Breakpoint: Cell Wall and Glycoproteins and their Crucial Role in the Phytopathogenic Fungi Infection

2020 ◽  
Vol 21 (3) ◽  
pp. 227-244 ◽  
Author(s):  
Verónica Plaza ◽  
Evelyn Silva-Moreno ◽  
Luis Castillo
Keyword(s):  
Cell Wall ◽  
Signaling Pathways ◽  
Crucial Role ◽  
Intracellular Signaling ◽  
Cell Walls ◽  
Wall Stress ◽  
Appressorium Formation ◽  
Cell Wall Degrading Enzymes ◽  
Lytic Enzymes ◽  
Fungal Cell

The cell wall that surrounds fungal cells is essential for their survival, provides protection against physical and chemical stresses, and plays relevant roles during infection. In general, the fungal cell wall is composed of an outer layer of glycoprotein and an inner skeletal layer of β-glucans or α- glucans and chitin. Chitin synthase genes have been shown to be important for septum formation, cell division and virulence. In the same way, chitin can act as a potent elicitor to activate defense response in several plant species; however, the fungi can convert chitin to chitosan during plant infection to evade plant defense mechanisms. Moreover, α-1,3-Glucan, a non-degradable polysaccharide in plants, represents a key feature in fungal cell walls formed in plants and plays a protective role for this fungus against plant lytic enzymes. A similar case is with β-1,3- and β-1,6-glucan which are essential for infection, structure rigidity and pathogenicity during fungal infection. Cell wall glycoproteins are also vital to fungi. They have been associated with conidial separation, the increase of chitin in conidial cell walls, germination, appressorium formation, as well as osmotic and cell wall stress and virulence; however, the specific roles of glycoproteins in filamentous fungi remain unknown. Fungi that can respond to environmental stimuli distinguish these signals and relay them through intracellular signaling pathways to change the cell wall composition. They play a crucial role in appressorium formation and penetration, and release cell wall degrading enzymes, which determine the outcome of the interaction with the host. In this review, we highlight the interaction of phypatophogen cell wall and signaling pathways with its host and their contribution to fungal pathogenesis.

Melanin deposition in the hyphae of a species of Phomopsis

1975 ◽  
Vol 21 (4) ◽  
pp. 442-452 ◽  
Author(s):  
D. H. Ellis ◽  
D. A. Griffiths
Keyword(s):  
Cell Wall ◽  
Surface Analysis ◽  
Cell Walls ◽  
Lytic Enzymes ◽  
Fungal Cell ◽  
Ionizing Radiations ◽  
Dopa Melanin ◽  
Fungal Cell Walls ◽  
Cellular Organelles

Hyaline hyphae of Phomopsis become pigmented when exposed to short periods of light. Pigment was deposited in the form of melanin granules both within the cell wall and within mucilaginous excrescences that were developed irregularly over the hyphal surface. Analysis of the pigment showed it to have properties similar to that of "Dopa" melanin and to pigments previously isolated from fungal cell walls. Lysis of both hyaline and pigmented hyphal walls by means of lytic enzymes was minimal. It is suggested that the major role of melanin in this fungus is the protection of cellular organelles from harmful ionizing radiations.

scholarly journals Induction of Fusarium lytic Enzymes by Extracts from Resistant and Susceptible Cultivars of Pea (Pisum sativum L.)

Pathogens ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 976
Author(s):  
Lakshmipriya Perincherry ◽  
Chaima Ajmi ◽  
Souheib Oueslati ◽  
Agnieszka Waśkiewicz ◽  
Łukasz Stępień
Keyword(s):  
Cell Wall ◽  
Plant Extracts ◽  
Plant Cell Wall ◽  
Pathogenic Fungi ◽  
Human Beings ◽  
Cell Wall Degrading Enzymes ◽  
Lytic Enzymes ◽  
Mycelium Growth ◽  
Oat Bran

Being pathogenic fungi, Fusarium produce various extracellular cell wall-degrading enzymes (CWDEs) that degrade the polysaccharides in the plant cell wall. They also produce mycotoxins that contaminate grains, thereby posing a serious threat to animals and human beings. Exposure to mycotoxins occurs through ingestion of contaminated grains, inhalation and through skin absorption, thereby causing mycotoxicoses. The toxins weaken the host plant, allowing the pathogen to invade successfully, with the efficiency varying from strain to strain and depending on the plant infected. Fusariumoxysporum predominantly produces moniliformin and cyclodepsipeptides, whereas F. proliferatum produces fumonisins. The aim of the study was to understand the role of various substrates and pea plant extracts in inducing the production of CWDEs and mycotoxins. Additionally, to monitor the differences in their levels when susceptible and resistant pea plant extracts were supplemented. The cultures of F. proliferatum and F. oxysporum strains were supplemented with various potential inducers of CWDEs. During the initial days after the addition of substrates, the fungus cocultivated with pea extracts and other carbon substrates showed increased activities of β-glucosidase, xylanase, exo-1,4-glucanase and lipase. The highest inhibition of mycelium growth (57%) was found in the cultures of F. proliferatum strain PEA1 upon the addition of cv. Sokolik extract. The lowest fumonisin content was exhibited by the cultures with the pea extracts and oat bran added, and this can be related to the secondary metabolites and antioxidants present in these substrates.

scholarly journals Screening and Antifungal Activity of a β-Carboline Derivative against Cryptococcus neoformans and C. gattii

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Kátia Santana Cruz ◽  
Emerson Silva Lima ◽  
Marcia de Jesus Amazonas da Silva ◽  
Erica Simplício de Souza ◽  
Andreia Montoia ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Antifungal Activity ◽  
Cryptococcus Neoformans ◽  
Active Compound ◽  
Cell Walls ◽  
Human Fibroblasts ◽  
Lead Compound ◽  
Fungal Cell ◽  
Fungal Cell Walls

Background. Cryptococcosis is a fungal disease of bad prognosis due to its pathogenicity and the toxicity of the drugs used for its treatment. The aim of this study was to investigate the medicinal potential of carbazole and β-carboline alkaloids and derivatives against Cryptococcus neoformans and C. gattii. Methods. MICs were established in accordance with the recommendations of the Clinical and Laboratory Standards Institute for alkaloids and derivatives against C. neoformans and C. gattii genotypes VNI and VGI, respectively. A single active compound was further evaluated against C. neoformans genotypes VNII, VNIII, and VNIV, C. gattii genotypes VGI, VGIII, and VGIV, Candida albicans ATCC 36232, for cytotoxicity against the MRC-5 lineage of human fibroblasts and for effects on fungal cells (cell wall, ergosterol, and leakage of nucleic acids). Results. Screening of 11 compounds revealed 8-nitroharmane as a significant inhibitor (MIC 40 μg/mL) of several C. neoformans and C. gattii genotypes. It was not toxic to fibroblasts (IC50 > 50 µg/mL) nor did it alter fungal cell walls or the concentration of ergosterol in C. albicans or C. neoformans. It increased leakage of substances that absorb at 260 nm. Conclusions. The synthetic β-carboline 8-nitroharmane significantly inhibits pathogenic Cryptococcus species and is interesting as a lead compound towards new therapy for Cryptococcus infections.

scholarly journals Evaluation of Antifungal Activity and Mode of Action of New Coumarin Derivative, 7-Hydroxy-6-nitro-2H-1-benzopyran-2-one, againstAspergillusspp.

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Felipe Queiroga Sarmento Guerra ◽  
Rodrigo Santos Aquino de Araújo ◽  
Janiere Pereira de Sousa ◽  
Fillipe de Oliveira Pereira ◽  
Francisco J. B. Mendonça-Junior ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mode Of Action ◽  
Cell Walls ◽  
Coumarin Derivative ◽  
Antifungal Drugs ◽  
Azole Resistance ◽  
Subinhibitory Concentration ◽  
Fungal Cell ◽  
Mycelia Growth

Aspergillusspp. produce a wide variety of diseases. For the treatment of such infections, the azoles and Amphotericin B are used in various formulations. The treatment of fungal diseases is often ineffective, because of increases in azole resistance and their several associated adverse effects. To overcome these problems, natural products and their derivatives are interesting alternatives. The aim of this study was to examine the effects of coumarin derivative, 7-hydroxy-6-nitro-2H-1-benzopyran-2-one (Cou-NO2), both alone and with antifungal drugs. Its mode of action againstAspergillusspp. Cou-NO2was tested to evaluate its effects on mycelia growth and germination of fungal conidia ofAspergillusspp. We also investigated possible Cou-NO2action on cell walls (0.8 M sorbitol) and on Cou-NO2to ergosterol binding in the cell membrane. The study shows that Cou-NO2is capable of inhibiting both the mycelia growth and germination of conidia for the species tested, and that its action affects the structure of the fungal cell wall. At subinhibitory concentration, Cou-NO2enhanced thein vitroeffects of azoles. Moreover, in combination with azoles (voriconazole and itraconazole) Cou-NO2displays an additive effect. Thus, our study supports the use of coumarin derivative 7-hydroxy-6-nitro-2H-1-benzopyran-2-one as an antifungal agent againstAspergillusspecies.

scholarly journals The Transcription Factor SomA Synchronously Regulates Biofilm Formation and Cell Wall Homeostasis in Aspergillus fumigatus

mBio ◽  
2020 ◽  
Vol 11 (6) ◽  
Author(s):  
Yuan Chen ◽  
Francois Le Mauff ◽  
Yan Wang ◽  
Ruiyang Lu ◽  
Donald C. Sheppard ◽  
...  
Keyword(s):  
Cell Wall ◽  
Transcription Factor ◽  
Aspergillus Fumigatus ◽  
Biofilm Formation ◽  
Wall Stress ◽  
Fungal Cell ◽  
Glucan Synthase ◽  
Content Type ◽  
Cell Wall Stress ◽  
Chitin Synthases

ABSTRACT Polysaccharides are key components of both the fungal cell wall and biofilm matrix. Despite having distinct assembly and regulation pathways, matrix exopolysaccharide and cell wall polysaccharides share common substrates and intermediates in their biosynthetic pathways. It is not clear, however, if the biosynthetic pathways governing the production of these polysaccharides are cooperatively regulated. Here, we demonstrate that cell wall stress promotes production of the exopolysaccharide galactosaminogalactan (GAG)-depend biofilm formation in the major fungal pathogen of humans Aspergillus fumigatus and that the transcription factor SomA plays a crucial role in mediating this process. A core set of SomA target genes were identified by transcriptome sequencing and chromatin immunoprecipitation coupled to sequencing (ChIP-Seq). We identified a novel SomA-binding site in the promoter regions of GAG biosynthetic genes agd3 and ega3, as well as its regulators medA and stuA. Strikingly, this SomA-binding site was also found in the upstream regions of genes encoding the cell wall stress sensors, chitin synthases, and β-1,3-glucan synthase. Thus, SomA plays a direct regulation of both GAG and cell wall polysaccharide biosynthesis. Consistent with these findings, SomA is required for the maintenance of normal cell wall architecture and compositions in addition to its function in biofilm development. Moreover, SomA was found to globally regulate glucose uptake and utilization, as well as amino sugar and nucleotide sugar metabolism, which provides precursors for polysaccharide synthesis. Collectively, our work provides insight into fungal adaptive mechanisms in response to cell wall stress where biofilm formation and cell wall homeostasis were synchronously regulated. IMPORTANCE The cell wall is essential for fungal viability and is absent from human hosts; thus, drugs disrupting cell wall biosynthesis have gained more attention. Caspofungin is a member of a new class of clinically approved echinocandin drugs to treat invasive aspergillosis by blocking β-1,3-glucan synthase, thus damaging the fungal cell wall. Here, we demonstrate that caspofungin and other cell wall stressors can induce galactosaminogalactan (GAG)-dependent biofilm formation in the human pathogen Aspergillus fumigatus. We further identified SomA as a master transcription factor playing a dual role in both biofilm formation and cell wall homeostasis. SomA plays this dual role by direct binding to a conserved motif upstream of GAG biosynthetic genes and genes involved in cell wall stress sensors, chitin synthases, and β-1,3-glucan synthase. Collectively, these findings reveal a transcriptional control pathway that integrates biofilm formation and cell wall homeostasis and suggest SomA as an attractive target for antifungal drug development.

scholarly journals The composition of the cell wall of Fusicoccum amygdali

1971 ◽  
Vol 125 (2) ◽  
pp. 461-471 ◽  
Author(s):  
K. W. Buck ◽  
M. A. Obaidah
Keyword(s):  
Cell Wall ◽  
Sodium Hydroxide ◽  
Cell Walls ◽  
Digestive Enzymes ◽  
Helix Pomatia ◽  
Water Soluble ◽  
Extracellular Polysaccharides ◽  
Lytic Enzymes ◽  
Similar Nature ◽  
Dark Blue

1. The cell wall of Fusicoccum amygdali consisted of polysaccharides (85%), protein (4–6%), lipid (5%) and phosphorus (0.1%). 2. The main carbohydrate constituent was d-glucose; smaller amounts of d-glucosamine, d-galactose, d-mannose, l-rhamnose, xylose and arabinose were also identified, and 16 common amino acids were detected. 3. Chitin, which accounted for most of the cell-wall glucosamine, was isolated in an undegraded form by an enzymic method. Chitosan was not detected, but traces of glucosamine were found in alkali-soluble and water-soluble fractions. 4. Cell walls were stained dark blue by iodine and were attacked by α-amylase, with liberation of glucose, maltose and maltotriose, indicating the existence of chains of α-(1→4)-linked glucopyranose residues. 5. Glucose and gentiobiose were liberated from cell walls by the action of an exo-β-(1→3)-glucanase, giving evidence for both β-(1→3)- and β-(1→6)-glucopyranose linkages. 6. Incubation of cell walls with Helix pomatia digestive enzymes released glucose, N-acetyl-d-glucosamine and a non-diffusible fraction, containing most of the cell-wall galactose, mannose and rhamnose. Part of this fraction was released by incubating cell walls with Pronase; acid hydrolysis yielded galactose 6-phosphate and small amounts of mannose 6-phosphate and glucose 6-phosphate as well as other materials. Extracellular polysaccharides of a similar nature were isolated and may be formed by the action of lytic enzymes on the cell wall. 7. About 30% of the cell wall was resistant to the action of the H. pomatia digestive enzymes; the resistant fraction was shown to be a predominantly α-(1→3)-glucan. 8. Fractionation of the cell-wall complex with 1m-sodium hydroxide gave three principal glucan fractions: fraction BB had [α]D +236° (in 1m-sodium hydroxide) and showed two components on sedimentation analysis; fraction AA2 had [α]D −71° (in 1m-sodium hydroxide) and contained predominantly β-linkages; fraction AA1 had [α]D +40° (in 1m-sodium hydroxide) and may contain both α- and β-linkages.

scholarly journals Fusarium oxysporum gas1 Encodes a Putative β-1, 3-Glucanosyltransferase Required for Virulence on Tomato Plants

2005 ◽  
Vol 18 (11) ◽  
pp. 1140-1147 ◽  
Author(s):  
Zaira Caracuel ◽  
Ana Lilia Martínez-Rocha ◽  
Antonio Di Pietro ◽  
Marta P. Madrid ◽  
M. Isabel G. Roncero
Keyword(s):  
Cell Wall ◽  
Fusarium Oxysporum ◽  
Mutational Analysis ◽  
Gene Knockout ◽  
Colony Growth ◽  
Cell Wall Degrading Enzymes ◽  
Gene Encoding ◽  
Fungal Cell ◽  
Ph Response

Glycosylphosphatidylinositol-anchored (β)-1,3-glucanosyltransferases play active roles in fungal cell wall biosynthesis and morphogenesis and have been implicated in virulence on mammals. The role of β-1,3-glucanosyltransferases in pathogenesis to plants has not been explored so far. Here, we report the cloning and mutational analysis of the gas1 gene encoding a putative β-1,3-glucanosyltransferase from the vascular wilt fungus Fusarium oxysporum. In contrast to Candida albicans, expression of gas1 in F. oxysporum was independent of ambient pH and of the pH response transcription factor PacC. Gene knockout mutants lacking a functional gas1 allele grew in a way similar to the wild-type strain in submerged culture but exhibited restricted colony growth on solid substrates. The restricted growth phenotype was relieved by the osmotic stabilizer sorbitol, indicating that it may be related to structural alterations in the cell wall. Consistent with this hypothesis, Δgas1 mutants exhibited enhanced resistance to cell wall-degrading enzymes and increased transcript levels of chsV and rho1, encoding a class V chitin synthase and a small monomeric G protein, respectively. The Δgas1 mutants showed dramatically reduced virulence on tomato, both in a root infection assay and in a fruit tissue-invasion model, thus providing the first evidence for an essential role of fungal β-1,3-glucanosyltransferases during plant infection.

Exploring structural definitions of mycorrhizas, with emphasis on nutrient-exchange interfaces

2004 ◽  
Vol 82 (8) ◽  
pp. 1074-1088 ◽  
Author(s):  
R. Larry Peterson ◽  
Hugues B Massicotte
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Cell Walls ◽  
Plant Cell Wall ◽  
Structural Characteristics ◽  
Primary Cell ◽  
Fungal Cell ◽  
Symbiotic Associations ◽  
Nutrient Exchange ◽  
Fungal Hyphae

The roots or other subterranean organs of most plants develop symbioses, mycorrhizas, with fungal symbionts. Historically, mycorrhizas have been placed into seven categories based primarily on structural characteristics. A new category has been proposed for symbiotic associations of some leafy liverworts. An important feature of mycorrhizas is the interface involved in nutrient exchange between the symbionts. With the exception of ectomycorrhizas, in which fungal hyphae remain external to plant cell walls, all mycorrhizas are characterized by fungal hyphae breaching cell walls but remaining separated from the cell cytoplasm by a plant-derived membrane and an interfacial matrix that forms an apoplastic compartment. The chemical composition of the interfacial matrix varies in complexity. In arbuscular mycorrhizas (both Arum-type and Paris-type), molecules typical of plant primary cell walls (i.e., cellulose, pectins, β-1,3-glucans, hydroxyproline-rich glycoproteins) are present. In ericoid mycorrhizas, only rhamnogalacturonans occur in the interfacial matrix surrounding intracellular hyphal complexes. The matrix around intracellular hyphal complexes in orchid mycorrhizas lacks plant cell wall compounds until hyphae begin to senesce, then molecules similar to those found in primary cell walls are deposited. The interfacial matrix has not been studied in arbutoid mycorrhizas and ectendomycorrhizas. In ectomycorrhizas, the apoplastic interface consists of plant cell wall and fungal cell wall; alterations in these may enhance nutrient transfer. In all mycorrhizas, nutrients must pass into the symplast of both partners at some point, and therefore current research is exploring the nature of the opposing membranes, particularly in relation to phosphorus and sugar transporters.Key words: interface, apoplastic compartment, Hartig net, arbuscule, intracellular complex, nutrient exchange.

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