L-Fucose-containing arabinogalactan-protein in radish leaves.

The carbohydrate moieties of arabinogalactan-proteins (AGPs) have β-(1 → 3)-galactan backbones to which side chains of (1 → 6)-linked β-Gal residues are attached through O-6. Some of these side chains are further substituted with other sugars. We investigated the structure of L-Fuc-containing oligosaccharides released from the carbohydrate moieties of a radish leaf AGP by digestion with α-L-arabinofuranosidase, followed by exo-β-(1 → 3)-galactanase. We detected a series of neutral β-(1 → 6)-galactooligosaccharides branching variously at O-3 of the Gal residues, together with corresponding acidic derivatives terminating in 4-O-methyl-GlcA (4-Me-GlcA) or GlcA at the non-reducing terminals. In neutral oligosaccharides with degree of polymerization (dp) mainly higher than 10, L-Fuc groups were attached through L-Ara residues as the sequence, α-L-Fucp-(1 → 2)-α-L-Araf-(1 →. This sequence was verified by isolation of the pentasaccharide α-L-Fuc-(1 → 2)-α-L-Araf-(1 → 3)-β-Gal-(1 → 6)-β-Gal-(1 → 6)-Gal upon digestion of the higher oligosaccharides with endo-β-(1 → 6)-galactanase. By contrast, in lower polymerized (predominantly dp 4) acidic oligosaccharides, L-Fuc groups were attached directly at the non-reducing terminals through α-(1 → 2)-linkages, resulting in the release of the tetrasaccharides, α-L-Fucp-(1 → 2)-β-GlcA-(1 → 6)-β-Gal-(1 → 6)-Gal and α-L-Fucp-(1 → 2)-β-4-Me-GlcA-(1 → 6)-β-Gal-(1 → 6)-Gal. In long acidic oligosaccharides with dp mainly higher than 13, L-Fuc groups localized on branches were attached to the uronic acids directly and/or L-Ara residues as in the neutral oligosaccharides.The authors would like to thank Prof. M. Hisamatsu, Mie University, Tsu, Japan, for a gift of cyclic β-(1→2)-glucan. This work was supported by the Ministry of Education, Culture, Sports, Science, and Technology of Japan (Grant-in-Aid for Scientific Research no. 23570048 to Y.T. and no. 24114006 to Y.T. and T.K.). Support was also provided by BBSRC Sustainable Bioenergy Centre: Cell wall sugars program (Grant No. BB/G016240/1) to P.D.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.carres.2015.07.00

Action of an endo-β-1,3(4)-glucanase on cellobiosyl unit structure in barley β-1,3:1,4-glucan.

β-1,3:1,4-Glucan is a major cell wall component accumulating in endosperm and young tissues in grasses. The mixed linkage glucan is a linear polysaccharide mainly consisting of cellotriosyl and cellotetraosyl units linked through single β-1,3-glucosidic linkages, but it also contains minor structures such as cellobiosyl units. In this study, we examined the action of an endo-β-1,3(4)-glucanase from Trichoderma sp. on a minor structure in barley β-1,3:1,4-glucan. To find the minor structure on which the endo-β-1,3(4)-glucanase acts, we prepared oligosaccharides from barley β-1,3:1,4-glucan by endo-β-1,4-glucanase digestion followed by purification by gel permeation and paper chromatography. The endo-β-1,3(4)-glucanase appeared to hydrolyze an oligosaccharide with degree of polymerization 5, designated C5-b. Based on matrix-assisted laser desorption/ionization (MALDI) time-of-flight (ToF)/ToF-mass spectrometry (MS)/MS analysis, C5-b was identified as β-Glc-1,3-β-Glc-1,4-β-Glc-1,3-β-Glc-1,4-Glc including a cellobiosyl unit. The results indicate that a type of endo-β-1,3(4)-glucanase acts on the cellobiosyl units of barley β-1,3:1,4-glucan in an endo-manner.This work was supported in part by a grant-in-aid for Scientific Research to T. Kotake [Grant-in-Aid for Scientific Research no. 25514001] from Japan Society of the Promotion of Science; Y. Tsumuraya and T. Kotake [Grant-in-Aid for Scientific Research no. 24114006] from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. Supports were also provided by BBSRC Sustainable Bioenergy Centre: Cell wall sugars program to P. Dupree [grant number BB/G016240/1].This is the final version of the article. It first appeared from Taylor & Francis via http://dx.doi.org/10.1080/09168451.2015.104636

The patterned structure of galactoglucomannan suggests it may bind to cellulose in seed mucilage

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOThe interaction between mannan polysaccharides and cellulose microfibrils contributes to cell wall properties in some vascular plants, but the molecular arrangement of mannan in the cell wall and the nature of the molecular bonding between mannan and cell178310111026FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2013/08293-7The authors would like to acknowledge Prof. George Lomonossoff (John Innes Centre, UK), who developed the pEAQ-HyperTrans expression system used in this study. Plant Bioscience Limited supplied the pEAQ-HT vector that was used in this wor

Hydroxycinnamic acid-modified xylan side chains and their cross-linking products in rice cell walls are reduced in the Xylosyl arabinosyl substitution of xylan 1 mutant.

The intricate architecture of cell walls and the complex cross-linking of their components hinders some industrial and agricultural applications of plant biomass. Xylan is a key structural element of grass cell walls, closely interacting with other cell wall components such as cellulose and lignin. The main branching points of grass xylan, 3-linked l-arabinosyl substitutions, can be modified by ferulic acid (a hydroxycinnamic acid), which cross-links xylan to other xylan chains and lignin. XAX1 (Xylosyl arabinosyl substitution of xylan 1), a rice (Oryza sativa) member of the glycosyltransferase family GT61, has been described to add xylosyl residues to arabinosyl substitutions modified by ferulic acid. In this study, we characterize hydroxycinnamic acid-decorated arabinosyl substitutions present on rice xylan and their cross-linking, in order to decipher the role of XAX1 in xylan synthesis. Our results show a general reduction of hydroxycinnamic acid-modified 3-linked arabinosyl substitutions in xax1 mutant rice regardless of their modification with a xylosyl residue. Moreover, structures resembling the direct cross-link between xylan and lignin (ferulated arabinosyl substitutions bound to lignin monomers and dimers), together with diferulates known to cross-link xylan, are strongly reduced in xax1. Interestingly, apart from feruloyl and p-coumaroyl modifications on arabinose, putative caffeoyl and oxalyl modifications were characterized, which were also reduced in xax1. Our results suggest an alternative function of XAX1 in the transfer of hydroxycinnamic acid-modified arabinosyl substitutions to xylan, rather than xylosyl transfer to arabinosyl substitutions. Ultimately, XAX1 plays a fundamental role in cross-linking, providing a potential target for the improvement of use of grass biomass

Rhamnogalacturonan-I as a nematode chemoattractant from Lotus corniculatus L. super-growing root culture

IntroductionThe soil houses a tremendous amount of micro-organisms, many of which are plant parasites and pathogens by feeding off plant roots for sustenance. Such root pathogens and parasites often rely on plant-secreted signaling molecules in the rhizosphere as host guidance cues. Here we describe the isolation and characterization of a chemoattractant of plant-parasitic root-knot nematodes (Meloidogyne incognita, RKN).MethodsThe Super-growing Root (SR) culture, consisting of excised roots from the legume species Lotus corniculatus L., was found to strongly attract infective RKN juveniles and actively secrete chemoattractants into the liquid culture media. The chemo-attractant in the culture media supernatant was purified using hydrophobicity and anion exchange chromatography, and found to be enriched in carbohydrates.ResultsMonosaccharide analyses suggest the chemo-attractant contains a wide array of sugars, but is enriched in arabinose, galactose and galacturonic acid. This purified chemoattractant was shown to contain pectin, specifically anti-rhamnogalacturonan-I and anti-arabinogalactan protein epitopes but not anti-homogalacturonan epitopes. More importantly, the arabinose and galactose sidechain groups were found to be essential for RKN-attracting activities. This chemo-attractant appears to be specific to M. incognita, as it wasn’t effective in attracting other Meloidogyne species nor Caenorhabditis elegans.DiscussionThis is the first report to identify the nematode attractant purified from root exudate of L corniculatus L. Our findings re-enforce pectic carbohydrates as important chemicals mediating micro-organism chemotaxis in the soil, and also highlight the unexpected utilities of the SR culture system in root pathogen research

Rice BRITTLE CULM 5 (BRITTLE NODE) is Involved in Secondary Cell Wall Formation in the Sclerenchyma Tissue of Nodes

Several brittle culm (bc) mutants known in grasses are considered excellent materials to study the process of secondary cell wall formation. The brittle phenotype of the rice bc5 (brittle node) mutant appears exclusively in the developed nodes, which is distinct from other bc mutants (bc1, 2, 3, 4, 6 and 7) that show the brittle phenotype in culms and leaves. To address the defects of the rice bc5 mutant in node-specific cell wall formation, we analyzed tissue morphology and cell wall composition. The bc5 mutation was found to affect the cell wall deposition of node sclerenchyma tissues at 1 week after heading, the stage at which the cell wall sugar content is reduced, in the bc5 nodes, compared with wild-type nodes. Moreover, decreased accumulation of lignin and thickness of cell walls in the sclerenchyma tissues were also observed in the bc5 nodes. The amounts of cellulose and hemicellulose were reduced to 53 and 65% of those in the wild-type plants, respectively. Sugar composition and glycosidic linkage analyses of the hemicellulose showed that the accumulation of glucuronosyl arabinoxylan in bc5 nodes was perturbed by the mutation. The bc5 locus was narrowed to an approximately 3.1 Mb region of chromosome 2, where none of the other bc genes is located. The bc5 mutation appeared to reduce the expression levels of the OsCesA genes in the nodes after heading. The results indicate that the BC5 gene regulates the development of secondary cell walls of node sclerenchyma tissues

Wolfberry genomes and the evolution of Lycium (Solanaceae)

AbstractWolfberry Lycium, an economically important genus of the Solanaceae family, contains approximately 80 species and shows a fragmented distribution pattern among the Northern and Southern Hemispheres. Although several herbaceous species of Solanaceae have been subjected to genome sequencing, thus far, no genome sequences of woody representatives have been available. Here, we sequenced the genomes of 13 perennial woody species of Lycium, with a focus on Lycium barbarum. Integration with other genomes provides clear evidence supporting a whole-genome triplication (WGT) event shared by all hitherto sequenced solanaceous plants, which occurred shortly after the divergence of Solanaceae and Convolvulaceae. We identified new gene families and gene family expansions and contractions that first appeared in Solanaceae. Based on the identification of self-incompatibility related-gene families, we inferred that hybridization hotspots are enriched for genes that might be functioning in gametophytic self-incompatibility pathways in wolfberry. Extremely low expression of LOCULE NUBER (LC) and COLORLESS NON-RIPENING (CNR) orthologous genes during Lycium fruit development and ripening processes suggests functional diversification of these two genes between Lycium and tomato. The existence of additional flowering locus C-like MADS-box genes might correlate with the perennial flowering cycle of Lycium. Differential gene expression involved in the lignin biosynthetic pathway between Lycium and tomato likely illustrates woody and herbaceous differentiation. We also provide evidence that Lycium migrated from Africa into Asia, and subsequently from Asia into North America. Our results provide functional insights into Solanaceae origins, evolution and diversification.</jats:p

Characterization of an Endo-β-1,6-Galactanase from Streptomyces avermitilis NBRC14893▿

The putative endo-β-1,6-galactanase gene from Streptomyces avermitilis was cloned and expressed in Escherichia coli, and the enzymatic properties of the recombinant enzyme were characterized. The gene consisted of a 1,476-bp open reading frame and encoded a 491-amino-acid protein, comprising an N-terminal secretion signal sequence and glycoside hydrolase family 5 catalytic module. The recombinant enzyme, Sa1,6Gal5A, catalyzed the hydrolysis of β-1,6-linked galactosyl linkages of oligosaccharides and polysaccharides. The enzyme produced galactose and a range of β-1,6-linked galacto-oligosaccharides, predominantly β-1,6-galactobiose, from β-1,6-galactan chains. There was a synergistic effect between the enzyme and Sa1,3Gal43A in degrading tomato arabinogalactan proteins. These results suggest that Sa1,6Gal5A is the first identified endo-β-1,6-galactanase from a prokaryote