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The α-l-arabinofuranosidase (AF) from the fungus Rhizomucor pusillus HHT-1 released arabinose at appreciable rates from (1→5)-α-l-arabinofuranooligosaccharides, sugar beet arabinan and debranched arabinan. This enzyme preferentially hydrolyzed the terminal arabinofuranosyl residue [α-(1→5)-linked] of the arabinan backbone rather than the arabinosyl side chain [α-(1→3)-linked residues]. The enzyme-hydrolyzed arabinan reacted at and debranched the arabinan almost at the same rate, and the degree of conversion for both cases was 65%. Methylation analysis of arabinan showed that the arabinosyl-linkage proportions were 2:2:2:1, respectively, for (1→5)-Araf, T-Araf, (1→3, 5)-Araf and (1→3)-Araf, while the ratios for the AF-digested arabinan shifted to 3:1:2:1. Enzyme digestion resulted in an increase in the proportion of (1→5)-linked arabinose and a decrease in the proportion of terminal arabinose indicated this AF cleaved the terminal arabinosyl residue of the arabinan back bone [α-(1→5)-linked residues]. Peak assignments in the 13C NMR spectra also confirmed this linkage composition of four kinds of arabinose residues. Both 1H and 13C NMR spectra are dominated by signals of the α-anomeric configuration of the arabinofuranosyl moieties. No signals were recorded for arabinopyranosyl moieties in the NMR spectra. Methylation and NMR analysis of native and AF-digested arabinan revealed that this α-l-arabinofuranosidase can only hydrolyse α-l-arabinofuranosyl residues of arabinan. [Copyright &y& Elsevier]

A pyrolysis/gas chromatography/mass spectrometry method (Py/GC/MS) was developed to determine the relative carbohydrate composition in chemical pulps. The composition was determined directly from the pyrograms without calibration against any wet-chemical analytical procedure. However, compensation was necessary due to differences in the response factors of the anhydrosugars from glucan and mannan. The pyrolysis temperature range that gave stable values for carbohydrate composition was found to be 500–700 °C. Various pre-treatment steps were investigated. It was shown that the treatments affected the analytical results and that milling should be avoided. The Py/GC/MS results agreed very well with results from other analytical methods. However, low levels of mannan (approx. 0.5–1%) were not detected. The main advantages of the method are its simplicity and shorter analysis time compared to any wet-chemical analytical procedures. [Copyright &y& Elsevier]

Two distinct extracellular α-l-arabinofuranosidases (AFases; EC 3.2.1.55) were purified from the culture filtrate of Penicillium chrysogenum 31B. The molecular masses of the enzymes were estimated to be 79 kDa (AFQ1) and 52 kDa (AFS1) by SDS-PAGE. Both enzymes had their highest activities at 50 °C and were stable up to 50 °C. Enzyme activities of AFQ1 and AFS1 were highest at pH 4.0 to 6.5 and pH 3.3 to 5.0, respectively. Addition of 10 mg/ml arabinose to the reaction mixture decreased the AFS1 activity but hardly affected AFQ1. Both enzymes displayed broad substrate specificities; they released arabinose from branched arabinan, debranched arabinan, arabinoxylan, arabinogalactan, and arabino-oligosaccharides. AFS1 also showed low activity towards p-nitrophenyl-β-d-xylopyranoside. An exo-arabinanase, which catalyzes the release of arabinobiose from linear arabinan at the nonreducing terminus, acted synergistically with both enzymes to produce l-arabinose from branched arabinan. [Copyright &y& Elsevier]

Cell wall composition of cortical and pith tissues of strawberry (Fragaria x ananassa Duchesne cv. Yolo) was investigated at three stages of ripeness: unripe, partially ripe and ripe. Cell walls from these tissues, isolated using Hepes-buffered phenol (pH 6.5), were sequentially extracted with aqueous 0.1 M Hepes buffer, 0.05 M CDTA, 0.05 M Na2CO3, 1 M KOH and 4 M KOH. The uronic acids, neutral sugars and cellulose contents in these fractions were estimated colorimetrically, while monosaccharide composition of the neutral noncellulosic polysaccharides was determined by gas chromatography. During ripening, total cell wall polysaccharides (CWP) of cortical tissues decreased more (1.7 to 1.0 g/100 g frozen tissue) than that of the pith tissues (1.5 to 1.2 g/100 g frozen tissue). Concomitantly, cortical CWP showed greater changes in the extent of solubilisation compared to that of the pith—this appeared to be due to highly soluble pectic substances and the disappearance of highly branched pectic material. For pith, changes in CWP appeared to be associated with a marked decrease in non-esterified pectins. Monosaccharide composition of both tissue types indicated that losses in highly branched pectic substances were mainly due to a decrease in arabinose residues. By comparison, the cell walls of both tissue types exhibited only small decreases in hemicellulose during ripening. Cellulose appeared to be a minor cell wall component of strawberry fruit and its amount remained relatively constant throughout ripening. [Copyright &y& Elsevier]

An arabinan (97% of Ara and 3% of hexuronic acid) was isolated from the alcohol-insoluble residue (AIR) of olive pomace by treatment with 0.02 M HNO3, at 80 °C, followed by graded precipitation with ethanol. It was separated from acidic pectic polysaccharides by anion-exchange chromatography, and by size-exclusion chromatography its molecular weight was estimated as 8.4 kDa. By methylation analysis, the linkage composition was established as 5:4:3:1 for (1→5)-Araf, T-Araf, (1→3,5)-Araf and (1→3)-Araf, respectively. 13C NMR spectroscopy confirmed this linkage composition, and allowed to assign the α anomeric configuration for the arabinofuranosyl residues, except for some terminally linked ones, that were seen to occur as T-β-Araf. By 2D NMR spectroscopy (1H and 13C), it was possible to conclude that the T-β-Araf was (1→5)-linked to a (1→5)-Araf residue. Also, in the arabinan (1→5)-Araf backbone, the branched (1→3,5)-Araf residues were always adjacent to linear (1→5)-Araf residues. A tentative structure is proposed. [Copyright &y& Elsevier]

Exhaustive extraction of the endosperm from the seed of Gleditsia triacanthos using water at room temperature and 50 °C left a residue, which was further extracted at 95 °C. Precipitation of this extract with 2-propanol yielded major amounts of galactomannan components, while the supernatant was mainly composed of arabinose-rich constituents. Two fractions were obtained by anion-exchange chromatography. The fraction that eluted with water is an arabinan with (1→5) α-l linkages and branching mainly on C-2, accompanied with equal amounts of a low-galactose galactomannan oligosaccharide, and a small proportion of a β-(1→4)-galactan. The fraction eluted with an increased ionic strength consists mainly of a similar arabinan, and lower proportions of a high-galactose galactomannan, galactan, and protein. The arabinan moiety in both fractions was characterized by chemical analysis and 1D and 2D NMR spectroscopic techniques. [Copyright &y& Elsevier]

When leaf disks from haploid plants of Nicotiana plumbaginifolia Viv. were transformed with T-DNA and cultured on shoot-inducing medium, non-organogenic callus, designated nolac (for non-organogenic callus with loosely attached cells), appeared on approximately 7% of leaf disks. In contrast, normal callus was generated on T-DNA-transformed leaf disks from diploid plants and on non-transformed leaf disks from haploid and diploid plants. Transmission electron microscopy revealed that the middle lamellae and the cell walls of one line of mutant callus (nolac-H14) were barely stained by ruthenium red, even after demethylesterification with NaOH, whereas the entire cell wall and the middle lamella were strongly stained in normal callus. In cultures of nolac-H14 callus, the level of sugar components of pectic polysaccharides in the hemicellulose fraction was reduced and that in the culture medium was elevated, as compared with cultures of normal callus. These results indicate that pectic polysaccharides are not retained in the cell walls and middle lamellae of nolac-H14 callus. In nolac-H14, the ratio of arabinose to galactose was low in the pectic polysaccharides purified from all cell wall fractions and from the medium, in particular, in the hemicellulose fractions. The low levels of arabinofuranosyl (T-Araf, 5-Araf, 2,5-Araf and 3,5-Araf) residues in the pectic polysaccharides of the hemicellulosic fraction of nolac-H14 indicated that no neutral-sugar side chains, composed mainly of linear arabinan, were present in nolac-H14. Arabinose-rich pectins, which are strongly associated with cellulose-hemicellulose complexes, might play an important role in intercellular attachment in the architecture of the cell wall. [ABSTRACT FROM AUTHOR]

We recently showed that yellow lupine is highly sensitive to soil water deficits since this stressor disrupts nodule structure and functioning, and at the same time triggers flower separation through abscission zone (AZ) activation in the upper part of the plant. Both processes require specific transformations including cell wall remodeling. However, knowledge about the involvement of particular cell wall elements in nodulation and abscission in agronomically important, nitrogen-fixing crops, especially under stressful conditions, is still scarce. Here, we used immuno-fluorescence techniques to visualize dynamic changes in cell wall compounds taking place in the root nodules and flower AZ of Lupinus luteus following drought. The reaction of nodules and the flower AZ to drought includes the upregulation of extensins, galactans, arabinans, xylogalacturonan, and xyloglucans. Additionally, modifications in the localization of high- and low-methylated homogalacturonans and arabinogalactan proteins were detected in nodules. Collectively, we determined for the first time the drought-associated modification of cell wall components responsible for their remodeling in root nodules and the flower AZ of L. luteus. The involvement of these particular molecules and their possible interaction in response to stress is also deeply discussed herein. [ABSTRACT FROM AUTHOR]

Pectins extracted from sugar beet pulp are promising additives for the food and beverage industry due to their good emulsifying properties. However, the relationship between molecular structure and emulsifying properties is still not fully understood; thus, systematic optimization of pectin extraction for a better emulsifying activity is not possible. In this study, we assess the underlying relationship between molecular structure and emulsifying properties by linking relevant structural parameters of 43 acid-extracted sugar beet pectins to their emulsifying properties. Sugar beet pectins with distinct structural characteristics were produced by acid extraction using varying conditions. The extracted polysaccharides were used as emulsifying agents in oil-in-water emulsions. Resulting droplet sizes were measured to correlate molecular characteristics with emulsifying properties. Analyses of protein content, degree of methylation, degree of acetylation, mean molecular weights, and trans -ferulic acid contents showed that these parameters affect the emulsifying properties to some degree, but cannot fully explain the differences observed among all pectins. However, a linear correlation between the proportion of neutral sugar side chains and droplet sizes was observed. The influence of galactose (18–30 mol%) was negligible, but increasing amounts of branched arabinans (up to 57 mol% arabinose) positively affected the emulsification result. Based on these results, it can be concluded that particularly branched arabinan side chains play an important role in the sugar beet pectin-based stabilization of emulsions. Thus, the arabinose content appears to be a suitable indicator to estimate the emulsifying properties of acid-extracted sugar beet pectins. [Display omitted] • 43 sugar beet pectins with different molecular structures were extracted. • Structures and emulsifying properties of all pectins were analyzed. • Pectins with higher protein contents did not lead to smaller oil droplets. • Ferulic acid, molecular weight, DM, and DAc had neglectable to moderate impact. • Higher portions of arabinan side chains clearly resulted in smaller droplets. [ABSTRACT FROM AUTHOR]

Quantitative and qualitative changes in cell wall polysaccharides of asparagus (Asparagus officinalis L.) during somatic embryogenesis and plantlet development were determined by methylation analysis. The globular embryos developed from the stable embryogenic calli in suspension culture for 15 d. The embryos developed into plantlets on a solid (2.5% agar) medium in 50 d. The root and other parts were separately sampled from the plantlet for sugar analysis of the cell walls. The percentage of cellulose was maintained at a low level (20%) during somatic embryogenesis and increased in the root and shoot after plantlet development (40–50%), while that of pectic polysaccharides decreased from 45 to 20–30% after embryogenesis. Hemicellulose was maintained at a constant percentage (30–40%) throughout the experiment. Methylation analysis of hemi-celluloses revealed that 5- and 3,5-linked arabinose transiently increased during embryogenesis and then steadily decreased during plantlet development. The contents of 4-linked xylose, the main component of xylan, and 4- and 4,6-linked glucose, found in the glucan backbone of xyloglucans, increased after plantlet development. These results suggested that branched arabinan was actively synthesized in embryonic calli but degraded during the course of differentiation, while xylan and xyloglucan were massively synthesized in the root and shoot as plantlet developed. [ABSTRACT FROM AUTHOR]

Carrot (Daucus carota L. cv. Kintoki) cell cultures secrete an α‐L‐arabinofuranosidase (α‐L‐AFase, EC 3.2.1.55) into their culture medium during growth. The extracellular α‐L‐AFase (α‐L‐AFase‐II) was purified to electrophoretic homogeneity from the concentrated medium using ammonium sulfate precipitation, chromatography on DEAE‐Sepharose CL‐6B, CM‐Sepharose CL‐6B, Sephacryl S‐200HR and Concanavalin A‐Sepharose, and preparative PAGE. The molecular mass of the purified enzyme was estimated to be 84 kDa by Sephacryl S‐200HR gel‐permeation, and 80 kDa by SDS‐PAGE under denaturing conditions. The enzyme contained carbohydrate and protein in a ratio of 1:5 (w/w), and was analyzed for amino acid composition and the sequence of the first 21 amino acids of the N‐terminus. The isoelectric point was pH 5.6, the pH optimum 3.8, and the temperature optimum 55°C. The activity was inhibited by Zn2+, Ag2+, Cu2+, Hg2+ and p‐chloromercuribenzoate. The Km and Vmax values for p‐nitrophenyl‐α‐L‐arabinofuranoside were 0.22 mM and 0.11 mmol (mg protein)−1 h−1, respectively. The enzyme acted on beet arabinan in an exo‐fashion, and was capable of hydrolysing arabinose‐rich polymers purified from pectic polysaccha‐rides of carrot cell cultures. However, even after an exhaustive reaction, the enzyme had little or no effect on cell walls from carrot cell cultures. [ABSTRACT FROM AUTHOR]

An α-L-arabinofuranosidase (α-L-arabinofuranoside arabinofuranohydrolase, EC 3.2.1.55) was isolated from a homogenate of cell suspension cultures of carrot (Daucus carota L. cv. Kintoki). The buffer-soluble enzyme was purified to homogeneity by a procedure involving ammonium sulfate fractionation, chromatography on DEAE-Sephadex A-50, Sephadex G-150, Con A-Sepharose 4B and CM-Sephadex C-50, and preparative polyacrylamide gel electrophoresis. The size of this enzyme as determined by polyacrylamide gel electrophoresis in the presence of sodium laurylsulfate and by Sephadex G-200 gel filtration was 94 and 110 kDa, respectively. The isoelectric point was at pH 4.7. The Km and Vmax values for p-nitrophenyl α-L-arabinofuranoside were 1.33 mM and 20.2 μmol (mg protein)-1 h-1, respectively. The optimal activity occurred at pH 4.2 with McIlvaine buffer. The enzyme was stimulated by Ca2+ and Zn2+, whereas it was strongly inhibited by Cu2+, Ag2+, Hg2+, p-chloromercuribenzoate and L-arabono-1,4-lactone. The enzyme acted on beet arabinan in an exo-fashion. Furthermore, the enzyme was partially involved in the hydrolysis of the arabinogalactan and pectic polymer purified from carrot cell walls. [ABSTRACT FROM AUTHOR]

This review deals with recent advances in the structural characterization of pectins and the gels which they form, in relation to auxin-induced extension growth, the ripening of fruit, and cellular recognition. Pectins are block polysaccharides. Heavily branched, largely methyl-esterified blocks alternate with unbranched blocks of varying degrees of esterification. The unbranched, non-esterified blocks can aggregate through calcium binding to form the junction zones that hold a gel together. The aggregates are of two, or possibly four, chains at low calcium levels, and larger with excess calcium. The fall in wall pH during auxin-induced growth activates glycanase enzymes. These may attack some components of thc pectic fraction, as well as xyloglucans. Pectin-bound calcium ions may be displaced but this probably has little effect on gel strength. Pectins may be cross-linked by diferulate esters when growth stops. The softening of ripe fruit is due to loss of cohesion in the pectin gel. In apples this results from replacement of the pectins by more esterified forms. In many other fruits it results from depolymerization by polygalacturonases, assisted by pectinesterases, so that the remaining segments are too short for effective calcium binding. Pectins have a further role in the recognition reactions between plant cells and some of their bacterial and fungal pathogens. [ABSTRACT FROM AUTHOR]

Cell walls isolated from pollen of Nicotiana alata germinated in vitro contain glucose and arabinose as the predominant monosaccharides. Methylation analysis and cytochemical studies are consistent with the major polysaccharides being a (1→3)-β- D-glucan (callose) and an arabinan together with small amounts of cellulose. The cell walls contain 2.8% uronic acids. Alcian blue stains the pollen-tube walls intensely at the tip, indicating that acidic polysaccharides are concentrated in the tip. Synthetic aniline-blue fluorochrome is specific primarily for (1→3)-β- D-glucans and stains the pollen-tube walls, except at the tip. Protein (1.5%), containing hydroxyproline (2.4%), is present in the cell wall. [ABSTRACT FROM AUTHOR]

Some 22% of the dry weight of the cotyledons of resting seeds of Lupinus angustifolius cv. Unicrop has been shown to be non-starch polysaccharide material comprising the massively thickened walls of the storage mesophyll cells. On hydrolysis this material released galactose (76%), arabinose (13%), xylose (4%), uronic acid (7%): only traces of glucose were detected indicating the virtual absence of cellulose from the walls. Changes in the amount and composition of this material following germination have been studied in relation to parameters of seedling development and the mobilisation of protein, lipid and oligosaccharide reserves. Starch, which was not present in the resting seed, appeared transitorily following germination: under conditions of continuous darkness starch levels were reduced. During the period of bulk-reserve mobilisation, 92% of the non-starch polysaccharide material disappeared from the cotyledons. The residual cell-wall material released galactose (14%), arabinose (19%), xylose (24%) and uronic acid (43%). The galactose and arabinose residues of the cotyledonary cell walls clearly constitute a major storage material, quantitatively as important as protein. The overall role of the wall polysaccharides in seedling development is discussed. [ABSTRACT FROM AUTHOR]

Information on the biosynthesis of the D-arabinans of the cell wall of is rapidly emerging, with the promise of new targets for drug development against tuberculosis. Accordingly, arabinosyl transferase assays were developed utilizing synthesized [1–C]-β-D-arabinofuranosyl-1-monophosphoryldecaprenol as donor and a variety of - and -alkyl arabinosides as acceptors. These were: α-D-Ara-(1→5)-α-D-Ara-- and --alkyl di-arabinosides and α-D-Ara-(1→5)-α-D-Ara-(1→5)-α-D-Ara-- and --alkyl triarabinosides. Whereas the - and -alkyl monosaccharide acceptors were inactive, the - and -alkyl disaccharide and the - and -alkyl trisaccharide acceptors (

A species of was isolated from soil by enrichment culture and shown to secrete enzymes capable of degrading mycobacterial cell wall arabinogalactan, both the insoluble peptidoglycan-bound and base-solubilized forms. The major degradation product was purified and characterized as a hexa-arabinofuranoside, [β-D-Ara-(1←2)-α-Ara-(1←]←3,5-α-D-Ara(1←5)-D-Ara. The non-reducing ends of this unit are the sites of mycolic acid attachment and, as they also appear in lipoarabinomannan (LAM), the point of mannose capping in some mycobacteria. Thus, elaboration of the structure of this focal hexasaccharide is critical to our understanding of much of the physiology and pathogenesis of mycobacteria. The extracellular enzymes of sp. also released the disaccharide, α-D-Ara-(1←5)-D-Ara, from internal linear regions of arabinan and, surprisingly, convert the linear galactan backbone into cyclic oligosaccharides of the structure [←5-D-Gal-(1←6)-β-D-Gal-(1←], where is 2, 3 or 4. Thus, the preparation contains Schardinger-like enzyme activity. This group of enzymes are powerful tools for the dissection of the mycolylarabinogalactan-peptidoglycan (mAGP) complex of mycobacteria towards understanding its role in drug resistance, disease processes and mycobacterial physiology. [ABSTRACT FROM PUBLISHER]

In this article, the author discusses a research related to refining arabinan polysaccharides by alcohol extraction of the prune, Prunus domestica L. Topics discussed include arabinans appear in the primary cell walls of different families of plants including seeds, fruits, and roots as pectic polysaccharide side-chains or as free polymers, the polysaccharides were separated by ion-exchange chromatography, and terminal arabinosyl residues mostly occur as furanoses.

• The oxalate-extractable pectin (PA O) were isolated from P. abies greenery. • PA O core consists of 1,4-α-Gal p A, 1,4-α-Gal p A(OMe), and 1,4-α-Gal p A(OAc). • RG-I side chains are formed of branched 1,5-α- l -arabinan and arabinogalactan type I. • RG-I regions alternate with non-acetylated and non-methyl-esterified galacturonan. • PA O fraction also contained of the xylan and glucomannan. Structurally different polymers were derived from Picea abies foliage by successive extraction with water (PA W), HCl solution (PA A) and (NH 4) 2 C 2 O 4 solution (PA O). The P. abies foliage was found to contain basically low-methoxyl pectin extractable with an (NH 4) 2 C 2 O 4 solution. PA W was shown to comprise primarily arabinogalactan-proteins (AGPs); PA A was composed of mixed AGPs and pectic polysaccharides, with the latter prevailing; and polysaccharide PA O isolated in the highest yield included chiefly pectic polysaccharides. The major constituents of PA O were low-methoxyl and low-acetylated 1,4-α- d -galacturonan and partially acetylated RG-I. The sugar side chains of RG-I contained chiefly highly branched 1,5-α- l -arabinan and arabinogalactan type I as a minor constituent. RG-I whose side chains had 1,5-α- l -arabinan represented short regions alternating with non-acetylated and unmethylesterified galacturonan regions. In addition to pectins, polysaccharide PA O contained AGPs, xylanes and glucomannans, indicating that these polysaccharides are in an intimate interaction. [ABSTRACT FROM AUTHOR]

• Structure of P. granatum pectin (PG O) was characterized for the first time. • PG O core consists of 1,4-α-Gal p A, 1,4-α-Gal p A(O Me), and 1,4-α-Gal p A(O Ac). • RG-I side chains are formed of branched 1,5-α- l -arabinan and arabinogalactan type I. • PG O fraction also contained of the glucuronoxylan and xyloglucan. The polysaccharide PG O containing 76 % of uronic acids, was obtained from peels and membranes of Punica granatum fruits by extraction to the aqueous solution of (NH 4) 2 C 2 O 4. The chemical structure of PG O was characterized by enzymatic and partial acid hydrolyses, Smith degradation and 1D/2D NMR spectroscopy. It has been found that PG O consisted mainly of highly methyl-esterified and lowly acetylated pectin. Backbone of the macromolecule was represented by 1,4-α-D-Gal p A, 1,4-α-D-Gal p A(O Me), 1,4-α-D-Gal p A(O Ac). The branched region PG O contained minor segments of partially acetylated rhamnogalacturonan-I (RG-I). RG-I side chains were comprised of highly branched 1,5-α- l -arabinan and segments of arabinogalactan type I. In addition to pectins, PG O contained the glucuronoxylans and xyloglucans, indicating a close interaction of these polysaccharides with each other in the cell wall. It was concluded that P. granatum fruit could be a promising source of pectic polysaccharides. [ABSTRACT FROM AUTHOR]

• Pea pectin structure was delineated by enzymatic and biochemical approaches. • Various fungal pectin-degrading enzymes were used. • Arabinose content of pea pectin (molecular weight 488,000) is 50 %. • Arabinan, a side chain of rhamnogalacturonan-I (RG-I) is highly branched. • Pea pectin is composed of RG-I:homogalacturonan:xylogalacturonan (7:1:2). The chemical structure of pea pectin was delineated using pectin-degrading enzymes and biochemical methods. The molecular weight of the pea pectin preparation was 488,000, with 50 % arabinose content, and neutral sugar side chains attached to approximately 60 % of the rhamnose residues in rhamnogalacturonan-I (RG-I). Arabinan, an RG-I side chain, was highly branched, and the main chain was comprised of α-1,5- l -arabinan. Galactose and galactooligosaccharides were attached to approximately 35 % of the rhamnose residues in RG-I. Long chain β-1,4-galactan was also present. The xylose substitution rate in xylogalacturonan (XGA) was 63 %. The molar ratio of RG-I/homogalacturonan (HG)/XGA in the backbone of the pea pectin was approximately 3:3:4. When considering neutral sugar side chain content (arabinose, galactose, and xylose), the molar ratio of RG-I/HG/XGA regions in the pea pectin was 7:1:2. These data will help understand the properties of pea pectin. [ABSTRACT FROM AUTHOR]

• Hydrophobic polysaccharides were isolated from apple pomace. • Pectin-polyphenol-xyloglucan and arabinan-polyphenol complexes were identified. • Polysaccharide-polyphenol complexes are formed during apple processing. • Oxidized polyphenols are covalently bonded to polysaccharides in apple pomace. • Covalently bonded polyphenols modulate polysaccharides hydrophobicity. In this work, polysaccharides extracted with hot water from apple pomace were isolated by C18 cartridge solid-phase extraction at pH 7 (Fr7). Dialysis (12–14 kDa) of this fraction allowed to obtain 17% (w/w) of polymeric material composed by 65% of polysaccharides, mainly arabinose (58 mol%), galacturonic acid (16 mol%) and glucose (10 mol%). Folin-Ciocalteu assay showed 62 g of phloridzin equiv/kg of polyphenols. Moreover, adjusting to pH 3, it was possible to retain an additional fraction (Fr3) representing a further 4% of the polymeric material. Fr3 contained 53% of polysaccharides composed mainly by galacturonic acid (66 mol%) and polyphenols accounted for 37 g of phloridzin equiv/kg. Precipitation with ethanol and subsequent methylation and NMR spectroscopic analysis of Fr7 dialysate allowed the identification of covalently-linked pectic-polyphenol-xyloglucan and arabinan-polyphenol complexes. These structures are possibly formed as a result of polyphenol oxidation reactions during the industrial processing of apples, conferring hydrophobic characteristics to apple pomace polysaccharides. [ABSTRACT FROM AUTHOR]

Meloidogyne incognita is a root knot nematode (RKN) species which is among the most notoriously unmanageable crop pests with a wide host range. It inhabits plants and induces unique feeding site structures within host roots, known as giant cells (GCs). The cell walls of the GCs undergo the process of both thickening and loosening to allow expansion and finally support nutrient uptake by the nematode. In this study, a comparative in situ analysis of cell wall polysaccharides in the GCs of wild-type Col-0 and the microtubule-defective fra2 katanin mutant, both infected with M. incognita has been carried out. The fra2 mutant had an increased infection rate. Moreover, fra2 roots exhibited a differential pectin and hemicellulose distribution when compared to Col-0 probably mirroring the fra2 root developmental defects. Features of fra2 GC walls include the presence of high-esterified pectic homogalacturonan and pectic arabinan, possibly to compensate for the reduced levels of callose, which was omnipresent in GCs of Col-0. Katanin severing of microtubules seems important in plant defense against M. incognita, with the nematode, however, to be nonchalant about this "katanin deficiency" and eventually induce the necessary GC cell wall modifications to establish a feeding site. [ABSTRACT FROM AUTHOR]

In apple (Malus×domestica) fruit, the different layers of the exocarp (cuticle, epidermis, and hypodermis) protect and maintain fruit integrity, and resist the turgor-driven expansion of the underlying thin-walled cortical cells during growth. Using in situ immunolocalization and size exclusion epitope detection chromatography, distinct cell type differences in cell wall composition in the exocarp were revealed during apple fruit development. Epidermal cell walls lacked pectic (1→4)-β-d-galactan (associated with rigidity), whereas linear (1→5)-α-l-arabinan (associated with flexibility) was exclusively present in the epidermal cell walls in expanding fruit and then appeared in all cell types during ripening. Branched (1→5)-α-l-arabinan was uniformly distributed between cell types. Laser capture microdissection and RNA sequencing (RNA-seq) were used to explore transcriptomic differences controlling cell type-specific wall modification. The RNA-seq data indicate that the control of cell wall composition is achieved through cell-specific gene expression of hydrolases. In epidermal cells, this results in the degradation of galactan side chains by possibly five β-galactosidases (BGAL2, BGAL7, BGAL10, BGAL11, and BGAL103) and debranching of arabinans by α-arabinofuranosidases AF1 and AF2. Together, these results demonstrate that flexibility and rigidity of the different cell layers in apple fruit during development and ripening are determined, at least in part, by the control of cell wall pectin remodelling., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Guavira is a plant that belongs to Myrtaceae family, being widespread in the Brazilian Cerrado. In this study, pectic and hemicellulosic polysaccharides from guavira pomace, an agroindustry residue from pulp production, were structurally characterized using GPC, monosaccharide composition, methylation and NMR experiments. The absolute configurations of monosaccharides and the nature of uronic acids were attributed according to numerous data on the composition of related plant arabinogalactans and hemicelluloses present in the literature. An arabinan was purified, presenting Ara (85.0%), Rha (3.3%), Gal (7.7%) and GalA (4.0%). Mono and bidimensional NMR analyses of this arabinan demonstrated the presence of terminal β-L-Araf units, whose occurrence has been scarcely reported in the literature. Hemicellulosic fraction contained a glucuronoxylan, with α-D-GlcpA/4-O-methyl-α-D-GlcpA group linked to O-2 of a (1 → 4)-β-D-xylan, presenting one uronic acid residue for every six xylose units. These findings about guavira pomace polysaccharides could contribute to develop future nutraceutical and technological uses for this industrial waste., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The objective of the study was to determine the changes brought about by malting/germination on the pectic polysaccharides (PP's), the major components of soluble fibres present in chickpea ( Cicer arietinum L .) hull. Chickpea hull PP's were extracted sequentially using ammonium oxalate (AO) and ethylenediaminetetraacetic acid (EDTA), and a comparative study was conducted in native (unprocessed, N-PP) and after subjecting to 48 h malting process (M-PP). Malting process did not show a significant change in the respective yields of AO and EDTA extracted pectic polysaccharides. The degree of esterification of N-PP-EDTA through Fourier transform infrared spectroscopy was found to be five times (~ 21%) more than N-PP-AO (~ 4%). AO isolated PP's have more complexed xylogalacturonan with relatively more galactan side chains compared to EDTA isolated PPs. Proton ( 1 H) nuclear magnetic resonance result further suggested the occurrence of arabinan rich rhamnogalacturonan in chickpea hull and malting process showed no significant changes in structure.