scholarly journals Competitive Fitness of Fluconazole-Resistant Clinical Candida albicans Strains

2017 ◽  
Vol 61 (7) ◽  
Author(s):  
Christina Popp ◽  
Irene A. I. Hampe ◽  
Tobias Hertlein ◽  
Knut Ohlsen ◽  
P. David Rogers ◽  
...  
Keyword(s):  
Gene Expression ◽  
Drug Resistance ◽  
Candida Albicans ◽  
Transcription Factors ◽  
Mouse Model ◽  
Ergosterol Biosynthesis ◽  
Fitness Costs ◽  
Content Type ◽  
Constitutive Overexpression ◽  
Fluconazole Resistant

ABSTRACT The pathogenic yeast Candida albicans can develop resistance to the widely used antifungal agent fluconazole, which inhibits ergosterol biosynthesis. Resistance is often caused by gain-of-function mutations in the transcription factors Mrr1 and Tac1, which result in constitutive overexpression of multidrug efflux pumps, and Upc2, which result in constitutive overexpression of ergosterol biosynthesis genes. However, the deregulated gene expression that is caused by hyperactive forms of these transcription factors also reduces the fitness of the cells in the absence of the drug. To investigate whether fluconazole-resistant clinical C. albicans isolates have overcome the fitness costs of drug resistance, we assessed the relative fitness of C. albicans isolates containing resistance mutations in these transcription factors in competition with matched drug-susceptible isolates from the same patients. Most of the fluconazole-resistant isolates were outcompeted by the corresponding drug-susceptible isolates when grown in rich medium without fluconazole. On the other hand, some resistant isolates with gain-of-function mutations in MRR1 did not exhibit reduced fitness under these conditions. In a mouse model of disseminated candidiasis, three out of four tested fluconazole-resistant clinical isolates did not exhibit a significant fitness defect. However, all four fluconazole-resistant isolates were outcompeted by the matched susceptible isolates in a mouse model of gastrointestinal colonization, demonstrating that the effects of drug resistance on in vivo fitness depend on the host niche. Collectively, our results indicate that the fitness costs of drug resistance in C. albicans are not easily remediated, especially when proper control of gene expression is required for successful adaptation to life within a mammalian host.

scholarly journals A Gain-of-Function Mutation in the Transcription Factor Upc2p Causes Upregulation of Ergosterol Biosynthesis Genes and Increased Fluconazole Resistance in a Clinical Candida albicans Isolate

2008 ◽  
Vol 7 (7) ◽  
pp. 1180-1190 ◽  
Author(s):  
Nico Dunkel ◽  
Teresa T. Liu ◽  
Katherine S. Barker ◽  
Ramin Homayouni ◽  
Joachim Morschhäuser ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Candida Albicans ◽  
Clinical Isolates ◽  
Resistant Isolate ◽  
Ergosterol Biosynthesis ◽  
Gain Of Function ◽  
Zinc Cluster ◽  
Fluconazole Resistant ◽  
Lanosterol Demethylase

ABSTRACT In the pathogenic yeast Candida albicans, the zinc cluster transcription factor Upc2p has been shown to regulate the expression of ERG11 and other genes involved in ergosterol biosynthesis upon exposure to azole antifungals. ERG11 encodes lanosterol demethylase, the target enzyme of this antifungal class. Overexpression of UPC2 reduces azole susceptibility, whereas its disruption results in hypersusceptibility to azoles and reduced accumulation of exogenous sterols. Overexpression of ERG11 leads to the increased production of lanosterol demethylase, which contributes to azole resistance in clinical isolates of C. albicans, but the mechanism for this has yet to be determined. Using genome-wide gene expression profiling, we found UPC2 and other genes involved in ergosterol biosynthesis to be coordinately upregulated with ERG11 in a fluconazole-resistant clinical isolate compared with a matched susceptible isolate from the same patient. Sequence analysis of the UPC2 alleles of these isolates revealed that the resistant isolate contained a single-nucleotide substitution in one UPC2 allele that resulted in a G648D exchange in the encoded protein. Introduction of the mutated allele into a drug-susceptible strain resulted in constitutive upregulation of ERG11 and increased resistance to fluconazole. By comparing the gene expression profiles of the fluconazole-resistant isolate and of strains carrying wild-type and mutated UPC2 alleles, we identified target genes that are controlled by Upc2p. Here we show for the first time that a gain-of-function mutation in UPC2 leads to the increased expression of ERG11 and imparts resistance to fluconazole in clinical isolates of C. albicans.

scholarly journals Regulation of Efflux Pump Expression and Drug Resistance by the Transcription Factors Mrr1, Upc2, and Cap1 in Candida albicans

2011 ◽  
Vol 55 (5) ◽  
pp. 2212-2223 ◽  
Author(s):  
Sabrina Schubert ◽  
Katherine S. Barker ◽  
Sadri Znaidi ◽  
Sabrina Schneider ◽  
Franziska Dierolf ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Candida Albicans ◽  
Transcription Factors ◽  
Target Genes ◽  
Efflux Pump ◽  
Binding Studies ◽  
Gain Of Function ◽  
Content Type ◽  
Zinc Cluster ◽  
Constitutively Active

ABSTRACTConstitutive overexpression of the Mdr1 efflux pump is an important mechanism of acquired drug resistance in the yeastCandida albicans. The zinc cluster transcription factor Mrr1 is a central regulator ofMDR1expression, but other transcription factors have also been implicated inMDR1regulation. To better understand howMDR1-mediated drug resistance is achieved in this fungal pathogen, we studied the interdependence of Mrr1 and two otherMDR1regulators, Upc2 and Cap1, in the control ofMDR1expression. A mutated, constitutively active Mrr1 could upregulateMDR1and confer drug resistance in the absence of Upc2 or Cap1. On the other hand, Upc2 containing a gain-of-function mutation only slightly activated theMDR1promoter, and this activation depended on the presence of a functionalMRR1gene. In contrast, a C-terminally truncated, activated form of Cap1 could upregulateMDR1in a partially Mrr1-independent fashion. The induction ofMDR1expression by toxic chemicals occurred independently of Upc2 but required the presence of Mrr1 and also partially depended on Cap1. Transcriptional profiling andin vivoDNA binding studies showed that a constitutively active Mrr1 binds to and upregulates most of its direct target genes in the presence or absence of Cap1. Therefore, Mrr1 and Cap1 cooperate in the environmental induction ofMDR1expression in wild-typeC. albicans, but gain-of-function mutations in either of the two transcription factors can independently mediate efflux pump overexpression and drug resistance.

scholarly journals ERG2andERG24Are Required for Normal Vacuolar Physiology as Well as Candida albicans Pathogenicity in a Murine Model of Disseminated but Not Vaginal Candidiasis

2015 ◽  
Vol 14 (10) ◽  
pp. 1006-1016 ◽  
Author(s):  
Arturo Luna-Tapia ◽  
Brian M. Peters ◽  
Karen E. Eberle ◽  
Morgan E. Kerns ◽  
Timothy P. Foster ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Mouse Model ◽  
Hyphal Growth ◽  
Vaginal Candidiasis ◽  
Ergosterol Biosynthesis ◽  
Vaginal Infections ◽  
Gene Encoding ◽  
Content Type ◽  
Disseminated Candidiasis ◽  
The Impact

ABSTRACTSeveral important classes of antifungal agents, including the azoles, act by blocking ergosterol biosynthesis. It was recently reported that the azoles cause massive disruption of the fungal vacuole in the prevalent human pathogenCandida albicans. This is significant because normal vacuolar function is required to supportC. albicanspathogenicity. This study examined the impact of the morpholine antifungals, which inhibit later steps of ergosterol biosynthesis, onC. albicansvacuolar integrity. It was found that overexpression of either theERG2orERG24gene, encoding C-8 sterol isomerase or C-14 sterol reductase, respectively, suppressedC. albicanssensitivity to the morpholines. In addition, botherg2Δ/Δanderg24Δ/Δmutants were hypersensitive to the morpholines. These data are consistent with the antifungal activity of the morpholines depending upon the simultaneous inhibition of both Erg2p and Erg24p. The vacuoles within botherg2Δ/Δanderg24Δ/ΔC. albicansstrains exhibited an aberrant morphology and accumulated large quantities of the weak base quinacrine, indicating enhanced vacuolar acidification compared with that of control strains. Bothergmutants exhibited significant defects in polarized hyphal growth and were avirulent in a mouse model of disseminated candidiasis. Surprisingly, in a mouse model of vaginal candidiasis, both mutants colonized mice at high levels and induced a pathogenic response similar to that with the controls. Thus, while targeting Erg2p or Erg24p alone could provide a potentially efficacious therapy for disseminated candidiasis, it may not be an effective strategy to treat vaginal infections. The potential value of drugs targeting these enzymes as adjunctive therapies is discussed.

scholarly journals Evaluation of Differential Gene Expression in Fluconazole-Susceptible and -Resistant Isolates of Candida albicans by cDNA Microarray Analysis

2002 ◽  
Vol 46 (11) ◽  
pp. 3412-3417 ◽  
Author(s):  
P. David Rogers ◽  
Katherine S. Barker
Keyword(s):  
Gene Expression ◽  
Drug Resistance ◽  
Candida Albicans ◽  
Microarray Analysis ◽  
Molecular Mechanisms ◽  
Cell Stress ◽  
Differentially Expressed ◽  
Ergosterol Biosynthesis ◽  
Azole Resistance ◽  
Lipid Fatty Acid

ABSTRACT The opportunistic fungal pathogen Candida albicans is the major causative agent of oropharyngeal candidiasis (OPC) in AIDS. The development of azoles, such as fluconazole, for the treatment of OPC has proven effective except in cases where C. albicans develops resistance to fluconazole during the course of treatment. In the present study, we used microarray technology to examine differences in gene expression from a fluconazole-susceptible and a fluconazole-resistant well-characterized, clinically obtained matched set of C. albicans isolates to identify genes which are differentially expressed in association with azole resistance. Among genes found to be differentially expressed were those involved in amino acid and carbohydrate metabolism; cell stress, cell wall maintenance; lipid, fatty acid, and sterol metabolism; and small molecule transport. In addition to CDR1, which has previously been demonstrated to be associated with azole resistance, the drug resistance gene RTA3, the ergosterol biosynthesis gene ERG2, and the cell stress genes CRD2, GPX1, and IFD5 were found to be upregulated. Several genes, such as the mitochondrial aldehyde dehydrogenase gene ALD5, the glycosylphosphatidylinositol synthesis gene GPI1, and the iron transport genes FET34 and FTR2 were found to be downregulated. Further study of these differentially regulated genes is warranted to evaluate how they may be involved in azole resistance. In addition to these novel findings, we demonstrate the utility of microarray analysis for studying the molecular mechanisms of drug resistance in pathogenic organisms.

scholarly journals Candida albicans Ferric Reductases Are Differentially Regulated in Response to Distinct Forms of Iron Limitation by the Rim101 and CBF Transcription Factors

2008 ◽  
Vol 7 (7) ◽  
pp. 1168-1179 ◽  
Author(s):  
Yong-Un Baek ◽  
Mingchun Li ◽  
Dana A. Davis
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Candida Albicans ◽  
Transcription Factors ◽  
Iron Acquisition ◽  
Mammalian Host ◽  
Regulatory Sequence ◽  
Ferric Reductase ◽  
Reductase Gene ◽  
Ferric Reductases

ABSTRACT Iron is an essential nutrient that is severely limited in the mammalian host. Candida albicans encodes a family of 15 putative ferric reductases, which are required for iron acquisition and utilization. Despite the central role of ferric reductases in iron acquisition and mobilization, relatively little is known about the regulatory networks that govern ferric reductase gene expression in C. albicans. Here we have demonstrated the differential regulation of two ferric reductases, FRE2 and FRP1, in response to distinct iron-limited environments. FRE2 and FRP1 are both induced in alkaline-pH environments directly by the Rim101 transcription factor. However, FRP1 but not FRE2 is also induced by iron chelation. We have identified a CCAAT motif as the critical regulatory sequence for chelator-mediated induction and have found that the CCAAT binding factor (CBF) is essential for FRP1 expression in iron-limited environments. We found that a hap5Δ/hap5Δ mutant, which disrupts the core DNA binding activity of CBF, is unable to grow under iron-limited conditions. C. albicans encodes three CBF-dependent transcription factors, and we identified the Hap43 protein as the CBF-dependent transcription factor required for iron-limited responses. These studies provide key insights into the regulation of ferric reductase gene expression in the fungal pathogen C. albicans.

scholarly journals FgHtf1 Regulates Global Gene Expression towards Aerial Mycelium and Conidiophore Formation in the Cereal Fungal Pathogen Fusarium graminearum

2020 ◽  
Vol 86 (9) ◽  
Author(s):  
Gaili Fan ◽  
Huawei Zheng ◽  
Kai Zhang ◽  
Veena Devi Ganeshan ◽  
Stephen Obol Opiyo ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Gene Family ◽  
Fusarium Graminearum ◽  
Target Genes ◽  
Homeobox Gene ◽  
Global Gene Expression ◽  
Binding Motifs ◽  
Content Type ◽  
Aerial Growth

ABSTRACT The homeobox gene family of transcription factors (HTF) controls many developmental pathways and physiological processes in eukaryotes. We previously showed that a conserved HTF in the plant-pathogenic fungus Fusarium graminearum, Htf1 (FgHtf1), regulates conidium morphology in that organism. This study investigated the mechanism of FgHtf1-mediated regulation and identified putative FgHtf1 target genes by a chromatin immunoprecipitation assay combined with parallel DNA sequencing (ChIP-seq) and RNA sequencing. A total of 186 potential binding peaks, including 142 genes directly regulated by FgHtf1, were identified. Subsequent motif prediction analysis identified two DNA-binding motifs, TAAT and CTTGT. Among the FgHtf1 target genes were FgHTF1 itself and several important conidiation-related genes (e.g., FgCON7), the chitin synthase pathway genes, and the aurofusarin biosynthetic pathway genes. In addition, FgHtf1 may regulate the cAMP-protein kinase A (PKA)-Msn2/4 and Ca2+-calcineurin-Crz1 pathways. Taken together, these results suggest that, in addition to autoregulation, FgHtf1 also controls global gene expression and promotes a shift to aerial growth and conidiation in F. graminearum by activation of FgCON7 or other conidiation-related genes. IMPORTANCE The homeobox gene family of transcription factors is known to be involved in the development and conidiation of filamentous fungi. However, the regulatory mechanisms and downstream targets of homeobox genes remain unclear. FgHtf1 is a homeobox transcription factor that is required for phialide development and conidiogenesis in the plant pathogen F. graminearum. In this study, we identified FgHtf1-controlled target genes and binding motifs. We found that, besides autoregulation, FgHtf1 also controls global gene expression and promotes conidiation in F. graminearum by activation of genes necessary for aerial growth, FgCON7, and other conidiation-related genes.

scholarly journals Role of Matrix β-1,3 Glucan in Antifungal Resistance of Non-albicans Candida Biofilms

2013 ◽  
Vol 57 (4) ◽  
pp. 1918-1920 ◽  
Author(s):  
K. F. Mitchell ◽  
H. T. Taff ◽  
M. A. Cuevas ◽  
E. L. Reinicke ◽  
H. Sanchez ◽  
...  
Keyword(s):  
Health Care ◽  
Drug Resistance ◽  
Candida Albicans ◽  
Care Setting ◽  
Antifungal Susceptibility ◽  
Antifungal Drug ◽  
Content Type ◽  
The Matrix ◽  
Biofilm Matrix

ABSTRACTCandidabiofilm infections pose an increasing threat in the health care setting due to the drug resistance associated with this lifestyle. Several mechanisms underlie the resistance phenomenon. InCandida albicans, one mechanism involves drug impedance by the biofilm matrix linked to β-1,3 glucan. Here, we show this is important for otherCandidaspp. We identified β-1,3 glucan in the matrix, found that the matrix sequesters antifungal drug, and enhanced antifungal susceptibility with matrix β-1,3 glucan hydrolysis.

scholarly journals Effect of biogenic selenium nanoparticles on ERG11 and CDR1 gene expression in both fluconazole-resistant and -susceptible Candida albicans isolates

2017 ◽  
Vol 3 (3) ◽  
pp. 16-20 ◽  
Author(s):  
Nasrin Parsamehr ◽  
Sasan Rezaie ◽  
Sadegh Khodavaisy ◽  
Samira Salari ◽  
Sanaz Hadizadeh ◽  
...  
Keyword(s):  
Gene Expression ◽  
Candida Albicans ◽  
Selenium Nanoparticles ◽  
Fluconazole Resistant ◽  
Biogenic Selenium Nanoparticles

scholarly journals Chromatin Profiling of the Repetitive and Nonrepetitive Genomes of the Human Fungal Pathogen Candida albicans

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Robert Jordan Price ◽  
Esther Weindling ◽  
Judith Berman ◽  
Alessia Buscaino
Keyword(s):  
Gene Expression ◽  
Candida Albicans ◽  
Histone Modifications ◽  
Chromatin Structure ◽  
Fungal Pathogen ◽  
Histone H3 ◽  
Content Type ◽  
Chromatin States ◽  
Genome Wide ◽  
Chromatin Profiling

ABSTRACT Eukaryotic genomes are packaged into chromatin structures that play pivotal roles in regulating all DNA-associated processes. Histone posttranslational modifications modulate chromatin structure and function, leading to rapid regulation of gene expression and genome stability, key steps in environmental adaptation. Candida albicans, a prevalent fungal pathogen in humans, can rapidly adapt and thrive in diverse host niches. The contribution of chromatin to C. albicans biology is largely unexplored. Here, we generated the first comprehensive chromatin profile of histone modifications (histone H3 trimethylated on lysine 4 [H3K4me3], histone H3 acetylated on lysine 9 [H3K9Ac], acetylated lysine 16 on histone H4 [H4K16Ac], and γH2A) across the C. albicans genome and investigated its relationship to gene expression by harnessing genome-wide sequencing approaches. We demonstrated that gene-rich nonrepetitive regions are packaged into canonical euchromatin in association with histone modifications that mirror their transcriptional activity. In contrast, repetitive regions are assembled into distinct chromatin states; subtelomeric regions and the ribosomal DNA (rDNA) locus are assembled into heterochromatin, while major repeat sequences and transposons are packaged in chromatin that bears features of euchromatin and heterochromatin. Genome-wide mapping of γH2A, a marker of genome instability, identified potential recombination-prone genomic loci. Finally, we present the first quantitative chromatin profiling in C. albicans to delineate the role of the chromatin modifiers Sir2 and Set1 in controlling chromatin structure and gene expression. This report presents the first genome-wide chromatin profiling of histone modifications associated with the C. albicans genome. These epigenomic maps provide an invaluable resource to understand the contribution of chromatin to C. albicans biology and identify aspects of C. albicans chromatin organization that differ from that of other yeasts. IMPORTANCE The fungus Candida albicans is an opportunistic pathogen that normally lives on the human body without causing any harm. However, C. albicans is also a dangerous pathogen responsible for millions of infections annually. C. albicans is such a successful pathogen because it can adapt to and thrive in different environments. Chemical modifications of chromatin, the structure that packages DNA into cells, can allow environmental adaptation by regulating gene expression and genome organization. Surprisingly, the contribution of chromatin modification to C. albicans biology is still largely unknown. For the first time, we analyzed C. albicans chromatin modifications on a genome-wide basis. We demonstrate that specific chromatin states are associated with distinct regions of the C. albicans genome and identify the roles of the chromatin modifiers Sir2 and Set1 in shaping C. albicans chromatin and gene expression.

scholarly journals The Paralogous Transcription Factors Stp1 and Stp2 of Candida albicans Have Distinct Functions in Nutrient Acquisition and Host Interaction

2020 ◽  
Vol 88 (5) ◽  
Author(s):  
Pedro Miramón ◽  
Andrew W. Pountain ◽  
Ambro van Hoof ◽  
Michael C. Lorenz
Keyword(s):  
Candida Albicans ◽  
Transcription Factors ◽  
Amino Acid ◽  
Cell Damage ◽  
Nutrient Acquisition ◽  
Acid Uptake ◽  
Content Type ◽  
Host Interaction ◽  
Amino Acid Utilization

ABSTRACT Nutrient acquisition is a central challenge for all organisms. For the fungal pathogen Candida albicans, utilization of amino acids has been shown to be critical for survival, immune evasion, and escape, while the importance of catabolism of host-derived proteins and peptides in vivo is less well understood. Stp1 and Stp2 are paralogous transcription factors (TFs) regulated by the Ssy1-Ptr3-Ssy5 (SPS) amino acid sensing system and have been proposed to have distinct, if uncertain, roles in protein and amino acid utilization. We show here that Stp1 is required for proper utilization of peptides but has no effect on amino acid catabolism. In contrast, Stp2 is critical for utilization of both carbon sources. Commensurate with this observation, we found that Stp1 controls a very limited set of genes, while Stp2 has a much more extensive regulon that is partly dependent on the Ssy1 amino acid sensor (amino acid uptake and catabolism) and partly Ssy1 independent (genes associated with filamentous growth, including the regulators UME6 and SFL2). The ssy1Δ/Δ and stp2Δ/Δ mutants showed reduced fitness in a gastrointestinal (GI) colonization model, yet induced greater damage to epithelial cells and macrophages in a manner that was highly dependent on the growth status of the fungal cells. Surprisingly, the stp1Δ/Δ mutant was better able to colonize the gut but the mutation had no effect on host cell damage. Thus, proper protein and amino acid utilization are both required for normal host interaction and are controlled by an interrelated network that includes Stp1 and Stp2.

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