Characterization of Cell Wall Composition of Radish (Raphanus sativus L. var. sativus) and Maturation Related Changes.
Schäfer, J., Brett, A., Trierweiler, B. & Bunzel, M. (2016). Journal of Agricultural and Food Chemistry, 64(45), 8625-8632.
Cell wall composition affects the texture of plant-based foods. In addition, the main components of plant cell walls are dietary fiber constituents and are responsible for potential physiological effects that are largely affected by the structural composition of the cell walls. Radish (Raphanus sativus L. var. sativus) is known to develop a woody and firm texture during maturation and ripening, most likely due to changes in the cell wall composition. To describe these changes chemically, radish was cultivated and harvested at different time points, followed by detailed chemical analysis of insoluble fiber polysaccharides and lignin. During maturation, changes in polysaccharide profiles were observed, with a decrease in the portion of neutral pectic side chains and an increase in the xylan portion being predominant. Radish lignin was characterized by unexpectedly high incorporation of p-coumaryl alcohol into the polymer. Maturation dependent increases in lignin contents were accompanied by compositional changes of the lignin polymers with sinapyl alcohol being preferentially incorporated.
Novel and selective substrates for the assay of endo-arabinanase.
McCleary, B. V. (1989). "Gums and Stabilisers for the Food Industry, Vol 5”, (G. O. Phillips, D. J. Wedlock and P. A.Williams, Eds.), IRL Press, pp. 291-298.
Substrates and assay procedures for the measurement of endo-1,5-α-L-arabinanase in crude, technical pectinase preparations have been developed. The method of choice employs carboxymethy1-debranched beet araban as substrateT and rate of hydrolysis is measured using the Nelson-Somogyi reducing-sugar procedure with arabinose as the standard. The substrate is physically and chemically stable in solution, and the assay procedure is simple, reliable and specific. Other assay procedures for the measurement of endo-arabinanase which employ dyed debranched araban substrates, are also briefly described.
Comparison of endolytic hydrolases that depolymerize 1,4-β-D-mannan, 1,5-α-L-arabinan and 1,4-β-D-galactan.
McCleary, B. V. (1991). “Enzymes in Biomass Conversion”, (M. E. Himmel and G. F. Leatham, Eds.), ACS Symposium Series 460, Chapter 34, pp. 437-449. American Chemical Society, Washington.
Hydrolysis of mannan-type polysaccharides by β-mannanase is dependent on substitution on and within the main-chain as well as the source of the β-mannanase employed. Characterisation of reaction products can be used to define the sub-site binding requirements of the enzymes as well as the fine-structures of the polysaccharides. Action of endo-arabinanase and endo-galactanase on arabinans and arabinogalactans is described. Specific assays for endo-arabinanase and arabinan (in fruit-juice concentrates) are reported.
Effect of nanocoating with rhamnogalacturonan‐I on surface properties and osteoblasts response.
Gurzawska, K., Svava, R., Syberg, S., Yihua, Y., Haugshøj, K. B., Damager, I., Ulvskov, P., Christensen, L. H., Gotfredsen, K. & Jørgensen, N. R. (2012). Journal of Biomedical Materials Research Part A, 100(3), 654-664.
Long-term stability of titanium implants are dependent on a variety of factors. Nanocoating with organic molecules is one of the methods used to improve osseointegration. Therefore, the aim of this study is to evaluate the in vitro effect of nanocoating with pectic rhamnogalacturonan-I (RG-I) on surface properties and osteoblasts response. Three different RG-Is from apple and lupin pectins were modified and coated on amino-functionalized tissue culture polystyrene plates (aminated TCPS). Surface properties were evaluated by scanning electron microscopy, contact angle measurement, atomic force microscopy, and X-ray photoelectron spectroscopy. The effects of nanocoating on proliferation, matrix formation and mineralization, and expression of genes (real-time PCR) related to osteoblast differentiation and activity were tested using human osteoblast-like SaOS-2 cells. It was shown that RG-I coatings affected the surface properties. All three RG-I induced bone matrix formation and mineralization, which was also supported by the finding that gene expression levels of alkaline phosphatase, osteocalcin, and collagen type-1 were increased in cells cultured on the RG-I coated surface, indicating a more differentiated osteoblastic phenotype. This makes RG-I coating a promising and novel candidate for nanocoatings of implants.
Changes in cell wall biomechanical properties in the xyloglucan-deficient xxt1/xxt2 mutant of Arabidopsis.
Park, Y. B. & Cosgrove, D. J. (2012). Plant Physiology, 158(1), 465-475.
The main load-bearing network in the primary cell wall of most land plants is commonly depicted as a scaffold of cellulose microfibrils tethered by xyloglucans. However, a xyloglucan-deficient mutant (xylosyltransferase1/xylosyltransferase2 [xxt1/xxt2]) was recently developed that was smaller than the wild type but otherwise nearly normal in its development, casting doubt on xyloglucan’s role in wall structure. To assess xyloglucan function in the Arabidopsis (Arabidopsis thaliana) wall, we compared the behavior of petiole cell walls from xxt1/xxt2 and wild-type plants using creep, stress relaxation, and stress/strain assays, in combination with reagents that cut or solubilize specific components of the wall matrix. Stress/strain assays showed xxt1/xxt2 walls to be more extensible than wild-type walls (supporting a reinforcing role for xyloglucan) but less extensible in creep and stress relaxation processes mediated by α-expansin. Fusicoccin-induced “acid growth” was likewise reduced in xxt1/xxt2 petioles. The results show that xyloglucan is important for wall loosening by α-expansin, and the smaller size of the xxt1/xxt2 mutant may stem from the reduced effectiveness of α-expansins in the absence of xyloglucan. Loosening agents that act on xylans and pectins elicited greater extension in creep assays of xxt1/xxt2 cell walls compared with wild-type walls, consistent with a larger mechanical role for these matrix polymers in the absence of xyloglucan. Our results illustrate the need for multiple biomechanical assays to evaluate wall properties and indicate that the common depiction of a cellulose-xyloglucan network as the major load-bearing structure is in need of revision.
Remodeling of pectin and hemicelluloses in tomato pericarp during fruit growth.
Guillon, F., Moïse, A., Quemener, B., Bouchet, B., Devaux, M. F., Alvarado, C. & Lahaye, M. (2017). Plant Science, 257, 48-62.
Tomato fruit texture depends on histology and cell wall architecture, both under genetic and developmental controls. If ripening related cell wall modifications have been well documented with regard to softening, little is known about cell wall construction during early fruit development. Identification of key events and their kinetics with regard to tissue architecture and cell wall development can provide new insights on early phases of texture elaboration. In this study, changes in pectin and hemicellulose chemical characteristics and location were investigated in the pericarp tissue of tomato (Solanum lycopersicon var Levovil) at four stages of development (7, 14 and 21 day after anthesis (DPA) and mature green stages). Analysis of cell wall composition and polysaccharide structure revealed that both are continuously modified during fruit development. At early stages, the relative high rhamnose content in cell walls indicates a high synthesis of rhamnogalacturonan I next to homogalacturonan. Fine tuning of rhamnogalacturonan I side chains appears to occur from the cell expansion phase until prior to the mature green stage. Cell wall polysaccharide remodelling also concerns xyloglucans and (galacto)glucomannans, the major hemicelluloses in tomato cell walls. In situ localization of cell wall polysaccharides in pericarp tissue revealed non-ramified RG-I rich pectin and XyG at cellular junctions and in the middle lamella of young fruit. Blocks of non-methyl esterified homogalacturonan are detected as soon as 14 DPA in the mesocarp and remained restricted to cell corner and middle lamella whatever the stages. These results point to new questions about the role of pectin RGI and XyG in cell adhesion and its maintenance during cell expansion.
Characterization and comparison of polysaccharides from Lycium barbarum in China using saccharide mapping based on PACE and HPTLC.
Wu, D. T., Cheong, K. L., Deng, Y., Lin, P. C., Wei, F., Lv, X. J., Long, Z. R., Zhoa, J., Ma, S. C. & Li, S. P. (2015). Carbohydrate polymers, 134, 12-19.
Water-soluble polysaccharides from 51 batches of fruits of L. barbarum (wolfberry) in China were investigated and compared using saccharide mapping, partial acid hydrolysis, single and composite enzymatic digestion, followed by polysaccharide analysis by using carbohydrate gel electrophoresis (PACE) analysis and high performance thin layer chromatography (HPTLC) analysis, respectively. Results showed that multiple PACE and HPTLC fingerprints of partial acid and enzymatic hydrolysates of polysaccharides from L. barbarum in China were similar, respectively. In addition, results indicated that β-1,3-glucosidic, α-1,4-galactosiduronic and α-1,5-arabinosidic linkages existed in polysaccharides from L. barbarum collected in China, and the similarity of polysaccharides in L. barbarum collected from different regions of China was pretty high, which are helpful for the improvement of the performance of polysaccharides from L. barbarum in functional/health foods area. Furthermore, polysaccharides from Panax notoginseng, Angelica sinensis, and Astragalus membranaceus var. mongholicus were successfully distinguished from those of L. barbarum based on their PACE fingerprints. These results were beneficial to improve the quality control of polysaccharides from L. barabrum and their products, which suggested that saccharide mapping based on PACE and HPTLC analysis could be a routine approach for quality control of polysaccharides.
Cell wall composition and penetration resistance against the fungal pathogen Colletotrichum higginsianum are affected by impaired starch turnover in Arabidopsis mutants.
Engelsdorf, T., Will, C., Hofmann, J., Schmitt, C., Merritt, B. B., Rieger, L., Frenger, M. S., Marschall, A.,Franke, R. B., Pattathil, S. & Voll, L. M. (2016). Journal of Experimental Botany, 68(3), 701-713.
Penetration resistance represents the first level of plant defense against phytopathogenic fungi. Here, we report that the starch-deficient Arabidopsis thaliana phosphoglucomutase (pgm) mutant has impaired penetration resistance against the hemibiotrophic fungus Colletotrichum higginsianum. We could not determine any changes in leaf cutin and epicuticular wax composition or indolic glucosinolate levels, but detected complex alterations in the cell wall monosaccharide composition of pgm. Notably, other mutants deficient in starch biosynthesis (adg1) or mobilization (sex1) had similarly affected cell wall composition and penetration resistance. Glycome profiling analysis showed that both overall cell wall polysaccharide extractability and relative extractability of specific pectin and xylan epitopes were affected in pgm, suggesting extensive structural changes in pgm cell walls. Screening of mutants with alterations in content or modification of specific cell wall monosaccharides indicated an important function of pectic polymers for penetration resistance and hyphal growth of C. higginsianum during the biotrophic interaction phase. While mutants with affected pectic rhamnogalacturonan-I (mur8) were hypersusceptible, penetration frequency and morphology of fungal hyphae were impaired on pmr5 pmr6 mutants with increased pectin levels. Our results reveal a strong impact of starch metabolism on cell wall composition and suggest a link between carbohydrate availability, cell wall pectin and penetration resistance.
Structural characterization and immunomodulatory activity of a water soluble polysaccharide isolated from Botrychium ternatum.
Zhao, X., Li, J., Liu, Y., Wu, D., Cai, P. & Pan, Y. (2017). Carbohydrate Polymers, 171, 136-142.
As a folk medicine, Botrychium ternatum has been used for thousands of years in China. In the present work, a water soluble polysaccharide BTp1 was extracted and purified from B. ternatum. Based on the MALDI matrix 3-aminoquinoline-α-cyano-4-hydroxycinnamic acid, the molecular weight of BTp1 was determined to be 11638 Da directly. Monosaccharide analysis showed that BTp1 was composed of arabinose (Ara). Combining enzymatic hydrolysis and subsequent MALDI-TOF analysis, a linear backbone of BTp1, consisted of (1 → 5)-linked α-L -Araf, was inferred quickly. Then according to NMR experiments, the whole structure of BTp1 was established. The repeating unit of BTp1 was deduced as a linear backbone with branches at O-2, O-3 and its neighboring O-2 positions terminated with (1 → )-linked α-L-Araf, respectively. The immunomodulatory assay exhibited that BTp1 could significantly enhance the viability and promote the release of NO in RAW 264.7 cells, suggesting that BTp1 could be a potential immunomodulatory agent in pharmacological fields.