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1.
A wall with integrity: surveillance and maintenance of the plant cell wall under stress.
Rui, Y, Dinneny, JR
The New phytologist. 2020;(4):1428-1439
Abstract
The structural and functional integrity of the cell wall needs to be constantly monitored and fine-tuned to allow for growth while preventing mechanical failure. Many studies have advanced our understanding of the pathways that contribute to cell wall biosynthesis and how these pathways are regulated by external and internal cues. Recent evidence also supports a model in which certain aspects of the wall itself may act as growth-regulating signals. Molecular components of the signaling pathways that sense and maintain cell wall integrity have begun to be revealed, including signals arising in the wall, sensors that detect changes at the cell surface, and downstream signal transduction modules. Abiotic and biotic stress conditions provide new contexts for the study of cell wall integrity, but the nature and consequences of wall disruptions due to various stressors require further investigation. A deeper understanding of cell wall signaling will provide insights into the growth regulatory mechanisms that allow plants to survive in changing environments.
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2.
How much water can wood cell walls hold? A triangulation approach to determine the maximum cell wall moisture content.
Thybring, EE, Digaitis, R, Nord-Larsen, T, Beck, G, Fredriksson, M
PloS one. 2020;(8):e0238319
Abstract
Wood is a porous, hygroscopic material with engineering properties that depend significantly on the amount of water (moisture) in the material. Water in wood can be present in both cell walls and the porous void-structure of the material, but it is only water in cell walls that affects the engineering properties. An important characteristic of wood is therefore the capacity for water of its solid cell walls, i.e. the maximum cell wall moisture content. However, this quantity is not straight-forward to determine experimentally, and the measured value may depend on the experimental technique used. In this study, we used a triangulation approach to determine the maximum cell wall moisture content by using three experimental techniques based on different measurement principles: low-field nuclear magnetic resonance (LFNMR) relaxometry, differential scanning calorimetry (DSC), and the solute exclusion technique (SET). The LFNMR data were furthermore analysed by two varieties of exponential decay analysis. These techniques were used to determine the maximum cell wall moisture contents of nine different wood species, covering a wide range of densities. The results from statistical analysis showed that LFNMR yielded lower cell wall moisture contents than DSC and SET, which were fairly similar. Both of the latter methods include factors that could either under-estimate or over-estimate the measured cell wall moisture content. Because of this and the fact that the DSC and SET methods are based on different measurement principles, it is likely that they provide realistic values of the cell wall moisture content in the water-saturated state.
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3.
Synthetic Oligosaccharides Mimicking Fungal Cell Wall Polysaccharides.
Krylov, VB, Nifantiev, NE
Current topics in microbiology and immunology. 2020;:1-16
Abstract
The cell wall of pathogenic fungi is highly important for the development of fungal infections and is the first cellular component to interact with the host immune system. The fungal cell wall is mainly built up of different polysaccharides representing ligands for pattern recognition receptors (PRRs) on immune cells and antibodies. Purified fungal polysaccharides are not easily available; in addition, they are structurally heterogenic and have wide molecular weight distribution that limits the possibility to use natural polysaccharides to assess the structure of their active determinants. The synthetic oligosaccharides of definite structure representing distinct polysaccharide fragments are indispensable tools for a variety of biological investigations and represent an advantageous alternative to natural polysaccharides. The attachment of a spacer group to these oligosaccharides permits their efficient transformation into immunogenic glycoconjugates as well as their immobilization on plates or microbeads. Herein, we summarize current information on synthetic availability of the variety of oligosaccharides related to main types of fungal cell wall components: galactomannan, α- and β-mannan, α- and β-(1 → 3)-glucan, chitin, chitosan, and others. These data are supplemented with published results of biochemical and immunological applications of synthetic oligosaccharides as molecular probes especially as the components of thematic glycoarrays suitable for characterization of anti-polysaccharide antibodies and cellular lectins or PRRs.
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4.
Dietary fiber polysaccharides of amaranth, buckwheat and quinoa grains: A review of chemical structure, biological functions and food uses.
Zhu, F
Carbohydrate polymers. 2020;:116819
Abstract
Seeds of amaranth (Amaranthus spp.), buckwheat (Fagopyrum esculentum and F. tataricum) and quinoa (Chenopodium quinoa) become popular foods due to their attractive health effects. Cell wall polysaccharides are the major components of dietary fiber and significantly contribute to diverse health effects of the grains. This review summarizes chemical and physical structure, biological functions and food uses of the cell wall polysaccharides and fractions as fiber components from the 3 pseudocereals. The properties and uses of the polysaccharides and fractions are compared with those of fiber polysaccharides from common sources such as fruits and vegetables. Overall, the fiber polysaccharide composition of the pseudocereals is more similar to that of fruits and vegetables than to that of cereals. The fiber polysaccharides showed a range of biological functions such as antioxidation, anticancer and immunomodulation. The fiber polysaccharides of amaranth, buckwheat and quinoa have potential to be used in formulations of functional foods.
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5.
Changes of cell wall components during embryogenesis of Castanea mollissima.
Du, B, Zhang, Q, Cao, Q, Xing, Y, Qin, L, Fang, K
Journal of plant research. 2020;(2):257-270
Abstract
The Chinese chestnut (Castanea mollissima Blume) 'Huaihuang' was chosen as the experimental material to observe embryogenesis and the dynamic changes of cell wall components during this process. Various developmental stages of embryos, including globular embryos, heart embryos, torpedo embryos and cotyledon embryos, were observed. The results showed that during embryogenesis, cellulose increased, and callose rapidly degraded. In the cell walls of developing embryos, pectic homogalacturonan (HG), especially low-esterified HG, was abundant, suggesting rapid synthesis and de-methyl-esterification of HG. Extensin and galactan increased with the development of the embryos. In contrast, the arabinan epitopes decreased in developing embryos but were more abundant than galactan epitopes at all stages. Xylan epitopes showed explicit boundaries between the outer epidermal wall and the rest of the inner tissues, and the fluorescence intensity of the outer epidermal wall was significantly higher than that of the inner tissues. Furthermore, the results indicated that the outer epidermal wall contained high amounts of cellulose, HG pectin and hemicellulose, especially arabinan and xylan. These results suggested the presence of rapid pectin metabolism, cellulose synthesis, rapid degradation of callose, different distributive patterns and dynamic changes of hemicellulose (galactan, arabinan and xylan) and extensin during embryogenesis. Various cell wall components exist in different tissues of the embryo, and dynamic changes in cell wall components are involved in the embryonic development process.
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6.
Cell Wall-Modifying Antifungal Drugs.
Perlin, DS
Current topics in microbiology and immunology. 2020;:255-275
Abstract
Antifungal therapy is a critical component of patient management for invasive fungal diseases. Yet, therapeutic choices are limited as only a few drug classes are available to treat systemic disease, and some infecting strains are resistant to one or more drug classes. The ideal antifungal inhibits a fungal-specific essential target not present in human cells to avoid off-target toxicities. The fungal cell wall is an ideal drug target because its integrity is critical to cell survival and a majority of biosynthetic enzymes and wall components is unique to fungi. Among currently approved antifungal agents and those in clinical development, drugs targeting biosynthetic enzymes of the cell wall show safe and efficacious antifungal properties, which validates the cell wall as a target. The echinocandins, which inhibit β-1,3-glucan synthase, are recommended as first-line therapy for Candida infections. Newer cell wall-active drugs in clinical development encompass next-generation glucan synthase inhibitors including a novel echinocandin and an enfumafungin, an inhibitor of Gwt1, a key component of GPI anchor protein biosynthesis, and a classic inhibitor of chitin biosynthesis. As the cell wall is rich in potential drug discovery targets, it is primed to help deliver the next generation of antifungal drugs.
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7.
Breakpoint: Cell Wall and Glycoproteins and their Crucial Role in the Phytopathogenic Fungi Infection.
Plaza, V, Silva-Moreno, E, Castillo, L
Current protein & peptide science. 2020;(3):227-244
Abstract
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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8.
Cell wall polysaccharides from pathogenic fungi for diagnosis of fungal infectious disease.
Ahamefula Osibe, D, Lei, S, Wang, B, Jin, C, Fang, W
Mycoses. 2020;(7):644-652
Abstract
Invasive fungal diseases are associated with significant morbidity and mortality, particularly in immunocompromised individuals. Early and accurate diagnosis is crucial for effective treatment. Despite traditional methods such as microbiological culture, histopathology, radiology and direct microscopy are available, antigen/antibody-based diagnostics are emerging for diagnosis of invasive fungal infections (IFI). Fungal cell wall is a unique structure composed of polysaccharides that are well correlated with fungal burden during fungal infections. Based on this feature, cell wall polysaccharides have been explored as antigens in IFIs diagnostics such as the galactomannan assay, mannan test, β-glucan assay and cryptococcal CrAg test. Herein, we provide an overview on the cell wall polysaccharides from three opportunistic pathogens: Aspergillus fumigatus, Candida albicans and Cryptococcus neoformans, and their applications for IFIs diagnosis. The clinical outcome of newly developed cell wall polysaccharides-based diagnostics is also discussed.
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9.
Scedosporium Cell Wall: From Carbohydrate-Containing Structures to Host-Pathogen Interactions.
Rollin-Pinheiro, R, Xisto, MIDDS, Rochetti, VP, Barreto-Bergter, E
Mycopathologia. 2020;(6):931-946
Abstract
Scedosporium species are filamentous fungi usually found in sewage and soil from human-impacted areas. They cause a wide range of diseases in humans, from superficial infections, such as mycetoma, to invasive and disseminated cases, especially associated in immunocompromised patients. Scedosporium species are also related to lung colonization in individuals presenting cystic fibrosis and are considered one of the most frequent fungal pathogens associated to this pathology. Scedosporium cell wall contains glycosylated molecules involved in important biological events related to virulence and pathogenicity and represents a significant source of antigens. Polysaccharides, peptidopolysaccharides, O-linked oligosaccharides and glycosphingolipids have been identified on the Scedosporium surface. Their primary structures were determined based on a combination of techniques including gas chromatography, ESI-MS, and 1H and 13C nuclear magnetic resonance. Peptidorhamnnomannans are common cell wall components among Scedosporium species. Comparing different species, minor structural differences in the carbohydrate portions were detected which could be useful to understand variations in virulence observed among the species. N- and O-linked peptidorhamnomannans are major pathogen-associated molecular patterns and, along with α-glucans, play important roles in triggering host innate immunity. Glycosphingolipids, such as glucosylceramides, have highly conserved structures in Scedosporium species and are crucial for fungal growth and virulence. The present review presents current knowledge on structural and functional aspects of Scedosporium glycoconjugates that are relevant for understanding pathogenicity mechanisms and could contribute to the design of new agents capable of inhibiting growth and differentiation of Scedosporium species. Other cell components such as melanin and ectophosphatases will be also included.
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10.
Banana MaBZR1/2 associate with MaMPK14 to modulate cell wall modifying genes during fruit ripening.
Shan, W, Guo, YF, Wei, W, Chen, JY, Lu, WJ, Yuan, DB, Su, XG, Kuang, JF
Plant cell reports. 2020;(1):35-46
Abstract
Banana MaBZR1/2 interact with MaMPK14 to enhance the transcriptional inhibition of cell wall modifying genes including MaEXP2, MaPL2 and MaXET5. Fruit ripening and softening, the major attributes to perishability in fleshy fruits, are modulated by various plant hormones and gene expression. Banana MaBZR1/2, the central transcription factors of brassinosteroid (BR) signaling, mediate fruit ripening through regulation of ethylene biosynthesis, but their possible roles in fruit softening as well as the underlying mechanisms remain to be determined. In this work, we found that MaBZR1/2 directly bound to and repressed the promoters of several cell wall modifying genes such as MaEXP2, MaPL2 and MaXET5, whose transcripts were elevated concomitant with fruit ripening. Moreover, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays indicated that MaBZR1/2 physically interacted with a mitogen-activated protein kinase MaMPK14, and this interaction strengthened the MaBZR1/2-mediated transcriptional inhibitory abilities. Collectively, our study provides insight into the mechanism of MaBZR1/2 contributing to fruit ripening and softening, which may have potential for banana molecular improvement.