scholarly journals N-Acetylglucosamine Regulates Morphogenesis and Virulence Pathways in Fungi

2019 ◽  
Vol 6 (1) ◽  
pp. 8 ◽  
Author(s):  
Kyunghun Min ◽  
Shamoon Naseem ◽  
James B. Konopka
Keyword(s):  
Cell Wall ◽  
Stress Responses ◽  
Hyphal Growth ◽  
Amino Sugar ◽  
Model Organisms ◽  
Animal Cells ◽  
Epigenetic Switch ◽  
Wide Range ◽  
Extracellular Environment

N-acetylglucosamine (GlcNAc) is being increasingly recognized for its ability to stimulate cell signaling. This amino sugar is best known as a component of cell wall peptidoglycan in bacteria, cell wall chitin in fungi and parasites, exoskeletons of arthropods, and the extracellular matrix of animal cells. In addition to these structural roles, GlcNAc is now known to stimulate morphological and stress responses in a wide range of organisms. In fungi, the model organisms Saccharomyces cerevisiae and Schizosaccharomyces pombe lack the ability to respond to GlcNAc or catabolize it, so studies with the human pathogen Candida albicans have been providing new insights into the ability of GlcNAc to stimulate cellular responses. GlcNAc potently induces C. albicans to transition from budding to filamentous hyphal growth. It also promotes an epigenetic switch from White to Opaque cells, which differ in morphology, metabolism, and virulence properties. These studies have led to new discoveries, such as the identification of the first eukaryotic GlcNAc transporter. Other results have shown that GlcNAc can induce signaling in C. albicans in two ways. One is to act as a signaling molecule independent of its catabolism, and the other is that its catabolism can cause the alkalinization of the extracellular environment, which provides an additional stimulus to form hyphae. GlcNAc also induces the expression of virulence genes in the C. albicans, indicating it can influence pathogenesis. Therefore, this review will describe the recent advances in understanding the role of GlcNAc signaling pathways in regulating C. albicans morphogenesis and virulence.

scholarly journals (472) Yeast Expressed Tomato β-Galactosidases 1, 4, and 5 Have Activity against Synthetic and Plant-derived Cell Wall Substrates

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1092B-1092 ◽  
Author(s):  
Megumi Ishimaru ◽  
David L. Smith ◽  
Kenneth C. Gross
Keyword(s):  
Cell Wall ◽  
Tomato Fruit ◽  
Wall Material ◽  
Wall Structure ◽  
Fruit Softening ◽  
Pectic Polysaccharides ◽  
Wide Range ◽  
Fruit Pericarp ◽  
Galactosyl Residues

Fruit softening occurs by several mechanisms, including modifications of cell wall structure by wall degrading enzymes. The most prominent change in tomato fruit pericarp wall composition is the loss of galactosyl residues throughout development and especially during ripening. In order to understand the role of galactosyl turnover in fruit softening, we successfully produced three recombinant tomato β-galactosidase/exo-galactanase (TBG) fusion proteins in yeast. TBG1, 4 and 5 enzyme properties and substrate specificities were assessed. Optimum pH of TBG1, 4 and 5 was 5.0, 4.0, and 4.5 and optimum temperature was 40∼50, 40, and 40 °C, respectively. The K ms for TBG1, 4 and 5 were 7.99, 0.09, and 2.42 mm, respectively, using p-nitrophenyl-β-D-galactopyranoside as substrate. Using synthetic and plant-derived substrates, TBG1 and 5 released galactosyl residues from 1 → 4 linkages. TBG4 released galactosyl residues from a wide range of plant-derived oligosaccharides and polysaccharides. Using tomato fruit cell wall material, TBG1, TBG4 and TBG5 released galactosyl residues from a variety of fruit stages and cell wall fractions. TBG4 released the most galactosyl residues from the ASP fraction and especially the ASP fraction from fruit at the turning stage. Interestingly, even though walls from Turning fruit stage contain less total galactosyl residues than at the Mature Green stage, TBG4 released 3–4 fold more galactose from the CSP and ASP fractions from Turning fruit. These results suggest that changes in structure of wall pectic polysaccharides leading up to the Turning stage may cause the wall to become more susceptible to hydrolysis by the TBG4 product.

scholarly journals SUN-Family Protein UvSUN1 Regulates the Development and Virulence of Ustilaginoidea virens

2021 ◽  
Vol 12 ◽  
Author(s):  
Mina Yu ◽  
Junjie Yu ◽  
Huijuan Cao ◽  
Tianqiao Song ◽  
Xiayan Pan ◽  
...  
Keyword(s):  
Cell Wall ◽  
Hyphal Growth ◽  
Cell Wall Integrity ◽  
Signal Recognition ◽  
Phenotypic Analysis ◽  
Ustilaginoidea Virens ◽  
Group I ◽  
Family Protein ◽  
False Smut

Ustilaginoidea virens, the causal agent of rice false smut disease, is an important plant pathogen that causes severe quantitative and qualitative losses in rice worldwide. UvSUN1 is the only member of Group-I SUN family proteins in U. virens. In this work, the role of UvSUN1 in different aspects of the U. virens biology was studied by phenotypic analysis of Uvsun1 knockout strains. We identified that UvSUN1 was expressed during both conidial germination and the infection of rice. Disruption of the Uvsun1 gene affected the hyphal growth, conidiation, morphology of hyphae and conidia, adhesion and virulence. We also found that UvSUN1 is involved in the production of toxic compounds, which are able to inhibit elongation of the germinated seeds. Moreover, RNA-seq data showed that knockout of Uvsun1 resulted in misregulation of a subset of genes involved in signal recognition and transduction system, glycometabolism, cell wall integrity, and secondary metabolism. Collectively, this study reveals that Uvsun1 is required for growth, cell wall integrity and pathogenicity of U. virens, thereby providing new insights into the function of SUN family proteins in the growth and pathogenesis of this pathogen.

scholarly journals Plant Protein O-Arabinosylation

2021 ◽  
Vol 12 ◽  
Author(s):  
Bent Larsen Petersen ◽  
Cora A. MacAlister ◽  
Peter Ulvskov
Keyword(s):  
Cell Wall ◽  
Stress Responses ◽  
Secretory Pathway ◽  
Peptide Hormones ◽  
Common Denominator ◽  
Small Peptide ◽  
Structural Cell ◽  
Additional Layer ◽  
Wide Range ◽  
Diverse Groups

A wide range of proteins with diverse functions in development, defense, and stress responses areO-arabinosylated at hydroxyprolines (Hyps) within distinct amino acid motifs of continuous stretches of Hyps, as found in the structural cell wall extensins, or at non-continuous Hyps as, for example, found in small peptide hormones and a variety of plasma membrane proteins involved in signaling. PlantO-glycosylation relies on hydroxylation of Prolines to Hyps in the protein backbone, mediated by prolyl-4-hydroxylase (P4H) which is followed byO-glycosylation of the Hyp C4-OH group by either galactosyltransferases (GalTs) or arabinofuranosyltranferases (ArafTs) yielding either Hyp-galactosylation or Hyp-arabinosylation. A subset of the P4H enzymes with putative preference to hydroxylation of continuous prolines and presumably all ArafT enzymes needed for synthesis of the substituted arabinose chains of one to four arabinose units, have been identified and functionally characterized. Truncated root-hair phenotype is one common denominator of mutants of Hyp formation and Hyp-arabinosylation glycogenes, which act on diverse groups ofO-glycosylated proteins, e.g., the small peptide hormones and cell wall extensins. Dissection of different substrate derived effects may not be regularly feasible and thus complicate translation from genotype to phenotype. Recently, lack of proper arabinosylation on arabinosylated proteins has been shown to influence their transport/fate in the secretory pathway, hinting to an additional layer of functionality ofO-arabinosylation. Here, we provide an update on the prevalence and types ofO-arabinosylated proteins and the enzymatic machinery responsible for their modifications.

scholarly journals Pleiotropic Function of the Putative Zinc-Finger Protein MoMsn2 in Magnaporthe oryzae

2014 ◽  
Vol 27 (5) ◽  
pp. 446-460 ◽  
Author(s):  
Haifeng Zhang ◽  
Qian Zhao ◽  
Xianxian Guo ◽  
Min Guo ◽  
Zhongqiang Qi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Magnaporthe Oryzae ◽  
Stress Responses ◽  
Zinc Finger Protein ◽  
Affinity Purification ◽  
Hyphal Growth ◽  
Mitogen Activated Protein Kinase ◽  
Phenotypic Characterization ◽  
Cell Wall Biosynthesis ◽  
Appressorium Formation

The mitogen-activated protein kinase MoOsm1–mediated osmoregulation pathway plays crucial roles in stress responses, asexual and sexual development, and pathogenicity in Magnaporthe oryzae. Utilizing an affinity purification approach, we identified the putative transcriptional activator MoMsn2 as a protein that interacts with MoOsm1 in vivo. Disruption of the MoMSN2 gene resulted in defects in aerial hyphal growth, conidial production, and infection of host plants. Quantitative reverse transcription-polymerase chain reaction analysis showed that the expression of several genes involved in conidiophore formation was reduced in ΔMomsn2, suggesting that MoMsn2 might function as a transcriptional regulator of these genes. Subsequently, MoCos1 was identified as one of the MoMsn2 targets through yeast one-hybrid analysis in which MoMsn2 binds to the AGGGG and CCCCT motif of the MoCOS1 promoter region. Phenotypic characterization showed that MoMsn2 was required for appressorium formation and penetration and pathogenicity. Although the ΔMomsn2 mutant was tolerant to the cell-wall stressor Calcofluor white, it was sensitive to common osmotic stressors. Further analysis suggests that MoMsn2 is involved in the regulation of the cell-wall biosynthesis pathway. Finally, transcriptome data revealed that MoMsn2 modulates numerous genes participating in conidiation, infection, cell-wall integrity, and stress response. Collectively, our results led to a model in which MoMsn2 mediates a series of downstream genes that control aerial hyphal growth, conidiogenesis, appressorium formation, cell-wall biosynthesis, and infection and that also offer potential targets for the development of new disease management strategies.

scholarly journals Role of Transcription Factor CaNdt80p in Cell Separation, Hyphal Growth, and Virulence in Candida albicans

2010 ◽  
Vol 9 (4) ◽  
pp. 634-644 ◽  
Author(s):  
Adnane Sellam ◽  
Christopher Askew ◽  
Elias Epp ◽  
Faiza Tebbji ◽  
Alaka Mullick ◽  
...  
Keyword(s):  
Cell Wall ◽  
Transcription Factor ◽  
Candida Albicans ◽  
Cell Separation ◽  
Hyphal Growth ◽  
Functional Domain ◽  
Transcription Factor Family ◽  
Content Type ◽  
Genes Encoding

ABSTRACT The NDT80/PhoG transcription factor family includes ScNdt80p, a key modulator of the progression of meiotic division in Saccharomyces cerevisiae. In Candida albicans, a member of this family, CaNdt80p, modulates azole sensitivity by controlling the expression of ergosterol biosynthesis genes. We previously demonstrated that CaNdt80p promoter targets, in addition to ERG genes, were significantly enriched in genes related to hyphal growth. Here, we report that CaNdt80p is indeed required for hyphal growth in response to different filament-inducing cues and for the proper expression of genes characterizing the filamentous transcriptional program. These include noteworthy genes encoding cell wall components, such as HWP1, ECE1, RBT4, and ALS3. We also show that CaNdt80p is essential for the completion of cell separation through the direct transcriptional regulation of genes encoding the chitinase Cht3p and the cell wall glucosidase Sun41p. Consistent with their hyphal defect, ndt80 mutants are avirulent in a mouse model of systemic candidiasis. Interestingly, based on functional-domain organization, CaNdt80p seems to be a unique regulator characterizing fungi from the CTG clade within the subphylum Saccharomycotina. Therefore, this study revealed a new role of the novel member of the fungal NDT80 transcription factor family as a regulator of cell separation, hyphal growth, and virulence.

scholarly journals Tuning the flagellar motor

Microbiology ◽  
2010 ◽  
Vol 156 (5) ◽  
pp. 1275-1283 ◽  
Author(s):  
Kai M. Thormann ◽  
Anja Paulick
Keyword(s):  
Cell Wall ◽  
Environmental Conditions ◽  
Survival Advantage ◽  
Sodium Ion ◽  
Flagellar Motor ◽  
Numerous Species ◽  
Flagellar Motors ◽  
Wide Range ◽  
Flagellar Rotation

Many bacteria are motile by means of flagella, semi-rigid helical filaments rotated at the filament's base and energized by proton or sodium-ion gradients. Torque is created between the two major components of the flagellar motor: the rotating switch complex and the cell-wall-associated stators, which are arranged in a dynamic ring-like structure. Being motile provides a survival advantage to many bacteria, and thus the flagellar motor should work optimally under a wide range of environmental conditions. Recent studies have demonstrated that numerous species possess a single flagellar system but have two or more individual stator systems that contribute differentially to flagellar rotation. This review describes recent findings on rotor–stator interactions, on the role of different stators, and on how stator selection could be regulated. An emerging model suggests that bacterial flagellar motors are dynamic and can be tuned by stator swapping in response to different environmental conditions.

scholarly journals N-Acetylglucosamine Functions in Cell Signaling

Scientifica ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
James B. Konopka
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Cell Signaling ◽  
Amino Sugar ◽  
Animal Cells ◽  
Fungal Cell ◽  
E Coli ◽  
Human Fungal Pathogen ◽  
Surface Signaling ◽  
Cell Surface Signaling

The amino sugar N-acetylglucosamine (GlcNAc) is well known for the important structural roles that it plays at the cell surface. It is a key component of bacterial cell wall peptidoglycan, fungal cell wall chitin, and the extracellular matrix of animal cells. Interestingly, recent studies have also identified new roles for GlcNAc in cell signaling. For example, GlcNAc stimulates the human fungal pathogenCandida albicansto undergo changes in morphogenesis and expression of virulence genes. PathogenicE. coliresponds to GlcNAc by altering the expression of fimbriae and CURLI fibers that promote biofilm formation and GlcNAc stimulates soil bacteria to undergo changes in morphogenesis and production of antibiotics. Studies with animal cells have revealed that GlcNAc influences cell signaling through the posttranslational modification of proteins by glycosylation. O-linked attachment of GlcNAc to Ser and Thr residues regulates a variety of intracellular proteins, including transcription factors such as NFκB, c-myc, and p53. In addition, the specificity of Notch family receptors for different ligands is altered by GlcNAc attachment to fucose residues in the extracellular domain. GlcNAc also impacts signal transduction by altering the degree of branching of N-linked glycans, which influences cell surface signaling proteins. These emerging roles of GlcNAc as an activator and mediator of cellular signaling in fungi, animals, and bacteria will be the focus of this paper.

scholarly journals MNN5 Encodes an Iron-Regulated α-1,2-Mannosyltransferase Important for Protein Glycosylation, Cell Wall Integrity, Morphogenesis, and Virulence in Candida albicans

2006 ◽  
Vol 5 (2) ◽  
pp. 238-247 ◽  
Author(s):  
Chen Bai ◽  
Xiao-Li Xu ◽  
Fong-Yee Chan ◽  
Raymond Teck Ho Lee ◽  
Yue Wang
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Iron Homeostasis ◽  
Pathogenic Fungus ◽  
Hyphal Growth ◽  
Protein Glycosylation ◽  
Host Cells ◽  
Microbial Pathogens ◽  
Solid Media ◽  
Wide Range

ABSTRACT The cell walls of microbial pathogens mediate physical interactions with host cells and hence play a key role in infection. Mannosyltransferases have been shown to determine the cell wall properties and virulence of the pathogenic fungus Candida albicans. We previously identified a C. albicans α-1,2-mannosyltransferase, Mnn5, for its novel ability to enhance iron usage in Saccharomyces cerevisiae. Here we have studied the enzymatic properties of purified Mnn5 and characterized its function in its natural host. Mnn5 catalyzes the transfer of mannose to both α-1,2- and α-1,6-mannobiose, and this activity requires Mn2+ as a cofactor and is regulated by the Fe2+ concentration. An mnn5Δ mutant showed a lowered ability to extend O-linked, and possibly also N-linked, mannans, hypersensitivity to cell wall-damaging agents, and a reduction of cell wall mannosylphosphate content, phenotypes typical of many fungal mannosyltransferase mutants. The mnn5Δ mutant also exhibited some unique defects, such as impaired hyphal growth on solid media and attenuated virulence in mice. An unanticipated phenotype was the mnn5Δ mutant's resistance to killing by the iron-chelating protein lactoferrin, rendering it the first protein found that mediates lactoferrin killing of C. albicans. In summary, MNN5 deletion impairs a wide range of cellular events, most likely due to its broad substrate specificity. Of particular interest was the observed role of iron in regulating the enzymatic activity, suggesting an underlying relationship between Mnn5 activity and cellular iron homeostasis.

scholarly journals Plasma Membrane Localization Is Required for RasA-Mediated Polarized Morphogenesis and Virulence of Aspergillus fumigatus

2012 ◽  
Vol 11 (8) ◽  
pp. 966-977 ◽  
Author(s):  
Jarrod R. Fortwendel ◽  
Praveen R. Juvvadi ◽  
Luise E. Rogg ◽  
Yohannes G. Asfaw ◽  
Kimberlie A. Burns ◽  
...  
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Aspergillus Fumigatus ◽  
Structural Changes ◽  
Hyphal Growth ◽  
Membrane Association ◽  
Ras Signaling ◽  
Ras Proteins ◽  
Content Type

ABSTRACT Ras is a highly conserved GTPase protein that is essential for proper polarized morphogenesis of filamentous fungi. Localization of Ras proteins to the plasma membrane and endomembranes through posttranslational addition of farnesyl and palmitoyl residues is an important mechanism through which cells provide specificity to Ras signal output. Although the Aspergillus fumigatus RasA protein is known to be a major regulator of growth and development, the membrane distribution of RasA during polarized morphogenesis and the role of properly localized Ras signaling in virulence of a pathogenic mold remain unknown. Here we demonstrate that Aspergillus fumigatus RasA localizes primarily to the plasma membrane of actively growing hyphae. We show that treatment with the palmitoylation inhibitor 2-bromopalmitate disrupts normal RasA plasma membrane association and decreases hyphal growth. Targeted mutations of the highly conserved RasA palmitoylation motif also mislocalized RasA from the plasma membrane and led to severe hyphal abnormalities, cell wall structural changes, and reduced virulence in murine invasive aspergillosis. Finally, we provide evidence that proper RasA localization is independent of the Ras palmitoyltransferase homolog, encoded by erfB , but requires the palmitoyltransferase complex subunit, encoded by erfD . Our results demonstrate that plasma membrane-associated RasA is critical for polarized morphogenesis, cell wall stability, and virulence in A. fumigatus .

scholarly journals Micafungin-Induced Cell Wall Damage Stimulates Morphological Changes Consistent with Microcycle Conidiation in Aspergillus nidulans

2021 ◽  
Vol 7 (7) ◽  
pp. 525
Author(s):  
Samantha Reese ◽  
Cynthia Chelius ◽  
Wayne Riekhof ◽  
Mark R. Marten ◽  
Steven D. Harris
Keyword(s):  
Cell Wall ◽  
Aspergillus Nidulans ◽  
Morphological Changes ◽  
Hyphal Growth ◽  
Fungal Cell ◽  
Cell Wall Damage ◽  
Morphological Studies ◽  
General Response ◽  
Microcycle Conidiation

Fungal cell wall receptors relay messages about the state of the cell wall to the nucleus through the Cell Wall Integrity Signaling (CWIS) pathway. The ultimate role of the CWIS pathway is to coordinate repair of cell wall damage and to restore normal hyphal growth. Echinocandins such as micafungin represent a class of antifungals that trigger cell wall damage by affecting synthesis of β-glucans. To obtain a better understanding of the dynamics of the CWIS response and its multiple effects, we have coupled dynamic transcriptome analysis with morphological studies of Aspergillus nidulans hyphae in responds to micafungin. Our results reveal that expression of the master regulator of asexual development, BrlA, is induced by micafungin exposure. Further study showed that micafungin elicits morphological changes consistent with microcycle conidiation and that this effect is abolished in the absence of MpkA. Our results suggest that microcycle conidiation may be a general response to cell wall perturbation which in some cases would enable fungi to tolerate or survive otherwise lethal damage.

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