Studies on Wheat Endosperm I. Chemical Composition and Ultrastructure of the Cell Walls

JMares, D; Stone, BA

doi:10.1071/bi9730793

Cited by 218 publications

(138 citation statements)

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“…The arabinoxylan has a linear ,3-1,4-xylan backbone, with 33% of the xylosyl residues substituted nonrandomly at the 2 and/or 3 position with single arabinofuranosyl groups (19). Aleurone cell walls thus resemble starchy endosperm cell walls as characterized in wheat (17,18). This finding makes possible for the first time a detailed study of the enzymology of aleurone cell wall degradation.…”

mentioning

confidence: 75%

Production of Cell Wall Hydrolyzing Enzymes by Barley Aleurone Layers in Response to Gibberellic Acid

Taiz¹,

Honigman²

1976

Plant Physiol.

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The cell wails of barley (Hordeum vulgare var. Himalaya) aleurone layers undergo extensive degradation during the tissue's response to gibbereilic acid. Previous work had shown that these cell wails consist almost entirely of arabinoxylan. In this study we show that gibbereilic acid stimulates endo-fi-1,4-xylanase activity in isolated aleurone layers. In addition, gibbereilic acid enhances the activity of two glycosidases: /8-xylopyranosidase and a-arabinofuranosidase. No gibbereilic acid-stimulated ceilulase activity was detected. Germination studies showed a similar pattern of enzyme development in intact seeds.Aleurone layers of barley and other cereal grains respond to gibberellic acid by synthesizing and releasing a select group of hydrolases, including a-amylase, protease, ribonuclease, f8-1,3-glucanase, and phosphatase (14, 25). These enzymes serve to solubilize the stored food reserves of the endosperm for use by the growing embryo. Hydrolase secretion is accompanied by the nearly complete autolysis of aleurone cell cytoplastic constitutents, as well as the thick cell walls (13,16,23 aleurone layers. We also extend previous cytological studies to include scanning electron microscopy in order to monitor the physical degradation of the wall. MATERIALS AND METHODSPlant Material. Barley seeds (Hordeum vulgare L. cv. Himalaya, 1972 harvest) were either sown directly into moist Vermieulite or were surface sterilized for 25 min in 20 % Clorox, rinsed with sterile distilled H20, and sown on moist, sterile sand in 250-ml Erlenmeyer flasks. The seeds were germinated in a growth chamber at a photoperiod of 14 hr and a constant temperature of 25 C.Isolated aleurone layers were prepared from imbibed halfseeds and treated with gibberellic acid by the procedure of Chrispeels and Varner (5), with the exception that succinate buffer (20 mm, pH 5.2) was substituted for acetate buffer (6, 12).Enzyme Assays. At the end of the incubation period, the medium from the GA-treated aleurone layers was decanted into 12-ml conical centrifuge tubes. The layers were rinsed once with 3 ml of succinate buffer (20 mm, pH 5.2) containing 10 mM CaCl2, and the combined medium and washings were centrifuged at 3000g for 5 min. Extractable enzyme was prepared by grinding the aleurone layers to a paste with a small amount of sand in a mortar which had been previously rinsed with succinate-CaCl2 buffer. Five ml of the buffer were added and the homogenate was poured into centrifuge tubes and centrifuged as above. Germinating seeds were extracted in the same manner after first removing the embryos. The supernatants obtained were either used directly or were further treated by precipitation with cold ethanol as described by Taiz and Jones (23) or with 75 % ammonium sulfate. The ammonium sulfate precipitate was redissolved in 1 ml of grinding buffer and dialyzed overnight at 4 C against the same buffer before use. Although initial experiments were carried out using the ethanol procedure it was subsequently determined that precipitation with ...

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confidence: 75%

Production of Cell Wall Hydrolyzing Enzymes by Barley Aleurone Layers in Response to Gibberellic Acid

Taiz¹,

Honigman²

1976

Plant Physiol.

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“…9). Similarly, immunolabeling showed the presence of mannan (all of which is considered to be present as glucomannan; Mares and Stone, 1973a) at all stages of development and the presence of traces of xyloglucan in early stages only (Fig. 9).…”

Section: Irx8mentioning

confidence: 99%

“…The starchy endosperm cell walls constitute 2% to 3% of white flour, have important effects on physical properties such as viscosity (Saulnier et al, 2007a;Faik, 2010), and provide a source of dietary fiber (Topping, 2007). Due to their importance, the composition of the cell walls of mature wheat starchy endosperm has been extensively studied and reported to comprise approximately 70% arabinoxylan (AX), 20% 1,3;1,4-b-D-glucan, 7% glucomannan, and 4% cellulose (Mares and Stone, 1973a;Bacic and Stone, 1980). The wheat starchy endosperm also represents an excellent system for studying grass cell walls, which differ fundamentally from those of dicots, being characterized by a greater abundance of xylan, which has more arabinosyl substitution, smaller amounts of xyloglucan and pectin and the presence of 1,3;1,4-b-D-glucan, and feruloylation of AX or glucuronoarabinoxylan (GAX; Carpita, 1996;Fincher, 2009;Scheller and Ulvskov, 2010).…”

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confidence: 99%

Cell Walls of Developing Wheat Starchy Endosperm: Comparison of Composition and RNA-Seq Transcriptome

et al. 2011

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The transcriptome of the developing starchy endosperm of hexaploid wheat (Triticum aestivum) was determined using RNASeq isolated at five stages during grain fill. This resource represents an excellent way to identify candidate genes responsible for the starchy endosperm cell wall, which is dominated by arabinoxylan (AX), accounting for 70% of the cell wall polysaccharides, with 20% (1,3;1,4)-b-D-glucan, 7% glucomannan, and 4% cellulose. A complete inventory of transcripts of 124 glycosyltransferase (GT) and 72 glycosylhydrolase (GH) genes associated with cell walls is presented. The most highly expressed GT transcript (excluding those known to be involved in starch synthesis) was a GT47 family transcript similar to Arabidopsis (Arabidopsis thaliana) IRX10 involved in xylan extension, and the second most abundant was a GT61. Profiles for GT43 IRX9 and IRX14 putative orthologs were consistent with roles in AX synthesis. Low abundances were found for transcripts from genes in the acyl-coA transferase BAHD family, for which a role in AX feruloylation has been postulated. The relative expression of these was much greater in whole grain compared with starchy endosperm, correlating with the levels of bound ferulate. Transcripts associated with callose (GSL), cellulose (CESA), pectin (GAUT), and glucomannan (CSLA) synthesis were also abundant in starchy endosperm, while the corresponding cell wall polysaccharides were confirmed as low abundance (glucomannan and callose) or undetectable (pectin) in these samples. Abundant transcripts from GH families associated with the hydrolysis of these polysaccharides were also present, suggesting that they may be rapidly turned over. Abundant transcripts in the GT31 family may be responsible for the addition of Gal residues to arabinogalactan peptide.

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“…AX constitutes a larger proportion (85%) of the NSP found in wheat grain (Mares & Stone, 1973). The presence of WEAX in wheat mainly depends upon variety, soil and method of isolation.…”

Section: Introductionmentioning

confidence: 99%

Water-extractable arabinoxylan content in milling fractions of spring wheats Contenido de arabinoxilano extraíble en agua en fracciones pulverizadas de trigos de primavera

Saeed

Pasha

Anjum

et al. 2011

CyTA - Journal of Food

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Studies on Wheat Endosperm I. Chemical Composition and Ultrastructure of the Cell Walls

Abstract: A method is described for the isolation of wheat endosperm cell walls free from non-endospermic cell walls in a 70 % ethanol medium which prevents the loss of watersoluble polymeric components.

Cited by 218 publications

References 3 publications

Production of Cell Wall Hydrolyzing Enzymes by Barley Aleurone Layers in Response to Gibberellic Acid

Production of Cell Wall Hydrolyzing Enzymes by Barley Aleurone Layers in Response to Gibberellic Acid

Cell Walls of Developing Wheat Starchy Endosperm: Comparison of Composition and RNA-Seq Transcriptome

Water-extractable arabinoxylan content in milling fractions of spring wheats Contenido de arabinoxilano extraíble en agua en fracciones pulverizadas de trigos de primavera

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