in the opportunistic fungal pathogen Candida albicans. The protein encoded by the MLT1 gene is highly similar to Multiple Drug Resistance-associated Protein (MRP)-like transporters of yeast and higher organisms that form the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)/MRP subfamily of ABC transporters, a class of proteins so far not characterized in C. albicans. MLT1 expression is extensively growth phase-regulated, and gene transcripts are inducible by metabolic poisons. Gene replacement mutants generated in wild-type C. albicans with the dominant selection marker MPAR showed a profound reduction in virulence in a mouse peritonitis model that was reversed by complementation with an intact MLT1 gene. Hence, this report provides primary evidence for the involvement of vacuolar ABC transporters in fungal virulence.
Collapse
Affiliation(s)
- Stephanie Theiss
- Zentrum für Infektionsforschung, Universität Würzburg, D-97070 Würzburg, Germany
| | | | | | | | | | | | | |
Collapse
|
34
|
Wirsching S, Moran GP, Sullivan DJ, Coleman DC, Morschhäuser J. MDR1-mediated drug resistance in Candida dubliniensis. Antimicrob Agents Chemother 2001; 45:3416-21. [PMID: 11709317 PMCID: PMC90846 DOI: 10.1128/aac.45.12.3416-3421.2001] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Candida dubliniensis is a recently described opportunistic fungal pathogen that is closely related to Candida albicans. Candida dubliniensis readily develops resistance to the azole antifungal agent fluconazole, both in vitro and in infected patients, and this resistance is usually associated with upregulation of the CdMDR1 gene, encoding a multidrug efflux pump of the major facilitator superfamily. To determine the role of CdMDR1 in drug resistance in C. dubliniensis, we constructed an mdr1 null mutant from the fluconazole-resistant clinical isolate CM2, which overexpressed the CdMDR1 gene. Sequential deletion of both CdMDR1 alleles was performed by the MPA(R)-flipping method, which is based on the repeated use of a dominant mycophenolic acid resistance marker for selection of integrative transformants and its subsequent deletion from the genome by FLP-mediated, site-specific recombination. In comparison with its parental strain, the mdr1 mutant showed decreased resistance to fluconazole but not to the related drug ketoconazole. In addition, we found that CdMDR1 confers resistance to the structurally unrelated drugs 4-nitroquinoline-N-oxide, cerulenin, and brefeldin A, since the enhanced resistance to these compounds of the parent strain CM2 compared with the matched susceptible isolate CM1 was abolished in the mdr1 mutant. In contrast, CdMDR1 inactivation did not cause increased susceptibility to amorolfine, terbinafine, fluphenazine, and benomyl, although overexpression of CdMDR1 in a hypersusceptible Saccharomyces cerevisiae strain had previously been shown to confer resistance to these compounds. The effect of CdMDR1 inactivation was identical to that seen in two similarly constructed C. albicans mdr1 mutants. Therefore, despite species-specific differences in the amino acid sequences of the Mdr1 proteins, overexpression of CaMDR1 and CdMDR1 in clinical C. albicans and C. dubliniensis strains seems to confer the same drug resistance profile in both species.
Collapse
Affiliation(s)
- S Wirsching
- Zentrum für Infektionsforschung, Universität Würzburg, D-97070 Würzburg, Germany
| | | | | | | | | |
Collapse
|
35
|
Current awareness on yeast. Yeast 2001; 18:1091-8. [PMID: 11481679 DOI: 10.1002/yea.688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
|
36
|
Eggleston P, Zhao Y. Gene targeting in mosquito cells: a demonstration of 'knockout' technology in extrachromosomal gene arrays. BMC Genet 2001; 2:11. [PMID: 11513755 PMCID: PMC37536 DOI: 10.1186/1471-2156-2-11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2001] [Accepted: 07/31/2001] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Gene targeting would offer a number of advantages over current transposon-based strategies for insect transformation. These include freedom from both position effects associated with quasi-random integration and concerns over transgene instability mediated by endogenous transposases, independence from phylogenetic restrictions on transposon mobility and the ability to generate gene knockouts. RESULTS We describe here our initial investigations of gene targeting in the mosquito. The target site was a hygromycin resistance gene, stably maintained as part of an extrachromosomal array. Using a promoter-trap strategy to enrich for targeted events, a neomycin resistance gene was integrated into the target site. This resulted in knockout of hygromycin resistance concurrent with the expression of high levels of neomycin resistance from the resident promoter. PCR amplification of the targeted site generated a product that was specific to the targeted cell line and consistent with precise integration of the neomycin resistance gene into the 5' end of the hygromycin resistance gene. Sequencing of the PCR product and Southern analysis of cellular DNA subsequently confirmed this molecular structure. CONCLUSIONS These experiments provide the first demonstration of gene targeting in mosquito tissue and show that mosquito cells possess the necessary machinery to bring about precise integration of exogenous sequences through homologous recombination. Further development of these procedures and their extension to chromosomally located targets hold much promise for the exploitation of gene targeting in a wide range of medically and economically important insect species.
Collapse
Affiliation(s)
- Paul Eggleston
- School of Life Sciences, Keele University, Huxley Building, Keele, Staffordshire, ST5 5BG, UK
| | - Yuguang Zhao
- Current address: Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, OX3 9DS, UK
| |
Collapse
|