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Paulo A.s. Mourão - One of the best experts on this subject based on the ideXlab platform.
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Is the antithrombotic effect of sulfated Galactans independent of serpin
Journal of thrombosis and haemostasis : JTH, 2014Co-Authors: Ana Luíza Gomes Quinderé, Gustavo R.c. Santos, Stephan-nicollas M. C. G. Oliveira, Bianca F. Glauser, Bruno Pedrosa Fontes, Ismael Nilo Lino De Queiroz, Norma Maria Barros Benevides, Vitor H. Pomin, Paulo A.s. MourãoAbstract:Summary Background Sulfated Galactans are polysaccharides with heterogeneous structures that frequently show anticoagulant activity. Their anticoagulant mechanisms are complex and distinct from those observed for heparin. Sulfated Galactans act through a combination of effects involving serpin-dependent and serpin-independent mechanisms. Interestingly, these polymers can also induce blood coagulation due to activation of factor XII (FXII). Objectives The structure of a complex sulfated Galactan from the red alga Acanthophora muscoides was characterized by solution nuclear magnetic resonance. This polysaccharide and another previously characterized algal sulfated Galactan from Botryocladia occidentalis were each used in in vitro and in vivo anticoagulant and antithrombotic assays to understand the possible structural determinants of their functional effects. Results and Conclusions The serpin-dependent anticoagulant effects and FXII-related procoagulant effects of the sulfated Galactans decreased in parallel with the molecular size. The serpin-independent anticoagulation also correlated with the chemical structure of the sulfated Galactans. The sulfated Galactan from A. muscoides, which showed mostly serpin-independent anticoagulant activity and reduced activation of FXII, drastically reduced arterial thrombus formation. However, the sulfated Galactans produced opposite effects on venous thrombosis; this difference appears to result from the tenuous balance between the various effects on coagulation, including serpin-dependent and serpin-independent anticoagulation and FXIIa-dependent procoagulation. This study of novel sulfated polysaccharides with distinct effects on coagulation and thrombosis helps to establish the minimal structural-function relationship required for the development of antithrombotic drugs.
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Sulfated α-L-Galactans from the sea urchin ovary: Selective 6-desulfation as eggs are spawned
Glycobiology, 2010Co-Authors: Leonardo Paes Cinelli, Ana Paula Valente, Leonardo R Andrade, Paulo A.s. MourãoAbstract:The sea urchin eggs are surrounded by a jelly coat, which contains sulfated polysaccharides with unique structures. These molecules are responsible for inducing the speciesspecific acrosome reaction, an obligatory event for the binding of sperm and fusion with the egg. The mechanism of biosynthesis of these sulfated polysaccharides is virtually unknown. The egg jelly of the sea urchin Echinometra lucunter contains a simple 2-sulfated, 3-linked α-LGalactan. Here, we pulse labeled the sea urchin ovary in vitro with 35 S-sulfate to follow the biosynthesis of the sulfated α-L-Galactan. We found that the ovary contains a 2,6-disulfated, 3-linked α-L-Galactan, which incorporates 35 S-sulfate more avidly than the 2-sulfated isoform. The 2,6-disulfated α-L-Galactan was purified by anion exchange chromatography, analyzed by electrophoresis and characterized by 1D and 2D nuclear magnetic resonance spectra. We also investigated the location of the sulfated polysaccharides on the oocytes using histochemical procedures. The stain revealed high amounts of sulfated polysaccharide in mature oocytes and accessory cells. The amount of intracellular sulfated polysaccharides decreased as oocytes are spawned. We speculate that 2,6-disulfated Galactan is initially synthesized in the ovary and that 6-sulfate ester is removed when the polysaccharide is secreted into the egg jelly. Similar events related to remodeling of sulfated polysaccharides have been reported in other biological systems.
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a unique 2 sulfated β Galactan from the egg jelly of the sea urchin glyptocidaris crenularis conformation flexibility versus induction of the sperm acrosome reaction
Journal of Biological Chemistry, 2009Co-Authors: M Castro, Vitor H. Pomin, Livia Loiola Dos Santos, Anacristina E S Vilelasilva, Noritaka Hirohashi, Laercio Polfachin, Hugo Verli, Paulo A.s. MourãoAbstract:Sulfated polysaccharides from the egg jelly of sea urchins act as species-specific inducers of the sperm acrosome reaction, which is a rare molecular mechanism of carbohydrate-induced signal-transduction event in animal cells. The sea urchin polysaccharides differ in monosaccharide composition (l-fucose or l-galactose), glycosylation, and sulfation sites, but they are always in the α-anomeric configuration. Herein, structural analysis of the polysaccharide from the sea urchin Glyptocidaris crenularis surprisingly revealed a unique sulfated β-d-Galactan composed by (3-β-d-Galp-2(OSO3)-1→3-β-d-Galp-1)n repeating units. Subsequently, we used the G. crenularis Galactan to compare different 2-sulfated polysaccharides as inducers of the acrosome reaction using homologous and heterologous sperm. We also tested the effect of chemically over-sulfated Galactans. Intriguingly, the anomeric configuration of the glycosidic linkage rather than the monosaccharide composition (galactose or fucose) is the preferential structural requirement for the effect of these polysaccharides on sea urchin fertilization. Nuclear magnetic resonance and molecular dynamics indicate that sulfated α-Galactan or α-fucan have less dynamic structural behavior, exhibiting fewer conformational populations, with an almost exclusive conformational state with glycosidic dihedral angles Φ/Ψ = −102°/131°. The preponderant conformer observed in the sulfated α-Galactan or α-fucan is not observed among populations in the β-form despite its more flexible structure in solution. Possibly, a proper spatial arrangement is required for interaction of the sea urchin-sulfated polysaccharides with the specific sperm receptor.
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Anticoagulant activity of a sulfated Galactan: Serpin-independent effect and specific interaction with factor Xa
Thrombosis and haemostasis, 2009Co-Authors: Bianca F. Glauser, Mariana S. Pereira, Fabio R Melo, Ricardo M. Rezende, Ivo M. B. Francischetti, Robson Q. Monteiro, Alireza R. Rezaie, Paulo A.s. MourãoAbstract:An algal sulfated Galactan has high anticoagulant and antithrombotic activities. Its serpin-dependent anticoagulant action is due to promoting thrombin and factor (F)Xa inhibition by antithrombin and heparin cofactor II. Here, we evaluated the anticoagulant effect of the algal sulfated Galactan using serpin-free plasma. In contrast to heparin, the sulfated Galactan is still able to prolong coagulation time and delay thrombin and FXa generation in serpin-free plasma. We further investigated this effect using purified blood coagulation proteins, discovering that sulfated Galactan inhibits the intrinsic tenase and prothrombinase complexes, which are critical for FXa and thrombin generation, respectively. We also investigated the mechanism by which sulfated Galactan promotes FXa inhibition by antithrombin using specific recombinant mutants of the protease. We show that sulfated Galactan interacts with the heparin-binding exosite of FXa and Arg-236 and Lys-240 of this site are critical residues for this interaction, as observed for heparin. Thus, sulfated Galactan and heparin have similar high-affinity and specificity for interaction with FXa, though they have differences in their chemical structures. Similar to heparin, the ability of sulfated Galactan to potentiate FXa inhibition by antithrombin is calcium-dependent. However, in contrast to heparin, this effect is not entirely dependent on the conformation of the γ-carboxyglutamic acid-rich domain of the protease. In conclusion, sulfated Galactan and heparin have some similar effects on blood coagulation, but also differ significantly at the molecular level. This sulfated Galactan opens new perspective for the development of antithrombotic drugs.
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a preponderantly 4 sulfated 3 linked Galactan from the green alga codium isthmocladum
Glycobiology, 2007Co-Authors: Eduardo H C Farias, Ana Paula Valente, Vitor H. Pomin, Helena B Nader, Hugo Alexandre Oliveira Rocha, Paulo A.s. MourãoAbstract:The green algae of the genus Codium have recently been demonstrated to be an important source of sulfated Galactans from the marine environment. Here, a sulfated Galactan was isolated from the species Codium isthmocladum and its structure was studied by a combination of chemical analyses and NMR spectroscopy. Two fractions (SG 1, approximately 14 kDa, and SG 2, approximately 20 kDa) were derived from this highly polydisperse and heterogeneous polysaccharide. Both exhibited similar structures in (1)H 1D NMR spectra. The structural features of SG 2 and its desulfated derivative were analyzed by COSY, TOCSY, DEPT-HSQC, HSQC, and HMBC. This sulfated Galactan is composed preponderantly of 4-sulfated, 3-linked beta-D-galactopyranosyl units. In minor amounts, it is sulfated and glycosylated at C-6. Pyruvate groups are also found, forming five-membered cyclic ketals as 3,4-O-(1'carboxy)-ethylidene-beta-D-galactose residues. A comparison of sulfated Galactans from different marine taxonomic groups revealed similar backbones of 3-beta-D-Galp-1.
Marina Ciancia - One of the best experts on this subject based on the ideXlab platform.
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Structural Diversity in Galactans From Red Seaweeds and Its Influence on Rheological Properties.
Frontiers in plant science, 2020Co-Authors: Marina Ciancia, María C. Matulewicz, Rando TuvikeneAbstract:Galactans are important components of many plant cell walls. Besides, they are the major polysaccharides in extracellular matrixes from different seaweeds, and other marine organisms, which have an acidic character due to the presence of sulfate groups in their structures. In particular, most of the red seaweeds biosynthesize sulfated Galactans with very special linear backbones, constituted by alternating (1→3)-β-d-galactopyranose units (A-unit) and (1→4)-α-galactopyranose residues (B-unit). In the industrially significant seaweeds as source of hydrocolloids, B-units belong either to the d-series and they produce carrageenans (as in the order Gigartinales), or to the l-series, and they are sources of agarose and/or structurally related polymers (i.e., Gelidiales, Gracilariales). In both cases, the latter units appear as cyclized 3,6-anhydro-α-galactose in certain amounts, which can be increased by alkaline cyclization of α-galactose 6-sulfate units. Besides, it has been clearly shown that some red algae produce different amounts of both Galactan structures, known as d/l-hybrids. It is not yet clear if they comprise both diasteromeric types of units in the same molecule, or if they are mixtures of carrageenans and agarans that are very difficult to separate. It has been reported that the biosynthesis of these Galactans, showing that the nucleotide transport for d-galactopyranose units is UDP-d-Gal, while for l-galactose, it is GDP-l-Gal, so, there is a different pathway in the biosynthesis of agarans. However, at least in those seaweeds that produce carrageenans as major Galactans, but also agarans, both synthetic pathways should coexist. Another interesting characteristic of these Galactans is the important variation in the sulfation patterns, which modulate their physical behavior in aqueous solutions. Although the most common carrageenans are of the κ/ι- and λ-types (with A-units sulfated at the 4- and 2-positions, respectively) and usually in agarans, when sulfated, is at the 6-position, many other sulfate arrangements have been reported, greatly influencing the functional properties of the corresponding Galactans. Other substituents can modify their structures, as methyl ethers, pyruvic acid ketals, acetates, and single stubs of xylose or other monosaccharides. It has been shown that structural heterogeneity at some extent is essential for the proper functional performance of red algal Galactans.
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Determination of Substitution Patterns of Galactans from Green Seaweeds of the Bryopsidales.
Methods in molecular biology (Clifton N.J.), 2015Co-Authors: Paula Ximena Arata, Paula Virginia Fernández, Marina CianciaAbstract:Sulfated and pyruvylated Galactans are the major soluble polysaccharides produced by seaweeds of the Bryopsidales. Their backbones have a complex and variable pattern of substitution which, until now, has only been elucidated for a few species. Methods for determination of sulfate and pyruvic acid content, and chemical strategies to determine their position in the Galactan chain are outlined here. These methods can also be applied to other sulfated and/or pyruvylated polysaccharides.
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Characterization of cell wall polysaccharides of the coencocytic green seaweed bryopsis plumosa (bryopsidaceae, chlorophyta) from the argentine coast
Journal of Phycology, 2012Co-Authors: Marina Ciancia, Josefina S. Alberghina, Paula Ximena Arata, Hugo Benavides, Frederik Leliaert, Heroen Verbruggen, Jose Manuel EstevezAbstract:Bryopsis sp. from a restricted area of the rocky shore of Mar del Plata (Argentina) on the Atlantic coast was identified as Bryopsis plumosa (Hudson) C. Agardh (Bryopsidales, Chlorophyta) based on morphological characters and rbcL and tufA DNA barcodes. To analyze the cell wall polysaccharides of this seaweed, the major room temperature (B1) and 90°C (X1) water extracts were studied. By linkage analysis and NMR spectroscopy, the structure of a sulfated Galactan was determined, and putative sulfated rhamnan structures and furanosidic nonsulfated arabinan structures were also found. By anion exchange chromatography of X1, a fraction (F4), comprising a sulfated Galactan as major structure was isolated. Structural analysis showed a linear backbone constituted of 3-linked β-d-galactose units, partially sulfated on C-6 and partially substituted with pyruvic acid forming an acetal linked to O-4 and O-6. This Galactan has common structural features with those of green seaweeds of the genus Codium (Bryopsidales, Chlorophyta), but some important differences were also found. This is the first report about the structure of the water-soluble polysaccharides biosynthesized by seaweeds of the genus Bryopsis. These sulfated Galactans and rhamnans were in situ localized mostly in two layers, one close to the plasma membrane and the other close to the apoplast, leaving a middle amorphous, unstained cell wall zone. In addition, fibrillar polysaccharides, comprising (1→3)-β-d-xylans and cellulose, were obtained by treatment of the residue from the water extractions with an LiCl/DMSO solution at high temperature. These polymers were also localized in a bilayer arrangement.
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novel dl Galactan hybrids from the red seaweed gymnogongrus torulosus are potent inhibitors of herpes simplex virus and dengue virus
Antiviral Chemistry & Chemotherapy, 2002Co-Authors: Carlos A Pujol, Marina Ciancia, José M. Estevez, Alberto S. Cerezo, Maria Josefina Carlucci, Elsa B DamonteAbstract:A novel series of DL-Galactan hybrids extracted from the red seaweed Gymnogongrus torulosus, was evaluated for its in vitro antiviral properties against herpes simplex virus type 2 (HSV-2) and dengue virus 2 (DEN-2). These compounds were very active against both viruses with inhibitory concentration 50% (IC50) values in the range 0.6–16 μg/ml for HSV-2 and 0.19–1.7 μg/ml for DEN-2, respectively, as determined in a virus plaque reduction assay in Vero cells. The DL-Galactans lacked of cytotoxic effects, on stationary as well as on actively dividing cells, and anticoagulant properties. Some of the compounds showed a variable level of direct inactivating effect on both virions, with virucidal concentration 50% values exceeding the IC50s obtained by plaque reduction assay. Full inhibitory activity was achieved when the Galactans were present during virus adsorption period, suggesting that the mode of action of these compounds is an interference in the binding of the surface envelope glycoprotein with the cell...
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dl-Galactan hybrids and agarans from gametophytes of the red seaweed Gymnogongrus torulosus
Carbohydrate research, 2001Co-Authors: José M. Estevez, Marina Ciancia, Alberto S. CerezoAbstract:Abstract Seaweeds from the genus Gymnogongrus are known to be carrageenophytes; nevertheless, fractionation techniques used previously for the separation of gel-forming and ‘soluble’ carrageenans, applied to the Galactans of Gymnogongrus torulosus together with enantiomeric analysis of the sugar components and (when possible) of the structural units, suggested that the system of Galactans biosynthesized by the seaweed was formed by dl -Galactan hybrids having major amounts of carrageenan-type or agaran-type chains, with minor quantities of agarans with unusual structural details.
Ana Paula Valente - One of the best experts on this subject based on the ideXlab platform.
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Occurrence of sulfated Galactans in marine angiosperms: Evolutionary implications. Glycobiology 2005
2015Co-Authors: Rafael S. Aquino, Ana Paula Valente, Leonardo R Andrade, Ana M. L, Paulo A. S. Mour~aoAbstract:We report for the first time that marine angiosperms (seagrasses) possess sulfated polysaccharides, which are absent in terrestrial and freshwater plants. The structure of the sulfated polysaccharide from the seagrass Ruppia maritima was determined. It is a sulfated D-Galactan com-posed of the following regular tetrasaccharide repeating unit: [3-b-D-Gal-2(OSO3)-1!4-a-D-Gal-1!4-a-D-Gal-1!3-b-D-Gal-4(OSO3)-1!]. Sulfated Galactans have been described previously in red algae and in marine inver-tebrates (ascidians and sea urchins). The sulfated Galactan from the marine angiosperm has an intermediate structure when compared with the polysaccharides from these two other groups of organisms. Like marine invertebrate galac-tan, it expresses a regular repeating unit with a homo-genous sulfation pattern. However, seagrass galacta
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Sulfated α-L-Galactans from the sea urchin ovary: Selective 6-desulfation as eggs are spawned
Glycobiology, 2010Co-Authors: Leonardo Paes Cinelli, Ana Paula Valente, Leonardo R Andrade, Paulo A.s. MourãoAbstract:The sea urchin eggs are surrounded by a jelly coat, which contains sulfated polysaccharides with unique structures. These molecules are responsible for inducing the speciesspecific acrosome reaction, an obligatory event for the binding of sperm and fusion with the egg. The mechanism of biosynthesis of these sulfated polysaccharides is virtually unknown. The egg jelly of the sea urchin Echinometra lucunter contains a simple 2-sulfated, 3-linked α-LGalactan. Here, we pulse labeled the sea urchin ovary in vitro with 35 S-sulfate to follow the biosynthesis of the sulfated α-L-Galactan. We found that the ovary contains a 2,6-disulfated, 3-linked α-L-Galactan, which incorporates 35 S-sulfate more avidly than the 2-sulfated isoform. The 2,6-disulfated α-L-Galactan was purified by anion exchange chromatography, analyzed by electrophoresis and characterized by 1D and 2D nuclear magnetic resonance spectra. We also investigated the location of the sulfated polysaccharides on the oocytes using histochemical procedures. The stain revealed high amounts of sulfated polysaccharide in mature oocytes and accessory cells. The amount of intracellular sulfated polysaccharides decreased as oocytes are spawned. We speculate that 2,6-disulfated Galactan is initially synthesized in the ovary and that 6-sulfate ester is removed when the polysaccharide is secreted into the egg jelly. Similar events related to remodeling of sulfated polysaccharides have been reported in other biological systems.
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a preponderantly 4 sulfated 3 linked Galactan from the green alga codium isthmocladum
Glycobiology, 2007Co-Authors: Eduardo H C Farias, Ana Paula Valente, Vitor H. Pomin, Helena B Nader, Hugo Alexandre Oliveira Rocha, Paulo A.s. MourãoAbstract:The green algae of the genus Codium have recently been demonstrated to be an important source of sulfated Galactans from the marine environment. Here, a sulfated Galactan was isolated from the species Codium isthmocladum and its structure was studied by a combination of chemical analyses and NMR spectroscopy. Two fractions (SG 1, approximately 14 kDa, and SG 2, approximately 20 kDa) were derived from this highly polydisperse and heterogeneous polysaccharide. Both exhibited similar structures in (1)H 1D NMR spectra. The structural features of SG 2 and its desulfated derivative were analyzed by COSY, TOCSY, DEPT-HSQC, HSQC, and HMBC. This sulfated Galactan is composed preponderantly of 4-sulfated, 3-linked beta-D-galactopyranosyl units. In minor amounts, it is sulfated and glycosylated at C-6. Pyruvate groups are also found, forming five-membered cyclic ketals as 3,4-O-(1'carboxy)-ethylidene-beta-D-galactose residues. A comparison of sulfated Galactans from different marine taxonomic groups revealed similar backbones of 3-beta-D-Galp-1.
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structure and anticoagulant activity of a sulfated Galactan from the red alga gelidium crinale is there a specific structural requirement for the anticoagulant action
Carbohydrate Research, 2005Co-Authors: Maria G Pereira, Ana Paula Valente, Fabio R Melo, Norma Maria Barros Benevides, Marcia R S Melo, Paulo A.s. MourãoAbstract:Marine red algae are an abundant source of sulfated Galactans with potent anticoagulant activity. However, the specific structural motifs that confer biological activity remain to be elucidated. We have now isolated and purified a sulfated Galactan from the marine red alga, Gellidium crinale. The structure of this polysaccharide was determined using NMR spectroscopy. It is composed of the repeating structure -4-alpha-Galp-(1-->3)-beta-Galp1--> but with a variable sulfation pattern. Clearly 15% of the total alpha-units are 2,3-di-sulfated and another 55% are 2-sulfated. No evidence for the occurrence of 3,6-anhydro alpha-galactose units was observed in the NMR spectra. We also compared the anticoagulant activity of this sulfated Galactan with a polysaccharide from the species, Botryocladia occidentalis, with a similar saccharide chain but with higher amounts of 2,3-di-sulfated alpha-units. The sulfated Galactan from G. crinale has a lower anticoagulant activity on a clotting assay when compared with the polysaccharide from B. occidentalis. When tested in assays using specific proteases and coagulation inhibitors, these two Galactans showed significant differences in their activity. They do not differ in thrombin inhibition mediated by antithrombin, but in assays where heparin cofactor II replaces antithrombin, the sulfated Galactan from G. crinale requires a significantly higher concentration to achieve the same inhibitory effect as the polysaccharide from B. occidentalis. In contrast, when factor Xa instead of thrombin is used as the target protease, the sulfated Galactan from G. crinale is a more potent anticoagulant. These observations suggest that the proportion and/or the distribution of 2,3-di-sulfated alpha-units along the Galactan chain may be a critical structural motif to promote the interaction of the protease with specific protease and coagulation inhibitors.
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Occurrence of sulfated Galactans in marine angiosperms: evolutionary implications.
Glycobiology, 2004Co-Authors: Rafael S. Aquino, Ana Paula Valente, Leonardo R Andrade, Ana M. Landeira-fernandez, Paulo A.s. MourãoAbstract:We report for the first time that marine angiosperms (seagrasses) possess sulfated polysaccharides, which are absent in terrestrial and freshwater plants. The structure of the sulfated polysaccharide from the seagrass Ruppia maritima was determined. It is a sulfated D-Galactan composed of the following regular tetrasaccharide repeating unit: [3-b-D-Gal-2(OSO3)-1!4-a-D-Gal-1!4-a-D-Gal1!3-b-D-Gal-4(OSO3)-1!]. Sulfated Galactans have been described previously in red algae and in marine invertebrates (ascidians and sea urchins). The sulfated Galactan from the marine angiosperm has an intermediate structure when compared with the polysaccharides from these two other groups of organisms. Like marine invertebrate Galactan, it expresses a regular repeating unit with a homogenous sulfation pattern. However, seagrass Galactan contains the D-enantiomer of galactose instead of the L-isomer found in marine invertebrates. Like red algae, the marine angiosperm polysaccharide contains both a and b units of D-galactose; however, these units are not distributed in an alternating order, as in algal Galactan. Sulfated Galactan is localized in the plant cell walls, mostly in rhizomes and roots, indicative of a relationship with the absorption of nutrients and of a possible structural function. The occurrence of sulfated Galactans in marine organisms may be the result of physiological adaptations, which are not correlated with phylogenetic proximity. We suggest that convergent adaptation, due to environment pressure, may explain the occurrence of sulfated Galactans in many marine organisms.
Henrik Vibe Scheller - One of the best experts on this subject based on the ideXlab platform.
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cell wall β 1 4 Galactan regulated by the bpc1 bpc2 gals1 module aggravates salt sensitivity in arabidopsis thaliana
Molecular Plant, 2021Co-Authors: Jingwei Yan, Henrik Vibe Scheller, Ya Liu, Lan Yang, Yun Huang, Lin Fang, Mingyi Jiang, Aying ZhangAbstract:Salinity severely reduces plant growth and limits agricultural productivity. Dynamic changes and rearrangement of the plant cell wall is an important response to salt stress, but relatively little is known about the biological importance of specific cell wall components in the response. Here, we demonstrate a specific function of β-1,4-Galactan in salt hypersensitivity. We found that salt stress induces the accumulation of β-1,4-Galactan in root cell walls by up regulating the expression of Galactan SYNTHASE 1 (GALS1), which encodes a β-1,4-Galactan synthase. The accumulation of β-1,4-Galactan negatively affects salt tolerance. Exogenous application of D-galactose (D-Gal) causes an increase in β-1,4-Galactan levels in the wild type and GALS1 mutants, especially in GALS1 overexpressors, which correlated with the aggravated salt hypersensitivity. Furthermore, we discovered that the BARLEY B RECOMBINANT/BASIC PENTACYSTEINE transcription factors BPC1/BPC2 positively regulate plant salt tolerance by repressing GALS1 expression and β-1,4-Galactan accumulation. Genetic analysis suggested that GALS1 is genetically epistatic to BPC1/BPC2 with respect to the control of salt sensitivity as well as accumulation of β-1,4-Galactan. Taken together, our results reveal a new regulatory mechanism by which β-1,4-Galactan regulated by the BPC1/BPC2-GALS1 module aggravates salt sensitivity in Arabidopsis thaliana.
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Cell wall β-1,4-Galactan regulated by the BPC1/BPC2-GALS1 module aggravates salt sensitivity in Arabidopsis thaliana.
Molecular plant, 2020Co-Authors: Jingwei Yan, Henrik Vibe Scheller, Ya Liu, Lan Yang, Yun Huang, Lin Fang, Mingyi Jiang, Aying ZhangAbstract:Salinity severely reduces plant growth and limits agricultural productivity. Dynamic changes and rearrangement of the plant cell wall is an important response to salt stress, but relatively little is known about the biological importance of specific cell wall components in the response. Here, we demonstrate a specific function of β-1,4-Galactan in salt hypersensitivity. We found that salt stress induces the accumulation of β-1,4-Galactan in root cell walls by up regulating the expression of Galactan SYNTHASE 1 (GALS1), which encodes a β-1,4-Galactan synthase. The accumulation of β-1,4-Galactan negatively affects salt tolerance. Exogenous application of D-galactose (D-Gal) causes an increase in β-1,4-Galactan levels in the wild type and GALS1 mutants, especially in GALS1 overexpressors, which correlated with the aggravated salt hypersensitivity. Furthermore, we discovered that the BARLEY B RECOMBINANT/BASIC PENTACYSTEINE transcription factors BPC1/BPC2 positively regulate plant salt tolerance by repressing GALS1 expression and β-1,4-Galactan accumulation. Genetic analysis suggested that GALS1 is genetically epistatic to BPC1/BPC2 with respect to the control of salt sensitivity as well as accumulation of β-1,4-Galactan. Taken together, our results reveal a new regulatory mechanism by which β-1,4-Galactan regulated by the BPC1/BPC2-GALS1 module aggravates salt sensitivity in Arabidopsis thaliana.
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Bifunctional glycosyltransferases catalyze both extension and termination of pectic Galactan oligosaccharides
The Plant journal : for cell and molecular biology, 2018Co-Authors: Tomas Laursen, Mads Hartvig Clausen, Solomon Stonebloom, Venkataramana R. Pidatala, Devon Birdseye, Jenny C. Mortimer, Henrik Vibe SchellerAbstract:Pectins are the most complex polysaccharides of the plant cell wall. Based on the number of methylations, acetylations and glycosidic linkages present in their structures, it is estimated that up to 67 transferase activities are involved in pectin biosynthesis. Pectic Galactans constitute a major part of pectin in the form of side-chains of rhamnogalacturonan-I. In Arabidopsis, Galactan synthase 1 (GALS1) catalyzes the addition of galactose units from UDP-Gal to growing β-1,4-Galactan chains. However, the mechanisms for obtaining varying degrees of polymerization remain poorly understood. In this study, we show that AtGALS1 is bifunctional, catalyzing both the transfer of galactose from UDP-α-d-Gal and the transfer of an arabinopyranose from UDP-β-l-Arap to Galactan chains. The two substrates share a similar structure, but UDP-α-d-Gal is the preferred substrate, with a 10-fold higher affinity. Transfer of Arap to Galactan prevents further addition of galactose residues, resulting in a lower degree of polymerization. We show that this dual activity occurs both in vitro and in vivo. The herein described bifunctionality of AtGALS1 may suggest that plants can produce the incredible structural diversity of polysaccharides without a dedicated glycosyltransferase for each glycosidic linkage.
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pectin biosynthesis gals1 in arabidopsis thaliana is a β 1 4 Galactan β 1 4 galactosyltransferase
The Plant Cell, 2012Co-Authors: April J M Liwanag, Henrik Vibe Scheller, Berit Ebert, Yves Verhertbruggen, Emilie A Rennie, Carsten Rautengarten, Ai Oikawa, Mathias Christian Franch Andersen, Mads Hartvig ClausenAbstract:β-1,4-Galactans are abundant polysaccharides in plant cell walls, which are generally found as side chains of rhamnogalacturonan I. Rhamnogalacturonan I is a major component of pectin with a backbone of alternating rhamnose and galacturonic acid residues and side chains that include α-1,5-arabinans, β-1,4-Galactans, and arabinoGalactans. Many enzymes are required to synthesize pectin, but few have been identified. Pectin is most abundant in primary walls of expanding cells, but β-1,4-Galactan is relatively abundant in secondary walls, especially in tension wood that forms in response to mechanical stress. We investigated enzymes in glycosyltransferase family GT92, which has three members in Arabidopsis thaliana, which we designated Galactan SYNTHASE1, (GALS1), GALS2 and GALS3. Loss-of-function mutants in the corresponding genes had a decreased β-1,4-Galactan content, and overexpression of GALS1 resulted in plants with 50% higher β-1,4-Galactan content. The plants did not have an obvious growth phenotype. Heterologously expressed and affinity-purified GALS1 could transfer Gal residues from UDP-Gal onto β-1,4-galactopentaose. GALS1 specifically formed β-1,4-galactosyl linkages and could add successive β-1,4-galactosyl residues to the acceptor. These observations confirm the identity of the GT92 enzyme as β-1,4-Galactan synthase. The identification of this enzyme could provide an important tool for engineering plants with improved bioenergy properties.
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rhamnogalacturonan i in solanum tuberosum tubers contains complex arabinoGalactan structures
Phytochemistry, 2004Co-Authors: Jens Obro, Jesper Harholt, Henrik Vibe Scheller, Caroline OrfilaAbstract:A rhamnogalacturonan I polysaccharide was isolated from potato (Solanum tuberosum cv. Posmo) tuber cell walls and characterised by enzymatic digestion with an endo-β-1 → 4-Galactanase and an endo-α-1 → 5-arabinanase, individually or in combination. The reaction products were separated using size-exclusion chromatography and further analysed for monosaccharide composition and presence of epitopes using the LM5 anti-β-1 → 4-Galactan and LM6 anti-α-1 → 5-arabinan monoclonal antibodies. The analyses point to distinct structural features of potato tuber rhamnogalacturonan I, such as the abundance of β-1 → 4-Galactan side chains that are poorly substituted with short arabinose-containing side chains, the presence of α-1 → 5-arabinan side chains substituted with β-1 → 4-Galactan oligomers (degree of polymerisation >4), and the presence of α-1 → 5-arabinans that resist enzymatic degradation. A synergy between the enzymes was observed towards the degradation of arabinans but not towards the degradation of Galactans. The effect of the enzymes on isolated RG I is discussed in relation to documented effects of enzymes heterologously expressed in potato tubers. In addition, a novel and rapid method for the determination of the monosaccharide and uronic acid composition of cell wall polysaccharides using high-performance anion exchange chromatography with pulsed amperometric detection is described.
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Characterization of cell wall polysaccharides of the coencocytic green seaweed bryopsis plumosa (bryopsidaceae, chlorophyta) from the argentine coast
Journal of Phycology, 2012Co-Authors: Marina Ciancia, Josefina S. Alberghina, Paula Ximena Arata, Hugo Benavides, Frederik Leliaert, Heroen Verbruggen, Jose Manuel EstevezAbstract:Bryopsis sp. from a restricted area of the rocky shore of Mar del Plata (Argentina) on the Atlantic coast was identified as Bryopsis plumosa (Hudson) C. Agardh (Bryopsidales, Chlorophyta) based on morphological characters and rbcL and tufA DNA barcodes. To analyze the cell wall polysaccharides of this seaweed, the major room temperature (B1) and 90°C (X1) water extracts were studied. By linkage analysis and NMR spectroscopy, the structure of a sulfated Galactan was determined, and putative sulfated rhamnan structures and furanosidic nonsulfated arabinan structures were also found. By anion exchange chromatography of X1, a fraction (F4), comprising a sulfated Galactan as major structure was isolated. Structural analysis showed a linear backbone constituted of 3-linked β-d-galactose units, partially sulfated on C-6 and partially substituted with pyruvic acid forming an acetal linked to O-4 and O-6. This Galactan has common structural features with those of green seaweeds of the genus Codium (Bryopsidales, Chlorophyta), but some important differences were also found. This is the first report about the structure of the water-soluble polysaccharides biosynthesized by seaweeds of the genus Bryopsis. These sulfated Galactans and rhamnans were in situ localized mostly in two layers, one close to the plasma membrane and the other close to the apoplast, leaving a middle amorphous, unstained cell wall zone. In addition, fibrillar polysaccharides, comprising (1→3)-β-d-xylans and cellulose, were obtained by treatment of the residue from the water extractions with an LiCl/DMSO solution at high temperature. These polymers were also localized in a bilayer arrangement.
