scholarly journals Aequorin as a Useful Calcium-Sensing Reporter in Candida albicans

2021 ◽  
Vol 7 (4) ◽  
pp. 319
Author(s):  
Dominique Sanglard
Keyword(s):  
Candida Albicans ◽  
Fungal Pathogen ◽  
Expression System ◽  
Cell Polarization ◽  
Water Soluble ◽  
Alkaline Stress ◽  
Extracellular Medium ◽  
Calcium Sensing ◽  
Contact Sensing

In Candida albicans, calcium ions (Ca2+) regulate the activity of several signaling pathways, especially the calcineurin signaling pathway. Ca2+ homeostasis is also important for cell polarization, hyphal extension, and plays a role in contact sensing. It is therefore important to obtain accurate tools with which Ca2+ homeostasis can be addressed in this fungal pathogen. Aequorin from Aequorea victoria has been used in eukaryotic cells for detecting intracellular Ca2+. A codon-adapted aequorin Ca2+-sensing expression system was therefore designed for probing cytosolic Ca2+ flux in C. albicans. The availability of a novel water-soluble formulation of coelenterazine, which is required as a co-factor, made it possible to measure bioluminescence as a readout of intracellular Ca2+ levels in C. albicans. Alkaline stress resulted in an immediate influx of Ca2+ from the extracellular medium. This increase was exacerbated in a mutant lacking the vacuolar Ca2+ transporter VCX1, thus confirming its role in Ca2+ homeostasis. Using mutants in components of a principal Ca2+ channel (MID1, CCH1), the alkaline-dependent Ca2+ spike was greatly reduced, thus highlighting the crucial role of this channel complex in Ca2+ uptake and homeostasis. Exposure to the antiarrhythmic drug amiodarone, known to perturb Ca2+ trafficking, resulted in increased cytoplasmic Ca2+ within seconds that was abrogated by the chelation of Ca2+ in the external medium. Ca2+ import was also dependent on the Cch1/Mid1 Ca2+ channel in amiodarone-exposed cells. In conclusion, the aequorin Ca2+ sensing reporter developed here is an adequate tool with which Ca2+ homeostasis can be investigated in C. albicans.

scholarly journals Role of the WOR1 Promoter of Candida albicans in Opaque Commitment

mBio ◽  
2021 ◽  
Author(s):  
Thomas P. Conway ◽  
Kayla Conway ◽  
Frank A. Boksa ◽  
Claude Pujol ◽  
Deborah Wessels ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Gastrointestinal Tract ◽  
Fungal Pathogen ◽  
Lower Gastrointestinal Tract ◽  
Content Type ◽  
Phenotypic Transition

Candida albicans , the most pervasive fungal pathogen colonizing humans, undergoes a phenotypic transition between a white and opaque phenotype. The unique opaque phenotype is necessary for mating and colonization of the lower gastrointestinal tract.

scholarly journals MFα1, the Gene Encoding the α Mating Pheromone of Candida albicans

2003 ◽  
Vol 2 (6) ◽  
pp. 1350-1360 ◽  
Author(s):  
Sneh L. Panwar ◽  
Melanie Legrand ◽  
Daniel Dignard ◽  
Malcolm Whiteway ◽  
Paul. T. Magee
Keyword(s):  
Candida Albicans ◽  
Fungal Pathogen ◽  
Null Mutant ◽  
Mating Pheromone ◽  
Gene Encoding ◽  
Human Fungal Pathogen ◽  
Isolation And Characterization ◽  
Α Pheromone

ABSTRACT Candida albicans, the single most frequently isolated human fungal pathogen, was thought to be asexual until the recent discovery of the mating-type-like locus (MTL). Homozygous MTL strains were constructed and shown to mate. Furthermore, it has been demonstrated that opaque-phase cells are more efficient in mating than white-phase cells. The similarity of the genes involved in the mating pathway in Saccharomyces cerevisiae and C. albicans includes at least one gene (KEX2) that is involved in the processing of the α mating pheromone in the two yeasts. Taking into account this similarity, we searched the C. albicans genome for sequences that would encode the α pheromone gene. Here we report the isolation and characterization of the gene MFα1, which codes for the precursor of the α mating pheromone in C. albicans. Two active α-peptides, 13 and 14 amino acids long, would be generated after the precursor molecule is processed in C. albicans. To examine the role of this gene in mating, we constructed an mfα1 null mutant of C. albicans. The mfα1 null mutant fails to mate as MTLα, while MTLa mfα1 cells are still mating competent. Experiments performed with the synthetic α-peptides show that they are capable of inducing growth arrest, as demonstrated by halo tests, and also induce shmooing in MTLa cells of C. albicans. These peptides are also able to complement the mating defect of an MTLα kex2 mutant strain when added exogenously, thereby confirming their roles as α mating pheromones.

scholarly journals Effects of Ploidy and Mating Type on Virulence of Candida albicans

2005 ◽  
Vol 73 (11) ◽  
pp. 7366-7374 ◽  
Author(s):  
Ashraf S. Ibrahim ◽  
B. B. Magee ◽  
D. C. Sheppard ◽  
Molly Yang ◽  
Sarah Kauffman ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Mating Type ◽  
Murine Model ◽  
Fungal Pathogen ◽  
Opposite Mating Type ◽  
Type Locus ◽  
Disseminated Candidiasis ◽  
Strain Background ◽  
Do So

ABSTRACT Candida albicans is the most common fungal pathogen of humans. The recent discovery of sexuality in this organism has led to the demonstration of a mating type locus which is usually heterozygous, although some isolates are homozygous. Tetraploids can be formed between homozygotes of the opposite mating type. However, the role of the mating process and tetraploid formation in virulence has not been investigated. We describe here experiments using a murine model of disseminated candidiasis which demonstrate that in three strains, including CAI-4, the most commonly used strain background, tetraploids are less virulent than diploids and can undergo changes in ploidy during infection. In contrast to reports with other strains, we find that MTL homozygotes are almost as virulent as the heterozygotes. These results show that the level of ploidy in Candida albicans can affect virulence, but the mating type configuration does not necessarily do so.

scholarly journals Exogenous reproductive hormones nor Candida albicans colonization alter the near neutral mouse vaginal pH

2020 ◽  
Author(s):  
Jian Miao ◽  
Hubertine M. E. Willems ◽  
Brian M Peters
Keyword(s):  
Candida Albicans ◽  
Fungal Pathogen ◽  
Reproductive Hormones ◽  
Vulvovaginal Candidiasis ◽  
Phenol Red ◽  
Ph Indicator ◽  
Physiological Factor ◽  
Vaginal Ph ◽  
Indicator Dye

While human vaginal pH in childbearing aged women is conclusively acidic, the mouse vaginal pH is reported as being near neutral. However, this information appears to be somewhat anecdotal with respect to vulvovaginal candidiasis as such claims in the literature frequently lack citations of studies that specifically address this physiological factor. Given the disparate pH between mice and humans, the role of exogenous hormones and colonization by the fungal pathogen Candida albicans in shaping vaginal pH was assessed. Use of a convenient modified vaginal lavage technique with the pH indicator dye phenol red demonstrated that indeed vaginal pH was near neutral (7.2 ± 0.24) and was not altered by delivery of progesterone or estrogen in C57BL/6 mice. These trends were conserved in DBA/2 and CD-1 mouse backgrounds commonly used in the mouse model of vaginitis. It was also determined that vaginal colonization with C. albicans did not alter the globally neutral vaginal pH over the course of one week. Construction and validation of a C. albicans reporter strain expressing GFPy driven by the pH-responsive PHR1 promoter confirmed that the murine vaginal pH to be at least ≥ 6.0. Collectively, our data convincingly demonstrate a stable and conserved near neutrality of the mouse vaginal pH during vulvovaginal candidiasis and should serve as a definitive source for future reference. Implications and rationale for disparate pH in this model system are also discussed.

scholarly journals Roles of the Transcription Factors Sfl2 and Efg1 in White-Opaque Switching in a/α Strains ofCandida albicans

mSphere ◽  
2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Yang-Nim Park ◽  
Kayla Conway ◽  
Thomas P. Conway ◽  
Karla J. Daniels ◽  
David R. Soll
Keyword(s):  
Candida Albicans ◽  
Transcription Factors ◽  
Carbon Source ◽  
Environmental Conditions ◽  
Fungal Pathogen ◽  
Type Locus ◽  
Content Type ◽  
Physiological Conditions ◽  
Ofcandida Albicans

ABSTRACTCandida albicansremains the most pervasive fungal pathogen colonizing humans. The majority of isolates from hosts are heterozygous at the mating type locus (MTLa/α), and a third of these have recently been shown to be capable of switching to the opaque phenotype. Here we have investigated the roles of two transcription factors (TFs) Sfl2 and Efg1, in repressing switching ina/α strains. Deleting either gene results in the capacity ofa/α cells to switch to opaque en masse under facilitating environmental conditions, which includeN-acetylglucosamine (GlcNAc) as the carbon source, physiological temperature (37°C), and high CO2(5%). These conditions are similar to those in the host. Our results further reveal that while glucose is a repressor ofsfl2Δ andefg1Δ switching, GlcNAc is an inducer. Finally, we show that when GlcNAc is the carbon source, and the temperature is low (25°C), theefg1Δ mutants, but not thesfl2Δ mutants, form a tiny, elongate cell, which differentiates into an opaque cell when transferred to conditions optimal fora/α switching. These results demonstrate that at least two TFs, Sfl2 and Efg1, repress switching ina/α cells and thata/α strains with either ansfl2Δ orefg1Δ mutation can switch en masse but only under physiological conditions. The role of opaquea/α cells in commensalism and pathogenesis must, therefore, be investigated.IMPORTANCEMore than 95% ofCandida albicansstrains isolated from humans areMTLa/α, and approximately a third of these can undergo the white-to-opaque transition. Therefore, besides being a requirement forMTL-homozygous strains to mate, the opaque phenotype very likely plays a role in the commensalism and pathogenesis of nonmating,a/α populations colonizing humans.

scholarly journals A conserved regulator controls asexual sporulation in the fungal pathogen Candida albicans

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Arturo Hernández-Cervantes ◽  
Sadri Znaidi ◽  
Lasse van Wijlick ◽  
Iryna Denega ◽  
Virginia Basso ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Chromatin Immunoprecipitation ◽  
Fungal Pathogen ◽  
Hyphal Growth ◽  
Second Phase ◽  
Asexual Sporulation ◽  
Expression Of Genes ◽  
Genome Wide ◽  
Genome Wide Expression

AbstractTranscription factor Rme1 is conserved among ascomycetes and regulates meiosis and pseudohyphal growth in Saccharomyces cerevisiae. The genome of the meiosis-defective pathogen Candida albicans encodes an Rme1 homolog that is part of a transcriptional circuitry controlling hyphal growth. Here, we use chromatin immunoprecipitation and genome-wide expression analyses to study a possible role of Rme1 in C. albicans morphogenesis. We find that Rme1 binds upstream and activates the expression of genes that are upregulated during chlamydosporulation, an asexual process leading to formation of large, spherical, thick-walled cells during nutrient starvation. RME1 deletion abolishes chlamydosporulation in three Candida species, whereas its overexpression bypasses the requirement for chlamydosporulation cues and regulators. RME1 expression levels correlate with chlamydosporulation efficiency across clinical isolates. Interestingly, RME1 displays a biphasic pattern of expression, with a first phase independent of Rme1 function and dependent on chlamydospore-inducing cues, and a second phase dependent on Rme1 function and independent of chlamydospore-inducing cues. Our results indicate that Rme1 plays a central role in chlamydospore development in Candida species.

scholarly journals Farnesol and Cyclic AMP Signaling Effects on the Hypha-to-Yeast Transition in Candida albicans

2012 ◽  
Vol 11 (10) ◽  
pp. 1219-1225 ◽  
Author(s):  
Allia K. Lindsay ◽  
Aurélie Deveau ◽  
Amy E. Piispanen ◽  
Deborah A. Hogan
Keyword(s):  
Candida Albicans ◽  
Cyclic Amp ◽  
Fungal Pathogen ◽  
Hyphal Growth ◽  
Morphological Plasticity ◽  
Camp Signaling ◽  
Environmental Cues ◽  
Transcriptional Repressors ◽  
Content Type

ABSTRACTCandida albicans, a fungal pathogen of humans, regulates its morphology in response to many environmental cues and this morphological plasticity contributes to virulence. Farnesol, an autoregulatory molecule produced byC. albicans, inhibits the induction of hyphal growth by inhibiting adenylate cyclase (Cyr1). The role of farnesol and Cyr1 in controlling the maintenance of hyphal growth has been less clear. Here, we demonstrate that preformed hyphae transition to growth as yeast in response to farnesol and that strains with increased cyclic AMP (cAMP) signaling exhibit more resistance to farnesol. Exogenous farnesol did not induce the hypha-to-yeast transition in mutants lacking the Tup1 or Nrg1 transcriptional repressors in embedded conditions. Although body temperature is not required for embedded hyphal growth, we found that the effect of farnesol on the hypha-to-yeast transition varies inversely with temperature. Our model of Cyr1 activity being required for filamentation is also supported by our liquid assay data, which show increased yeast formation when preformed filaments are treated with farnesol. Together, these data suggest that farnesol can modulate morphology in preformed hyphal cells and that the repression of hyphal growth maintenance likely occurs through the inhibition of cAMP signaling.

scholarly journals The role of aneuploidy in the emergence of echinocandin resistance in human fungal pathogen Candida albicans

2021 ◽  
Vol 17 (5) ◽  
pp. e1009564
Author(s):  
Sudisht Kumar Sah ◽  
Jeffrey Joseph Hayes ◽  
Elena Rustchenko
Keyword(s):  
Candida Albicans ◽  
Fungal Pathogen ◽  
Human Fungal Pathogen ◽  
Echinocandin Resistance

scholarly journals Global Roles of Ssn6 in Tup1- and Nrg1-dependent Gene Regulation in the Fungal Pathogen,Candida albicans

2005 ◽  
Vol 16 (6) ◽  
pp. 2913-2925 ◽  
Author(s):  
Susana García-Sánchez ◽  
Abigail L. Mavor ◽  
Claire L. Russell ◽  
Silvia Argimon ◽  
Paul Dennison ◽  
...  
Keyword(s):  
Gene Regulation ◽  
Candida Albicans ◽  
Fungal Pathogen ◽  
Budding Yeast ◽  
Pathogenic Fungus ◽  
Phenotypic Switching ◽  
Specific Gene ◽  
Cellular Morphogenesis ◽  
Number Of Genes

In budding yeast, Tup1 and Ssn6/Cyc8 form a corepressor that regulates a large number of genes. This Tup1-Ssn6 corepressor appears to be conserved from yeast to man. In the pathogenic fungus Candida albicans, Tup1 regulates cellular morphogenesis, phenotypic switching, and metabolism, but the role of Ssn6 remains unclear. We show that there are clear differences in the morphological and invasive phenotypes of C. albicans ssn6 and tup1 mutants. Unlike Tup1, Ssn6 depletion promoted morphological events reminiscent of phenotypic switching rather than filamentous growth. Transcript profiling revealed minimal overlap between the Ssn6 and Tup1 regulons. Hypha-specific genes, which are repressed by Tup1 and Nrg1, were not derepressed in ssn6 cells under the conditions studied. In contrast, the phase specific gene WH11 was derepressed in ssn6 cells, but not in tup1 or nrg1 cells. Hence Ssn6 and Tup1 play distinct roles in C. albicans. Nevertheless, both Ssn6 and Tup1 were required for the Nrg1-mediated repression of an artificial NRE promoter, and lexA-Nrg1 mediated repression in the C. albicans one-hybrid system. These observations are explained in models that are generally consistent with the Tup1-Ssn6 paradigm in budding yeast.

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