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The xyloglucans of monocotyledons are known to vary in the abundance of fucosylated side chains, with most commelinid monocotyledons having xyloglucans with lower proportions than non-commelinid monocotyledons. In many commelinid species, and some non-commelinid species that have lower proportions of fucosylated side chains, these side chains have been shown to be cell-type specific. To determine whether it is just the fucosylated side chains that are cell-type specific, or whether xyloglucan is cell-type specific in these species, we used the monoclonal antibody LM15 in conjunction with immmunofluorescence microscopy. We examined the distribution of cell-wall labelling among cell types in these species. The primary walls of all cell types were shown to contain xyloglucans in all species that had cell-type specific distributions of fucosylated side chains. This indicates that it is the fucosylated side chains of xyloglucans that is cell-type specific. Although the functional significance of xyloglucan fucosylation remains unknown, such cell-type specificity supports hypotheses that the fucosylated side chains may indeed have a functional role within the cell wall., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Background: Compression wood (CW) forms on the underside of tilted stems of coniferous gymnosperms and opposite wood (OW) on the upperside. The tracheid walls of these wood types differ structurally and chemically. Although much is known about the most severe form of CW, severe CW (SCW), mild CWs (MCWs), also occur, but less is known about them. In this study, tracheid wall structures and compositions of two grades of MCWs (1 and 2) and SCW were investigated and compared with OW in slightly tilted radiata pine (Pinus radiata) stems., Results: The four wood types were identified by the distribution of lignin in their tracheid walls. Only the tracheid walls of OW and MCW1 had a S3 layer and this was thin in MCW1. The tracheid walls of only SCW had a S2 layer with helical cavities in the inner region (S2i). Using immunomicroscopy, (1 → 4)-β-D-galactans and (1 → 3)-β-D-glucans were detected in the tracheid walls of all CWs, but in only trace amounts in OW. The (1 → 4)-β-D-galactans were located in the outer region of the S2 layer, whereas the (1 → 3)-β-D-glucans were in the inner S2i region. The areas and intensities of labelling increased with CW severity. The antibody for (1 → 4)-β-D-galactans was also used to identify the locations and relative amounts of these galactans in whole stem cross sections based on the formation of an insoluble dye. Areas containing the four wood types were clearly differentiated depending on colour intensity. The neutral monosaccharide compositions of the non-cellulosic polysaccharides of these wood types were determined on small, well defined discs, and showed the proportion of galactose was higher for CWs and increased with severity., Conclusion: The presence of an S3 wall layer is a marker for very MCW and the presence of helical cavities in the S2 wall layer for SCW. The occurrence and proportions of (1 → 4)-β-D-galactans and (1 → 3)-β-D-glucans can be used as markers for CW and its severity. The proportions of galactose were consistent with the labelling results for (1 → 4)-β-D-galactans.

Little is known about the structures of the xyloglucans in the primary cell walls of vascular plants (tracheophytes) other than angiosperms. Xyloglucan structures were examined in 13 species of gymnosperms, 13 species of monilophytes (ferns sensu lato), and two species of lycophytes. Wall preparations were obtained, extracted with 6 M sodium hydroxide, and the extracts treated with a xyloglucan-specific endo-(1→4)-β-glucanase preparation. The oligosaccharides released were analysed by matrix-assisted laser-desorption ionisation time-of-flight mass spectrometry and by high-performance anion-exchange chromatography. The xyloglucan oligosaccharide profiles from the gymnosperm walls were similar to those from the walls of most eudicotyledons and non-commelinid monocotyledons, indicating that the xyloglucans were fucogalactoxyloglucans, containing the fucosylated units XXFG and XLFG. The xyloglucan oligosaccharide profiles for six of the monilophyte species were similar to those of the gymnosperms, indicating they were also fucogalactoxyloglucans. Phylogenetically, these monilophyte species were from both basal and more derived orders. However, the profiles for the other monilophyte species showed various significant differences, including additional oligosaccharides. In three of the species, these additional oligosaccharides contained arabinosyl residues which were most abundant in the profile of Equisetum hyemale. The two species of lycophytes examined, Selaginella kraussiana and Lycopodium cernuum, had quite different xyloglucan oligosaccharide profiles, but neither were fucogalactoxyloglucans. The S. kraussiana profile had abundant oligosaccharides containing arabinosyl residues. The L. cernuum profile indicated the xyloglucan had a very complex structure., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Xyloglucans in the non-lignified primary cell walls of different species of monocotyledons have diverse structures, with widely varying proportions of oligosaccharide units that contain fucosylated side chains (F side chains). To determine whether fucosylated xyloglucans occur in all non-lignified walls in a range of monocotyledon species, we used immunofluorescence microscopy with the monoclonal antibody CCRC-M1. The epitope of this antibody, α-L-Fucp-(1→2)-β-D-Galp, occurs in F side chains. In most non-commelinid monocotyledons, the epitope was found in all non-lignified walls. A similar distribution was found in the palm Phoenix canariensis, which is a member of the basal commelinid order Arecales. However, in the other commelinid orders Zingiberales, Commelinales, and Poales, the occurrence of the epitope was restricted, sometimes occurring in only the phloem walls, but often also in walls of other cell types including stomatal guard and subsidiary cells and raphide idioblasts. No epitope was found in the walls of the commelinids Tradescantia virginiana (Commelinaceae, Commelinales) and Zea mays (Poaceae, Poales), but it occurred in the phloem walls of two other Poaceae species, Lolium multiflorum and L. perenne. The distribution of the epitope is discussed in relation to xyloglucan structures in the different taxa. However, the functional significance of the restricted distributions is unknown.

To investigate possible molecular interactions between xyloglucans (XGs) and cellulose in plant cell walls, a model composite was produced using cellulose from the bacterium Gluconacetobacter xylinus and XG from the walls of a tobacco cell-suspension culture that had been incubated with (13)C-labeled glucose. Solid-state (13)C NMR with cross-polarization (CP) and magic-angle spinning (MAS) was used in combination with proton spin-relaxation editing to separate signals from crystalline (rigid) and less rigid domains of the composite. Signals from XG were confined to subspectra of less rigid domains, with no detectable signals from XG attached to surfaces of cellulose crystallites. Signal displacements indicated XGs were more rigid than the mobile coil (twisted backbone) conformation expected for unattached XGs. Similar (13)C chemical shifts were observed in a single-pulse excitation experiment. The results were not compatible with extensive hydrogen bonding between XG and cellulose, but were consistent with a composite structure in which cellulose crystallites were embedded in a matrix of XG with a semirigid (straightened backbone) conformation, that is, a matrix that is partly ordered rather than amorphous.

Except in the Poaceae, little is known about the structures of the xyloglucans in the primary walls of monocotyledons. Xyloglucan structures in a range of monocotyledon species were examined. Wall preparations were isolated, extracted with 6 M sodium hydroxide, and the extracts treated with a xyloglucan-specific endo-(1-->4)-beta-glucanase preparation. The oligosaccharides released were analyzed by high-performance anion-exchange chromatography and by matrix-assisted laser-desorption ionization time-of-flight mass spectrometry. Oligosaccharide profiles of the non-commelinid monocotyledons were similar to those of most eudicotyledons, indicating the xyloglucans were fucogalactoxyloglucans, with a XXXG a core motif and the fucosylated units XXFG and XLFG. An exception was Lemna minor (Araceae), which yielded no fucosylated oligosaccharides and had both XXXG and XXGn core motifs. Except for the Arecales (palms) and the Dasypogonaceae, which had fucogalactoxyloglucans, the xyloglucans of the commelinid monocotyledons were structurally different. The Zingiberales and Commelinales had xyloglucans with both XXGn and XXXG core motifs; small proportions of XXFG units, but no XLFG units, were present. In the Poales, the Poaceae had xyloglucans with a XXGn core motif and no fucosylated units. In the other Poales families, some had both XXXG and XXGn core motifs, others had only XXXG; XXFG units were present, but XLFG units were not.

- Model composites, produced using cellulose from stationary cultures of the bacterium Gluconoacetobacter xylinus and tamarind xyloglucan, were examined by wide-angle X-ray scattering (WAXS) and CP/MAS solid-state (13)C NMR spectroscopy. The dominant crystallite allomorph of cellulose produced in culture media with or without xyloglucan was cellulose I(alpha) (triclinic). The presence of xyloglucan in the culture medium reduced the cross-section dimensions of the cellulose crystallites, but did not affect the crystallite allomorph. However, when the composites were refluxed in buffer, the proportion of cellulose I(beta) allomorph increased relative to that of cellulose I(alpha). In contrast, cellulose I(alpha) remained the dominant form when cellulose, produced in the absence of xyloglucan, was then heated in the buffer. Hence the presence of xyloglucan has a profound effect on the formation of the cellulose crystallites by G. xylinus.

Xyloglucans (XG) with different mobilities were identified in the primary cell walls of mung beans (Vigna radiata L.) by solid-state 13C-NMR spectroscopy. To improve the signal:noise ratios compared with unlabelled controls, Glc labelled at either C-1 or C-4 with 13C-isotope was incorporated into the cell-wall polysaccharides of mung bean hypocotyls. Using cell walls from seedlings labelled with d-[1-13C]glucose and, by exploiting the differences in rotating-frame and spin-spin proton relaxation, a small signal was detected which was assigned to Xyl of XGs with rigid glucan backbones. After labelling seedlings with d-[4-13C]glucose and using a novel combination of spin-echo spectroscopy with proton spin relaxation-editing, signals were detected that had 13C-spin relaxations and chemical shifts which were assigned to partly-rigid XGs surrounded by mobile non-cellulosic polysaccharides. Although quantification of these two mobility types of XG was difficult, the results indicated that the partly-rigid XGs were predominant in the cell walls. The results lend support to the postulated new cell-wall models in which only a small proportion of the total surface area of the cellulose microfibrils has XG adsorbed on to it. In these new models, the partly-rigid XGs form cross-links between adjacent cellulose microfibrils and/or between cellulose microfibrils and other non-cellulosic polysaccharides, such as pectic polysaccharides.

Solid-state CP/MAS 13C NMR spectroscopy was used to determine the effects of three different sequential extraction procedures, used to remove non-cellulosic polysaccharides, on the molecular ordering of cellulose in a cell-wall preparation containing mostly primary cell walls obtained from the leaves of the model dicotyledon, Arabidopsis thaliana. The extractions were 50 mM trans-1,2-diaminocyclohexane N,N,N',N'-tetraacetic acid (CDTA) and 50 mM sodium carbonate (giving Residue 1); 50 mM CDTA, 50 mM sodium carbonate and 1 M KOH (giving Residue 2); and 50 mM CDTA, 50 mM sodium carbonate and 4 M KOH (giving Residue 3). The molecular ordering of cellulose in Residue 1 was similar to that in unextracted walls: the cellulose was almost all crystalline, with 43% of molecules contained in crystallite interiors and similar proportions of the triclinic (I(alpha)) and monoclinic (I(beta)) crystal forms. Residue 2 was partly decrystallized and the remaining crystallites were mostly in the I(beta) form. Residue 3 was a mixture of cellulose II, cellulose I and amorphous cellulose. The presence of signals at 100.0 and 102.3 ppm in the spectra of Residues 1 and 2, but not of unextracted cell walls, suggested that the extractions giving these residues caused some of the non-cellulosic polysaccharides, possibly xyloglucans and galactoglucomannans, to become relatively well ordered, for example through interactions with cellulose crystallite surfaces.

Background: Compression wood (CW) forms on the underside of tilted stems of coniferous gymnosperms and opposite wood (OW) on the upperside. The tracheid walls of these wood types differ structurally and chemically. Although much is known about the most severe form of CW, severe CW (SCW), mild CWs (MCWs), also occur, but less is known about them. In this study, tracheid wall structures and compositions of two grades of MCWs (1 and 2) and SCW were investigated and compared with OW in slightly tilted radiata pine (Pinus radiata) stems. Results: The four wood types were identified by the distribution of lignin in their tracheid walls. Only the tracheid walls of OW and MCW1 had a S3 layer and this was thin in MCW1. The tracheid walls of only SCW had a S2 layer with helical cavities in the inner region (S2i). Using immunomicroscopy, (1→4)-β-D-galactans and (1→3)-β-D-glucans were detected in the tracheid walls of all CWs, but in only trace amounts in OW. The (1→4)-β-D-galactans were located in the outer region of the S2 layer, whereas the (1→3)-β-D-glucans were in the inner S2i region. The areas and intensities of labelling increased with CW severity. The antibody for (1→4)-β-D-galactans was also used to identify the locations and relative amounts of these galactans in whole stem cross sections based on the formation of an insoluble dye. Areas containing the four wood types were clearly differentiated depending on colour intensity. The neutral monosaccharide compositions of the non-cellulosic polysaccharides of these wood types were determined on small, well defined discs, and showed the proportion of galactose was higher for CWs and increased with severity. Conclusion: The presence of an S3 wall layer is a marker for very MCW and the presence of helical cavities in the S2 wall layer for SCW. The occurrence and proportions of (1→4)-β-D-galactans and (1→3)-β-D-glucans can be used as markers for CW and its severity. The proportions of galactose were consistent with the labelling results for (1→4)-β-D-galactans. [ABSTRACT FROM AUTHOR]

Abstract: - Model composites, produced using cellulose from stationary cultures of the bacterium Gluconoacetobacter xylinus and tamarind xyloglucan, were examined by wide-angle X-ray scattering (WAXS) and CP/MAS solid-state 13C NMR spectroscopy. The dominant crystallite allomorph of cellulose produced in culture media with or without xyloglucan was cellulose Iα (triclinic). The presence of xyloglucan in the culture medium reduced the cross-section dimensions of the cellulose crystallites, but did not affect the crystallite allomorph. However, when the composites were refluxed in buffer, the proportion of cellulose Iβ allomorph increased relative to that of cellulose Iα. In contrast, cellulose Iα remained the dominant form when cellulose, produced in the absence of xyloglucan, was then heated in the buffer. Hence the presence of xyloglucan has a profound effect on the formation of the cellulose crystallites by G. xylinus. [Copyright &y& Elsevier]

(1↵3),(1↵4)-β-Glucans had previously been detected in nonlignified cell wall preparations of only the Poaceae and five other families in the graminoid clade of the Poales (s.l.). Cell walls of vegetative organs of 12 species in nine families of the Poales (s.l.) were examined by immunogold labeling using a monoclonal antibody to (1↵3),(1↵4)-β-glucans. Three types of wall-labeling patterns were identified depending on the density of labeling of the nonlignified walls of epidermal and parenchyma cells and the lignified walls of sclerenchyma fibers and xylem tracheary elements: type 1 in Poaceae and Flagellariaceae, type 2 in Restionaceae and Xyridaceae, and type 3 in Cyperaceae and Juncaceae. Type 1 had the heaviest labeling of nonlignified walls and type 2 the heaviest labeling of lignified walls. Type 3 had the least wall labeling, with only very light labeling of nonlignified and lignified walls. No labeling was found over walls of Typhaceae, Sparganiaceae, or Bromeliaceae. The results are discussed in relation to Poales phylogeny. [ABSTRACT FROM AUTHOR]

Summary • (1 → 3),(1 → 4)-β-Glucans occur only in the cell walls of the family Poaceae (grasses and cereals) and related families, but little is known about their distribution among walls of different cell types or within walls. • The locations of (1 → 3)- and (1 → 3),(1 → 4)-β-glucans in the walls of the coleoptile, first leaf and root tip of barley (Hordeum vulgare ) seedlings were determined using immunogold labelling. • All the walls were labelled with the (1 → 3),(1 → 4)-β-glucan antibody, except those of the outer root cap cells. Labelling of the primary walls was heavy in the coleoptile and leaf, but light or very light in the root tip. Two types of primary wall labelling occurred: in the coleoptiles (except the walls of the epidermis and two layers of parenchyma under this) and in the leaf, labelling was throughout the walls; in the root tips, labelling was only adjacent to the plasma membrane. Small amounts of labelling occurred with the (1 → 3)-β-glucan antibody, mostly over plasmodesmata. Both antibodies labelled cell plates. • (1 → 3),(1 → 4)-β-Glucans occur widely in the cell walls of vegetative organs of the barley seedlings, including the walls of meristematic tissues. [ABSTRACT FROM AUTHOR]

The molecular mobility of the non-cellulosic polysaccharides in hydrated primary cell walls of three monocotyledons (Italian ryegrass, pineapple and onion) and one dicotyledon (cabbage) was studied using solid-state 13C NMR spectroscopy. These cell walls were chosen as they have different non-cellulosic polysaccharide compositions. By exploiting proton rotating-frame and spin-spin relaxation time constants three different cell wall domains which responded to cross-polarization experiments were identified. Most of the non-cellulosic polysaccharides occupied a mobile domain (C), but some occupied a partly rigid domain (B). Crystalline cellulose occupied a highly rigid domain (A). In the cell walls of Italian ryegrass and pineapple, domain C contained mainly glucuronoarabinoxylans and small amounts of rhamnogalacturonans; domain B contained small amounts of xyloglucans and galacturonans. However, in the cell walls of onion and cabbage, domain C contained mainly rhamnogalacturonans with galactans (in onion) or arabinans (in cabbage) as side chains; domain B contained galacturonans and xyloglucans. Single-pulse excitation was used on Italian ryegrass and cabbage cell walls to reveal signals from a highly mobile fourth domain (D). In Italian ryegrass cell walls domain D contained glucuronoarabinoxylans and small amounts of rhamnogalacturonan, whereas in cabbage cell walls it contained arabinan side chains of rhamnogalacturonans. A novel feature of the research was the use of solid-state 13C NMR spectroscopy to examine the molecular mobilities of the polysaccharides in monocotyledon cell walls that contain glucuronoarabinoxylans. [ABSTRACT FROM AUTHOR]