Structure of the xyloglucan produced by suspension-cultured tomato cells.
ABSTRACT The xyloglucan secreted by suspension-cultured tomato (Lycopersicon esculentum) cells was structurally characterized by analysis of the oligosaccharides generated by treating the polysaccharide with a xyloglucan-specific endoglucanase (XEG). These oligosaccharide subunits were chemically reduced to form the corresponding oligoglycosyl alditols, which were isolated by high-performance liquid chromatography (HPLC). Thirteen of the oligoglycosyl alditols were structurally characterized by a combination of matrix-assisted laser-desorption ionization mass spectrometry and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. Nine of the oligoglycosyl alditols (GXGGol, XXGGol, GSGGol, XSGGol, LXGGol, XTGGol, LSGGol, LLGGol, and LTGGol, [see, Fry, S.C.; York, W.S., et al., Physiologia Plantarum 1993, 89, 1-3, for this nomenclature]) are derived from oligosaccharide subunits that have a cellotetraose backbone. Very small amounts of oligoglycosyl alditols (XGGol, XGGXXGGol, XXGGXGGol, and XGGXSGGol) derived from oligosaccharide subunits that have a cellotriose or celloheptaose backbone were also purified and characterized. The results demonstrate that the xyloglucan secreted by suspension-cultured tomato cells is very complex and is composed predominantly of 'XXGG-type' subunits with a cellotetraose backbone. The rigorous characterization of the oligoglycosyl alditols and assignment of their 1H and 13C NMR spectra constitute a robust data set that can be used as the basis for rapid and accurate structural profiling of xyloglucans produced by Solanaceous plant species and the characterization of enzymes involved in the synthesis, modification, and breakdown of these polysaccharides.
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ABSTRACT: Xyloglucan is the dominant hemicellulose present in the primary cell walls of dicotyledonous plants. Unlike Arabidopsis xyloglucan, which contains galactosyl and fucosyl-substituents, tomato (Solanum lycopersicum) xyloglucan contains arabinofuranosyl-residues. To investigate the biological function of these differing substituents we used a functional complementation approach. Candidate glycosyltransferases were identified from tomato by using comparative genomics with known xyloglucan galactosyltransferase genes from Arabidopsis. These candidate genes were expressed in an Arabidopsis mutant lacking xyloglucan galactosylation and two of them resulted in the production of arabinosylated xyloglucan, a structure not previously found in this plant species. These genes may therefore encode xyloglucan arabinofuranosyltransferases. Moreover, the addition of arabinofuranosyl-residues to the xyloglucan of this Arabidopsis mutant rescued a growth and cell wall biomechanics phenotype, demonstrating that the function of xyloglucan in plant growth, development and mechanics has considerable flexibility in terms of the specific residues in the side chains. These experiments also highlight the potential of re-engineering the sugar substituents on plant wall polysaccharides without compromising growth or viability.Plant physiology 07/2013; · 6.56 Impact Factor
- Plants. 01/2014; 3(4):526-542.
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ABSTRACT: Variations in polysaccharide fine-structures (carbohydrate schematics using the symbols listed below) diversify the available nutrient niches in the gut (small circles within the central illustration of the human colon). Some bacteria have adapted their enzymatic and sensory abilities to accomodate these variations.Journal of Molecular Biology. 01/2014;