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1
Ouellette, G. B., H. Chamberland, A. Goulet, M. Lachapelle, and J. G. Lafontaine. "Fine structure of the extracellular sheath and cell walls inOphiostoma novo-ulmigrowing on various substrates." Canadian Journal of Microbiology 45, no. 7 (August 1, 1999): 582–97. http://dx.doi.org/10.1139/w99-045.
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The presence of microfilamentous-like structures of tubular appearance (MFS) in cell walls and extracellular sheath material (ES) in a number of isolates of Ophiostoma novo-ulmi Brasier grown on various substrates and following various treatments is reported. Standard fixation or high-pressure freezing methods were used, and cytochemical tests were carried out to detect fungal and host wall components and, in some cases, fungal DNA. In some cases, serial 0.2-μm-thick sections were examined at 120 kV and tilted to obtain stereoscopic images. Whether the fungal cell walls were thick and composed of an outer opaque and inner more electron-lucent layers, or thin and barely perceptible, MFS were observed to extend from the cell cytoplasm as parallel structures across the walls into the surrounding medium, including host cell components in infected elm tissues. MFS were associated (in samples from inoculated trees) with cleavage and desquamation of fungal walls. ES and MFS did not label for cellulose or chitin, but generally labelled slightly for β-(1-3)-glucan and mannose, and strongly for galactose. Only the lucent, inner fungal wall layer labelled for chitin and cellulose. DNA labelling was confined to nuclei and mitochondria in fungal cells from cultures on agar medium; in cells from cultures on millipore membranes, it was pronounced over imprecisely delimited cell regions. The possible ontogeny of MFS components and their importance are discussed. Key words: chitin, Dutch elm disease, fungal fimbriae, fungal walls, gold-complexed probes, microfilamentous structures (MFS).
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Benhamou, Nicole, Karen Broglie, Richard Broglie, and Ilan Chet. "Antifungal effect of bean endochitinase on Rhizoctonia solani: ultrastructural changes and cytochemical aspects of chitin breakdown." Canadian Journal of Microbiology 39, no. 3 (March 1, 1993): 318–28. http://dx.doi.org/10.1139/m93-045.
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A chitinase, purified to homogeneity from ethylene-treated bean leaves, was applied to actively growing mycelial cells of Rhizoctonia solani to evaluate a potential antifungal activity. Light microscopic investigations at 30-min intervals following enzyme exposure revealed the induction of morphological changes such as swelling of hyphal tips and hyphal distortions. More precise information concerning fungal cell alteration was obtained by ultrastructural observation and cytochemical detection of chitin distribution in fungal cell walls. Chitin breakdown was found to be an early event preceding wall disruption and cytoplasm leakage. The large amounts of chitin present in the walls of control R. solani cells and the rapid chitin hydrolysis upon chitinase treatment lead us to suggest that this polysaccharide is one of the main components of this fungal cell wall and is readily accessible to chitinase, especially in the apical zone. By 60 min after enzyme treatment, labeled molecules were observed in the vicinity of some fungal cells, suggesting the release of chitin oligosaccharides from fungal cell walls. The antifungal activity of the bean chitinase on cells of R. solani grown in culture is discussed in relation to the potential of genetically modified transgenic plants to resist attack by R. solani through an antimicrobial activity in planta.Key words: gold labeling, wheat germ agglutinin, cytochemistry, Rhizoctonia solani, bean endochitinase.
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Plaza, Verónica, Evelyn Silva-Moreno, and Luis Castillo. "Breakpoint: Cell Wall and Glycoproteins and their Crucial Role in the Phytopathogenic Fungi Infection." Current Protein & Peptide Science 21, no. 3 (March 26, 2020): 227–44. http://dx.doi.org/10.2174/1389203720666190906165111.
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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.
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Mora-Montes, Héctor M., Mihai G. Netea, Gerben Ferwerda, Megan D. Lenardon, Gordon D. Brown, Anita R. Mistry, Bart Jan Kullberg, et al. "Recognition and Blocking of Innate Immunity Cells by Candida albicans Chitin." Infection and Immunity 79, no. 5 (February 28, 2011): 1961–70. http://dx.doi.org/10.1128/iai.01282-10.
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ABSTRACTChitin is a skeletal cell wall polysaccharide of the inner cell wall of fungal pathogens. As yet, little about its role during fungus-host immune cell interactions is known. We show here that ultrapurified chitin fromCandida albicanscell walls did not stimulate cytokine production directly but blocked the recognition ofC. albicansby human peripheral blood mononuclear cells (PBMCs) and murine macrophages, leading to significant reductions in cytokine production. Chitin did not affect the induction of cytokines stimulated by bacterial cells or lipopolysaccharide (LPS), indicating that blocking was not due to steric masking of specific receptors. Toll-like receptor 2 (TLR2), TLR4, and Mincle (the macrophage-inducible C-type lectin) were not required for interactions with chitin. Dectin-1 was required for immune blocking but did not bind chitin directly. Cytokine stimulation was significantly reduced upon stimulation of PBMCs with heat-killed chitin-deficientC. albicanscells but not with live cells. Therefore, chitin is normally not exposed to cells of the innate immune system but is capable of influencing immune recognition by blocking dectin-1-mediated engagement with fungal cell walls.
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Chrissian, Christine, Coney Pei-Chen Lin, Emma Camacho, Arturo Casadevall, Aaron M. Neiman, and Ruth E. Stark. "Unconventional Constituents and Shared Molecular Architecture of the Melanized Cell Wall of C. neoformans and Spore Wall of S. cerevisiae." Journal of Fungi 6, no. 4 (December 1, 2020): 329. http://dx.doi.org/10.3390/jof6040329.
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The fungal cell wall serves as the interface between the cell and the environment. Fungal cell walls are composed largely of polysaccharides, primarily glucans and chitin, though in many fungi stress-resistant cell types elaborate additional cell wall structures. Here, we use solid-state nuclear magnetic resonance spectroscopy to compare the architecture of cell wall fractions isolated from Saccharomyces cerevisiae spores and Cryptococcus neoformans melanized cells. The specialized cell walls of these two divergent fungi are highly similar in composition. Both use chitosan, the deacetylated derivative of chitin, as a scaffold on which a polyaromatic polymer, dityrosine and melanin, respectively, is assembled. Additionally, we demonstrate that a previously identified but uncharacterized component of the S. cerevisiae spore wall is composed of triglycerides, which are also present in the C. neoformans melanized cell wall. Moreover, we identify a tyrosine-derived constituent in the C. neoformans wall that, although it is not dityrosine, is a non-pigment constituent of the cell wall. The similar composition of the walls of these two phylogenetically distant species suggests that triglycerides, polyaromatics, and chitosan are basic building blocks used to assemble highly stress-resistant cell walls and the use of these constituents may be broadly conserved in other fungal species.
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Vogt, Stephan, Marco Kelkenberg, Tanja Nöll, Benedikt Steinhoff, Holger Schönherr, Hans Merzendorfer, and Gilbert Nöll. "Rapid determination of binding parameters of chitin binding domains using chitin-coated quartz crystal microbalance sensor chips." Analyst 143, no. 21 (2018): 5255–63. http://dx.doi.org/10.1039/c8an01453a.
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Lopez-Moya, Federico, Marta Suarez-Fernandez, and Luis Lopez-Llorca. "Molecular Mechanisms of Chitosan Interactions with Fungi and Plants." International Journal of Molecular Sciences 20, no. 2 (January 15, 2019): 332. http://dx.doi.org/10.3390/ijms20020332.
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Chitosan is a versatile compound with multiple biotechnological applications. This polymer inhibits clinically important human fungal pathogens under the same carbon and nitrogen status as in blood. Chitosan permeabilises their high-fluidity plasma membrane and increases production of intracellular oxygen species (ROS). Conversely, chitosan is compatible with mammalian cell lines as well as with biocontrol fungi (BCF). BCF resistant to chitosan have low-fluidity membranes and high glucan/chitin ratios in their cell walls. Recent studies illustrate molecular and physiological basis of chitosan-root interactions. Chitosan induces auxin accumulation in Arabidopsis roots. This polymer causes overexpression of tryptophan-dependent auxin biosynthesis pathway. It also blocks auxin translocation in roots. Chitosan is a plant defense modulator. Endophytes and fungal pathogens evade plant immunity converting chitin into chitosan. LysM effectors shield chitin and protect fungal cell walls from plant chitinases. These enzymes together with fungal chitin deacetylases, chitosanases and effectors play determinant roles during fungal colonization of plants. This review describes chitosan mode of action (cell and gene targets) in fungi and plants. This knowledge will help to develop chitosan for agrobiotechnological and medical applications.
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van den Burg, Harrold A., Stuart J. Harrison, Matthieu H. A. J. Joosten, Jacques Vervoort, and Pierre J. G. M. de Wit. "Cladosporium fulvum Avr4 Protects Fungal Cell Walls Against Hydrolysis by Plant Chitinases Accumulating During Infection." Molecular Plant-Microbe Interactions® 19, no. 12 (December 2006): 1420–30. http://dx.doi.org/10.1094/mpmi-19-1420.
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Resistance against the leaf mold fungus Cladosporium fulvum is mediated by the tomato Cf proteins which belong to the class of receptor-like proteins and indirectly recognize extracellular avirulence proteins (Avrs) of the fungus. Apart from triggering disease resistance, Avrs are believed to play a role in pathogenicity or virulence of C. fulvum. Here, we report on the avirulence protein Avr4, which is a chitin-binding lectin containing an invertebrate chitin-binding domain (CBM14). This domain is found in many eukaryotes, but has not yet been described in fungal or plant genomes. We found that interaction of Avr4 with chitin is specific, because it does not interact with other cell wall polysaccharides. Avr4 binds to chitin oligomers with a minimal length of three N-acetyl glucosamine residues. In vitro, Avr4 protects chitin against hydrolysis by plant chitinases. Avr4 also binds to chitin in cell walls of the fungi Trichoderma viride and Fusarium solani f. sp. phaseoli and protects these fungi against normally deleterious concentrations of plant chitinases. In situ fluorescence studies showed that Avr4 also binds to cell walls of C. fulvum during infection of tomato, where it most likely protects the fungus against tomato chitinases, suggesting that Avr4 is a counter-defensive virulence factor.
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COUSIN, M. A. "Chitin as a Measure of Mold Contamination of Agricultural Commodities and Foods†." Journal of Food Protection 59, no. 1 (January 1, 1996): 73–81. http://dx.doi.org/10.4315/0362-028x-59.1.73.
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Chitin is a polysaccharide of β-(1→4)-linked 2-acetamido-2-deoxy-d-glucose (N-acetyl-d-glucosamine) that is found in the cell walls of fungi. In an effort to develop new methods to detect fungi in plant and animal tissues, chemical analyses based on fungal cell wall components have been evaluated. Chitin is not present in plant or most food animal tissues; therefore, the entire sample can be hydrolyzed and analyzed for fungal chitin. Acid, alkaline, and enzymatic hydrolysis have been used to cleave the β-(1→4)-glycosidic bond to produce glucosamine, chitosan, or N-acetylglucosamine. The major methods used to analyze these degradation products have included colorimetry; chromatography (gas chromatography, high performance liquid chromatography, amino acid analysis); microscopy, using fluorescent, nonfluorescent or immunofluorescent dyes; near-infrared spectroscopy; and titrametric assays. Chitin has been used to estimate and quantify fungal growth in plants, wood, grains, hay, and foods. There was an increase in the chitin content as the mold increased; however, the chitin assay showed more variability than other assays for detecting fungal contamination. The future use of the chitin assay will depend upon improvements in sensitivity, assay time, simplified methodology and equipment, and development of reliable conversion factors for converting chitin to fungal dry weight.
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Volk, Helena, Kristina Marton, Marko Flajšman, Sebastjan Radišek, Hui Tian, Ingo Hein, Črtomir Podlipnik, et al. "Chitin-Binding Protein of Verticillium nonalfalfae Disguises Fungus from Plant Chitinases and Suppresses Chitin-Triggered Host Immunity." Molecular Plant-Microbe Interactions® 32, no. 10 (October 2019): 1378–90. http://dx.doi.org/10.1094/mpmi-03-19-0079-r.
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During fungal infections, plant cells secrete chitinases, which digest chitin in the fungal cell walls. The recognition of released chitin oligomers via lysin motif (LysM)-containing immune host receptors results in the activation of defense signaling pathways. We report here that Verticillium nonalfalfae, a hemibiotrophic xylem-invading fungus, prevents these digestion and recognition processes by secreting a carbohydrate-binding motif 18 (CBM18)-chitin-binding protein, VnaChtBP, which is transcriptionally activated specifically during the parasitic life stages. VnaChtBP is encoded by the Vna8.213 gene, which is highly conserved within the species, suggesting high evolutionary stability and importance for the fungal lifestyle. In a pathogenicity assay, however, Vna8.213 knockout mutants exhibited wilting symptoms similar to the wild-type fungus, suggesting that Vna8.213 activity is functionally redundant during fungal infection of hop. In a binding assay, recombinant VnaChtBP bound chitin and chitin oligomers in vitro with submicromolar affinity and protected fungal hyphae from degradation by plant chitinases. Moreover, the chitin-triggered production of reactive oxygen species from hop suspension cells was abolished in the presence of VnaChtBP, indicating that VnaChtBP also acts as a suppressor of chitin-triggered immunity. Using a yeast-two-hybrid assay, circular dichroism, homology modeling, and molecular docking, we demonstrated that VnaChtBP forms dimers in the absence of ligands and that this interaction is stabilized by the binding of chitin hexamers with a similar preference in the two binding sites. Our data suggest that, in addition to chitin-binding LysM (CBM50) and Avr4 (CBM14) fungal effectors, structurally unrelated CBM18 effectors have convergently evolved to prevent hydrolysis of the fungal cell wall against plant chitinases and to interfere with chitin-triggered host immunity.
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Jashni, Mansoor Karimi, Ivo H. M. Dols, Yuichiro Iida, Sjef Boeren, Henriek G. Beenen, Rahim Mehrabi, Jérôme Collemare, and Pierre J. G. M. de Wit. "Synergistic Action of a Metalloprotease and a Serine Protease from Fusarium oxysporum f. sp. lycopersici Cleaves Chitin-Binding Tomato Chitinases, Reduces Their Antifungal Activity, and Enhances Fungal Virulence." Molecular Plant-Microbe Interactions® 28, no. 9 (September 2015): 996–1008. http://dx.doi.org/10.1094/mpmi-04-15-0074-r.
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As part of their defense strategy against fungal pathogens, plants secrete chitinases that degrade chitin, the major structural component of fungal cell walls. Some fungi are not sensitive to plant chitinases because they secrete chitin-binding effector proteins that protect their cell wall against these enzymes. However, it is not known how fungal pathogens that lack chitin-binding effectors overcome this plant defense barrier. Here, we investigated the ability of fungal tomato pathogens to cleave chitin-binding domain (CBD)-containing chitinases and its effect on fungal virulence. Four tomato CBD chitinases were produced in Pichia pastoris and were incubated with secreted proteins isolated from seven fungal tomato pathogens. Of these, Fusarium oxysporum f. sp. lycopersici, Verticillium dahliae, and Botrytis cinerea were able to cleave the extracellular tomato chitinases SlChi1 and SlChi13. Cleavage by F. oxysporum removed the CBD from the N-terminus, shown by mass spectrometry, and significantly reduced the chitinase and antifungal activity of both chitinases. Both secreted metalloprotease FoMep1 and serine protease FoSep1 were responsible for this cleavage. Double deletion mutants of FoMep1 and FoSep1 of F. oxysporum lacked chitinase cleavage activity on SlChi1 and SlChi13 and showed reduced virulence on tomato. These results demonstrate the importance of plant chitinase cleavage in fungal virulence.
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Chen, Li-Hung, Stjepan K. Kračun, Karen S. Nissen, Jozef Mravec, Bodil Jørgensen, John Labavitch, and Ioannis Stergiopoulos. "A diverse member of the fungal Avr4 effector family interacts with de-esterified pectin in plant cell walls to disrupt their integrity." Science Advances 7, no. 19 (May 2021): eabe0809. http://dx.doi.org/10.1126/sciadv.abe0809.
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Effectors are small, secreted proteins that promote pathogen virulence. Although key to microbial infections, unlocking the intrinsic function of effectors remains a challenge. We have previously shown that members of the fungal Avr4 effector family use a carbohydrate-binding module of family 14 (CBM14) to bind chitin in fungal cell walls and protect them from host chitinases during infection. Here, we show that gene duplication in the Avr4 family produced an Avr4-2 paralog with a previously unknown effector function. Specifically, we functionally characterize PfAvr4-2, a paralog of PfAvr4 in the tomato pathogen Pseudocercospora fuligena, and show that although it contains a CBM14 domain, it does not bind chitin or protect fungi against chitinases. Instead, PfAvr4-2 interacts with highly de-esterified pectin in the plant’s middle lamellae or primary cell walls and interferes with Ca2+-mediated cross-linking at cell-cell junction zones, thus loosening the plant cell wall structure and synergizing the activity of pathogen secreted endo-polygalacturonases.
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B. Ouellette, Guillemond, Robert P. Baayen, Danny Rioux, and Marie Simard. "Peculiar ultrastructural characteristics of fungal cells and of other elements apposed to and in vessel walls in plants of a susceptible carnation cultivar, infected with Fusarium oxysporum f.sp. dianthi race 2." Phytoprotection 85, no. 3 (June 13, 2005): 121–38. http://dx.doi.org/10.7202/010905ar.
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Abstract Ultrastructural characteristics and cytochemical reactions of unusual, irregular elements (IE) in vessel elements in susceptible carnation plants infected with Fusarium oxysporum are reported. As revealed by labelling for chitin, fungal cells in contact with host cell walls or content had altered or defective lucent layers, and labelling was frequently associated with their outer, opaque layer or matter located outside the cells. Coating matter on vessel walls occurred at all stages of infection, and IEs only in later stages. IEs were delineated by opaque, often folded bands, some contouring pit borders, and contained membranous and vesicular structures mixed with other fine components. Only then, IEs were strongly but not uniformly labelled for chitin. Coating, IE-delineating bands, and the opaque outer layer of typical fungal cells were texturally similar, not labelled for chitin or cellulose, except where they impinged upon host walls. Both probes for chitin and cellulose strongly attached to vessel secondary walls. IEs were often confluent with coating, and with fungal cells connected to them by means of microfilamentous structures. Similar microfilamentous structures and opaque bands connected to IEs, the coating, and the microhyphae, or protruding from fungal cells reached into host walls, associated with alterations of these walls. The possible malleable IEs might be a counterpart of the coating, and although they do not occur in the initial stages of the disease, they could play an important role in the final stages of tissue degradation.
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Baker, Lorina G., Charles A. Specht, and Jennifer K. Lodge. "Chitinases Are Essential for Sexual Development but Not Vegetative Growth in Cryptococcus neoformans." Eukaryotic Cell 8, no. 11 (September 4, 2009): 1692–705. http://dx.doi.org/10.1128/ec.00227-09.
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ABSTRACT Cryptococcus neoformans is an opportunistic pathogen that mainly infects immunocompromised individuals. The fungal cell wall of C. neoformans is an excellent target for antifungal therapies since it is an essential organelle that provides cell structure and integrity. Importantly, it is needed for localization or attachment of known virulence factors, including melanin, phospholipase, and the polysaccharide capsule. The polysaccharide fraction of the cryptococcal cell wall is a complex structure composed of chitin, chitosan, and glucans. Chitin is an indispensable component of many fungal cell walls that contributes significantly to cell wall strength and integrity. Fungal cell walls are very dynamic, constantly changing during cell division and morphogenesis. Hydrolytic enzymes, such as chitinases, have been implicated in the maintenance of cell wall plasticity and separation of the mother and daughter cells at the bud neck during vegetative growth in yeast. In C. neoformans we identified four predicted endochitinases, CHI2, CHI21, CHI22, and CHI4, and a predicted exochitinase, hexosaminidase, HEX1. Enzymatic analysis indicated that Chi2, Chi22, and Hex1 actively degraded chitinoligomeric substrates. Chi2 and Hex1 activity was associated mostly with the cellular fraction, and Chi22 activity was more prominent in the supernatant. The enzymatic activity of Hex1 increased when grown in media containing only N-acetylglucosamine as a carbon source, suggesting that its activity may be inducible by chitin degradation products. Using a quadruple endochitinase deletion strain, we determined that the endochitinases do not affect the growth or morphology of C. neoformans during asexual reproduction. However, mating assays indicated that Chi2, Chi21, and Chi4 are each involved in sexual reproduction. In summary, the endochitinases were found to be dispensable for routine vegetative growth but not sexual reproduction.
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Ouellette, Guillemond B., Mohamed Cherif, Marie Simard, and Louis Bernier. "Histopathology of Fusarium wilt of staghorn sumac (Rhus typhina) caused by Fusarium oxysporum f. sp. callistephi race 3. I. Modes of tissue colonization and pathogen peculiarities." Phytoprotection 86, no. 3 (June 15, 2006): 157–74. http://dx.doi.org/10.7202/013074ar.
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Abstract Light and transmission electron microscope studies of naturally infected or inoculated staghorn sumac plants by Fusarium oxysporum f. sp. callistephi race 3 are reported. Diverse extrinsic material (including latex in some instances) or elements occurred in vessel lumina. Some of this material labelled for pectin, often in association with tyloses, as did other opaque matter in paratracheal cells, related to alterations of their protective layer. Pronounced alterations of pit membranes of bordered pits occurred, with their outer portions disrupted into bodies of opaque matter, strongly labelled for cellulose, and their middle portions as unlabelled shreds. Similarly labelled opaque bodies occasionally occurred on vessel walls and lumina. Direct penetration of host cell secondary walls by the pathogen occurred, but these were degraded to any extent only following intramural invasion. Vessel walls, at all stages of infection, were lined with variously structured matter: in their thinnest forms, by single or paired, equidistant or widely spaced opaque bands, and in their thickest forms as alternating opaque and less opaque layers. Other thin elements, often enclosing opaque material, vesicular structures, or occasionally particles of ribosomal appearance were also delineated by similar but frequently infolded bands. These elements were sometimes observed to be confluent with fungal cells and to label for chitin. Many fungal elements were bound by only a thin or defective lucent wall layer, practically unlabelled for chitin, or by a locally thickened, labelled one; labelling for this substrate was also frequently associated with the fungal cell outer opaque wall layer or with some outer extracellular matter. Fine filamentous structures, connected to fungal cells, to the vessel lining matter, and to these other elements, extended into host walls. The lining itself generally did not label for cellulose or chitin. These observations are discussed in comparison with similar observations made regarding other wilt diseases that we have studied.
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Lee, Keunsook K., Donna M. MacCallum, Mette D. Jacobsen, Louise A. Walker, Frank C. Odds, Neil A. R. Gow, and Carol A. Munro. "Elevated Cell Wall Chitin in Candida albicans Confers Echinocandin ResistanceIn Vivo." Antimicrobial Agents and Chemotherapy 56, no. 1 (October 10, 2011): 208–17. http://dx.doi.org/10.1128/aac.00683-11.
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ABSTRACTCandida albicanscells with increased cell wall chitin have reduced echinocandin susceptibilityin vitro. The aim of this study was to investigate whetherC. albicanscells with elevated chitin levels have reduced echinocandin susceptibilityin vivo. BALB/c mice were infected withC. albicanscells with normal chitin levels and compared to mice infected with high-chitin cells. Caspofungin therapy was initiated at 24 h postinfection. Mice infected with chitin-normal cells were successfully treated with caspofungin, as indicated by reduced kidney fungal burdens, reduced weight loss, and decreasedC. albicansdensity in kidney lesions. In contrast, mice infected with high-chitinC. albicanscells were less susceptible to caspofungin, as they had higher kidney fungal burdens and greater weight loss during early infection. Cells recovered from mouse kidneys at 24 h postinfection with high-chitin cells had 1.6-fold higher chitin levels than cells from mice infected with chitin-normal cells and maintained a significantly reduced susceptibility to caspofungin when testedin vitro. At 48 h postinfection, caspofungin treatment induced a further increase in chitin content ofC. albicanscells harvested from kidneys compared to saline treatment. Some of the recovered clones had acquired, at a low frequency, a point mutation inFKS1resulting in a S645Y amino acid substitution, a mutation known to confer echinocandin resistance. This occurred even in cells that had not been exposed to caspofungin. Our results suggest that the efficacy of caspofungin againstC. albicanswas reducedin vivodue to either elevation of chitin levels in the cell wall or acquisition ofFKS1point mutations.
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Tsuneda, A., and R. G. Thorn. "Interactions of wood decay fungi with other microorganisms, with emphasis on the degradation of cell walls." Canadian Journal of Botany 73, S1 (December 31, 1995): 1325–33. http://dx.doi.org/10.1139/b95-394.
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Interactions of two wood decay fungi, Lentinula edodes and Pleurotus ostreatus, with other wood inhabiting microorganisms were investigated on agar and in fagaceous wood, primarily by scanning electron microscopy. Micromorphologically, there were two principal modes of cell wall degradation: (i) selective removal of amorphous wall components, followed by the degradation of skeletal microfibrils, and (ii) simultaneous degradation of all wall components. These two modes were observed in three different degradation systems: (i) sapwood wall degradation by the wood decay fungi, (ii) hyphal wall degradation by mycoparasitic Trichoderma, and (iii) hyphal wall degradation by pathogenic bacteria. The simultaneous-type wall degradation in the systems i and ii was usually caused by hyphal tips. In addition to the three systems, bacteriolysis by the wood decay fungi was also studied. The bacterial cell walls, as well as microfibril bundles of wood cellulose and fungal chitin, were all fragmented into minute granules at later stages of microbial degradation and the granules were further degraded into smaller units. Frequency of occurrence and strength of mycoparasitic activity of Trichoderma harzianum were influenced by the degree of wood decay where the interaction occurred. Presence of both cellulose and chitin microfibrils apparently enhanced the mycoparasitic activity. In Quercus wood, P. ostreatus showed a unidirectional growth toward bacterial colonies, which formed as the result of decomposition of dead nematodes, and consumed the unidentified bacteria. In nitrogen-deficient wood, fungal and bacterial cell walls may serve as an important reservoir of nitrogen for wood inhabiting microorganisms. Key words: wood decay, mycoparasitism, bacteriolysis, cellulose, chitin.
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Badreddine, Ilham, Claude Lafitte, Laurent Heux, Nicholas Skandalis, Zacharoula Spanou, Yves Martinez, Marie-Thérèse Esquerré-Tugayé, Vincent Bulone, Bernard Dumas, and Arnaud Bottin. "Cell Wall Chitosaccharides Are Essential Components and Exposed Patterns of the Phytopathogenic Oomycete Aphanomyces euteiches." Eukaryotic Cell 7, no. 11 (September 19, 2008): 1980–93. http://dx.doi.org/10.1128/ec.00091-08.
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ABSTRACT Chitin is an essential component of fungal cell walls, where it forms a crystalline scaffold, and chitooligosaccharides derived from it are signaling molecules recognized by the hosts of pathogenic fungi. Oomycetes are cellulosic fungus-like microorganisms which most often lack chitin in their cell walls. Here we present the first study of the cell wall of the oomycete Aphanomyces euteiches, a major parasite of legume plants. Biochemical analyses demonstrated the presence of ca. 10% N-acetyl-d-glucosamine (GlcNAc) in the cell wall. Further characterization of the GlcNAc-containing material revealed that it corresponds to noncrystalline chitosaccharides associated with glucans, rather than to chitin per se. Two putative chitin synthase (CHS) genes were identified by data mining of an A. euteiches expressed sequence tag collection and Southern blot analysis, and full-length cDNA sequences of both genes were obtained. Phylogeny analysis indicated that oomycete CHS diversification occurred before the divergence of the major oomycete lineages. Remarkably, lectin labeling showed that the Aphanomyces euteiches chitosaccharides are exposed at the cell wall surface, and study of the effect of the CHS inhibitor nikkomycin Z demonstrated that they are involved in cell wall function. These data open new perspectives for the development of antioomycete drugs and further studies of the molecular mechanisms involved in the recognition of pathogenic oomycetes by the host plants.
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van Esse, H. Peter, Melvin D. Bolton, Ioannis Stergiopoulos, Pierre J. G. M. de Wit, and Bart P. H. J. Thomma. "The Chitin-Binding Cladosporium fulvum Effector Protein Avr4 Is a Virulence Factor." Molecular Plant-Microbe Interactions® 20, no. 9 (September 2007): 1092–101. http://dx.doi.org/10.1094/mpmi-20-9-1092.
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The biotrophic fungal pathogen Cladosporium fulvum (syn. Passalora fulva) is the causal agent of tomato leaf mold. The Avr4 protein belongs to a set of effectors that is secreted by C. fulvum during infection and is thought to play a role in pathogen virulence. Previous studies have shown that Avr4 binds to chitin present in fungal cell walls and that, through this binding, Avr4 can protect these cell walls against hydrolysis by plant chitinases. In this study, we demonstrate that Avr4 expression in Arabidopsis results in increased virulence of several fungal pathogens with exposed chitin in their cell walls, whereas the virulence of a bacterium and an oomycete remained unaltered. Heterologous expression of Avr4 in tomato increased the virulence of Fusarium oxysporum f. sp. lycopersici. Through tomato GeneChip analyses, we demonstrate that Avr4 expression in tomato results in the induced expression of only a few genes. Finally, we demonstrate that silencing of the Avr4 gene in C. fulvum decreases its virulence on tomato. This is the first report on the intrinsic function of a fungal avirulence protein that has a counter-defensive activity required for full virulence of the pathogen.
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Walker, Claire A., Beatriz L. Gómez, Héctor M. Mora-Montes, Kevin S. Mackenzie, Carol A. Munro, Alistair J. P. Brown, Neil A. R. Gow, Christopher C. Kibbler, and Frank C. Odds. "Melanin Externalization in Candida albicans Depends on Cell Wall Chitin Structures." Eukaryotic Cell 9, no. 9 (September 2010): 1329–42. http://dx.doi.org/10.1128/ec.00051-10.
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ABSTRACT The fungal pathogen Candida albicans produces dark-pigmented melanin after 3 to 4 days of incubation in medium containing l-3,4-dihydroxyphenylalanine (l-DOPA) as a substrate. Expression profiling of C. albicans revealed very few genes significantly up- or downregulated by growth in l-DOPA. We were unable to determine a possible role for melanin in the virulence of C. albicans. However, we showed that melanin was externalized from the fungal cells in the form of electron-dense melanosomes that were free or often loosely bound to the cell wall exterior. Melanin production was boosted by the addition of N-acetylglucosamine to the medium, indicating a possible association between melanin production and chitin synthesis. Melanin externalization was blocked in a mutant specifically disrupted in the chitin synthase-encoding gene CHS2. Melanosomes remained within the outermost cell wall layers in chs3Δ and chs2Δ chs3Δ mutants but were fully externalized in chs8Δ and chs2Δ chs8Δ mutants. All the CHS mutants synthesized dark pigment at equivalent rates from mixed membrane fractions in vitro, suggesting it was the form of chitin structure produced by the enzymes, not the enzymes themselves, that was involved in the melanin externalization process. Mutants with single and double disruptions of the chitinase genes CHT2 and CHT3 and the chitin pathway regulator ECM33 also showed impaired melanin externalization. We hypothesize that the chitin product of Chs3 forms a scaffold essential for normal externalization of melanosomes, while the Chs8 chitin product, probably produced in cell walls in greater quantity in the absence of CHS2, impedes externalization.
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Hu, Shu-Ping, Jun-Jiao Li, Nikhilesh Dhar, Jun-Peng Li, Jie-Yin Chen, Wei Jian, Xiao-Feng Dai, and Xing-Yong Yang. "Lysin Motif (LysM) Proteins: Interlinking Manipulation of Plant Immunity and Fungi." International Journal of Molecular Sciences 22, no. 6 (March 18, 2021): 3114. http://dx.doi.org/10.3390/ijms22063114.
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The proteins with lysin motif (LysM) are carbohydrate-binding protein modules that play a critical role in the host-pathogen interactions. The plant LysM proteins mostly function as pattern recognition receptors (PRRs) that sense chitin to induce the plant’s immunity. In contrast, fungal LysM blocks chitin sensing or signaling to inhibit chitin-induced host immunity. In this review, we provide historical perspectives on plant and fungal LysMs to demonstrate how these proteins are involved in the regulation of plant’s immune response by microbes. Plants employ LysM proteins to recognize fungal chitins that are then degraded by plant chitinases to induce immunity. In contrast, fungal pathogens recruit LysM proteins to protect their cell wall from hydrolysis by plant chitinase to prevent activation of chitin-induced immunity. Uncovering this coevolutionary arms race in which LysM plays a pivotal role in manipulating facilitates a greater understanding of the mechanisms governing plant-fungus interactions.
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Nicole, M., H. Chamberland, D. Rioux, X. Xixuan, G. B. Ouellette, R. A. Blanchette, and J. P. Geiger. "Wood degradation by Phellinus noxius: ultrastructure and cytochemistry." Canadian Journal of Microbiology 41, no. 3 (March 1, 1995): 253–65. http://dx.doi.org/10.1139/m95-035.
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An ultrastructural and cytochemical investigation of the development of Phellinus noxius, a white-rot fungus, in wood chips of Betula papyrifera was done to gain insight into the cellular mechanisms of wood cell wall degradation. Extracellular sheaths and microhyphae were seen to be involved in wood colonization. Close association was observed between these fungal structures and wood cell walls at both early and advanced stages of wood alteration. Fungal sheaths were often seen deep inside host cell walls, sometimes enclosing residual wood fragments. Investigations using gold probes indicated the occurrence of β-1,3-glucans within the fungal sheaths, while β-1,4-glucans were detected only within the fungal septa. The positive reaction with the PATAg test revealed that polysaccharides such as β-1,6-glucans were important components of the sheath. Chitin, pectin, β-glucosides, galactosamine, mannose, sialic acid, fucose, and fimbrial proteins were not found to be present in the sheath. Our data suggest that extracellular sheaths and microphyphae produced by P. noxius during wood cell wall colonization play an important role in wood degradation.Key words: cellulose, Phellinus, sheath, wood degradation.
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Jones, Mitchell, Marina Kujundzic, Sabu John, and Alexander Bismarck. "Crab vs. Mushroom: A Review of Crustacean and Fungal Chitin in Wound Treatment." Marine Drugs 18, no. 1 (January 18, 2020): 64. http://dx.doi.org/10.3390/md18010064.
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Chitin and its derivative chitosan are popular constituents in wound-treatment technologies due to their nanoscale fibrous morphology and attractive biomedical properties that accelerate healing and reduce scarring. These abundant natural polymers found in arthropod exoskeletons and fungal cell walls affect almost every phase of the healing process, acting as hemostatic and antibacterial agents that also support cell proliferation and attachment. However, key differences exist in the structure, properties, processing, and associated polymers of fungal and arthropod chitin, affecting their respective application to wound treatment. High purity crustacean-derived chitin and chitosan have been widely investigated for wound-treatment applications, with research incorporating chemically modified chitosan derivatives and advanced nanocomposite dressings utilizing biocompatible additives, such as natural polysaccharides, mineral clays, and metal nanoparticles used to achieve excellent mechanical and biomedical properties. Conversely, fungi-derived chitin is covalently decorated with -glucan and has received less research interest despite its mass production potential, simple extraction process, variations in chitin and associated polymer content, and the established healing properties of fungal exopolysaccharides. This review investigates the proven biomedical properties of both fungal- and crustacean-derived chitin and chitosan, their healing mechanisms, and their potential to advance modern wound-treatment methods through further research and practical application.
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Martín-Urdíroz, Magdalena, M. Isabel G. Roncero, José Antonio González-Reyes, and Carmen Ruiz-Roldán. "ChsVb, a Class VII Chitin Synthase Involved in Septation, Is Critical for Pathogenicity in Fusarium oxysporum." Eukaryotic Cell 7, no. 1 (November 9, 2007): 112–21. http://dx.doi.org/10.1128/ec.00347-07.
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ABSTRACT A new myosin motor-like chitin synthase gene, chsVb, has been identified in the vascular wilt fungus Fusarium oxysporum f. sp. lycopersici. Phylogenetic analysis of the deduced amino acid sequence of the chsVb chitin synthase 2 domain (CS2) revealed that ChsVb belongs to class VII chitin synthases. The ChsVb myosin motor-like domain (MMD) is shorter than the MMD of class V chitin synthases and does not contain typical ATP-binding motifs. Targeted disrupted single (ΔchsVb) and double (ΔchsV ΔchsVb) mutants were unable to infect and colonize tomato plants or grow invasively on tomato fruit tissue. These strains were hypersensitive to compounds that interfere with fungal cell wall assembly, produced lemon-like shaped conidia, and showed swollen balloon-like structures in hyphal subapical regions, thickened walls, aberrant septa, and intrahyphal hyphae. Our results suggest that the chsVb gene is likely to function in polarized growth and confirm the critical importance of cell wall integrity in the complex infection process of this fungus.
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Krahmer, R. L., J. J. Morrell, and A. Choi. "Double-Staining to Improve Visualisation of Wood Decay Hyphae in Wood Sections." IAWA Journal 7, no. 2 (1986): 165–67. http://dx.doi.org/10.1163/22941932-90000981.
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Combining fluorescent-labeled wheat germ agglutinin (a chitin-specific lectin) with conventional histological stains offers a simple, efficient method for studying fungal hyphae in deteriorating wood. Cell walls stain dark red with safranin 0, providing excellent contrast for the green-fluorescing hyphae. Staining sections with brilliant vital red markedly enhances the visibility of fungal bore holes.
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Majtán, Juraj, Grigorij Kogan, Elena Kováčová, Katarína Bíliková, and Jozef Šimúth. "Stimulation of TNF-α Release by Fungal Cell Wall Polysaccharides." Zeitschrift für Naturforschung C 60, no. 11-12 (December 1, 2005): 921–26. http://dx.doi.org/10.1515/znc-2005-11-1216.
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Carboxymethylated derivatives were prepared from the (1→3)-β-ᴅ-glucan isolated from the cell wall of baker’s yeast Saccharomyces cerevisiae and from the chitin-glucan complex of the mycelium of the industrial filamentous fungus Aspergillus niger. The polysaccharides were applied to peritoneal mouse macrophages and after a 2-h incubation the release of TNF-α by the stimulated macrophages was measured using an enzyme-linked immunosorbent assay. As the third polysaccharide stimulant, a water-soluble derivative of chitin was assayed and the observed cytokine release was compared with the control experiment. In three concentrations of the polysaccharides applied, carboxymethyl glucan revealed a dramatic increase in the TNF-α release, while addition of carboxymethyl chitin-glucan resulted only in a moderate enhancement, and carboxymethyl chitin was inactive. The results indicate that fungal polysaccharides, especially (1→3)-β-ᴅ-glucan, are potent macrophage stimulators and activators of TNF-α release, which implies their potential application in antitumor therapy.
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Aktuganov, G., A. Melentjev, N. Galimzianova, E. Khalikova, T. Korpela, and P. Susi. "Wide-range antifungal antagonism ofPaenibacillus ehimensisIB-X-b and its dependence on chitinase and β-1,3-glucanase production." Canadian Journal of Microbiology 54, no. 7 (July 2008): 577–87. http://dx.doi.org/10.1139/w08-043.
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Previously, we isolated a strain of Bacillus that had antifungal activity and produced lytic enzymes with fungicidal potential. In the present study, we identified the bacterium as Paenibacillus ehimensis and further explored its antifungal properties. In liquid co-cultivation assays, P. ehimensis IB-X-b decreased biomass production of several pathogenic fungi by 45%–75%. The inhibition was accompanied by degradation of fungal cell walls and alterations in hyphal morphology. Residual medium from cultures of P. ehimensis IB-X-b inhibited fungal growth, indicating the inhibitors were secreted into the medium. Of the 2 major lytic enzymes, chitinases were only induced by chitin-containing substrates, whereas β-1,3-glucanase showed steady levels in all carbon sources. Both purified chitinase and β-1,3-glucanase degraded cell walls of macerated fungal mycelia, whereas only the latter also degraded cell walls of intact mycelia. The results indicate synergism between the antifungal action mechanisms of these enzymes in which β-1,3-glucanase is the initiator of the cell wall hydrolysis, whereas the degradation process is reinforced by chitinases. Paenibacillus ehimensis IB-X-b has pronounced antifungal activity with a wide range of fungi and has potential as a biological control agent against plant pathogenic fungi.
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Vega, Karina, and Markus Kalkum. "Chitin, Chitinase Responses, and Invasive Fungal Infections." International Journal of Microbiology 2012 (2012): 1–10. http://dx.doi.org/10.1155/2012/920459.
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The human immune system is capable of recognizing and degrading chitin, an important cell wall component of pathogenic fungi. In the context of host-immune responses to fungal infections, herein we review the particular contributions and interplay of fungus and chitin recognition, and chitin-degrading enzymes, known as chitinases. The mechanisms of host chitinase responses may have implications for diagnostic assays as well as novel therapeutic approaches for patients that are at risk of contracting fatal fungal infections.
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Boine, Barbara, Richard L. Kingston, and Michael N. Pearson. "Recombinant expression of the coat protein of Botrytis virus X and development of an immunofluorescence detection method to study its intracellular distribution in Botrytis cinerea." Journal of General Virology 93, no. 11 (November 1, 2012): 2502–11. http://dx.doi.org/10.1099/vir.0.043869-0.
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Botrytis cinerea is infected by many mycoviruses with varying phenotypical effects on the fungal host, including Botrytis virus X (BVX), a mycovirus that has been found in several B. cinerea isolates worldwide with no obvious effects on growth. Here we present results from serological and immunofluorescence microscopy (IFM) studies using antiserum raised against the coat protein of BVX expressed in Escherichia coli fused to maltose-binding protein. Due to the high yield of recombinant protein it was possible to raise antibodies that recognized BVX particles. An indirect ELISA, using BVX antibodies, detected BVX in partially purified virus preparations from fungal isolates containing BVX alone and in mixed infection with Botrytis virus F. The BVX antiserum also proved suitable for IFM studies. Intensely fluorescing spots (presumed to be virus aggregates) were found to be localized in hyphal cell compartments and spores of natural and experimentally infected B. cinerea isolates using IFM. Immunofluorescently labelled sections through fungal tissue, as well as fixed mycelia grown on glass slides, showed aggregations of virions closely associated with fungal cell membranes and walls, next to septal pores, and in hyphal tips. Also, calcofluor white staining of mature cell walls of virus-transfected Botrytis clones revealed numerous cell wall areas with increased amounts of chitin/glycoproteins. Our results indicate that some BVX aggregates are closely associated with the fungal cell wall and raise the question of whether mycoviruses may be able to move through the wall and therefore not be totally dependent on intracellular routes of transmission.
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Bohse, Megan L., and Jon P. Woods. "Surface Localization of the Yps3p Protein of Histoplasma capsulatum." Eukaryotic Cell 4, no. 4 (April 2005): 685–93. http://dx.doi.org/10.1128/ec.4.4.685-693.2005.
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ABSTRACT The YPS3 gene of Histoplasma capsulatum encodes a protein that is both resident in the cell wall and also released into the culture medium. This protein is produced only during the pathogenic yeast phase of infection and is also expressed differently in H. capsulatum strains that differ in virulence. We investigated the cellular localization of Yps3p. We demonstrated that the cell wall fraction of Yps3p was surface localized in restriction fragment length polymorphism class 2 strains. We also established that Yps3p released into the G217B culture supernatant binds to the surface of strains that do not naturally express the protein. This binding was saturable and occurred within 5 min of exposure and occurred similarly with live and heat-killed H. capsulatum. Flow cytometric analysis of H. capsulatum after enzymatic treatments was consistent with Yps3p binding to chitin, a carbohydrate polymer that is a component of fungal cell walls. Polysaccharide binding assays demonstrated that chitin but not cellulose binds to and extracts Yps3p from culture supernatants.
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Subramanyam, C., and S. L. N. Rao. "An enzymic method for the determination of chitin and chitosan in fungal cell walls." Journal of Biosciences 12, no. 2 (June 1987): 125–29. http://dx.doi.org/10.1007/bf02702963.
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Adams, David J. "Fungal cell wall chitinases and glucanases." Microbiology 150, no. 7 (July 1, 2004): 2029–35. http://dx.doi.org/10.1099/mic.0.26980-0.
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The fungal cell wall is a complex structure composed of chitin, glucans and other polymers, and there is evidence of extensive cross-linking between these components. The wall structure is highly dynamic, changing constantly during cell division, growth and morphogenesis. Hydrolytic enzymes, closely associated with the cell wall, have been implicated in the maintenance of wall plasticity and may have roles during branching and cross-linking of polymers. Most fungal cell wall hydrolases identified to date have chitinase or glucanase activity and this short article reviews the apparent functions of these enzymes in unicellular and filamentous fungi, and the mechanisms that regulate enzyme activity in yeasts.
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AHMAD LAFI, AHMAD SHEHAB, JACINTA SANTHANAM, TZAR MOHD NIZAM KHAITHIR, NUR FASHYA MUSA, and FAHRUL HUYOP. "Evaluation of Chitin as a Biomarker of Pathogenic Fungal Isolates." Sains Malaysiana 50, no. 3 (March 31, 2021): 735–42. http://dx.doi.org/10.17576/jsm-2021-5003-15.
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Chitin is a polysaccharide component of the inner cell wall of fungi that has been used to estimate fungal invasion in plant products. However, its detection in major pathogenic fungal species has not been investigated. The present study aimed to determine the chitin contents of pathogenic fungal species in order to evaluate its diagnostic potential as a biomarker for fungal infections. High performance liquid chromatography (HPLC) was used to measure chitin content. Pure chitin was acid hydrolyzed and the fluorescence of 9-fluorenylmethylchloroformate (FMOC-CI) derivatives of glucosamine produced were measured. The chitin contents of ten pathogenic fungal isolates were determined per mycelial dry weight. They varied from 18.61 (± 0.09) to 47.12 (± 0.50) μg/mg dry mycelial weight. Candida albicans and Cryptococcus neoformans exhibited the highest and lowest levels of chitin, respectively. Based upon relative amounts of chitin produced, three groups namely: high (Candida albicans, Cryptococcus gattii, Aspergillus niger and Penicilliumat 47.12, 46.98, 46.05, and 44.15 μg/mg respectively), medium (Rhizopus, Aspergillus fumigatus, Fusarium solani, andMucor at 36.61, 36.30, 35.03, and 34.84 μg/mg, respectively), and low (Candida tropicalis and Cryptococcus neoformans at 20.78 and 18.61 μg/mg, respectively), were identified. Chitin was not detectable in bacterial isolates used as controls. The chitin detection method offers a sensitive and specific tool for the quantification of chitin in pathogenic fungal isolates. The detection of chitin may be a useful assay for the diagnosis of fungal infections in clinical samples.
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Šrobárová, A., G. Kogan, L. Tamas, and E. Machová. "Protective activity of the fungal polysaccharides against fusariosis." Plant Protection Science 38, SI 2 - 6th Conf EFPP 2002 (December 31, 2017): 617–19. http://dx.doi.org/10.17221/10571-pps.
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Most of the experiments carried out in the area of plant protection have used chitin and chitosan obtained from the crustacean chitin which production is rather expensive. In our study we have applied the chitin-glucan complex prepared from the waste mycelia of filamentous fungi, from baker’s yeast. Five different polysaccharides have been used for the preparation of water-soluble compounds and the assay of their antifungal activity against plant pathogen Fusarium oxysporum. In the field experiments, application of the polysaccharides led to the diminished infestation as well as to significantly increased productivity of fresh weight of the plants (tomato). The results demonstrated that application of the polysaccharides led to increased production of cell wall and some outher and intermembrane-bound proteins. Although the nature of the observed proteins has not been yet established, it can be speculated that they represent some enzymes involved in the antiinfective defense mechanisms in plants.
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Złotko, Katarzyna, Adrian Wiater, Adam Waśko, Małgorzata Pleszczyńska, Roman Paduch, Jolanta Jaroszuk-Ściseł, and Andrzej Bieganowski. "A Report on Fungal (1→3)-α-d-glucans: Properties, Functions and Application." Molecules 24, no. 21 (November 2, 2019): 3972. http://dx.doi.org/10.3390/molecules24213972.
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The cell walls of fungi are composed of glycoproteins, chitin, and α- and β-glucans. Although there are many reports on β-glucans, α-glucan polysaccharides are not yet fully understood. This review characterizes the physicochemical properties and functions of (1→3)-α-d-glucans. Particular attention has been paid to practical application and the effect of glucans in various respects, taking into account unfavourable effects and potential use. The role of α-glucans in plant infection has been proven, and collected facts have confirmed the characteristics of Aspergillus fumigatus infection associated with the presence of glucan in fungal cell wall. Like β-glucans, there are now evidence that α-glucans can also stimulate the immune system. Moreover, α-d-glucans have the ability to induce mutanases and can thus decompose plaque.
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Sanz, María, Lucia Carrano, Cristina Jiménez, Gianpaolo Candiani, José A. Trilla, Angel Durán, and César Roncero. "Candida albicans strains deficient in CHS7, a key regulator of chitin synthase III, exhibit morphogenetic alterations and attenuated virulence." Microbiology 151, no. 8 (August 1, 2005): 2623–36. http://dx.doi.org/10.1099/mic.0.28093-0.
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Chitin is a structural polysaccharide present in most fungal cell walls, whose synthesis depends on a family of enzymic activities named chitin synthases (CSs). The specific role of each of them, as well as of their regulatory proteins, in cell morphogenesis and virulence is not well understood. Here, it is shown that most chitin synthesis in Candida albicans, one of the fungi most commonly isolated from opportunistic mycoses and infections, depends on CHS7. Thus, C. albicans chs7Δ null mutants showed reduced levels of chitin and CS activity, and were resistant to Calcofluor. Despite the sequence similarity and functional relationship with ScChs7p, CaChs7p was unable to restore CSIII activity in a Saccharomyces cerevisiae chs7Δ null mutant, because it was unable to direct ScChs3p export from the endoplasmic reticulum. C. albicans chs7Δ null mutants did not show any defect in growth rate, but yeast cells displayed minor morphogenetic defects affecting septum formation, and showed an increased tendency to form filaments. CaChs7p was not required for germ-tube emission, and null mutant strains underwent the dimorphic transition correctly. However, colony morphology appeared distinctively affected. chs7Δ hyphae were very curved and had irregular lateral walls, resulting in very compact colonies that seemed unable to spread out radially on the surface, unlike the wild-type. This growth pattern may be associated with the reduced virulence and high clearance rate observed when the chs7Δ strain was used in a murine model of infection. Therefore, CaChs7p is required for normal hyphal morphogenesis, suggesting that in C. albicans CSIII plays an important role in maintaining cell wall integrity, being essential when invading surrounding tissues.
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Donzelli, Bruno Giuliano Garisto, and Gary E. Harman. "Interaction of Ammonium, Glucose, and Chitin Regulates the Expression of Cell Wall-Degrading Enzymes inTrichoderma atroviride Strain P1." Applied and Environmental Microbiology 67, no. 12 (December 1, 2001): 5643–47. http://dx.doi.org/10.1128/aem.67.12.5643-5647.2001.
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ABSTRACT Chitinolytic and glucanolytic fungal cell wall-degrading enzymes have been suggested to be primary determinants of biocontrol byTrichoderma spp. We examined the effects of ammonium, glucose, chitin, and chito-oligomers on transcription of specific genes and secretion of fungal cell wall-degrading enzymes. The genesech42, nag1, andgluc78 were examined, as were the enzymes they encode (endochitinase CHIT42, N-acetylhexosaminidase CHIT73, and glucan exo-1,3-β-glucanase GLUC78, respectively).gluc78 could be induced by nitrogen starvation alone, while both ech42 and nag1 required nitrogen starvation and the presence of chitin for induction. Starvation for both ammonium and glucose resulted in very early expression and secretion of all cell wall-degrading enzymes examined. In the presence of low levels of ammonium (10 mM), both chito-oligomers and chitin triggered CHIT42 and CHIT40 (chitobiosidase) production. CHIT73 secretion occurred in the presence ofN-acetylglucosamine and chito-oligomers, while chitin was less effective. The presence of different chito-oligomers resulted in secretion of specific N-acetylhexosaminidases, of which CHIT73 is one. Our results indicate that the expression and secretion of cell wall-degrading enzymes is nitrogen repressed, that effects of carbon and nitrogen nutrition are interactive, and that especially for chitinolytic enzymes, the inductive effect of chitin is altered by the level of ammonium or glucose in the medium.
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Curry, Kenneth J., Maritza Abril, Jana B. Avant, and Barbara J. Smith. "Strawberry Anthracnose: Histopathology of Colletotrichum acutatum and C. fragariae." Phytopathology® 92, no. 10 (October 2002): 1055–63. http://dx.doi.org/10.1094/phyto.2002.92.10.1055.
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Ontogeny of the invasion process by Colletotrichum acutatum and C. fragariae was studied on petioles and stolons of the strawberry cultivar Chandler using light and electron microscopy. The invasion of host tissue by each fungal species was similar; however, each invasion event occurred more rapidly with C. fragariae than with C. acutatum. Following cuticular penetration via an appressorium, subsequent steps of invasion involved hyphal growth within the cuticle and within the cell walls of epidermal, subepidermal, and subtending cells. Both species of fungi began invasion with a brief biotrophic phase before entering an extended necrotrophic phase. Acervuli formed once the cortical tissue had been moderately disrupted and began with the development of a stroma just beneath the outer periclinal epidermal walls. Acervuli erupted through the cuticle and released conidia. Invasion of the vascular tissue typically occurred after acervulus maturation and remained minimal. Chitin distribution in walls of C. fragariae was visualized with gold-labeled wheat germ agglutinin. The outer layer of bilayered walls of conidia, germ tubes, and appressoria contained less chitin than unilayered hyphae in planta.
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Suchodolski, Jakub, Daria Derkacz, Jakub Muraszko, Jarosław J. Panek, Aneta Jezierska, Marcin Łukaszewicz, and Anna Krasowska. "Fluconazole and Lipopeptide Surfactin Interplay During Candida albicans Plasma Membrane and Cell Wall Remodeling Increases Fungal Immune System Exposure." Pharmaceutics 12, no. 4 (April 1, 2020): 314. http://dx.doi.org/10.3390/pharmaceutics12040314.
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Recognizing the β-glucan component of the Candida albicans cell wall is a necessary step involved in host immune system recognition. Compounds that result in exposed β-glucan recognizable to the immune system could be valuable antifungal drugs. Antifungal development is especially important because fungi are becoming increasingly drug resistant. This study demonstrates that lipopeptide, surfactin, unmasks β-glucan when the C. albicans cells lack ergosterol. This observation also holds when ergosterol is depleted by fluconazole. Surfactin does not enhance the effects of local chitin accumulation in the presence of fluconazole. Expression of the CHS3 gene, encoding a gene product resulting in 80% of cellular chitin, is downregulated. C. albicans exposure to fluconazole changes the composition and structure of the fungal plasma membrane. At the same time, the fungal cell wall is altered and remodeled in a way that makes the fungi susceptible to surfactin. In silico studies show that surfactin can form a complex with β-glucan. Surfactin forms a less stable complex with chitin, which in combination with lowering chitin synthesis, could be a second anti-fungal mechanism of action of this lipopeptide.
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Baker, Lorina G., Charles A. Specht, Maureen J. Donlin, and Jennifer K. Lodge. "Chitosan, the Deacetylated Form of Chitin, Is Necessary for Cell Wall Integrity in Cryptococcus neoformans." Eukaryotic Cell 6, no. 5 (March 30, 2007): 855–67. http://dx.doi.org/10.1128/ec.00399-06.
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ABSTRACT Cryptococcus neoformans is an opportunistic fungal pathogen that causes cryptococcal meningoencephalitis, particularly in immunocompromised patients. The fungal cell wall is an excellent target for antifungal therapies as it is an essential organelle that provides cell structure and integrity, it is needed for the localization or attachment of known virulence factors, including the polysaccharide capsule, melanin, and phospholipase, and it is critical for host-pathogen interactions. In C. neoformans, chitosan produced by the enzymatic removal of acetyl groups from nascent chitin polymers has been implicated as an important component of the vegetative cell wall. In this study, we identify four putative chitin/polysaccharide deacetylases in C. neoformans. We have demonstrated that three of these deacetylases, Cda1, Cda2, and Cda3, can account for all of the chitosan produced during vegetative growth in culture, but the function for one, Fpd1, remains undetermined. The data suggest a model for chitosan production in vegetatively growing C. neoformans where the three chitin deacetylases convert chitin generated by the chitin synthase Chs3 into chitosan. Utilizing a collection of chitin/polysaccharide deacetylase deletion strains, we determined that during vegetative growth, chitosan helps to maintain cell integrity and aids in bud separation. Additionally, chitosan is necessary for maintaining normal capsule width and the lack of chitosan results in a “leaky melanin” phenotype. Our analysis indicates that chitin deacetylases and the chitosan made by them may prove to be excellent antifungal targets.
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Rapaka, Rekha R., David M. Ricks, John F. Alcorn, Kong Chen, Shabaana A. Khader, Mingquan Zheng, Scott Plevy, Eva Bengtén, and Jay K. Kolls. "Conserved natural IgM antibodies mediate innate and adaptive immunity against the opportunistic fungus Pneumocystis murina." Journal of Experimental Medicine 207, no. 13 (December 13, 2010): 2907–19. http://dx.doi.org/10.1084/jem.20100034.
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Host defense against opportunistic fungi requires coordination between innate and adaptive immunity for resolution of infection. Antibodies generated in mice vaccinated with the fungus Pneumocystis prevent growth of Pneumocystis organisms within the lungs, but the mechanisms whereby antibodies enhance antifungal host defense are poorly defined. Nearly all species of fungi contain the conserved carbohydrates β-glucan and chitin within their cell walls, which may be targets of innate and adaptive immunity. In this study, we show that natural IgM antibodies targeting these fungal cell wall carbohydrates are conserved across many species, including fish and mammals. Natural antibodies bind fungal organisms and enhance host defense against Pneumocystis in early stages of infection. IgM antibodies influence recognition of fungal antigen by dendritic cells, increasing their migration to draining pulmonary lymph nodes. IgM antibodies are required for adaptive T helper type 2 (Th2) and Th17 cell differentiation and guide B cell isotype class-switch recombination during host defense against Pneumocystis. These experiments suggest a novel role for the IgM isotype in shaping the earliest steps in recognition and clearance of this fungus. We outline a mechanism whereby serum IgM, containing ancient specificities against conserved fungal antigens, bridges innate and adaptive immunity against fungal organisms.
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Richards, Thomas A., Guy Leonard, Frédéric Mahé, Javier del Campo, Sarah Romac, Meredith D. M. Jones, Finlay Maguire, et al. "Molecular diversity and distribution of marine fungi across 130 European environmental samples." Proceedings of the Royal Society B: Biological Sciences 282, no. 1819 (November 22, 2015): 20152243. http://dx.doi.org/10.1098/rspb.2015.2243.
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Environmental DNA and culture-based analyses have suggested that fungi are present in low diversity and in low abundance in many marine environments, especially in the upper water column. Here, we use a dual approach involving high-throughput diversity tag sequencing from both DNA and RNA templates and fluorescent cell counts to evaluate the diversity and relative abundance of fungi across marine samples taken from six European near-shore sites. We removed very rare fungal operational taxonomic units (OTUs) selecting only OTUs recovered from multiple samples for a detailed analysis. This approach identified a set of 71 fungal ‘OTU clusters' that account for 66% of all the sequences assigned to the Fungi. Phylogenetic analyses demonstrated that this diversity includes a significant number of chytrid-like lineages that had not been previously described, indicating that the marine environment encompasses a number of zoosporic fungi that are new to taxonomic inventories. Using the sequence datasets, we identified cases where fungal OTUs were sampled across multiple geographical sites and between different sampling depths. This was especially clear in one relatively abundant and diverse phylogroup tentatively named Novel Chytrid-Like-Clade 1 (NCLC1). For comparison, a subset of the water column samples was also investigated using fluorescent microscopy to examine the abundance of eukaryotes with chitin cell walls. Comparisons of relative abundance of RNA-derived fungal tag sequences and chitin cell-wall counts demonstrate that fungi constitute a low fraction of the eukaryotic community in these water column samples. Taken together, these results demonstrate the phylogenetic position and environmental distribution of 71 lineages, improving our understanding of the diversity and abundance of fungi in marine environments.
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Kulikov, S. N., Yu A. Tyurin, D. A. Dolbin, R. S. Fassakhov, S. N. Kulikov, Iu A. Turin, D. A. Dolbin, and R. S. Fassakhov. "Chitin and chitinases in allergic reactions." Russian Journal of Allergy 6, no. 1 (March 15, 2009): 18–23. http://dx.doi.org/10.36691/rja1015.
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Chitin - the structural component of fungal cell wall, arthropodal exoskeleton, microfilarial sheat and egg of helminths. Allergens of this organisms cause allergic diseases. The potential role of chitin in allergic reactions has been discussed. Other studies have suggested that chitin preparations may skew immunity away from T-helper-2-mediated allergic responses. Chitinases, enzymes that can degrade chitin polymer, and chitinase-like proteins might also play an important role in allergic disease pathogenesis.
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Itoh, Takafumi, Takao Hibi, Yutaka Fujii, Ikumi Sugimoto, Akihiro Fujiwara, Fumiko Suzuki, Yukimoto Iwasaki, Jin-Kyung Kim, Akira Taketo, and Hisashi Kimoto. "Cooperative Degradation of Chitin by Extracellular and Cell Surface-Expressed Chitinases from Paenibacillus sp. Strain FPU-7." Applied and Environmental Microbiology 79, no. 23 (September 27, 2013): 7482–90. http://dx.doi.org/10.1128/aem.02483-13.
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ABSTRACTChitin, a major component of fungal cell walls and invertebrate cuticles, is an exceedingly abundant polysaccharide, ranking next to cellulose. Industrial demand for chitin and its degradation products as raw materials for fine chemical products is increasing. A bacterium with high chitin-decomposing activity,Paenibacillussp. strain FPU-7, was isolated from soil by using a screening medium containing α-chitin powder. Although FPU-7 secreted several extracellular chitinases and thoroughly digested the powder, the extracellular fluid alone broke them down incompletely. Based on expression cloning and phylogenetic analysis, at least seven family 18 chitinase genes were found in the FPU-7 genome. Interestingly, the product of only one gene (chiW) was identified as possessing three S-layer homology (SLH) domains and two glycosyl hydrolase family 18 catalytic domains. Since SLH domains are known to function as anchors to the Gram-positive bacterial cell surface, ChiW was suggested to be a novel multimodular surface-expressed enzyme and to play an important role in the complete degradation of chitin. Indeed, the ChiW protein was localized on the cell surface. Each of the seven chitinase genes (chiAtochiFandchiW) was cloned and expressed inEscherichia colicells for biochemical characterization of their products. In particular, ChiE and ChiW showed high activity for insoluble chitin. The high chitinolytic activity of strain FPU-7 and the chitinases may be useful for environmentally friendly processing of chitin in the manufacture of food and/or medicine.
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Takeshita, Norio, Akinori Ohta, and Hiroyuki Horiuchi. "CsmA, a Class V Chitin Synthase with a Myosin Motor-like Domain, Is Localized through Direct Interaction with the Actin Cytoskeleton inAspergillus nidulans." Molecular Biology of the Cell 16, no. 4 (April 2005): 1961–70. http://dx.doi.org/10.1091/mbc.e04-09-0761.
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One of the essential features of fungal morphogenesis is the polarized synthesis of cell wall components such as chitin. The actin cytoskeleton provides the structural basis for cell polarity in Aspergillus nidulans, as well as in most other eukaryotes. A class V chitin synthase, CsmA, which contains a myosin motor-like domain (MMD), is conserved among most filamentous fungi. The ΔcsmA null mutant showed remarkable abnormalities with respect to cell wall integrity and the establishment of polarity. In this study, we demonstrated that CsmA tagged with 9× HA epitopes localized near actin structures at the hyphal tips and septation sites and that its MMD was able to bind to actin. Characterization of mutants bearing a point mutation or deletion in the MMD suggests that the interaction between the MMD and actin is not only necessary for the proper localization of CsmA, but also for CsmA function. Thus, the finding of a direct interaction between the chitin synthase and the actin cytoskeleton provides new insight into the mechanisms of polarized cell wall synthesis and fungal morphogenesis.
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Valasques Junior, Gildomar Lima, Pâmala Évelin Pires Cedro, Tátilla Putumujú Santana Mendes, Alana Caise dos Anjos Miranda, Aldo Barbosa Côrtes Filho, Danyo Maia Lima, Maíra Mercês Barreto, Antônio Anderson Freitas Pinheiro, and Lucas Miranda Marques. "Characterization and biological activities of polysaccharides extracted from the filamentous fungal cell wall: an updated literature review." Research, Society and Development 9, no. 11 (November 28, 2020): e62191110217. http://dx.doi.org/10.33448/rsd-v9i11.10217.
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Filamentous fungi are eukaryotic organisms with several industrial and pharmaceutical applications. Polysaccharides are the principal components of cell walls from Fungi and other organisms like diatoms, and have been reported in the industrial and medical fields as products with a huge number of different biological activities and applications. The objectives of this narrative review were to assess the characterization methods and and biological activities of polysaccharides extracted from the filamentous fungal cell wall. Glucans, chitin and galactomannans are the most common polysaccharide often found in the cell walls of fungi. These polysaccharides can contain different glycosidic linkage either an α or β-configuration and at various positions, such as (1-3,1-4, 1-6), as well as several molecular sizes. This leads to an almost limitless diversity in their structure and biological activity. There are many methods for polysaccharides characterization, among them; the methods commonly used involve Infrared Spectrometry (FT-IR), Nuclear Magnetic Resonance Spectroscopy (MRS), and gas chromatography-mass spectrometry (CG-MS). Typically, cell wall polysaccharides from filamentous fungi have been shown to possess complex, important and multifaceted biological activities including mainly antioxidant, anti-inflammatory, immunomodulatory, antinociceptive, antitumor and hypoglycemic activities. Due to the large number of filamentous fungi genus and species capable of producing useful polysaccharides, perform scientific researches, and produce novel scientific knowledge and information are particularly interesting in order to identify polysaccharides with potential biological activity and that can be used for medicinal purposes.
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Banks, Isaac R., Charles A. Specht, Maureen J. Donlin, Kimberly J. Gerik, Stuart M. Levitz, and Jennifer K. Lodge. "A Chitin Synthase and Its Regulator Protein Are Critical for Chitosan Production and Growth of the Fungal Pathogen Cryptococcus neoformans." Eukaryotic Cell 4, no. 11 (November 2005): 1902–12. http://dx.doi.org/10.1128/ec.4.11.1902-1912.2005.
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ABSTRACT Chitin is an essential component of the cell wall of many fungi. Chitin also can be enzymatically deacetylated to chitosan, a more flexible and soluble polymer. Cryptococcus neoformans is a fungal pathogen that causes cryptococcal meningoencephalitis, particularly in immunocompromised patients. In this work, we show that both chitin and chitosan are present in the cell wall of vegetatively growing C. neoformans yeast cells and that the levels of both rise dramatically as cells grow to higher density in liquid culture. C. neoformans has eight putative chitin synthases, and strains with any one chitin synthase deleted are viable at 30°C. In addition, C. neoformans genes encode three putative regulator proteins, which are homologs of Saccharomyces cerevisiae Skt5p. None of these three is essential for viability. However, one of the chitin synthases (Chs3) and one of the regulators (Csr2) are important for growth. Cells with deletions in either CHS3 or CSR2 have several shared phenotypes, including sensitivity to growth at 37°C. The similarity of their phenotypes also suggests that Csr2 specifically regulates chitin synthesis by Chs3. Lastly, both chs3Δ and the csr2Δ mutants are defective in chitosan production, predicting that Chs3-Csr2 complex with chitin deacetylases for conversion of chitin to chitosan. These data suggest that chitin synthesis could be an excellent antifungal target.
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Vogt, Marian Samuel, Gesa Felicitas Schmitz, Daniel Varón Silva, Hans-Ulrich Mösch, and Lars-Oliver Essen. "Structural base for the transfer of GPI-anchored glycoproteins into fungal cell walls." Proceedings of the National Academy of Sciences 117, no. 36 (August 24, 2020): 22061–67. http://dx.doi.org/10.1073/pnas.2010661117.
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The correct distribution and trafficking of proteins are essential for all organisms. Eukaryotes evolved a sophisticated trafficking system which allows proteins to reach their destination within highly compartmentalized cells. One eukaryotic hallmark is the attachment of a glycosylphosphatidylinositol (GPI) anchor to C-terminal ω-peptides, which are used as a zip code to guide a subset of membrane-anchored proteins through the secretory pathway to the plasma membrane. In fungi, the final destination of many GPI-anchored proteins is their outermost compartment, the cell wall. Enzymes of the Dfg5 subfamily catalyze the essential transfer of GPI-anchored substrates from the plasma membrane to the cell wall and discriminate between plasma membrane-resident GPI-anchored proteins and those transferred to the cell wall (GPI-CWP). We solved the structure of Dfg5 from a filamentous fungus and used in crystallo glycan fragment screening to reassemble the GPI-core glycan in a U-shaped conformation within its binding pocket. The resulting model of the membrane-bound Dfg5•GPI-CWP complex is validated by molecular dynamics (MD) simulations and in vivo mutants in yeast. The latter show that impaired transfer of GPI-CWPs causes distorted cell-wall integrity as indicated by increased chitin levels. The structure of a Dfg5•β1,3-glycoside complex predicts transfer of GPI-CWP toward the nonreducing ends of acceptor glycans in the cell wall. In addition to our molecular model for Dfg5-mediated transglycosylation, we provide a rationale for how GPI-CWPs are specifically sorted toward the cell wall by using GPI-core glycan modifications.
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Wiese, Gertrud, Doris Hugo-Wissemann, and Hans J. Grambow. "An Improved Procedure for the Quantitative Estimation of the Rust Fungus in Infected Plant Tissue." Zeitschrift für Naturforschung C 41, no. 11-12 (December 1, 1986): 1127–30. http://dx.doi.org/10.1515/znc-1986-11-1231.
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Abstract A quantitative estimation of the rust fungus in infected wheat leaves was possible following enzymatic hydrolysis of the chitin and colorimetric determination of the N-acetyl-glucosamine released. The apparently complex cell wall structure of the fungal structures made it necessary, however, to use an enzyme mixture of chitinase and cellulase in order to make accessible the chitin of the cell wall for digestion by chitinase. In applying this method the measurement is not appreciably influenced by already formed uredio-spores as would otherwise be the case were the chitin to be determined on the basis of glucosamine after chemical hydrolysis.
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Ye, Wenxiu, Shintaro Munemasa, Tomonori Shinya, Wei Wu, Tao Ma, Jiang Lu, Toshinori Kinoshita, Hanae Kaku, Naoto Shibuya, and Yoshiyuki Murata. "Stomatal immunity against fungal invasion comprises not only chitin-induced stomatal closure but also chitosan-induced guard cell death." Proceedings of the National Academy of Sciences 117, no. 34 (August 10, 2020): 20932–42. http://dx.doi.org/10.1073/pnas.1922319117.
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Many pathogenic fungi exploit stomata as invasion routes, causing destructive diseases of major cereal crops. Intensive interaction is expected to occur between guard cells and fungi. In the present study, we took advantage of well-conserved molecules derived from the fungal cell wall, chitin oligosaccharide (CTOS), and chitosan oligosaccharide (CSOS) to study how guard cells respond to fungal invasion. InArabidopsis, CTOS induced stomatal closure through a signaling mediated by its receptor CERK1, Ca2+, and a major S-type anion channel, SLAC1. CSOS, which is converted from CTOS by chitin deacetylases from invading fungi, did not induce stomatal closure, suggesting that this conversion is a fungal strategy to evade stomatal closure. At higher concentrations, CSOS but not CTOS induced guard cell death in a manner dependent on Ca2+but not CERK1. These results suggest that stomatal immunity against fungal invasion comprises not only CTOS-induced stomatal closure but also CSOS-induced guard cell death.