scholarly journals Development of a CRISPR-Cas9 System for Efficient Genome Editing of Candida lusitaniae

mSphere ◽  
2017 ◽  
Vol 2 (3) ◽  
Author(s):  
Emily L. Norton ◽  
Racquel K. Sherwood ◽  
Richard J. Bennett
Keyword(s):  
Genome Editing ◽  
Gene Targeting ◽  
Gene Deletion ◽  
Human Pathogen ◽  
Mechanistic Studies ◽  
Content Type ◽  
Dna Dsbs ◽  
Candida Lusitaniae ◽  
Species Specific ◽  
Genome Manipulation

ABSTRACT The ability to perform efficient genome editing is a key development for detailed mechanistic studies of a species. Candida lusitaniae is an important member of the Candida clade and is relevant both as an emerging human pathogen and as a model for understanding mechanisms of sexual reproduction. We highlight the development of a CRISPR-Cas9 system for efficient genome manipulation in C. lusitaniae and demonstrate the importance of species-specific promoters for expression of CRISPR components. We also demonstrate that the NHEJ pathway contributes to non-template-mediated repair of DNA DSBs and that removal of this pathway enhances efficiencies of gene targeting by CRISPR-Cas9. These results therefore establish important genetic tools for further exploration of C. lusitaniae biology. Candida lusitaniae is a member of the Candida clade that includes a diverse group of fungal species relevant to both human health and biotechnology. This species exhibits a full sexual cycle to undergo interconversion between haploid and diploid forms. C. lusitaniae is also an emerging opportunistic pathogen that can cause serious bloodstream infections in the clinic and yet has often proven to be refractory to facile genetic manipulations. In this work, we develop a clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated gene 9 (Cas9) system to enable genome editing of C. lusitaniae. We demonstrate that expression of CRISPR-Cas9 components under species-specific promoters is necessary for efficient gene targeting and can be successfully applied to multiple genes in both haploid and diploid isolates. Gene deletion efficiencies with CRISPR-Cas9 were further enhanced in C. lusitaniae strains lacking the established nonhomologous end joining (NHEJ) factors Ku70 and DNA ligase 4. These results indicate that NHEJ plays an important role in directing the repair of DNA double-strand breaks (DSBs) in C. lusitaniae and that removal of this pathway increases integration of gene deletion templates by homologous recombination. The described approaches significantly enhance the ability to perform genetic studies in, and promote understanding of, this emerging human pathogen and model sexual species. IMPORTANCE The ability to perform efficient genome editing is a key development for detailed mechanistic studies of a species. Candida lusitaniae is an important member of the Candida clade and is relevant both as an emerging human pathogen and as a model for understanding mechanisms of sexual reproduction. We highlight the development of a CRISPR-Cas9 system for efficient genome manipulation in C. lusitaniae and demonstrate the importance of species-specific promoters for expression of CRISPR components. We also demonstrate that the NHEJ pathway contributes to non-template-mediated repair of DNA DSBs and that removal of this pathway enhances efficiencies of gene targeting by CRISPR-Cas9. These results therefore establish important genetic tools for further exploration of C. lusitaniae biology.

scholarly journals Molecular Identification and Antifungal Susceptibility of Yeast Isolates Causing Fungemia Collected in a Population-Based Study in Spain in 2010 and 2011

2013 ◽  
Vol 58 (3) ◽  
pp. 1529-1537 ◽  
Author(s):  
Jesús Guinea ◽  
Óscar Zaragoza ◽  
Pilar Escribano ◽  
Estrella Martín-Mazuelos ◽  
Javier Pemán ◽  
...  
Keyword(s):  
Hot Spot ◽  
Antifungal Susceptibility ◽  
Point Mutations ◽  
Population Based ◽  
Candida Guilliermondii ◽  
Population Based Study ◽  
Content Type ◽  
Candida Lusitaniae ◽  
Species Specific

ABSTRACTWe report the molecular identifications and antifungal susceptibilities of the isolates causing fungemia collected in the CANDIPOP population-based study conducted in 29 Spanish hospitals. A total of 781 isolates (from 767 patients, 14 of them having mixed fungemia) were collected. The species found most frequently wereCandida albicans(44.6%),Candida parapsilosis(24.5%),Candida glabrata(13.2%),Candida tropicalis(7.6%),Candida krusei(1.9%),Candida guilliermondii(1.7%), andCandida lusitaniae(1.3%). OtherCandidaand non-Candidaspecies accounted for approximately 5% of the isolates. The presence of cryptic species was low. Compared to findings of previous studies conducted in Spain, the frequency ofC. glabratahas increased. Antifungal susceptibility testing was performed by using EUCAST and CLSI M27-A3 reference procedures; the two methods were comparable. The rate of fluconazole-susceptible isolates was 80%, which appears to be a decrease compared to findings of previous studies, explained mainly by the higher frequency ofC. glabrata. Using the species-specific breakpoints and epidemiological cutoff values, the rate of voriconazole and posaconazolein vitroresistance was low (<2%). In the case ofC. tropicalis, using the EUCAST procedure, the rate of azole resistance was around 20%. There was a correlation between the previous use of azoles and the presence of fluconazole-resistant isolates. Resistance to echinocandins was very rare (2%), and resistance to amphotericin B also was very uncommon. The sequencing of the hot spot (HS) regions fromFKS1orFKS2genes in echinocandin-resistant isolates revealed previously described point mutations. The decrease in the susceptibility to fluconazole in Spanish isolates should be closely monitored in future studies.

scholarly journals Candida albicans Gene Deletion with a Transient CRISPR-Cas9 System

mSphere ◽  
2016 ◽  
Vol 1 (3) ◽  
Author(s):  
Kyunghun Min ◽  
Yuichi Ichikawa ◽  
Carol A. Woolford ◽  
Aaron P. Mitchell
Keyword(s):  
Drug Resistance ◽  
Candida Albicans ◽  
Genetic Analysis ◽  
Genome Editing ◽  
Drug Targets ◽  
Gene Deletion ◽  
Genetic Manipulation ◽  
Content Type ◽  
Biological Features ◽  
Link Type

ABSTRACT The fungus Candida albicans is a major pathogen. Genetic analysis of this organism has revealed determinants of pathogenicity, drug resistance, and other unique biological features, as well as the identities of prospective drug targets. The creation of targeted mutations has been greatly accelerated recently through the implementation of CRISPR genome-editing technology by Vyas et al. [Sci Adv 1(3):e1500248, 2015, http://dx.doi.org/10.1126/sciadv.1500248 ]. In this study, we find that CRISPR elements can be expressed from genes that are present only transiently, and we develop a transient CRISPR system that further accelerates C. albicans genetic manipulation. Clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated gene 9 (CRISPR-Cas9) systems are used for a wide array of genome-editing applications in organisms ranging from fungi to plants and animals. Recently, a CRISPR-Cas9 system has been developed for the diploid fungal pathogen Candida albicans; the system accelerates genetic manipulation dramatically [V. K. Vyas, M. I. Barrasa, and G. R. Fink, Sci Adv 1(3):e1500248, 2015, http://dx.doi.org/10.1126/sciadv.1500248 ]. We show here that the CRISPR-Cas9 genetic elements can function transiently, without stable integration into the genome, to enable the introduction of a gene deletion construct. We describe a transient CRISPR-Cas9 system for efficient gene deletion in C. albicans. Our observations suggest that there are two mechanisms that lead to homozygous deletions: (i) independent recombination of transforming DNA into each allele and (ii) recombination of transforming DNA into one allele, followed by gene conversion of the second allele. Our approach will streamline gene function analysis in C. albicans, and our results indicate that DNA can function transiently after transformation of this organism. IMPORTANCE The fungus Candida albicans is a major pathogen. Genetic analysis of this organism has revealed determinants of pathogenicity, drug resistance, and other unique biological features, as well as the identities of prospective drug targets. The creation of targeted mutations has been greatly accelerated recently through the implementation of CRISPR genome-editing technology by Vyas et al. [Sci Adv 1(3):e1500248, 2015, http://dx.doi.org/10.1126/sciadv.1500248 ]. In this study, we find that CRISPR elements can be expressed from genes that are present only transiently, and we develop a transient CRISPR system that further accelerates C. albicans genetic manipulation.

scholarly journals Efficient Genome Engineering of a Virulent Klebsiella Bacteriophage Using CRISPR-Cas9

2018 ◽  
Vol 92 (17) ◽  
Author(s):  
Juntao Shen ◽  
Jinjie Zhou ◽  
Guo-Qiang Chen ◽  
Zhi-Long Xiu
Keyword(s):  
Genome Editing ◽  
Point Mutation ◽  
Gene Deletion ◽  
Phage Therapy ◽  
Phage Genome ◽  
Cost Effective ◽  
Bacteriophage Therapy ◽  
Time Saving ◽  
Content Type ◽  
Frameshift Deletion

ABSTRACT Klebsiella pneumoniae is one of the most common nosocomial opportunistic pathogens and usually exhibits multiple-drug resistance. Phage therapy, a potential therapeutic to replace or supplement antibiotics, has attracted much attention. However, very few Klebsiella phages have been well characterized because of the lack of efficient genome-editing tools. Here, Cas9 from Streptococcus pyogenes and a single guide RNA (sgRNA) were used to modify a virulent Klebsiella bacteriophage, phiKpS2. We first evaluated the distribution of sgRNA activity in phages and proved that it is largely inconsistent with the predicted activity from current models trained on eukaryotic cell data sets. A simple CRISPR-based phage genome-editing procedure was developed based on the discovery that homologous arms as short as 30 to 60 bp were sufficient to introduce point mutation, gene deletion, and swap. We also demonstrated that weak sgRNAs could be used for precise phage genome editing but failed to select random recombinants, possibly because inefficient cleavage can be tolerated through continuous repair by homologous recombination with the uncut genomes. Small frameshift deletion was proved to be an efficient way to evaluate the essentiality of phage genes. By using the abovementioned strategies, a putative promoter and nine genes of phiKpS2 were successfully deleted. Interestingly, the holin gene can be deleted with little effect on phiKpS2 infection, but the reason is not yet clear. This study established an efficient, time-saving, and cost-effective procedure for phage genome editing, which is expected to significantly promote the development of bacteriophage therapy. IMPORTANCE In the present study, we have addressed efficient, time-saving, and cost-effective CRISPR-based phage genome editing of Klebsiella phage, which has the potential to significantly expand our knowledge of phage-host interactions and to promote applications of phage therapy. The distribution of sgRNA activity was first evaluated in phages. Short homologous arms were proven to be enough to introduce point mutation, small frameshift deletion, gene deletion, and swap into phages, and weak sgRNAs were proven useful for precise phage genome editing but failed to select random recombinants, all of which makes the CRISPR-based phage genome-editing method easier to use.

scholarly journals Forced Recycling of an AMA1-Based Genome-Editing Plasmid Allows for Efficient Multiple Gene Deletion/Integration in the Industrial Filamentous Fungus Aspergillus oryzae

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Takuya Katayama ◽  
Hidetoshi Nakamura ◽  
Yue Zhang ◽  
Arnaud Pascal ◽  
Wataru Fujii ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Genetic Engineering ◽  
Genome Editing ◽  
Aspergillus Oryzae ◽  
Filamentous Fungus ◽  
Gene Deletion ◽  
Multiple Gene ◽  
Content Type ◽  
Industrial Strains ◽  
Marker Free

ABSTRACT Filamentous fungi are used for food fermentation and industrial production of recombinant proteins. They also serve as a source of secondary metabolites and are recently expected as hosts for heterologous production of useful secondary metabolites. Multiple-step genetic engineering is required to enhance industrial production involving these fungi, but traditional sequential modification of multiple genes using a limited number of selection markers is laborious. Moreover, efficient genetic engineering techniques for industrial strains have not yet been established. We have previously developed a clustered regulatory interspaced short palindromic repeats (CRISPR)/Cas9-based mutagenesis technique for the industrial filamentous fungus Aspergillus oryzae, enabling mutation efficiency of 10 to 20%. Here, we improved the CRISPR/Cas9 approach by including an AMA1-based autonomously replicating plasmid harboring the drug resistance marker ptrA. By using the improved mutagenesis technique, we successfully modified A. oryzae wild and industrial strains, with a mutation efficiency of 50 to 100%. Conditional expression of the Aoace2 gene from the AMA1-based plasmid severely inhibited fungal growth. This enabled forced recycling of the plasmid, allowing repeated genome editing. Further, double mutant strains were successfully obtained with high efficiency by expressing two guide RNA molecules from the genome-editing plasmid. Cotransformation of fungal cells with the genome-editing plasmid together with a circular donor DNA enabled marker-free multiplex gene deletion/integration in A. oryzae. The presented repeatable marker-free genetic engineering approach for mutagenesis and gene deletion/integration will allow for efficient modification of multiple genes in industrial fungal strains, increasing their applicability. IMPORTANCE Multiple gene modifications of specific fungal strains are required for achieving industrial-scale production of enzymes and secondary metabolites. In the present study, we developed an efficient multiple genetic engineering technique for the filamentous fungus Aspergillus oryzae. The approach is based on a clustered regulatory interspaced short palindromic repeats (CRISPR)/Cas9 system and recycling of an AMA1-based autonomous replicating plasmid. Because the plasmid harbors a drug resistance marker (ptrA), the approach does not require the construction of auxotrophic industrial strains prior to genome editing and allows for forced recycling of the gene-editing plasmid. The established plasmid-recycling technique involves an Aoace2-conditional expression cassette, whose induction severely impairs fungal growth. We used the developed genetic engineering techniques for highly efficient marker-free multiple gene deletion/integration in A. oryzae. The genome-editing approaches established in the present study, which enable unlimited repeatable genetic engineering, will facilitate multiple gene modification of industrially important fungal strains.

scholarly journals Species-Specific and Drug-Specific Differences in Susceptibility of Candida Biofilms to Echinocandins: Characterization of Less Common Bloodstream Isolates

2013 ◽  
Vol 57 (6) ◽  
pp. 2562-2570 ◽  
Author(s):  
Maria Simitsopoulou ◽  
Pavla Peshkova ◽  
Efthymia Tasina ◽  
Aspasia Katragkou ◽  
Daniela Kyrpitzi ◽  
...  
Keyword(s):  
Candida Guilliermondii ◽  
Growth Effect ◽  
Planktonic Cells ◽  
Content Type ◽  
Fungal Damage ◽  
Paradoxical Growth ◽  
Candida Lusitaniae ◽  
Species Specific ◽  
High Mics

ABSTRACTCandidaspecies other thanCandida albicansare increasingly recognized as causes of biofilm-associated infections. This is a comprehensive study that compared thein vitroactivities of all three echinocandins against biofilms formed by different common and infrequently identifiedCandidaisolates. We determined the activities of anidulafungin (ANID), caspofungin (CAS), and micafungin (MFG) against planktonic cells and biofilms of bloodstream isolates ofC. albicans(15 strains),Candida parapsilosis(6 strains),Candida lusitaniae(16 strains),Candida guilliermondii(5 strains), andCandida krusei(12 strains) by XTT [2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] assay. Planktonic and biofilm MICs were defined as ≥50% fungal damage. Planktonic cells of allCandidaspecies were susceptible to the three echinocandins, with MICs of ≤1 mg/liter. By comparison, differences in the MIC profiles of biofilms in response to echinocandins existed among theCandidaspecies. Thus,C. lusitaniaeandC. guilliermondiibiofilms were highly recalcitrant to all echinocandins, with MICs of ≥32 mg/liter. In contrast, the MICs of all three echinocandins forC. albicansandC. kruseibiofilms were relatively low (MICs ≤ 1 mg/liter). While echinocandins exhibited generally high MICs againstC. parapsilosisbiofilms, MFG exhibited the lowest MICs against these isolates (4 mg/liter). A paradoxical growth effect was observed with CAS concentrations ranging from 8 to 64 mg/liter againstC. albicansandC. parapsilosisbiofilms but not againstC. krusei,C. lusitaniae, orC. guilliermondii. While non-albicans Candidaplanktonic cells were susceptible to all echinocandins, there were drug- and species-specific differences in susceptibility among biofilms of the variousCandidaspecies, withC. lusitaniaeandC. guilliermondiiexhibiting profiles of high MICs of the three echinocandins.

scholarly journals Development of a CRISPR/Cas9-Based Tool for Gene Deletion in Issatchenkia orientalis

mSphere ◽  
2019 ◽  
Vol 4 (3) ◽  
Author(s):  
Vinh G. Tran ◽  
Mingfeng Cao ◽  
Zia Fatma ◽  
Xiaofei Song ◽  
Huimin Zhao
Keyword(s):  
Metabolic Engineering ◽  
Organic Acids ◽  
Genome Editing ◽  
Gene Deletion ◽  
Potential Candidate ◽  
Autonomously Replicating Sequence ◽  
Content Type ◽  
Issatchenkia Orientalis ◽  
Fuels And Chemicals ◽  
Acidic Conditions

ABSTRACT The nonconventional yeast Issatchenkia orientalis has emerged as a potential platform microorganism for production of organic acids due to its ability to grow robustly under highly acidic conditions. However, lack of efficient genetic tools remains a major bottleneck in metabolic engineering of this organism. Here we report that the autonomously replicating sequence (ARS) from Saccharomyces cerevisiae (ScARS) was functional for plasmid replication in I. orientalis, and the resulting episomal plasmid enabled efficient genome editing by the CRISPR/Cas9 system. The optimized CRISPR/Cas9-based system employed a fusion RPR1′-tRNA promoter for single guide RNA (sgRNA) expression and could attain greater than 97% gene disruption efficiency for various gene targets. Additionally, we demonstrated multiplexed gene deletion with disruption efficiencies of 90% and 47% for double gene and triple gene knockouts, respectively. This genome editing tool can be used for rapid strain development and metabolic engineering of this organism for production of biofuels and chemicals. IMPORTANCE Microbial production of fuels and chemicals from renewable and readily available biomass is a sustainable and economically attractive alternative to petroleum-based production. Because of its unusual tolerance to highly acidic conditions, I. orientalis is a promising potential candidate for the manufacture of valued organic acids. Nevertheless, reliable and efficient genetic engineering tools in I. orientalis are limited. The results outlined in this paper describe a stable episomal ARS-containing plasmid and the first CRISPR/Cas9-based system for gene disruptions in I. orientalis, paving the way for applying genome engineering and metabolic engineering strategies and tools in this microorganism for production of fuels and chemicals.

scholarly journals Development of an Unmarked Gene Deletion System for the Filamentous Fungi Aspergillus niger and Talaromyces versatilis

2014 ◽  
Vol 80 (11) ◽  
pp. 3484-3487 ◽  
Author(s):  
Stéphane Delmas ◽  
Agustina Llanos ◽  
Jean-Luc Parrou ◽  
Matthew Kokolski ◽  
Steven T. Pullan ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Filamentous Fungi ◽  
Gene Deletion ◽  
Transcriptional Regulator ◽  
Nonhomologous End Joining ◽  
Selection Marker ◽  
End Joining ◽  
Gene Encoding ◽  
Content Type ◽  
Genome Manipulation

ABSTRACTIn this article, we present a method to delete genes in filamentous fungi that allows recycling of the selection marker and is efficient in a nonhomologous end-joining (NHEJ)-proficient strain. We exemplify the approach by deletion of the gene encoding the transcriptional regulator XlnR in the fungusAspergillus niger. To show the efficiency and advantages of the method, we deleted 8 other genes and constructed a double mutant in this species. Moreover, we showed that the same principle also functions in a different genus of filamentous fungus (Talaromyces versatilis, basionymPenicillium funiculosum). This technique will increase the versatility of the toolboxes for genome manipulation of model and industrially relevant fungi.

scholarly journals CRISPR-Cas9 and CRISPR-Assisted Cytidine Deaminase Enable Precise and Efficient Genome Editing inKlebsiella pneumoniae

2018 ◽  
Vol 84 (23) ◽  
Author(s):  
Yu Wang ◽  
Shanshan Wang ◽  
Weizhong Chen ◽  
Liqiang Song ◽  
Yifei Zhang ◽  
...  
Keyword(s):  
Genome Editing ◽  
Genetic Manipulation ◽  
Cytidine Deaminase ◽  
Carbapenem Resistance ◽  
Human Pathogen ◽  
Content Type ◽  
Base Editing ◽  
Highly Efficient ◽  
Carbapenem Resistant ◽  
Recent Emergence

ABSTRACTKlebsiella pneumoniaeis a promising industrial microorganism as well as a major human pathogen. The recent emergence of carbapenem-resistantK. pneumoniaehas posed a serious threat to public health worldwide, emphasizing a dire need for novel therapeutic means against drug-resistantK. pneumoniae. Despite the critical importance of genetics in bioengineering, physiology studies, and therapeutic-means development, genome editing, in particular, the highly desirable scarless genetic manipulation inK. pneumoniae, is often time-consuming and laborious. Here, we report a two-plasmid system, pCasKP-pSGKP, used for precise and iterative genome editing inK. pneumoniae. By harnessing the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 genome cleavage system and the lambda Red recombination system, pCasKP-pSGKP enabled highly efficient genome editing inK. pneumoniaeusing a short repair template. Moreover, we developed a cytidine base-editing system, pBECKP, for precise C→T conversion in both the chromosomal and plasmid-borne genes by engineering the fusion of the cytidine deaminase APOBEC1 and a Cas9 nickase. By using both the pCasKP-pSGKP and the pBECKP tools, theblaKPC-2gene was confirmed to be the major factor that contributed to the carbapenem resistance of a hypermucoviscous carbapenem-resistantK. pneumoniaestrain. The development of the two editing tools will significantly facilitate the genetic engineering ofK. pneumoniae.IMPORTANCEGenetics is a key means to study bacterial physiology. However, the highly desirable scarless genetic manipulation is often time-consuming and laborious for the major human pathogenK. pneumoniae. We developed a CRISPR-Cas9-mediated genome-editing method and a cytidine base-editing system, enabling rapid, highly efficient, and iterative genome editing in both industrial and clinically isolatedK. pneumoniaestrains. We applied both tools in dissecting the drug resistance mechanism of a hypermucoviscous carbapenem-resistantK. pneumoniaestrain, elucidating that theblaKPC-2gene was the major factor that contributed to the carbapenem resistance of the hypermucoviscous carbapenem-resistantK. pneumoniaestrain. Utilization of the two tools will dramatically accelerate a wide variety of investigations in diverseK. pneumoniaestrains and relevantEnterobacteriaceaespecies, such as gene characterization, drug discovery, and metabolic engineering.

scholarly journals Versatile CRISPR/Cas9 Systems for Genome Editing in Ustilago maydis

2021 ◽  
Vol 7 (2) ◽  
pp. 149
Author(s):  
Sarah-Maria Wege ◽  
Katharina Gejer ◽  
Fabienne Becker ◽  
Michael Bölker ◽  
Johannes Freitag ◽  
...  
Keyword(s):  
Genome Editing ◽  
Cell Biology ◽  
Gene Deletion ◽  
Fluorescent Protein ◽  
Point Mutations ◽  
Model Organism ◽  
Ustilago Maydis ◽  
Genomic Locus ◽  
Targeted Gene Deletion ◽  
Molecular Cell Biology

The phytopathogenic smut fungus Ustilago maydis is a versatile model organism to study plant pathology, fungal genetics, and molecular cell biology. Here, we report several strategies to manipulate the genome of U. maydis by the CRISPR/Cas9 technology. These include targeted gene deletion via homologous recombination of short double-stranded oligonucleotides, introduction of point mutations, heterologous complementation at the genomic locus, and endogenous N-terminal tagging with the fluorescent protein mCherry. All applications are independent of a permanent selectable marker and only require transient expression of the endonuclease Cas9hf and sgRNA. The techniques presented here are likely to accelerate research in the U. maydis community but can also act as a template for genome editing in other important fungi.

scholarly journals Melanization in Cryptococcus neoformans Requires Complex Regulation

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Radames J. B. Cordero ◽  
Emma Camacho ◽  
Arturo Casadevall
Keyword(s):  
Cryptococcus Neoformans ◽  
Defense Mechanisms ◽  
Environmental Stressors ◽  
Antimicrobial Compounds ◽  
Human Pathogen ◽  
Content Type ◽  
Signaling Mechanisms ◽  
Complex Regulation ◽  
Multiple Levels ◽  
Melanin Binding

ABSTRACT The fungal human pathogen Cryptococcus neoformans undergoes melanization in response to nutrient starvation and exposure to exogenous melanin precursors. Melanization protects the fungus against host defense mechanisms such as oxidative damage and other environmental stressors (e.g., heat/cold stress, antimicrobial compounds, ionizing radiation). Conversely, the melanization process generates cytotoxic intermediates, and melanized cells are potentially susceptible to overheating and to certain melanin-binding drugs. Despite the importance of melanin in C. neoformans biology, the signaling mechanisms regulating its synthesis are poorly understood. The recent report by D. Lee, E.-H. Jang, M. Lee, S.-W. Kim, et al. [mBio 10(5):e02267-19, 2019, https://doi.org/10.1128/mBio.02267-19] provides new insights into how C. neoformans regulates melanization. The authors identified a core melanin regulatory network consisting of transcription factors and kinases required for melanization under low-nutrient conditions. The redundant and epistatic connections of this melanin-regulating network demonstrate that C. neoformans melanization is complex and carefully regulated at multiple levels. Such complex regulation reflects the multiple functions of melanin in C. neoformans biology.

Sign in / Sign up

Export Citation Format

Share Document