Microanalysis of Plant Cell Wall Polysaccharides

Abstract

Oligosaccharide Mass Profiling (OLIMP) allows a fast and sensitive assessment of cell wall polymer structure when coupled with Matrix Assisted Laser Desorption Ionisation Time Of Flight Mass Spectrometry (MALDI-TOF MS). The short time required for sample preparation and analysis makes possible the study of a wide range of plant organs, revealing a high degree of heterogeneity in the substitution pattern of wall polymers such as the cross-linking glycan xyloglucan and the pectic polysaccharide homogalacturonan. The high sensitivity of MALDI-TOF allows the use of small amounts of samples, thus making it possible to investigate the wall structure of single cell types when material is collected by such methods as laser micro-dissection. As an example, the analysis of the xyloglucan structure in the leaf cell types outer epidermis layer, entire epidermis cell layer, palisade mesophyll cells, and vascular bundles were investigated. OLIMP is amenable to in situ wall analysis, where wall polymers are analyzed on unprepared plant tissue itself without first isolating cell walls. In addition, OLIMP enables analysis of wall polymers in Golgi-enriched fractions, the location of nascent matrix polysaccharide biosynthesis, enabling separation of the processes of wall biosynthesis versus post-deposition apoplastic metabolism. These new tools will make possible a semi-quantitative analysis of the cell wall at an unprecedented level.

Update on Mechanisms of Plant Cell Wall Biosynthesis: How Plants Make Cellulose and Other (1→4)-β-d-Glycans

“…Most are primarily galactosylated, with a characteristic a-L-Fuc-(1/2)-b-D-Gal-(1/2)-a-D-Xyl trisaccharide extension (Bauer et al, 1973), but others, such as those of solanaceous species, have a truncated unit structure substituted with a-L-Ara-(1/2)-a-DXyl extensions instead of Gal (Sims et al, 1996), and the Asteridae and Oleales species have mixtures of these two forms of xyloglucan substitution (Hoffman et al, 2005). Furthermore, the xyloglucans synthesized in the Golgi are modified in ways that make them structurally different from those that are assembled onto the cellulose microfibrils in the wall (Obel et al, 2009).…”

XTH31, Encoding an in Vitro XEH/XET-Active Enzyme, Regulates Aluminum Sensitivity by Modulating in Vivo XET Action, Cell Wall Xyloglucan Content, and Aluminum Binding Capacity in Arabidopsis

“…In the standard nomenclature for xyloglucan structures, unsubstituted Glc residues are represented by G, while X, L, and F indicate Glc residues that are 6-O-substituted with a-D-Xylp, b-D-Galp-(1-2)-a-D-Xylp, and a-L-Fucp-(1-2)-b-D-Galp-(1-2)-a-D-Xylp side chains, respectively . Treatment of Arabidopsis xyloglucan with an endoglucanase (XEG) that attacks unsubstituted Glc residues yields an oligosaccharide mixture that includes XXXG, XXLG, XLXG, XXG, GXXG, XLLG, XXFG, and XLFG (the sequences are shown with the reducing end of the molecule positioned to the right; Madson et al, 2003;Obel et al, 2009;Sampedro et al, 2012).…”

Lack of α-Xylosidase Activity in Arabidopsis Alters Xyloglucan Composition and Results in Growth Defects

“…Conventionally, the reducing end of the molecule is positioned to the right. Treatment of Arabidopsis xyloglucan with an endoglucanase that attacks unsubstituted residues results in oligosaccharide mixtures that include XXG, GXXG, XXXG, XXLG, XLXG, XLLG, XXFG, and XLFG, with some of the Gal residues O-acetylated (Madson et al, 2003;Obel et al, 2009).…”