Xylan Biosynthesis: News from the Grass

Faïk, A.

doi:10.1104/pp.110.154237

Cited by 101 publications

(79 citation statements)

References 55 publications

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“…Regulation of the biosynthesis of SCW-related metabolites, such as cellulose and its precursor UDP-Glc, the hemicellulosic polysaccharide xylan, and lignin monomers, has attracted substantial attention (Faik, 2010;Vanholme et al, 2010;Bashline et al, 2014;McFarlane et al, 2014). However, we lack information about the regulation of primary metabolism during xylem vessel cell differentiation.…”

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confidence: 99%

“…The first detectable cytological sign of differentiation is the alignment of cortical microtubules, which determine patterned SCW thickening by guiding the cellulose synthase complex (Bashline et al, 2014;McFarlane et al, 2014). Next, cellulose and hemicellulose accumulate, followed by lignin deposition (Faik, 2010;Vanholme et al, 2010). Vacuole disruption triggers PCD, which results in proteases and nucleases being released into the cytosol (Bollhöner et al, 2012).…”

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confidence: 99%

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Primary Metabolism during Biosynthesis of Secondary Wall Polymers of Protoxylem Vessel Elements

et al. 2016

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Xylem vessels, the water-conducting cells in vascular plants, undergo characteristic secondary wall deposition and programmed cell death. These processes are regulated by the VASCULAR-RELATED NAC-DOMAIN (VND) transcription factors. Here, to identify changes in metabolism that occur during protoxylem vessel element differentiation, we subjected tobacco (Nicotiana tabacum) BY-2 suspension culture cells carrying an inducible VND7 system to liquid chromatography-mass spectrometry-based wide-target metabolome analysis and transcriptome analysis. Time-course data for 128 metabolites showed dynamic changes in metabolites related to amino acid biosynthesis. The concentration of glyceraldehyde 3-phosphate, an important intermediate of the glycolysis pathway, immediately decreased in the initial stages of cell differentiation. As cell differentiation progressed, specific amino acids accumulated, including the shikimate-related amino acids and the translocatable nitrogen-rich amino acid arginine. Transcriptome data indicated that cell differentiation involved the active up-regulation of genes encoding the enzymes catalyzing fructose 6-phosphate biosynthesis from glyceraldehyde 3-phosphate, phosphoenolpyruvate biosynthesis from oxaloacetate, and phenylalanine biosynthesis, which includes shikimate pathway enzymes. Concomitantly, active changes in the amount of fructose 6-phosphate and phosphoenolpyruvate were detected during cell differentiation. Taken together, our results show that protoxylem vessel element differentiation is associated with changes in primary metabolism, which could facilitate the production of polysaccharides and lignin monomers and, thus, promote the formation of the secondary cell wall. Also, these metabolic shifts correlate with the active transcriptional regulation of specific enzyme genes. Therefore, our observations indicate that primary metabolism is actively regulated during protoxylem vessel element differentiation to alter the cell's metabolic activity for the biosynthesis of secondary wall polymers.

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Primary Metabolism during Biosynthesis of Secondary Wall Polymers of Protoxylem Vessel Elements

et al. 2016

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“…The irregular xylem (irx) mutants, named for their collapsed xylem vessels due to their secondary cell wall deficiency, have been instrumental in elucidating the mechanisms of xylan biosynthesis in Arabidopsis thaliana (Arabidopsis). IRX9/IRX9L and IRX14/ IRX14L from the GT43 family and IRX10/IRX10L from GT47 are thought to be responsible for elongation of the xylan backbone (20)(21)(22)(23)(24)(25). IRX7 (FRA8)/IRX7L (F8H) (from GT47), IRX8 (GAUT12) (from GT8), and PARVUS (from GT8) may be responsible for synthesizing the oligosaccharide found at the reducing end of some Author contributions: D.C., V.S., C.R., J.D.K., H.V.S., and P.C.R.…”

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confidence: 99%

XAX1 from glycosyltransferase family 61 mediates xylosyltransfer to rice xylan

Chiniquy

Sharma

Schultink

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

176

161

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Xylan is the second most abundant polysaccharide on Earth and represents an immense quantity of stored energy for biofuel production. Despite its importance, most of the enzymes that synthesize xylan have yet to be identified. Xylans have a backbone of β-1,4–linked xylose residues with substitutions that include α-(1→2)–linked glucuronosyl, 4- O -methyl glucuronosyl, and α-1,2- and α-1,3-arabinofuranosyl residues. The substitutions are structurally diverse and vary by taxonomy, with grass xylan representing a unique composition distinct from dicots and other monocots. To date, no enzyme has yet been identified that is specific to grass xylan synthesis. We identified a xylose-deficient loss-of-function rice mutant in Os02g22380, a putative glycosyltransferase in a grass-specific subfamily of family GT61. We designate the mutant xax1 for x ylosyl a rabinosyl substitution of x ylan 1. Enzymatic fingerprinting of xylan showed the specific absence in the mutant of a peak, which was isolated and determined by 1 H-NMR to be (β-1,4-Xyl) 4 with a β-Xyl p -(1→2)-α-Ara f -(1→3). Rice xax1 mutant plants are deficient in ferulic and coumaric acid, aromatic compounds known to be attached to arabinosyl residues in xylan substituted with xylosyl residues. The xax1 mutant plants exhibit an increased extractability of xylan and increased saccharification, probably reflecting a lower degree of diferulic cross-links. Activity assays with microsomes isolated from tobacco plants transiently expressing XAX1 demonstrated xylosyltransferase activity onto endogenous acceptors. Our results provide insight into grass xylan synthesis and how substitutions may be modified for increased saccharification for biofuel generation.

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“…For example, (1) xylans are important functional ingredients in baked products [98]; (2) xylans can be potentially used for producing hydrogels as biodegradable coatings and also encapsulation matrices in many industrial applications; (3) xyl, the main constituent from xylans, can be converted to xylitol which is used as a natural food sweetener and a sugar substitute [99]; (4) xylans can be used for clarification of juices and improvement in the consistency of beer [100]; (5) xylans are also important for livestock industry as they are critical factors for silage digestibility; (6) xylans are major constituents in non-nutritional animal feed [101]; (7) xylans can be converted to sugars and then further to fuels and chemicals; (8) enzymes that degrade xylan can facilitate paper pulping and biobleaching of pulp [100].…”

Section: Xylanmentioning

confidence: 99%

Lignocelluloses Feedstock Biorefinery as Petrorefinery Substitutes

Cheng¹,

Wang²

2013

Biomass Now - Sustainable Growth and Use

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Lignocelluloses Feedstock Biorefinery as Petrorefinery Substitutes 349The LCF Biorefinery is a promising alternative due to the abundance and variety of available raw materials and the good position of the conversion products on the market [14]. Its profitability is also dependent on the technology employed to alter the structure of lignocellulosic biomass in order to produce high value co-products from its three main fractions i.e. cellulose, hemicellulose, and lignin [15].Currently the main feedstock for biorefineries is still based on starch. The practiced technologies in fuel ethanol industry are primarily based on the fermentation of sugars derived from starch and sugar crops, which are quite mature with little possibility of process improvements. However, using starch and sugar crops to produce ethanol also has been questioned since it draws its feedstock from a food stream. Lignocellulosic biomass is a more promising renewable resource as it is available in large quantities and does not compete with food or feed. Lignocellulosic biomass is a renewable resource that stores energy from sunlight in its chemical bonds, with great potentials for the production of affordable fuel ethanol [16,17]. Its main obstacle for a major breakthrough is the high production costs for bioenergy products.On the other hand, lignocellulosic biomass-derived products can significantly reduce green house gas emissions, compared to fossil-based products. Also, many common petrochemicals could be obtained with lower green house gas emissions from bio-based feedstocks. The maturity and economics of the conversion processes and logistics is a major challenge for lignocellulosic biomass [18].

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Xylan Biosynthesis: News from the Grass

Cited by 101 publications

References 55 publications

Primary Metabolism during Biosynthesis of Secondary Wall Polymers of Protoxylem Vessel Elements

Primary Metabolism during Biosynthesis of Secondary Wall Polymers of Protoxylem Vessel Elements

XAX1 from glycosyltransferase family 61 mediates xylosyltransfer to rice xylan

Lignocelluloses Feedstock Biorefinery as Petrorefinery Substitutes

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