scholarly journals Three Prevacuolar Compartment Rab GTPases Impact Candida albicans Hyphal Growth

2013 ◽  
Vol 12 (7) ◽  
pp. 1039-1050 ◽  
Author(s):  
Douglas A. Johnston ◽  
Arturo Luna Tapia ◽  
Karen E. Eberle ◽  
Glen E. Palmer
Keyword(s):  
Candida Albicans ◽  
Membrane Trafficking ◽  
Gene Deletion ◽  
Hyphal Growth ◽  
Rab Gtpases ◽  
Phenotypic Analysis ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Growth Defects ◽  
Vacuolar Trafficking

ABSTRACTDisruption of vacuolar biogenesis in the pathogenic yeastCandida albicanscauses profound defects in polarized hyphal growth. However, the precise vacuolar pathways involved in yeast-hypha differentiation have not been determined. Previously we focused on Vps21p, a Rab GTPase involved in directing vacuolar trafficking through the late endosomalprevacuolarcompartment (PVC). Herein, we identify two additional Vps21p-related GTPases, Ypt52p and Ypt53p, that colocalize with Vps21p and can suppress the hyphal defects of thevps21Δ/Δ mutant. Phenotypic analysis of gene deletion strains revealed that loss of bothVPS21andYPT52causes synthetic defects in endocytic trafficking to the vacuole, as well as delivery of the virulence-associated vacuolar membrane protein Mlt1p from the Golgi compartment. Transcription of all three GTPase-encoding genes is increased under hyphal growth conditions, and overexpression of the transcription factor Ume6p is sufficient to increase the transcription of these genes. While only thevps21Δ/Δ single mutant has hyphal growth defects, these were greatly exacerbated in avps21Δ/Δypt52Δ/Δ double mutant. On the basis of relative expression levels and phenotypic analysis of gene deletion strains, Vps21p is the most important of the three GTPases, followed by Ypt52p, while Ypt53p has an only marginal impact onC. albicansphysiology. Finally, disruption of a nonendosomal AP-3-dependent vacuolar trafficking pathway in thevps21Δ/Δypt52Δ/Δ mutant, further exacerbated the stress and hyphal growth defects. These findings underscore the importance of membrane trafficking through the PVC in sustaining the invasive hyphal growth form ofC. albicans.

scholarly journals Endosomal and AP-3-Dependent Vacuolar Trafficking Routes Make Additive Contributions to Candida albicans Hyphal Growth and Pathogenesis

2010 ◽  
Vol 9 (11) ◽  
pp. 1755-1765 ◽  
Author(s):  
Glen E. Palmer
Keyword(s):  
Candida Albicans ◽  
Double Mutant ◽  
Kidney Tissue ◽  
Hyphal Growth ◽  
Endosomal Trafficking ◽  
Transcriptional Responses ◽  
Transport Pathways ◽  
Content Type ◽  
Vacuolar Protein ◽  
Vacuolar Trafficking

ABSTRACT Candida albicans mutants deficient in vacuolar biogenesis are defective in polarized hyphal growth and virulence. However, the specific vacuolar trafficking routes required for hyphal growth and virulence are unknown. In Saccharomyces cerevisiae, two trafficking routes deliver material from the Golgi apparatus to the vacuole. One occurs via the late endosome and is dependent upon Vps21p, while the second bypasses the endosome and requires the AP-3 complex, including Aps3p. To determine the significance of these pathways in C. albicans hyphal growth and virulence, aps3Δ/Δ, vps21Δ/Δ, and aps3Δ/Δ vps21Δ/Δ mutant strains were constructed. Analysis of vacuolar morphology and localization of the vacuolar protein Mlt1p suggests that C. albicans Aps3p and Vps21p mediate two distinct transport pathways. The vps21Δ/Δ mutant has a minor reduction in hyphal elongation, while the aps3Δ/Δ mutant has no defect in hyphal growth. Interestingly, the aps3Δ/Δ vps21Δ/Δ double mutant has dramatically reduced hyphal growth. Overexpression of the Ume6p transcriptional activator resulted in constitutive hyphal growth of wild-type, aps3Δ/Δ, and vps21Δ/Δ strains and formation of highly vacuolated subapical compartments. Thus, Ume6p-dependent transcriptional responses are sufficient to induce subapical vacuolation. However, the aps3Δ/Δ vps21Δ/Δ mutant formed mainly pseudohyphae that lacked vacuolated compartments. The aps3Δ/Δ strain was virulent in a mouse model of disseminated infection; the vps21Δ/Δ mutant failed to kill mice but persisted within kidney tissue, while the double mutant was avirulent and cleared from the kidneys. These results suggest that while the AP-3 pathway alone has little impact on hyphal growth or virulence, it is much more significant when endosomal trafficking is disrupted.

scholarly journals Generation of Viable Candida albicans Mutants Lacking the “Essential” Protein Kinase Snf1 by Inducible Gene Deletion

mSphere ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Austin Mottola ◽  
Sonja Schwanfelder ◽  
Joachim Morschhäuser
Keyword(s):  
Candida Albicans ◽  
Protein Kinase ◽  
Gene Deletion ◽  
Metabolic Adaptation ◽  
Optimal Conditions ◽  
Powerful Method ◽  
Wild Type ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Inducible Gene

ABSTRACT The protein kinase Snf1, a member of the highly conserved AMP-activated protein kinase family, is a central regulator of metabolic adaptation. In the pathogenic yeast Candida albicans, Snf1 is considered to be essential, as previous attempts by different research groups to generate homozygous snf1Δ mutants were unsuccessful. We aimed to elucidate why Snf1 is required for viability in C. albicans by generating snf1Δ null mutants through forced, inducible gene deletion and observing the terminal phenotype before cell death. Unexpectedly, we found that snf1Δ mutants were viable and could grow, albeit very slowly, on rich media containing the preferred carbon source glucose. Growth was improved when the cells were incubated at 37°C instead of 30°C, and this phenotype enabled us to isolate homozygous snf1Δ mutants also by conventional, sequential deletion of both SNF1 alleles in a wild-type C. albicans strain. All snf1Δ mutants could grow slowly on glucose but were unable to utilize alternative carbon sources. Our results show that, under optimal conditions, C. albicans can live and grow without Snf1. Furthermore, they demonstrate that inducible gene deletion is a powerful method for assessing gene essentiality in C. albicans. IMPORTANCE Essential genes are those that are indispensable for the viability and growth of an organism. Previous studies indicated that the protein kinase Snf1, a central regulator of metabolic adaptation, is essential in the pathogenic yeast Candida albicans, because no homozygous snf1 deletion mutants of C. albicans wild-type strains could be obtained by standard approaches. In order to investigate the lethal consequences of SNF1 deletion, we generated conditional mutants in which SNF1 could be deleted by forced, inducible excision from the genome. Unexpectedly, we found that snf1 null mutants were viable and could grow slowly under optimal conditions. The growth phenotypes of the snf1Δ mutants explain why such mutants were not recovered in previous attempts. Our study demonstrates that inducible gene deletion is a powerful method for assessing gene essentiality in C. albicans.

scholarly journals Factors Supporting Cysteine Tolerance and Sulfite Production in Candida albicans

2013 ◽  
Vol 12 (4) ◽  
pp. 604-613 ◽  
Author(s):  
Florian Hennicke ◽  
Maria Grumbt ◽  
Ulrich Lermann ◽  
Nico Ueberschaar ◽  
Katja Palige ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Candida Albicans ◽  
Efflux Pump ◽  
Phenotypic Analysis ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Zinc Cluster ◽  
Enhanced Sensitivity ◽  
Hypha Formation

ABSTRACTThe amino acid cysteine has long been known to be toxic at elevated levels for bacteria, fungi, and humans. However, mechanisms of cysteine tolerance in microbes remain largely obscure. Here we show that the human pathogenic yeastCandida albicansexcretes sulfite when confronted with increasing cysteine concentrations. Mutant construction and phenotypic analysis revealed that sulfite formation from cysteine inC. albicansrelies on cysteine dioxygenase Cdg1, an enzyme with similar functions in humans. Environmental cysteine induced not only the expression of theCDG1gene inC. albicans, but also the expression ofSSU1, encoding a putative sulfite efflux pump. Accordingly, the deletion ofSSU1resulted in enhanced sensitivity of the fungal cells to both cysteine and sulfite. To study the regulation of sulfite/cysteine tolerance in more detail, we screened aC. albicanslibrary of transcription factor mutants in the presence of sulfite. This approach and subsequent independent mutant analysis identified the zinc cluster transcription factor Zcf2 to govern sulfite/cysteine tolerance, as well as cysteine-inducibleSSU1andCDG1gene expression.cdg1Δ andssu1Δ mutants displayed reduced hypha formation in the presence of cysteine, indicating a possible role of the newly proposed mechanisms of cysteine tolerance and sulfite secretion in the pathogenicity ofC. albicans. Moreover,cdg1Δ mutants induced delayed mortality in a mouse model of disseminated infection. Since sulfite is toxic and a potent reducing agent, its production byC. albicanssuggests diverse roles during host adaptation and pathogenicity.

scholarly journals Cell Wall-Related Bionumbers and Bioestimates of Saccharomyces cerevisiae and Candida albicans

2013 ◽  
Vol 13 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Frans M. Klis ◽  
Chris G. de Koster ◽  
Stanley Brul
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Candida Albicans ◽  
Cell Size ◽  
Pathogenic Fungus ◽  
Turgor Pressure ◽  
Hyphal Growth ◽  
Biological Research ◽  
Content Type ◽  
Starting Point

ABSTRACTBionumbers and bioestimates are valuable tools in biological research. Here we focus on cell wall-related bionumbers and bioestimates of the budding yeastSaccharomyces cerevisiaeand the polymorphic, pathogenic fungusCandida albicans. We discuss the linear relationship between cell size and cell ploidy, the correlation between cell size and specific growth rate, the effect of turgor pressure on cell size, and the reason why using fixed cells for measuring cellular dimensions can result in serious underestimation ofin vivovalues. We further consider the evidence that individual buds and hyphae grow linearly and that exponential growth of the population results from regular formation of new daughter cells and regular hyphal branching. Our calculations show that hyphal growth allowsC. albicansto cover much larger distances per unit of time than the yeast mode of growth and that this is accompanied by strongly increased surface expansion rates. We therefore predict that the transcript levels of genes involved in wall formation increase during hyphal growth. Interestingly, wall proteins and polysaccharides seem barely, if at all, subject to turnover and replacement. A general lesson is how strongly most bionumbers and bioestimates depend on environmental conditions and genetic background, thus reemphasizing the importance of well-defined and carefully chosen culture conditions and experimental approaches. Finally, we propose that the numbers and estimates described here offer a solid starting point for similar studies of other cell compartments and other yeast species.

scholarly journals Metabolic Reprogramming in the Opportunistic Yeast Candida albicans in Response to Hypoxia

mSphere ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Anaïs Burgain ◽  
Faiza Tebbji ◽  
Inès Khemiri ◽  
Adnane Sellam
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Metabolic Pathways ◽  
Membrane Lipids ◽  
Oxygen Depletion ◽  
Metabolic Reprogramming ◽  
Pathogenic Yeast ◽  
Fungal Virulence ◽  
Content Type ◽  
The Impact

ABSTRACT Hypoxia is the predominant condition that the human opportunistic fungus Candida albicans encounters in the majority of the colonized niches within the host. So far, the impact of such a condition on the overall metabolism of this important human-pathogenic yeast has not been investigated. Here, we have undertaken a time-resolved metabolomics analysis to uncover the metabolic landscape of fungal cells experiencing hypoxia. Our data showed a dynamic reprogramming of many fundamental metabolic pathways, such as glycolysis, the pentose phosphate pathway, and different metabolic routes related to fungal cell wall biogenesis. The C. albicans lipidome was highly affected by oxygen depletion, with an increased level of free fatty acids and biochemical intermediates of membrane lipids, including phospholipids, lysophospholipids, sphingolipids, and mevalonate. The depletion of oxygen-dependent lipids such as ergosterol or phosphatidylcholine with longer and polyunsaturated lateral fatty acid chains was observed only at the later hypoxic time point (180 min). Transcriptomics data supported the main metabolic response to hypoxia when matched to our metabolomic profiles. The hypoxic metabolome reflected different physiological alterations of the cell wall and plasma membrane of C. albicans under an oxygen-limiting environment that were confirmed by different approaches. This study provided a framework for future in vivo investigations to examine relevant hypoxic metabolic trajectories in fungal virulence and fitness within the host. IMPORTANCE A critical aspect of cell fitness is the ability to sense and adapt to variations in oxygen levels in their local environment. Candida albicans is an opportunistic yeast that is the most prevalent human fungal pathogen. While hypoxia is the predominant condition that C. albicans encounters in most of its niches, its impact on fungal metabolism remains unexplored so far. Here, we provided a detailed landscape of the C. albicans metabolome that emphasized the importance of many metabolic routes for the adaptation of this yeast to oxygen depletion. The fungal hypoxic metabolome identified in this work provides a framework for future investigations to assess the contribution of relevant metabolic pathways in the fitness of C. albicans and other human eukaryotic pathogens with similar colonized human niches. As hypoxia is present at most of the fungal infection foci in the host, hypoxic metabolic pathways are thus an attractive target for antifungal therapy.

scholarly journals Candida albicans sphingolipid C9-methyltransferase is involved in hyphal elongation

Microbiology ◽  
2010 ◽  
Vol 156 (4) ◽  
pp. 1234-1243 ◽  
Author(s):  
Takahiro Oura ◽  
Susumu Kajiwara
Keyword(s):  
Candida Albicans ◽  
Lipid Membrane ◽  
Hyphal Growth ◽  
Pathogenic Fungi ◽  
Wild Type ◽  
Membrane Structures ◽  
Pathogenic Yeast ◽  
Chain Base ◽  
Long Chain Base ◽  
Long Chain

C9-methylated glucosylceramide is a fungus-specific sphingolipid. This lipid is a major membrane component in the cell and is thought to play important roles in the growth and virulence of several fungal species. To investigate the importance of the methyl branch of the long-chain base in glucosylceramides in pathogenic fungi, we identified and characterized a sphingolipid C9-methyltransferase gene (MTS1, C9-MethylTransferase for Sphingolipid 1) in the pathogenic yeast Candida albicans. The mts1 disruptant lacked (E,E)-9-methylsphinga-4,8-dienine in its glucosylceramides and contained (E)-sphing-4-enine and (E,E)-sphinga-4,8-dienine. Reintroducing the MTS1 gene into the mts1 disruptant restored the synthesis of (E,E)-9-methylsphinga-4,8-dienine in the glucosylceramides. We also created a disruptant of the HSX11 gene, encoding glucosylceramide synthase, which catalyses the final step of glucosylceramide synthesis, in C. albicans and compared this mutant with the mts1 disruptant. The C. albicans mts1 and hsx11 disruptants both had a decreased hyphal growth rate compared to the wild-type strain. The hsx11 disruptant showed increased susceptibility to SDS and fluconazole, similar to a previously reported sld1 disruptant that contained only (E)-sphing-4-enine in its glucosylceramides, suggesting that these strains have defects in their cell membrane structures. In contrast, the mts1 disruptant grew similarly to wild-type in medium containing SDS or fluconazole. These results suggest that the C9-methyl group of a long-chain base in glucosylceramides plays an important role in the hyphal elongation of C. albicans independent of lipid membrane disruption.

scholarly journals Functional Dissection of a Candida albicans Zinc Cluster Transcription Factor, the Multidrug Resistance Regulator Mrr1

2011 ◽  
Vol 10 (8) ◽  
pp. 1110-1121 ◽  
Author(s):  
Sabrina Schubert ◽  
Christina Popp ◽  
P. David Rogers ◽  
Joachim Morschhäuser
Keyword(s):  
Transcription Factor ◽  
Candida Albicans ◽  
Transcriptional Activation ◽  
Efflux Pump ◽  
Major Facilitator Superfamily ◽  
Constitutive Activity ◽  
Activation Domain ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Zinc Cluster

ABSTRACTThe overexpression of theMDR1gene, which encodes a multidrug efflux pump of the major facilitator superfamily, is a frequent cause of resistance to the widely used antimycotic agent fluconazole and other toxic compounds in the pathogenic yeastCandida albicans. The zinc cluster transcription factor Mrr1 controlsMDR1expression in response to inducing chemicals, and gain-of-function mutations inMRR1are responsible for the constitutiveMDR1upregulation in fluconazole-resistantC. albicansstrains. To understand how Mrr1 activity is regulated, we identified functional domains of this transcription factor. A hybrid protein consisting of the N-terminal 106 amino acids of Mrr1 and the transcriptional activation domain of Gal4 fromSaccharomyces cerevisiaeconstitutively inducedMDR1expression, demonstrating that the DNA binding domain is sufficient to target Mrr1 to theMDR1promoter. Using a series of C-terminal truncations and systematic internal deletions, we could show that Mrr1 contains multiple activation and inhibitory domains. One activation domain (AD1) is located in the C terminus of Mrr1. When fused to the tetracycline repressor TetR, this distal activation domain induced gene expression from a TetR-dependent promoter. The deletion of an inhibitory region (ID1) located near the distal activation domain resulted in constitutive activity of Mrr1. The additional removal of AD1 abolished the constitutive activity, but the truncated Mrr1 still could activate theMDR1promoter in response to the inducer benomyl. These results demonstrate that the activity of Mrr1 is regulated in multiple ways and provide insights into the function of an important mediator of drug resistance inC. albicans.

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 Role for Endosomal and Vacuolar GTPases in Candida albicans Pathogenesis

2009 ◽  
Vol 77 (6) ◽  
pp. 2343-2355 ◽  
Author(s):  
Douglas A. Johnston ◽  
Karen E. Eberle ◽  
Joy E. Sturtevant ◽  
Glen E. Palmer
Keyword(s):  
Candida Albicans ◽  
Stress Resistance ◽  
Double Mutant ◽  
Hyphal Growth ◽  
Filamentous Growth ◽  
Rab Gtpases ◽  
Fungal Cell ◽  
Cellular Stresses ◽  
Vacuole Biogenesis

ABSTRACT The vacuole has crucial roles in stress resistance and adaptation of the fungal cell. Furthermore, in Candida albicans it has been observed to undergo dramatic expansion during the initiation of hyphal growth, to produce highly “vacuolated” subapical compartments. We hypothesized that these functions may be crucial for survival within the host and tissue-invasive hyphal growth. We also considered the role of the late endosome or prevacuole compartment (PVC), a distinct organelle involved in vacuolar and endocytic trafficking. We identified two Rab GTPases, encoded by VPS21 and YPT72, required for trafficking through the PVC and vacuole biogenesis, respectively. Deletion of VPS21 or YPT72 led to mild sensitivities to some cellular stresses. However, deletion of both genes resulted in a synthetic phenotype with severe sensitivity to cellular stress and impaired growth. Both the vps21Δ and ypt72Δ mutants had defects in filamentous growth, while the double mutant was completely deficient in polarized growth. The defects in hyphal growth were not suppressed by an “active” RIM101 allele or loss of the hyphal repressor encoded by TUP1. In addition, both single mutants had significant attenuation in a mouse model of hematogenously disseminated candidiasis, while the double mutant was rapidly cleared. Histological examination confirmed that the vps21Δ and ypt72Δ mutants are deficient in hyphal growth in vivo. We suggest that the PVC and vacuole are required on two levels during C. albicans infection: (i) stress resistance functions required for survival within tissue and (ii) a role in filamentous growth which may aid host tissue invasion.

scholarly journals Calcineurin and Calcium Channel CchA Coordinate the Salt Stress Response by Regulating Cytoplasmic Ca2+Homeostasis in Aspergillus nidulans

2016 ◽  
Vol 82 (11) ◽  
pp. 3420-3430 ◽  
Author(s):  
Sha Wang ◽  
Xiao Liu ◽  
Hui Qian ◽  
Shizhu Zhang ◽  
Ling Lu
Keyword(s):  
Salt Stress ◽  
Calcium Channel ◽  
Aspergillus Nidulans ◽  
Transient Receptor Potential ◽  
Feedback Inhibition ◽  
Calcium Influx ◽  
Hyphal Growth ◽  
Salt Stress Response ◽  
Content Type ◽  
Growth Defects

ABSTRACTThe eukaryotic calcium/calmodulin-dependent protein phosphatase calcineurin is crucial for the environmental adaption of fungi. However, the mechanism of coordinate regulation of the response to salt stress by calcineurin and the high-affinity calcium channel CchA in fungi is not well understood. Here we show that the deletion ofcchAsuppresses the hyphal growth defects caused by the loss of calcineurin under salt stress inAspergillus nidulans. Additionally, the hypersensitivity of the ΔcnaAstrain to extracellular calcium and cell-wall-damaging agents can be suppressed bycchAdeletion. Using the calcium-sensitive photoprotein aequorin to monitor the cytoplasmic Ca2+concentration ([Ca2+]c) in living cells, we found that calcineurin negatively regulates CchA on calcium uptake in response to external calcium in normally cultured cells. However, in salt-stress-pretreated cells, loss of eithercnaAorcchAsignificantly decreased the [Ca2+]c, but a deficiency in bothcnaAandcchAswitches the [Ca2+]cto the reference strain level, indicating that calcineurin and CchA synergistically coordinate calcium influx under salt stress. Moreover, real-time PCR results showed that the dysfunction ofcchAin the ΔcnaAstrain dramatically restored the expression ofenaA(a major determinant for sodium detoxification), which was abolished in the ΔcnaAstrain under salt stress. These results suggest that double deficiencies ofcnaAandcchAcould bypass the requirement of calcineurin to induceenaAexpression under salt stress. Finally, YvcA, a member of the transient receptor potential channel (TRPC) protein family of vacuolar Ca2+channels, was proven to compensate for calcineurin-CchA in fungal salt stress adaption.IMPORTANCEThe feedback inhibition relationship between calcineurin and the calcium channel Cch1/Mid1 has been well recognized from yeast. Interestingly, our previous study (S. Wang et al., PLoS One7:e46564, 2012,http://dx.doi.org/10.1371/journal.pone.0046564) showed that the deletion ofcchAcould suppress the hyphal growth defects caused by the loss of calcineurin under salt stress inAspergillus nidulans. In this study, our findings suggest that fungi are able to develop a unique mechanism for adapting to environmental salt stress. Compared to cells cultured normally, the NaCl-pretreated cells had a remarkable increase in transient [Ca2+]c. Furthermore, we show that calcineurin and CchA are required to modulate cellular calcium levels and synergistically coordinate calcium influx under salt stress. Finally, YvcA, a member of of the TRPC family of vacuolar Ca2+channels, was proven to compensate for calcineurin-CchA in fungal salt stress adaption. The findings in this study provide insights into the complex regulatory links between calcineurin and CchA to maintain cytoplasmic Ca2+homeostasis in response to different environments.

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