scholarly journals Stress-Induced Loss of Heterozygosity in Candida: a Possible Missing Link in the Ability to Evolve

mBio ◽  
2011 ◽  
Vol 2 (5) ◽  
Author(s):  
Susan M. Rosenberg
Keyword(s):  
Genetic Variation ◽  
Candida Albicans ◽  
Loss Of Heterozygosity ◽  
Dna Sequence ◽  
Cancer Development ◽  
Missing Link ◽  
Content Type ◽  
Entire Chromosome ◽  
Development And Evolution

ABSTRACT Diploid organisms are buffered against the effects of mutations by carrying two sets of each gene, which allows compensation if one is mutated. But recombination between “mom” and “dad” chromosomes causes loss of heterozygosity (LOH), stretches of “mom-only” or “dad-only” DNA sequence, suddenly revealing effects of mutations accumulated in entire chromosome arms. LOH creates new phenotypes from old mutations, drives cancer development and evolution, and, in a new study by Forche et al., is shown to be induced by stress in Candida albicans [Forche A, et al, mBio 2(4):e00129-11, 2011]. Stress-induced LOH could speed evolution of Candida specifically when it is poorly adapted to its environment. Moreover, the findings may provide a missing link between recombination-dependent mutagenesis in bacteria and yeast, suggesting that both might be stress induced, both maximizing genetic variation when populations could benefit most from diversity.

scholarly journals The Genome of the Human Pathogen Candida albicans Is Shaped by Mutation and Cryptic Sexual Recombination

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Joshua M. Wang ◽  
Richard J. Bennett ◽  
Matthew Z. Anderson
Keyword(s):  
Candida Albicans ◽  
Loss Of Heterozygosity ◽  
Genotypic Variation ◽  
Natural Populations ◽  
Detailed Examination ◽  
Mitochondrial Genomes ◽  
Nucleotide Polymorphisms ◽  
Genetic Changes ◽  
Content Type ◽  
Sexual Recombination

ABSTRACT The opportunistic fungal pathogen Candida albicans lacks a conventional sexual program and is thought to evolve, at least primarily, through the clonal acquisition of genetic changes. Here, we performed an analysis of heterozygous diploid genomes from 21 clinical isolates to determine the natural evolutionary processes acting on the C. albicans genome. Mutation and recombination shaped the genomic landscape among the C. albicans isolates. Strain-specific single nucleotide polymorphisms (SNPs) and insertions/deletions (indels) clustered across the genome. Additionally, loss-of-heterozygosity (LOH) events contributed substantially to genotypic variation, with most long-tract LOH events extending to the ends of the chromosomes suggestive of repair via break-induced replication. Consistent with a model of inheritance by descent, most polymorphisms were shared between closely related strains. However, some isolates contained highly mosaic genomes consistent with strains having experienced interclade recombination during their evolutionary history. A detailed examination of mitochondrial genomes also revealed clear examples of interclade recombination among sequenced strains. These analyses therefore establish that both (para)sexual recombination and mitotic mutational processes drive evolution of this important pathogen. To further facilitate the study of C. albicans genomes, we also introduce an online platform, SNPMap, to examine SNP patterns in sequenced isolates. IMPORTANCE Mutations introduce variation into the genome upon which selection can act. Defining the nature of these changes is critical for determining species evolution, as well as for understanding the genetic changes driving important cellular processes. The heterozygous diploid fungus Candida albicans is both a frequent commensal organism and a prevalent opportunistic pathogen. A prevailing theory is that C. albicans evolves primarily through the gradual buildup of mitotic mutations, and a pressing issue is whether sexual or parasexual processes also operate within natural populations. Here, we establish that the C. albicans genome evolves by a combination of localized mutation and both short-tract and long-tract loss-of-heterozygosity (LOH) events within the sequenced isolates. Mutations are more prevalent within noncoding and heterozygous regions and LOH increases towards chromosome ends. Furthermore, we provide evidence for genetic exchange between isolates, establishing that sexual or parasexual processes have contributed to the diversity of both nuclear and mitochondrial genomes.

scholarly journals Inducible and Constitutive Activation of Two Polymorphic Promoter Alleles of the Candida albicans Multidrug Efflux PumpMDR1

2012 ◽  
Vol 56 (8) ◽  
pp. 4490-4494 ◽  
Author(s):  
Christoph Sasse ◽  
Rebecca Schillig ◽  
Alexandra Reimund ◽  
Julia Merk ◽  
Joachim Morschhäuser
Keyword(s):  
Candida Albicans ◽  
Transcription Factors ◽  
Loss Of Heterozygosity ◽  
Efflux Pump ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Fluconazole Resistance ◽  
Content Type ◽  
Constitutive Activation ◽  
Strain Sc5314

ABSTRACTOverexpression of the multidrug efflux pumpMDR1confers resistance to the antifungal drug fluconazole onCandida albicans. It has been reported that two types ofMDR1promoters exist inC. albicansand that homozygosity for the allele with higher activity may promote fluconazole resistance. We found that the twoMDR1promoter alleles in strain SC5314 were equally well activated by inducing chemicals or hyperactive forms of the transcription factors Mrr1 and Cap1, which controlMDR1expression. In addition, no loss of heterozygosity at theMDR1locus was observed inMDR1-overexpressing clinicalC. albicansstrains that developed fluconazole resistance during therapy.

scholarly journals Stress Alters Rates and Types of Loss of Heterozygosity in Candida albicans

mBio ◽  
2011 ◽  
Vol 2 (4) ◽  
Author(s):  
A. Forche ◽  
D. Abbey ◽  
T. Pisithkul ◽  
M. A. Weinzierl ◽  
T. Ringstrom ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Genetic Diversity ◽  
Candida Albicans ◽  
Loss Of Heterozygosity ◽  
Mitotic Recombination ◽  
Stress Conditions ◽  
Dependent Manner ◽  
Content Type ◽  
Different Types ◽  
Stress Dependent

ABSTRACTGenetic diversity is often generated during adaptation to stress, and in eukaryotes some of this diversity is thought to arise via recombination and reassortment of alleles during meiosis.Candida albicans, the most prevalent pathogen of humans, has no known meiotic cycle, and yet it is a heterozygous diploid that undergoes mitotic recombination during somatic growth. It has been shown that clinical isolates as well as strains passaged once through a mammalian host undergo increased levels of recombination. Here, we tested the hypothesis that stress conditions increase rates of mitotic recombination inC. albicans, which is measured as loss of heterozygosity (LOH) at specific loci. We show that LOH rates are elevated duringin vitroexposure to oxidative stress, heat stress, and antifungal drugs. In addition, an increase in stress severity correlated well with increased LOH rates. LOH events can arise through local recombination, through homozygosis of longer tracts of chromosome arms, or by whole-chromosome homozygosis. Chromosome arm homozygosis was most prevalent in cultures grown under conventional lab conditions. Importantly, exposure to different stress conditions affected the levels of different types of LOH events, with oxidative stress causing increased recombination, while fluconazole and high temperature caused increases in events involving whole chromosomes. Thus,C. albicansgenerates increased amounts and different types of genetic diversity in response to a range of stress conditions, a process that we term “stress-induced LOH” that arises either by elevating rates of recombination and/or by increasing rates of chromosome missegregation.IMPORTANCEStress-induced mutagenesis fuels the evolution of bacterial pathogens and is mainly driven by genetic changes via mitotic recombination. Little is known about this process in other organisms.Candida albicans, an opportunistic fungal pathogen, causes infections that require adaptation to different host environmental niches. We measured the rates of LOH and the types of LOH events that appeared in the absence and in the presence of physiologically relevant stresses and found that stress causes a significant increase in the rates of LOH and that this increase is proportional to the degree of stress. Furthermore, the types of LOH events that arose differed in a stress-dependent manner, indicating that eukaryotic cells generate increased genetic diversity in response to a range of stress conditions. We propose that this “stress-induced LOH” facilitates the rapid adaptation ofC. albicans, which does not undergo meiosis, to changing environments within the host.

scholarly journals Chromosome 5 Monosomy of Candida albicans Controls Susceptibility to Various Toxic Agents, Including Major Antifungals

2013 ◽  
Vol 57 (10) ◽  
pp. 5026-5036 ◽  
Author(s):  
Feng Yang ◽  
Anatoliy Kravets ◽  
Gabor Bethlendy ◽  
Stephen Welle ◽  
Elena Rustchenko
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Fungal Pathogen ◽  
Copy Number ◽  
Wild Type ◽  
Chromosome 5 ◽  
Content Type ◽  
Regulatory Strategy ◽  
Toxic Agents ◽  
Entire Chromosome

ABSTRACTCandida albicansis a prevailing fungal pathogen with a diploid genome that can adapt to environmental stresses by losing or gaining an entire chromosome or a large portion of a chromosome. We have previously found that the loss of one copy of chromosome 5 (Ch5) allows for adaptation to the toxic sugarl-sorbose.l-Sorbose is similar to caspofungin and other antifungals from the echinocandins class, in that it represses synthesis of cell wall glucan in fungi. Here, we extended the study of the phenotypes controlled by Ch5 copy number. We examined 57 strains, either disomic or monosomic for Ch5 and representing five different genetic backgrounds, and found that the monosomy of Ch5 causes elevated levels of chitin and repressed levels of 1,3-β-glucan components of the cell wall, as well as diminished cellular ergosterol. Increased deposition of chitin in the cell wall could be explained, at least partially, by a 2-fold downregulation ofCHT2on the monosomic Ch5 that encodes chitinase and a 1.5-fold upregulation ofCHS7on Ch1 that encodes the protein required for wild-type chitin synthase III activity. Other important outcomes of Ch5 monosomy consist of susceptibility changes to agents representing four major classes of antifungals. Susceptibility to caspofungin increased or decreased and susceptibility to 5-fluorocytosine decreased, whereas susceptibility to fluconazole and amphotericin B increased. Our results suggest that Ch5 monosomy represents an unrecognizedC. albicansregulatory strategy that impinges on multiple stress response pathways.

scholarly journals Host association induces genome changes in Candida albicans which alters its virulence

2020 ◽  
Author(s):  
Amanda C. Smith ◽  
Meleah A. Hickman
Keyword(s):  
Genetic Variation ◽  
Candida Albicans ◽  
Loss Of Heterozygosity ◽  
Genetic Background ◽  
Large Scale ◽  
Environment Impact ◽  
Host Association ◽  
Parasexual Cycle ◽  
Genomic Changes

AbstractCandida albicans is an opportunistic fungal pathogen of humans that is typically diploid yet, has a highly labile genome that is tolerant of large-scale perturbations including chromosomal aneuploidy and loss-of-heterozygosity events. The ability to rapidly generate genetic variation is crucial for C. albicans to adapt to changing or stress environments, like those encountered in the host. Genetic variation occurs via stress-induced mutagenesis or can be generated through its parasexual cycle, which includes mating between diploids or stress-induced mitotic defects to produce tetraploids and non-meiotic ploidy reduction. However, it remains largely unknown how genetic background contributes to C. albicans genome instability in vitro or in vivo. Here, we tested how genetic background, ploidy and host environment impact C. albicans genome stability. We found that host association induced both loss-of-heterozygosity events and genome size changes, regardless of genetic background or ploidy. However, the magnitude and types of genome changes varied across C. albicans strains. We also assessed whether host-induced genomic changes resulted in any consequences on growth rate and virulence phenotypes and found that many host derived isolates had significant changes compared to their parental strains. Interestingly, host derivatives from diploid C. albicans predominantly displayed increased virulence, whereas host derivatives from tetraploid C. albicans had mostly reduced virulence. Together, these results are important for understanding how host-induced genomic changes in C. albicans alter the relationship between the host and C. albicans.

scholarly journals Host-Induced Genome Instability Rapidly Generates Phenotypic Variation across Candida albicans Strains and Ploidy States

mSphere ◽  
2020 ◽  
Vol 5 (3) ◽  
Author(s):  
Amanda C. Smith ◽  
Meleah A. Hickman
Keyword(s):  
Genetic Variation ◽  
Candida Albicans ◽  
Genome Size ◽  
Genetic Background ◽  
Genome Instability ◽  
Content Type ◽  
Host Environment ◽  
Genomic Changes ◽  
Opportunistic Fungal Pathogen

ABSTRACT Candida albicans is an opportunistic fungal pathogen of humans that is typically diploid yet has a highly labile genome tolerant of large-scale perturbations including chromosomal aneuploidy and loss-of-heterozygosity events. The ability to rapidly generate genetic variation is crucial for C. albicans to adapt to changing or stressful environments, like those encountered in the host. Genetic variation occurs via stress-induced mutagenesis or can be generated through its parasexual cycle, in which tetraploids arise via diploid mating or stress-induced mitotic defects and undergo nonmeiotic ploidy reduction. However, it remains largely unknown how genetic background contributes to C. albicans genome instability in vitro or in the host environment. Here, we tested how genetic background, ploidy, and the host environment impacts C. albicans genome stability. We found that host association induced both loss-of-heterozygosity events and genome size changes, regardless of genetic background or ploidy. However, the magnitude and types of genome changes varied across C. albicans strain background and ploidy state. We then assessed if host-induced genomic changes resulted in fitness consequences on growth rate and nonlethal virulence phenotypes and found that many host-derived isolates significantly changed relative to their parental strain. Interestingly, diploid host-associated C. albicans predominantly decreased host reproductive fitness, whereas tetraploid host-associated C. albicans increased host reproductive fitness. Together, these results are important for understanding how host-induced genomic changes in C. albicans alter its relationship with the host. IMPORTANCE Candida albicans is an opportunistic fungal pathogen of humans. The ability to generate genetic variation is essential for adaptation and is a strategy that C. albicans and other fungal pathogens use to change their genome size. Stressful environments, including the host, induce C. albicans genome instability. Here, we investigated how C. albicans genetic background and ploidy state impact genome instability, both in vitro and in a host environment. We show that the host environment induces genome instability, but the magnitude depends on C. albicans genetic background. Furthermore, we show that tetraploid C. albicans is highly unstable in host environments and rapidly reduces in genome size. These reductions in genome size often resulted in reduced virulence. In contrast, diploid C. albicans displayed modest host-induced genome size changes, yet these frequently resulted in increased virulence. Such studies are essential for understanding how opportunistic pathogens respond and potentially adapt to the host environment.

scholarly journals In VitroAnalyses of the Effects of Heparin and Parabens on Candida albicans Biofilms and Planktonic Cells

2011 ◽  
Vol 56 (1) ◽  
pp. 148-153 ◽  
Author(s):  
Marisa H. Miceli ◽  
Stella M. Bernardo ◽  
T. S. Neil Ku ◽  
Carla Walraven ◽  
Samuel A. Lee
Keyword(s):  
Candida Albicans ◽  
Metabolic Activity ◽  
Biofilm Formation ◽  
High Dose ◽  
Dependent Manner ◽  
Planktonic Cells ◽  
Content Type ◽  
Heparin Sodium ◽  
The Individual

ABSTRACTInfections and thromboses are the most common complications associated with central venous catheters. Suggested strategies for prevention and management of these complications include the use of heparin-coated catheters, heparin locks, and antimicrobial lock therapy. However, the effects of heparin onCandida albicansbiofilms and planktonic cells have not been previously studied. Therefore, we sought to determine thein vitroeffect of a heparin sodium preparation (HP) on biofilms and planktonic cells ofC. albicans. Because HP contains two preservatives, methyl paraben (MP) and propyl paraben (PP), these compounds and heparin sodium without preservatives (Pure-H) were also tested individually. The metabolic activity of the mature biofilm after treatment was assessed using XTT [2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction and microscopy. Pure-H, MP, and PP caused up to 75, 85, and 60% reductions of metabolic activity of the mature preformedC. albicansbiofilms, respectively. Maximal efficacy against the mature biofilm was observed with HP (up to 90%) compared to the individual compounds (P< 0.0001). Pure-H, MP, and PP each inhibitedC. albicansbiofilm formation up to 90%. A complete inhibition of biofilm formation was observed with HP at 5,000 U/ml and higher. When tested against planktonic cells, each compound inhibited growth in a dose-dependent manner. These data indicated that HP, MP, PP, and Pure-H havein vitroantifungal activity againstC. albicansmature biofilms, formation of biofilms, and planktonic cells. Investigation of high-dose heparin-based strategies (e.g., heparin locks) in combination with traditional antifungal agents for the treatment and/or prevention ofC. albicansbiofilms is warranted.

scholarly journals Novel Aggregation Properties of Candida albicans Secreted Aspartyl Proteinase Sap6 Mediate Virulence in Oral Candidiasis

2015 ◽  
Vol 83 (7) ◽  
pp. 2614-2626 ◽  
Author(s):  
Rohitashw Kumar ◽  
Darpan Saraswat ◽  
Swetha Tati ◽  
Mira Edgerton
Keyword(s):  
Candida Albicans ◽  
Epithelial Cells ◽  
Oral Candidiasis ◽  
Oral Microbiome ◽  
Proteinase Activity ◽  
Adhesion Properties ◽  
Content Type ◽  
Oral Epithelial Cells ◽  
Oral Epithelial ◽  
Cell Cell

Candida albicans, a commensal fungus of the oral microbiome, causes oral candidiasis in humans with localized or systemic immune deficiencies. Secreted aspartic proteinases (Saps) are a family of 10 related proteases and are virulence factors due to their proteolytic activity, as well as their roles in adherence and colonization of host tissues. We found that mice infected sublingually withC. albicanscells overexpressing Sap6 (SAP6OE and a Δsap8strain) had thicker fungal plaques and more severe oral infection, while infection with the Δsap6strain was attenuated. These hypervirulent strains had highly aggregative colony structurein vitroand higher secreted proteinase activity; however, the levels of proteinase activity ofC. albicansSaps did not uniformly match their abilities to damage cultured oral epithelial cells (SCC-15 cells). Hyphal induction in cells overexpressing Sap6 (SAP6OE and Δsap8cells) resulted in formation of large cell-cell aggregates. These aggregates could be produced in germinated wild-type cells by addition of native or heat-inactivated Sap6. Sap6 bound only to germinated cells and increasedC. albicansadhesion to oral epithelial cells. The adhesion properties of Sap6 were lost upon deletion of its integrin-binding motif (RGD) and could be inhibited by addition of RGD peptide or anti-integrin antibodies. Thus, Sap6 (but not Sap5) has an alternative novel function in cell-cell aggregation, independent of its proteinase activity, to promote infection and virulence in oral candidiasis.

scholarly journals Dectin-2-Targeted Antifungal Liposomes Exhibit Enhanced Efficacy

mSphere ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Suresh Ambati ◽  
Emma C. Ellis ◽  
Jianfeng Lin ◽  
Xiaorong Lin ◽  
Zachary A. Lewis ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Aspergillus Fumigatus ◽  
Effective Dose ◽  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Antifungal Drugs ◽  
Extracellular Matrices ◽  
Content Type ◽  
Order Of Magnitude ◽  
Life Threatening

ABSTRACT Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus cause life-threatening candidiasis, cryptococcosis, and aspergillosis, resulting in several hundred thousand deaths annually. The patients at the greatest risk of developing these life-threatening invasive fungal infections have weakened immune systems. The vulnerable population is increasing due to rising numbers of immunocompromised individuals as a result of HIV infection or immunosuppressed individuals receiving anticancer therapies and/or stem cell or organ transplants. While patients are treated with antifungals such as amphotericin B, all antifungals have serious limitations due to lack of sufficient fungicidal effect and/or host toxicity. Even with treatment, 1-year survival rates are low. We explored methods of increasing drug effectiveness by designing fungicide-loaded liposomes specifically targeted to fungal cells. Most pathogenic fungi are encased in cell walls and exopolysaccharide matrices rich in mannans. Dectin-2 is a mammalian innate immune membrane receptor that binds as a dimer to mannans and signals fungal infection. We coated amphotericin-loaded liposomes with monomers of Dectin-2’s mannan-binding domain, sDectin-2. sDectin monomers were free to float in the lipid membrane and form dimers that bind mannan substrates. sDectin-2-coated liposomes bound orders of magnitude more efficiently to the extracellular matrices of several developmental stages of C. albicans, C. neoformans, and A. fumigatus than untargeted control liposomes. Dectin-2-coated amphotericin B-loaded liposomes reduced the growth and viability of all three species more than an order of magnitude more efficiently than untargeted control liposomes and dramatically decreased the effective dose. Future efforts focus on examining pan-antifungal targeted liposomal drugs in animal models of fungal diseases. IMPORTANCE Invasive fungal diseases caused by Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus have mortality rates ranging from 10 to 95%. Individual patient costs may exceed $100,000 in the United States. All antifungals in current use have serious limitations due to host toxicity and/or insufficient fungal cell killing that results in recurrent infections. Few new antifungal drugs have been introduced in the last 2 decades. Hence, there is a critical need for improved antifungal therapeutics. By targeting antifungal-loaded liposomes to α-mannans in the extracellular matrices secreted by these fungi, we dramatically reduced the effective dose of drug. Dectin-2-coated liposomes loaded with amphotericin B bound 50- to 150-fold more strongly to C. albicans, C. neoformans, and A. fumigatus than untargeted liposomes and killed these fungi more than an order of magnitude more efficiently. Targeting drug-loaded liposomes specifically to fungal cells has the potential to greatly enhance the efficacy of most antifungal drugs.

scholarly journals An Efficient, Rapid, and Recyclable System for CRISPR-Mediated Genome Editing in Candida albicans

mSphere ◽  
2017 ◽  
Vol 2 (2) ◽  
Author(s):  
Namkha Nguyen ◽  
Morgan M. F. Quail ◽  
Aaron D. Hernday
Keyword(s):  
Candida Albicans ◽  
Genome Editing ◽  
Fungal Pathogen ◽  
Gene Knockout ◽  
Strain Engineering ◽  
Molecular Genetic Analysis ◽  
Content Type ◽  
Highly Efficient ◽  
Discovery Research ◽  
Gene Knockouts

ABSTRACT Candida albicans is the most common fungal pathogen of humans. Historically, molecular genetic analysis of this important pathogen has been hampered by the lack of stable plasmids or meiotic cell division, limited selectable markers, and inefficient methods for generating gene knockouts. The recent development of clustered regularly interspaced short palindromic repeat(s) (CRISPR)-based tools for use with C. albicans has opened the door to more efficient genome editing; however, previously reported systems have specific limitations. We report the development of an optimized CRISPR-based genome editing system for use with C. albicans. Our system is highly efficient, does not require molecular cloning, does not leave permanent markers in the genome, and supports rapid, precise genome editing in C. albicans. We also demonstrate the utility of our system for generating two independent homozygous gene knockouts in a single transformation and present a method for generating homozygous wild-type gene addbacks at the native locus. Furthermore, each step of our protocol is compatible with high-throughput strain engineering approaches, thus opening the door to the generation of a complete C. albicans gene knockout library. IMPORTANCE Candida albicans is the major fungal pathogen of humans and is the subject of intense biomedical and discovery research. Until recently, the pace of research in this field has been hampered by the lack of efficient methods for genome editing. We report the development of a highly efficient and flexible genome editing system for use with C. albicans. This system improves upon previously published C. albicans CRISPR systems and enables rapid, precise genome editing without the use of permanent markers. This new tool kit promises to expedite the pace of research on this important fungal pathogen.

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