Pectic Polysaccharides In Cell Walls Research Articles

Micronized natural talc affects the proteins and pectic cell wall polysaccharides during “Hojiblanca” virgin olive oil extraction

This work studies how using MNT affects cell wall polysaccharides and proteins of “Hojiblanca” paste during virgin olive oil extraction. Four doses of MNT were assessed: 0, 0.25, 0.5, and 1%. Three pectic fractions were extracted from alcohol insoluble solids (AIS): water‐soluble pectin (WSP), chelate‐soluble pectin (CSP), and non‐soluble pectin (NSP). In general, the content of the three pectic fractions decreased throughout the kneading step. This indicated a significant degradation and solubilization of pectins during processing. The same trend was observed for protein content and total pectin content while AIS yield increased. Addition of MNT at doses lower than 0.5% favored the formation of a chemical bound through electrostatic interactions between proteins and pectic polysaccharides which are held together and adsorbed onto the talc surface giving a decrease in their content. Higher MNT doses (1%) produced the opposite behavior. The lowest dose of MNT (0.25%) reduced the oil losses in the pomace. A certain tendency for the loss of oil in the pomace to decrease as the amount of total pectin and protein decreased was observed, indicating that the oil yield is at least in part, related to the pectin and protein content depending on the dose of MNT added during malaxation step.Practical application: We have demonstrated that the use of talc during the malaxation step greatly lessens the effect of the pectic substrates and proteins, principal emulsifier agents that influence the formation of oil‐in‐water emulsions during oil extraction process and enhance the extraction of the oil from the mesocarp cells by reducing its loose in the pomace. Excess of talk addition presented a reverse effect, though. It is, therefore, of the utmost importance that the information contained in this study is fully taken into account to establish the suitable dose of talc that should be applied when difficult pastes are formed during malaxation step and which at least partially depends on the content of proteins and pectin compounds of the processed olive paste.Proteins and pectic cell wall polysaccharides as affected by talc addition during virgin olive oil extraction.

Changes in Cell Wall Carbohydrate Extractability Are Correlated with Reduced Recalcitrance of HCT Downregulated Alfalfa Biomass

Downregulation of the expression of enzymes involved in lignin biosynthesis in alfalfa (Medicago sativa L.) has been shown to result in reduced cell wall recalcitrance and increased saccharification. Here we describe changes in the extractability of hemicellulosic and pectic polysaccharides in cell walls of alfalfa downregulated in the expression of hydroxycinnamoyl CoA:shikimate hydroxycinnamoyl transferase (HCT). Xylan and pectic polysaccharides are more readily solubilized from the cell walls of HCT downregulated transgenic lines than from empty vector control plants, suggesting alterations in lignin-polysaccharide interactions in the transgenic plants. Our studies show that reduced recalcitrance of HCT downregulated lines is also correlated with increased xylan extractability.

First Characterization of Bioactive Components in Soybean Tempe That Protect Human and Animal Intestinal Cells against Enterotoxigenic Escherichia coli (ETEC) Infection

Tempe extracts can inhibit the adhesion of enterotoxigenic Escherichia coli (ETEC) to intestinal cells and thereby can play a role in controlling ETEC-induced diarrhea. The component responsible for this adhesion inhibition activity is still unknown. This research describes the purification and partial characterization of this bioactive component of tempe. After heating, defatting, and protease treatment, the extracts were found to remain active. However, after treatment with polysaccharide-degrading enzyme mixtures the bioactivity was lost. Ultrafiltration revealed the active component to be >30 kDa. Further purification of the bioactive tempe extracts yielded an active fraction with an increased carbohydrate content of higher arabinose content than the nonactive fractions. In conclusion, the bioactive component contains arabinose and originates from the arabinan or arabinogalactan side chain of the pectic cell wall polysaccharides of the soybeans, which is probably released or formed during fermentation by enzymatic modifications.

Immunohistochemical changes in methyl-ester distribution of homogalacturonan and side chain composition of rhamnogalacturonan I as possible components of basal resistance in tomato inoculated with Ralstonia solanacearum

The composition and structure of pectic cell wall polysaccharides of stem sections were investigated in healthy and Ralstonia solanacearum-inoculated tomato genotypes L390 and Hawaii 7996, susceptible and resistant to bacterial wilt, respectively, by immunohistochemical analysis. Constitutive differences between genotypes manifested in methyl-ester distribution of homogalacturonan (HG), arabinan and galactan side chain composition of rhamnogalacturonan I (RG I) and arabinogalactan-protein (AGP) in the xylem parenchyma and in vessel cell walls. After inoculation increased labeling was observed with all the antibodies (JIM5, JIM7, LM2, LM5, LM6, LM7) specific for HG, RG I and AGP epitopes, in the xylem parenchyma and around xylem vessels of stem sections of L390, but not of Hawaii 7996. Also vessel cell walls were stronger stained after inoculation in L390, particularly for the non-blockwise de-esterification of HG, possibly indicating for the first time the non-blockwise action pattern of bacterial pectin methyl esterase. In genotype Hawaii 7996 a reaction to inoculation was observed only in vessel walls, with a significantly increased number of stained vessels—five- and nine-fold for arabinan and galactan epitopes of RG I, respectively. Differences in xylem cell wall structure may play a role as a constitutive resistance mechanism in the multigenic resistance of tomato against bacterial wilt, while changes after inoculation may contribute to induced basal resistance on cell wall level.

Alteration of pectic polysaccharides in cell walls, extracellular polysaccharides, and glycan-hydrolytic enzymes of growth-restricted carrot cells under calcium deficiency

Suspension-cultured carrot (Daucus carota L. cv. Kintoki) cells were grown in calcium (Ca 2 + )-deficient and normal liquid media. Cell growth was limited by the Ca 2+ deficiency. Similar amounts of pectic fractions were extracted from the walls of control and Ca 2+ -deprived cells, but the fractions from the walls of Ca 2+ -deprived cells showed a substantial decrease in galacturonic acid content. However, after 15 days of culture, Ca 2+ -deprived cells released galacturonic acid-rich extracellular polysaccharides at twice the rate of control cells. The polysaccharides consisted of a mixture of several polymers containing predominantly arabinose, galactose and galacturonic acid. Ca 2+ -deprived cells also secreted three times more extracellular proteins, containing many glycan-hydrolytic enzymes, into the medium than did normal cells. SDS-PAGE analysis revealed several distinct changes in the polypeptide pattern in the medium of control and Ca 2+ -deprived cells. Activities of α-galactosidase, β-glucosidase and exo-polygalacturonase increased considerably during Ca 2+ deficiency, whereas α-L-arabinofuranosidase and #-galactosidase activities were much reduced.

The mur4 mutant of arabidopsis is partially defective in the de novo synthesis of uridine diphospho L-arabinose.

To obtain information on the synthesis and function of arabinosylated glycans, the mur4 mutant of Arabidopsis was characterized. This mutation leads to a 50% reduction in the monosaccharide L-arabinose in most organs and affects arabinose-containing pectic cell wall polysaccharides and arabinogalactan proteins. Feeding L-arabinose to mur4 plants restores the cell wall composition to wild-type levels, suggesting a partial defect in the de novo synthesis of UDP-L-arabinose, the activated sugar used by arabinosyltransferases. The defect was traced to the conversion of UDP-D-xylose to UDP-L-arabinose in the microsome fraction of leaf material, indicating that mur4 plants are defective in a membrane-bound UDP-D-xylose 4-epimerase.

Borate-rhamnogalacturonan II bonding reinforced by Ca2+ retains pectic polysaccharides in higher-plant cell walls

The extent of in vitro formation of the borate-dimeric-rhamnogalacturonan II (RG-II) complex was stimulated by Ca2+. The complex formed in the presence of Ca2+ was more stable than that without Ca2+. A naturally occurring boron (B)-RG-II complex isolated from radish (Raphanus sativus L. cv Aokubi-daikon) root contained equimolar amounts of Ca2+ and B. Removal of the Ca2+ by trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid induced cleavage of the complex into monomeric RG-II. These data suggest that Ca2+ is a normal component of the B-RG-II complex. Washing the crude cell walls of radish roots with a 1.5% (w/v) sodium dodecyl sulfate solution, pH 6.5, released 98% of the tissue Ca2+ but only 13% of the B and 22% of the pectic polysaccharides. The remaining Ca2+ was associated with RG-II. Extraction of the sodium dodecyl sulfate-washed cell walls with 50 mM trans-1,2-diaminocyclohexane-N, N,N',N'-tetraacetic acid, pH 6.5, removed the remaining Ca2+, 78% of B, and 49% of pectic polysaccharides. These results suggest that not only Ca2+ but also borate and Ca2+ cross-linking in the RG-II region retain so-called chelator-soluble pectic polysaccharides in cell walls.

Boron and calcium, essential inorganic constituents of pectic polysaccharides in higher plant cell walls

Among 16 essential elements of higher plants, Ca2+ and B have been termed as apoplastic elements. This is mainly because of their localization in cell walls, however, it has turned to be highly likely that these two elements significantly contribute to maintain the integrity of cell walls through binding to pectic polysaccharides. Boron in cell walls exclusively forms a complex with rhamnogalacturonan II (RG-II), and the B-RG-II complex is ubiquitous in higher plants. Analysis of the structure of the B-RG-II complex revealed that the complex contains two molecules boric acid, two molecules Ca2+ and two chains of monomeric RG-II. This result indicates that pectic chains are cross-linked covalently with boric acid at their RG-II regions. The complex was reconstitutedin vitro only by mixing monomeric RG-II and boric acid, however, the complex decomposed spontaneously unless Ca2+ was supplemented. Furthermore, the native complex decomposed when it was incubated withtrans-1,2-diaminocyclohexane-N, N, N′, N′-tetraacetic acid (CDTA) which chelates Ca2+. When radish root cell walls were washed with a buffered 1.5% (w/v) sodium dodesyl sulfate (SDS) solution (pH 6.5), 96%, 13% and 6% of Ca2+, B and pectic polysaccharides of the cell walls, respectively, were released and the cell wall swelled twice. Subsequent extraction with 50 mM CDTA (pH 6.5) of the SDS-washed cell walls further released 4%, 80% and 61% of Ca2+, B and pectic polysaccharides, respectively. Pectinase hydrolysis of the SDS-treated cell walls yielded a B-RG-II complex and almost all the remaining Ca2+ was recovered in the complex. This result suggests that cell-wall bound Ca2+ is divided into at least two fractions, one anchors the CDTA-soluble pectic polysaccharides into cell walls together with B, and the other may control the properties of the pectic gel. These studies demonstrate that B functions to retain CDTA-soluble pectic polysaccharides in cell walls through its binding to the RG-II regions in collaboration with Ca2+.

Acetyl- and methyl-esterification of pectins of friable and compact sugar-beet calli: consequences for intercellular adhesion

Monoclonal antibodies (2F4), specific for a conformational epitope of homopolygalacturonic acid induced by calcium ions, were used to compare the nature and the distribution of the pectic polysaccharides in cell walls of compact and friable sugar-beet (Beta vulgaris L. var. altissima) calli, at the electron-microscope level. Labelings performed before or after de-esterification pretreatments of callus sections enabled three major types of pectic polysaccharides to be distinguished within compact calli: (i) acidic pectins, probably with few acetyl ester groups, detected without any de-esterification treatment in expanded areas of cell separation but never on middle lamellae between tightly associated cells; (ii) highly methyl-esterified pectins with an expected low acetyl ester content, recognized by the 2F4 antibodies after pectin methylesterase de-esterification, and mostly located on intercellular junctions and on middle lamellae in the central zones of the calli; (iii) highly methyl-esterified and largely acetylated pectins, only localized after alkaline de-esterification, in all primary walls of the compact calli. By contrast, all pectins of friable calli were highly methyland acetyl-esterified. This was consistent with an average degree of methyl-esterification of about 60% measured in both calli, and a higher average degree of acetylation for the friable callus line (85%) compared to the compact one (60%). Accordingly, the pectic fraction (acid-soluble) predominant in both calli was acetyl-esterified to 85% in friable callus and to 22% in compact callus cell walls. Friability of sugar-beet callus is thus correlated with an increase in acetylation of its pectin. Labelings of the Golgi apparatus indicate that the pectic polymers of both callus types are synthesized in dictyosomes in a highly methyl-esterified form and are probably subsequently acetyl-esterified.

Fractionation and Partial Characterization of Pectic Polysaccharides in Cell Walls from Liverwort (Marchantia polymorph) Cell Cultures

Konno, H., Yamasalu, Y. and Katoh, K. 1987. Fractionation and partial characterization of pectic polysaccharides in cell walls from liverwort (Marchantia polymorpha) cell cultures.—J exp. Bot. 38: 711–722. Pectic polysaccharides were extracted from the starch-free cell wall preparation of cell suspension cultures of Marchantia polymorpha. The polysaccharides were fractionated by DEAE-Sephadex A-50 ion-exchange chromatography yielding the five fractions, and the degree of polymerization and glycosyl composition determined for each fraction. The neutral rich and acidic pectic polymers were depolymerized by purified endoglucanase (l,4-β-D-glucan 4-glucanohydrolase, E.C. 3.2.1.4.) and endopolygalacturonase (poly-l,4-α-Dgalacturonide glycanohydrolase, E.C. 3.2.1.15), respectively. The degraded pectic fractions were fractionated by gel filtration chromatography on Bio-Gel A-5m and Bio-Gel P-2, and glycosyl composition determined for each fraction. The results indicate that pectic polysaccharides contain glucose-rich polymer, rhamnogalacturonan and homogalacturonan in a ratio of 1:4:0–6. In addition, pectic polysaccharides were released as five pectic fragments from the cell walls by purified endopectate lyase (poly-l,4-α-D-galacturonide lyase, E.C. 4.2.2.2). Based on the analysis of glycosyl composition of each fragment, the pectic polysaccharides of Marchantia cell walls are characterized

Phosphatidylinositol monophosphate in Lilium pollen and turnover of phospholipid during pollen tube extension Johannes P.F.G. Helsper

A considerable incorporation of [32P]orthophosphate into phospholipids was observed during germination of pollen of Lilium longiflorum, particularly during the period of most rapid pollen tube elongation. The major phospholipids were phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol and phosphatidic acid. The amount of lipid-bound phosphorus (0.05 μmol/mg pollen) did not change significantly during germination, suggesting that the incorporation was mainly due to turnover. myo-[2-3H]Inositol was incorporated into phospholipids as well as into pectic cell wall polysaccharides. The phospholipids labelled with both 3H and 32P were found to be phosphatidylinositol (90% of 3H-label) and phosphatidylinositol monophosphate. The identity of the latter was established by thin layer chromatography, by anion exchange column chromatography (with immobilized neomycin sulphate as the stationary phase), and by the formation of glycerylphosphoryl inositol phosphate and inositol bisphosphate during alkaline hydrolysis. Pulse-chase experiments suggested that about 40% of the myo-inositol moieties in phosphatidylinositol is exchanged during the 4 hr-period of most rapid pollen tube extension. This high figure may be a consequence of membrane flow known to take place during pollen tube elongation, proceeding at the high rate of approximately 1 mm/4 hr. Phosphatidylinositol phospholipase C activity, which could play a role in this turnover, was detected in pollen tube homogenates. Phospholipase activities towards the other major phospholipids were also observed.