Developmental complexity of arabinan polysaccharides and their processing in plant cell walls.
Verhertbruggen, Y., Marcus, S. E., Haeger, A., Verhoef, R., Schols, H. A., McCleary, B. V., McKee, L., Gilbert, H. J. & Paul Knox, J. (2009). The Plant Journal, 59(3), 413-425.
Plant cell walls are constructed from a diversity of polysaccharide components. Molecular probes directed to structural elements of these polymers are required to assay polysaccharide structures in situ, and to determine polymer roles in the context of cell wall biology. Here, we report on the isolation and the characterization of three rat monoclonal antibodies that are directed to 1,5-linked arabinans and related polymers. LM13, LM16 and LM17, together with LM6, constitute a set of antibodies that can detect differing aspects of arabinan structures within cell walls. Each of these antibodies binds strongly to isolated sugar beet arabinan samples in ELISAs. Competitive-inhibition ELISAs indicate the antibodies bind differentially to arabinans with the binding of LM6 and LM17 being effectively inhibited by short oligoarabinosides. LM13 binds preferentially to longer oligoarabinosides, and its binding is highly sensitive to arabinanase action, indicating the recognition of a longer linearized arabinan epitope. In contrast, the binding of LM16 to branched arabinan and to cell walls is increased by arabinofuranosidase action. The presence of all epitopes can be differentially modulated in vitro using glycoside hydrolase family 43 and family 51 arabinofuranosidases. In addition, the LM16 epitope is sensitive to the action of β-galactosidase. Immunofluorescence microscopy indicates that the antibodies can be used to detect epitopes in cell walls, and that the four antibodies reveal complex patterns of epitope occurrence that vary between organs and species, and relate both to the probable processing of arabinan structural elements and the differing mechanical properties of cell walls.
Cellulose microfibril angles and cell-wall polymers in different wood types of Pinus radiata.
Brennan, M., McLean, J. P., Altaner, C. M., Ralph, J. & Harris, P. J. (2012). Cellulose, 19(4), 1385-1404.
Four corewood types were examined from sapling trees of two clones of Pinus radiata grown in a glasshouse. Trees were grown either straight to produce normal corewood, tilted at 45° from the vertical to produce opposite corewood and compression corewood, or rocked to produce flexure corewood. Mean cellulose microfibril angle of tracheid walls was estimated by X-ray diffraction and longitudinal swelling measured between an oven dry and moisture saturated state. Lignin and acetyl contents of the woods were measured and the monosaccharide compositions of the cell-wall polysaccharides determined. Finely milled wood was analysed using solution-state 2D NMR spectroscopy of gels from finely milled wood in DMSO-d6/pyridine-d5. Although there was no significant difference in cellulose microfibril angle among the corewood types, compression corewood had the highest longitudinal swelling. A lignin content >32% and a galactosyl residue content >6% clearly divided severe compression corewood from the other corewood types. Relationships could be drawn between lignin content and longitudinal swelling, and between galactosyl residue content and longitudinal swelling. The 2D NMR spectra showed that the presence of H-units in lignin was exclusive to compression corewood, which also had a higher (1→4)-β-D-galactan content, defining a unique composition for that corewood type.
Purification and characterization of a xylanase and an arabinofuranosidase from Bacillus polymyxa.
Morales, P., Madarro, A., Flors, A., Sendra, J. & Pérez-González, J. (1995). Enzyme and Microbial Technology, 17(5), 424-429.
Two hemicellulases from Bacillus polymyxa were purified and characterized: a xylanase with a molecular mass of 61 kD and pl of 4.7 and an arabinofuranosidase with a molecular mass of 166 kD and pl of 4.7. The xylanase, which showed increased thermostability in the presence of MgCl2, showed a typical endo-action mode on xylans from several sources. The arabinofuranosidase was only active on (1→5)-α-L-arabinooligosaccharides but not on linear (1→5)-α-L-arabinan, arabinogalactan, and arabinoxylan. However, it was able to release arabinose from arabinoxylan when an active endoxylanase was also present in hydrolysis assays.
α-L-Arabinofuranosidases from Aspergillus terreus with potential application in enology: induction, purification, and characterization.
Le Clinche, F., Piñaga, F., Ramón, D. & Vallés, S. (1997). Journal of Agricultural and Food Chemistry, 45(7), 2379-2383.
In the presence of L-arabitol as sole carbon source, Aspergillus terreus CECT 2663 produces three α-L-arabinofuranosidases (ABFs) named ABF1, ABF2, and ABF3, with molecular masses of 90 000, 82 000, and 78 500 Da, respectively. The synthesis of these enzymes is under carbon catabolite repression. Western blotting revealed that ABF2 is immunologically related to the α-L-arabinofuranosidase B previously isolated from Aspergillus niger. The three A. terreus proteins have been purified to homogeneity. They are acidic proteins with optimal pHs of 5.0 for ABF1 and ABF2 and 5.5 for ABF3 and optimal temperatures of 50, 60, and 65°C, respectively. Kinetic constants for the purified enzymes on p-nitrophenyl α-L-arabinofuranoside (pNPA) as substrate have been determined. The three enzymes maintain elevated activities in the presence of ethanol or glucose at those concentrations normally present in must or wine.
Near-infrared Fourier-transform Raman spectroscopy of flax (Linum usitatissimum L.) stems.
Himmelsbach, D. S. & Akin, D. E. (1998). Journal of Agricultural and Food Chemistry, 46(3), 991-998.
Samples of flax (Linum usitatissimum L.) stem and its anatomical parts were studied by near-infrared Fourier transform Raman (NIR-FT-Raman) spectroscopy to determine if the major chemical components of each could be detected by this method. The Raman spectra of reference compounds from relatively pure materials served as models for the chemical components. Bands for cellulose were greatest in the fibers. Hemicellulosic polysaccharides were observed to be prevalent in bast tissue and fibers. Weak signals for pectins were observed in the bast, cuticle/epidermis, fibers, and stem. Bands for aromatic rings were detectable in all materials. Bands from waxes/fatty acid esters were detectable in the cuticle/epidermal tissue. The results indicated that NIR-FT-Raman could be used detect the major chemical components in flax in situ and provide a simple, rapid, and noninvasive assessment of their relative amounts and location within the tissues of the flax plant.
Purification, functional characterization, cloning, and identification of mutants of a seed-specific arabinan hydrolase in Arabidopsis.
Minic, Z., Do, C. T., Rihouey, C., Morin, H., Lerouge, P. & Jouanin, L. (2006). Journal of Experimental Botany, 57(10), 2339-2351.
This work describes the purification and characterization of an enzyme that exhibits arabinan hydrolase activity in seeds of Arabidopsis thaliana. The enzyme, designated XYL3, had an apparent molecular mass of 80 kDa when purified to homogeneity, and was identified using MALDI-TOF (matrix-assisted laser desorption ionization–time of flight) as a putative β-D-xylosidase that belongs to family 3 of glycoside hydrolases encoded by gene At5g09730. XYL3 hydrolysed synthetic substrates such as p-nitrophenyl-α-L-arabinofuranoside and p-nitrophenyl-β-D-xyloside with similar catalytic efficiency. XYL3 released L-arabinose from (1→5)-α-L-arabinofuranobiose, arabinoxylan, sugar beet arabinan, and debranched arabinan. The enzyme hydrolysed both arabinosyl-substituted side group residues and terminal arabinofuranosyl residues (1→5)-α-linked to the arabinan backbone. This indicates that XYL3 is able to degrade all terminal arabinosyl residues and suggests that it participates in the in-vivo hydrolysis of arabinan. Analysis of gene expression patterns by semi-quantitative RT-PCR, in-situ hybridization and a promoter–GUS fusion demonstrated that AtBX3 was specifically expressed in the seed endosperm at the globular stage of the embryo. Immunolocalization using LM6 anti-arabinan antisera found that arabinan, the XYL3 substrate, was also present in this seed tissue. T-DNA null mutants for AtBX3 were identified. The mutant plants lacked the α-L-arabinofuranosidase and β-D-xylosidase activities corresponding to XYL3. Mutants showed reduced seed size and are delayed in seedling germination compared with the wild type.