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Highlights • Comparative structural characterization of leaf cell walls of desiccation-tolerant and desiccation-sensitive Selaginella species. • Leaf cell walls Selaginella species are mainly composed of hemicellulosic polysaccharides namely arabinoxylan, mannan and xyloglucan. • Desiccation induces significant structural alterations of the xyloglucan and arabinoxylan in S. involvens compared to S. kraussiana and S. moellendorffii. • Structural remodeling of these hemicellulosic polysaccharides is an important process leading to desiccation tolerance in Selaginella plants. Abstract Drought-induced dehydration of vegetative tissues in lycopods affects growth and survival. Different species of Selaginella have evolved a series of specialized mechanisms to tolerate desiccation in vegetative tissues in response to water stress. In the present study, we report on the structural characterization of the leaf cell wall of the desiccation-tolerant species S. involvens and two desiccation-sensitive species, namely S. kraussiana and S. moellendorffii. Isolated cell walls from hydrated and desiccated leaves of each species were fractionated and the resulting oligosaccharide fragments were analyzed to determine their structural features. Our results demonstrate that desiccation induces substantial modifications in the cell wall composition and structure. Altogether, these data highlight the fact that structural remodeling of cell wall hemicellulosic polysaccharides including XXXG-rich xyloglucan, arabinoxylan and acetylated galactomannan is an important process in order to mitigate desiccation stress in Selaginella. [ABSTRACT FROM AUTHOR]

Plant cell walls provide essential functions in cell recognition, differentiation, adhesion and wound responses. Therefore, it is tempting to hypothesize that cell walls play a key role in grafting, but to date there are no quantitative studies targeting on cell wall changes during grafting. The aim of this work was to investigate the dynamics of pectic and hemicellulosic polysaccharides at the graft junctions in tomato homografts throughout the first 12 days after grafting. Cell wall fractionation, combined with ATR-FTIR spectroscopy and gas-chromatography, evidenced a marked increase in pectin content and a decrease in the degree of methyl-esterification of homogalacturonan in scion and rootstock throughout grafting. Also, recovery of tightly-bound hemicelluloses decreased at late times after grafting suggesting an increase of cross-linked hemicelluloses along grafting. In addition, immuno-dot assays revealed an increase in xyloglucan and arabinogalactan proteins in the first days after grafting, pointing to a presumed role in tissue adhesion-cohesion. [ABSTRACT FROM AUTHOR]

Abstract: To prepare and explore the structure of native hemicellulose from tomato, extraction of the natively acetylated polysaccharides was achieved from partially depectinated cell walls by DMSO doped with LiCl. DEAE anion exchange chromatography of the LiCl–DMSO extract allowed the removal of residual acidic pectin and the isolation of acetylated glucuronoxylan. The hemicellulose neutral fraction from the anion exchanger was fractionated by size exclusion chromatography into xyloglucan (XyG) and galactoglucomannan (GgM) either as single major constituents or as mixtures of both. Residual hemicellulose in the cell wall was extracted by 4.0M and not 1.0M KOH. The fine structure of all LiCl–DMSO fractions and alkali extracts was assessed by coupling β-glucanase, β-mannanase and β-xylanase enzymatic degradations to the analysis of the resulting fragments by HPAEC and MALDI-TOF mass spectrometry. This approach revealed substitutions in part of the GgM fractions by pentose residues, presumably arabinose and/or xylose occurring in highly substituted block domains. It also demonstrated a different glucanase hydrolysis profile from 4.0M KOH compared to LiCl–DMSO soluble fractions. The present extraction and purification scheme allow the recovery of several populations of acetylated hemicellulose families which emphasize the structural diversity and complexity of these polysaccharides. [Copyright &y& Elsevier]

Abstract: Salicornia brachiata is an extreme halophyte, growing opulently in salt marshes and considered as potential alternative crop for seawater agriculture. Salicornia seeds are rich in protein and tender-shoots are eaten as salad greens. Total cell wall carbohydrate was isolated from seedlings, digested with β-glucanase enzyme cocktail and oligosaccharide mass profiling (OLIMP) was performed by using MALDI TOF-TOF mass spectroscopy. Salicornia OLIMP is represented by characteristic mass peaks m/z 477.3297–2094.4363. MS spectra exhibit xyloglucan oligosaccharide building blocks, dominated by XXXG (1084.9927 m/z). Characteristic mass peaks (m/z) of xyloglucan oligomers (XXG, XXFG, XLXG and XLFG) were also detected, which showed resemblance to the mass profile of highly nutritious plant soybean. The present study is the first report on OLIMP for any edible halophyte, so far. OLIMP supports use of Salicornia as a potential source of dietary supplementation. Further linkage-analysis is required to get the structural information of oligosaccharides. [Copyright &y& Elsevier]

• Major amounts of glucuronoarabinoxylans (GAX) were obtained from bamboo shoots. • Exhaustive alkaline extraction and alternative extraction with DMSO were performed. • GAX showed acetylation mainly on C3, but also on C2 of some xylose units. • Arabinogalactans and pectins, mixed linkage glucans and xyloglucans were obtained. • The whole cell wall polysaccharide system from this raw material was characterized. Guadua is a genus of woody bamboos, native to the American continent, which comprises economically important species. Cell wall polysaccharides from young shoots of Guadua chacoensis showed glucuronoarabinoxylans (GAX) as the major hemicellulosic components (65%, of the recovered carbohydrates by extraction with aqueous solutions), which were obtained in major quantities with 1 M KOH (molar ratio Xyl:Ara:GlcA, 100:28:8). AGP and pectin polymers, as well as mixed linkage glucans and xyloglucans were present in smaller amounts (16% and 15%, respectively). Alternative extraction of GAX with solutions of DMSO allowed the characterization of alkali labile substituents, in particular, acetyl groups, which were linked mainly to C3 or, to a lesser extent, to C2 of some of the xylose residues. Besides, small amounts of phenolic compounds, released by saponification, were detected, linked to C5 of some α- l -arabinofuranose units. These results could be relevant for their use as a new resource for the food industry. [ABSTRACT FROM AUTHOR]