Wall Polysaccharides Research Articles

Role of cell-wall biogenesis in the initiation of auxin-mediated growth in coleoptiles of Zea mays L.

The involvement of cell-wall polymer synthesis in auxin-mediated elongation of coleoptile segments from Zea mays L. was investigated with particular regard to the growth-limiting outer epidermis. There was no effect of indole acetic acid (IAA) on the incorporation of labeled glucose into the major polysaccharide wall fractions (cellulose, hemicellulose) within the first 2 h of IAA-induced growth. 2,6-Dichlorobenzonitrile inhibited cellulose synthesis strongly but had no effect on IAA-induced segment elongation even after a pretreatment period of 24 h, indicating that the growth response is independent of the apposition of new cellulose microfibrils at the epidermal cell wall. The incorporation of labeled leucine into total and cell-wall protein of the epidermis was promoted by IAA during the first 30 min of IAA-induced growth. Inhibition of IAA-induced growth by protein and RNA-synthesis inhibitors (cycloheximide, cordycepin) was accompanied by an inhibition of leucine incorporation into the epidermal cell wall during the first 30 min of induced growth but had no effect on the concomitant incorporation of monosaccharide precursors into the cellulose or hemicellulose fractions of this wall. It is concluded that at least one of the epidermal cell-wall proteins fulfills the criteria for a 'growth-limiting protein' induced by IAA at the onset of the growth response. In contrast, the synthesis of the polysaccharide wall fractions cellulose and hemicellulose, as well as their transport and integration into the growing epidermal wall, appears to be independent of growth-limiting protein and these processes are therefore no part of the mechanism of growth control by IAA.

Influence of triethyllead on growth and ultrastructure of tobacco pollen tubes

The toxic effects of triethyllead (TriEL) on semi-vivo cultured pollen tubes of Nicotiana sylvestris were investigated by light and electron microscopy. TriEL caused severe retardation of pollen tube growth and induced three obvious alterations in pollen tube ultrastructure: (a) thickening of tube wall and accumulation of clumped fibrous wall materials in the apex, (b) formation of electron dense inclusions in the dilated portions of the rough ER cisternae and in the periplasmic space between the plasma membrane and tube wall, and (c) disappearance of microtubules in the sperm cells. A 50% reduction in pollen tube bundle lenght (ED 50 value) was observed at a TriEL concentration of 0.683 mg/l (2.1 μM). The tube growth inhibition might result from an irregular orientation and clumping of fibrous non-callosic, non-cellulosic polysaccharide wall materials and their accumulation in the apex and outer lateral wall layer.

Changes in the hemicellulosic polysaccharides of Avena coleoptile cell walls during growth of intact seedlings

The variations taking place in the major polysaccharides of the cell wall of Avena sativa L. cv. Victory coleoptiles were studied during growth. Two fractions were obtained, one corresponding to cellulose and the other to the hemicelluloses. The relative content of cellulose was greater in the basal regions of the coleoptiles and the proportion of this polysaccharide fraction increased in all regions during growth. The hemicellulosic fraction was composed of two parts, an insoluble one designated the HC A hemicellulosic fraction, whose main component was seen to be an insoluble xyloglucan, and a soluble part designated the HC B hemicellulosic fraction, composed of an arabinoxylan and a (β1-3)- or (β1-4)-glucan. This latter was degraded during the growth of the coleoptiles. The average molecular weight of hemicelluloses HC A and HC B decreased from the sub-apical zones to the basal zones of the coleoptiles; this was related to the growth capacity of each of the regions into which the coleoptiles were divided.

Effets d'une plasmolyse prolongée sur les tubes polliniques angiospermiens en culture in vitro : étude ultrastructurale

In angiosperm plants subjected to plasmolysis, pollen tubes may undergo substantial ultrastructural changes accompanied by a gradual deterioration of those processes involved in cell syntheses. However, some tubes quickly regenerate a polysaccharide wall and thus ensure their extension. Others undergo fragmentation of their cytoplasm and a serious breakdown in processes involved in cell wall synthesis. In these extreme cases, the endoplasmic reticulum is the only compartment that is readily discernible.

Structural studies of cell wall polysaccharides from Bifidobacterium breve YIT 4010 and related Bifidobacterium species.

The chemical compositions of the cell walls obtained from 8 strains in 5 species of Bifidobacterium were analyzed. These cell walls were shown to be composed of peptidoglycan and polysaccharide moieties. Some variations with respect to contents of neutral sugars and content of phosphorus were observed with some cell wall preparations from the same species. The neutral polysaccharides in cell walls of 4 strains of Bifidobacterium (B. bifidum YIT 4007, B. breve YIT 4010, B. infantis YIT 4025, and B. longum ATCC 15707) were purified and their chemical structures were analyzed. One of these polysaccharides, obtained from B. breve YIT 4010, was analyzed in detail by GLC, 1H- and 13C-NMR spectroscopic analyses, methylation, Smith degradation and acetolysis, and the results suggested the following structure for the repeating unit of the polysaccharide: (Formula: see text).

THE ECTOMYCORRHIZAL INFECTION ZONE AND ITS RELATION TO ACID POLYSACCHARIDES OF CORTICAL CELL WALLS

SUMMARYCortical cell walls of spruce [Picea abies (L.) Karst.] and pine (Pinus sylvestris L.) were found to contain large amounts of acid polysaccharide, which was absent from all other cell walls studied. In its staining characteristics, calcium content, extractability and structure it was similar to the pectic substance filling intercellular regions in the cortex, xylem and other tissues. The acid polysaccharide also formed a matrix embedding fungal cells of the Hartig net in mycorrhizal roots. Matrix substance in the mantle was of a different character.The distal limit of the acid polysaccharide wall incrustation marked the transition between the differentiation zone of the root tip and the mature cortex, and coincided exactly with the distal limit of the Hartig net and fungal penetration. The endodermis and, where present, the metacutis formed other barriers. Proximally, the onset of senescence and death of cortical cells made mycorrhiza formation impossible, or terminated the existing symbiotic relationship.Thus, ‘the mycorrhizal infection zone’, i.e. the part of the root where fungal colonization could take place, was defined by (a) a particular wall composition and (b) a physiological condition. Such limitation is consistent with the theory of mechanical fungal penetration during mycorrhiza formation‐the pectins increase the cell‐wall flexibility‐as well as the model for host‐mycobiont interaction proposed in an earlier study (Nylund & Unestam, 1982).

Biosynthesis and composition of gram-negative bacterial extracellular and wall polysaccharides.

Biosynthesis and composition of gram-negative bacterial extracellular and wall polysaccharides.

Thecal Plate Tabulation and Variation in Peridinium balticum (Pyrrhophyta: Peridiniales)

Thecal Plate Tabulation and Variation in Peridinium balticum (Pyrrhophyta: Peridiniales)

Stimulation of extracellular polysaccharide synthesis in oat protoplasts by the host-specific phytotoxin victorin

The host-specific phytotoxin victorin (HV-toxin) stimulates mesophyll protoplasts of susceptible but not of resistant oat (Avena sativa L.) to produce an amorphous, ethanol-insoluble extracellular material which stains with Calcofluor white and aniline blue. Over a 24-h period incorporation of [(14)C]glucose into ethanol-insoluble products is maximally stimulated by 60 pg victorin/ml, whereas at 6 ng/ml initial rates of incorporation are higher but the protoplasts collapse. The extracellular material produced in response to victorin is solubilized by cold 4.4 N NaOH and by commercial laminarinase and pectinase. Incorporation of [(14)C]glucose into cellulose (material resistant to Updegraff's acetic-nitric acid reagent) is stimulated as much as incorporation into other wall polysaccharides, but cellulose constitutes less than 15% of the total victorin-stimulated incorporation. Synthesis of ethanol-insoluble material that can be digested by pronase, i.e. protein, is inhibited by victorin above 60 pg victorin/ml. Formation of extracellular polysaccharide is stimulated at concentrations of victorin which cause almost complete inhibition of protein synthesis, indicating that de-novo protein synthesis is not involved. Preincubation of protoplasts with inhibitors of RNA or protein synthesis prevents both extracellular polysaccharide synthesis and cell death in response to victorin. Although previous studies have indicated a link between calcium and the action of victorin, several compounds which interact with calcium do not influence this response to victorin.

Biosynthesis and Composition of Gram-Negative Bacterial Extracellular and Wall Polysaccharides

Biosynthesis and Composition of Gram-Negative Bacterial Extracellular and Wall Polysaccharides

Three-dimensional reconstruction of the generative cell and its wall connection in mature bicellular pollen of Rhododendron

In mature pollen of several species of Rhododendrom, a PAS-positive connective has been found at the light microscope level, linking the outer tangential wall of the intine with the generative cell. Ultrastructural and cytochemical studies show that there is a polysaccharide wall ingrowth that is continuous with the periplasm between the generative cell plasma membrane and that of the vegetative cell. Three-dimensional reconstruction shows that the wall ingrowth is linked with one of two tails of the generative cell. These tails are sited one at either end of the elongate cell, and are coiled around its axis.

Optimal preparation of mycelia and arthrospores of Geotrichum candidum: a SEM, TEM and cytochemical study

Three morphological stages of Geotrichum candidum, viz. the mycelium, a cylindrical spore type, and an ellipsoidal spore type, were subjected to qualitative and quantitative morphological and cytochemical analyses using scanning and transmission electron microscopy. Considerable variation in total cell shrinkage as well as cell wall thickness was found with fixation procedure and cell type. Cell walls were best preserved with simultaneous fixation in aldehydes and osmium whereas optimal preservation of the cytoplasm required sequential fixation. Mechanical pretreatment improved the visualization of ultrastructural details in the thick–walled ellipsoidal spores. Wall polysaccharides and cytoplasmic glycogen stained positively with periodic acid–thiosemicarbohydrazide–silver proteinate and with alkaline bismuth subni–trate. In all three cell types an electron–transparent wall region was sandwiched between outer and inner electron–dense and PAS–positive regions. Wall thickness in cylindrical spores corresponded to that of mycelium whereas ellipsoidal spores had a 1.7 times thicker wall and a 1.9 times greater wall volume than cylindrical spores.

Comparison between maize root cells and their respective regenerating protoplasts: wall polysaccharides

The cell-wall polysaccharides from different parts of maize roots have been analysed. The arabinose, galactose and mannose contents are influenced by cell differentiation, whereas xylose, rhamnose and uronic-acid contents are not. In cap cells, the pectin content is low but rhamnose and fucose are present in larger quantities. The cell-wall polysaccharides from cells of the elongation zone and their respective regenerating protoplasts were also analysed. The walls of the protoplasts contained higher xylose and mannose levels and a much lower level of cellulose than the cells from which they were derived.

Structure of the Primary Cell Walls of Suspension-Cultured Rosa glauca Cells

Xyloglucans, characteristic hemicellulosic polysaccharides of plant primary walls, have been isolated from Rosa glauca suspension-cultured cells. The cell wall material was fractionated by two sequences of extraction based on solubilization of the hemicelluloses in alkaline and organic solvent systems, respectively. In both cases, only a part (about 50%) of the total xyloglucan could be extracted, the rest remaining tightly associated with cellulose and necessitating the use of acid to be solubilized. Purification of xyloglucans was effected by formation of a gel in appropriate mixtures of dimethyl sulfoxide and water. Further fractionation could be achieved on a cellulose column eluted with chaotropic solvents. This demonstrated the heterogeneity of xyloglucans in the primary cell walls. Analytical data show that all fractions are constituted with the same sugars: l-arabinose, l-fucose, d-galactose, d-xylose, and d-glucose, but their relative proportions differ, particularly the ratio of glucose to xylose which varies from 1.2 to 2 within the different xyloglucans. The structure of these hemicelluloses was established by methylation analysis and shown to consist of a (1 --> 4)-linked glucan backbone which carries substituents on the O-6 of glucose. Here again, the multiple forms of xyloglucans was suggested by the various patterns of substitutions found on the different fractions. The configuration of the linkages were established by (13)C nuclear magnetic resonance spectroscopy and shown to be beta for the glucan backbone, alpha for the xylosyl and fucosyl substituents, and beta for the galactosyl substituents. These configurations agree with the specific rotation of the xyloglucan.

The microcyst wall of Didymium iridis: chemical analyses

Chemical analyses of the microcyst cell wall of Didymium iridis were done to compare it with other well-studied organisms, Physarum polycephalum and Physarum flavicomum. Large wall fragments were obtained by breakage in a Braun homogenizer. Chemical analyses of purified walls identified neutral sugars, protein, and hexosamine as the major components. Wall polysaccharides were mostly composed of galactosamine with smaller amounts of glucose and galactose. The protein component consisted of large quantities of threonine and aspartate–asparagine with trace amounts of the sulfur-containing amino acids. Most of the wall protein was soluble in alkaline urea. Sodium dodecyl sulfate – polyacrylamide gel electrophoresis was used to identify seven major bands, at least four of which are acidic glycoproteins. Most of the galactosamine was associated with the urea – hot alkali insoluble fraction comprised mostly of glucose. This galactosaminoglucan was partially sulfated and acetylated and arranged as microfibrils that maintain cell shape.

The structure and histochemistry of sclerotia ofSclerotinia minor Jagger III. Changes in ultrastructure and loss of reserve materials during carpogenic germination

Cytoplasmic reserves and extracellular substances were progressively broken down and utilized during carpogenic germination of sclerotia ofSclerotinia minor. Glycogen, wall polysaccharides and polyphosphate granules were removed first from regions of the sclerotium distant from developing apothecia, while protein bodies near the base of apothecial stipes were hydrolysed before those further away. The number of profiles of mitochondria and endoplasmic reticulum in cortical and medullary hyphae increased at the onset of germination, indicating increased metabolism in the hyphae. In contrast to developing sclerotia, simple pores with Woronin bodies were frequent in walls and septa during germination. Hyphae that appeared to converge towards the base of apothecial initials retained their cytoplasm and organelles until late in germination and hydrolysis of their reserves was delayed; these are interpreted as translocatory hyphae, although further work is required to determine their role unequivocally. When apothecia were fully developed, hyphae throughout the sclerotium were empty and the walls and extracellular matrix of cortical and medullary hyphae had almost completely broken down.

Redistribution of Tritium during Germination of Grain Harvested from myo-[2-3H]Inositol- and scyllo-[R-3H]Inositol-Labeled Wheat

Wheat kernels from myo-[2-(3)H]inositol- or scyllo-[R-(3)H]inositol-labeled plants (Sasaki and Loewus 1980 Plant Physiol 66: 740-745) were used to study redistribution of (3)H into growing regions during germination. Most of the labeled 1-alpha-galactinol (or the analogous scyllo-inositol galactoside) was hydrolyzed within 1 day. Water-soluble phytate was dephosphorylated within 3 days. A large reserve of bound phytate continued to release myo-inositol over several days. Translocation of free myo-inositol to growing regions provided substrate for the myo-inositol oxidation pathway and incorporation of (3)H into new cell wall polysaccharides.Cell wall polysaccharides in the kernel were degraded during germination. The labeled residues were translocated to growing regions and reutilized for new cell wall formation. Pentosyl residues accounted for most of this label.Free scyllo-inositol followed a path of translocation from kernel to seedling similar to that of myo-inositol. Unlike myo-inositol, it did not furnish substrate for the myo-inositol oxidation pathway but accumulated as free scyllo-inositol in the seedling.The fate of phytate-derived myo-inositol during germination of wheat is discussed in relation to a recent scheme of phytate metabolism proposed by De and Biswas (1979 J Biol Chem 254: 8717-8719) for germinating mung bean seedlings.

Oriented structure of pectic polysaccharides in pea epidermal cell walls

Oriented structure of pectic polysaccharides in pea epidermal cell walls

Concanavalin A affects polysaccharidic wall formation and mitotic activity in Polyphysa (Acetabularia) cliftonii protoplasts

Cell wall formation, terminating the differentiation of protoplasts from nucleate cap ray cytoplasm of Polyphysa (Acetabularia) cliftonii, is inhibited by concanavalin A (ConA), depending on its concentration. The effect is completely reversible by application of the hapten sugar αMM, but not by NAcGal. It is concluded that ConA binds to certain glycosylated surface components, thus preventing the growth of the wall-polysaccharide chains, predominantly cellulose, or their attachment to ‘priming’ components. Normally, cell wall formation and nuclear divisions are strictly correlated. ConA, however, dissociates cell wall formation from the mitotic events reversibly in that it suppresses wall formation and leaves mitosis unmolested. In general, therefore, ConA revealed no mitogenic effect in the plant system under investigation. In special, the ConA effect might be regarded as a strong stimulation of mitotic events in relation to the normally existing correlation between mitosis and the presence of cell wall.

Changes in cell wall polysaccharides and monosaccharides during development and ripening of Japanese pear fruit1

Changes in polysaccharide and monosaccharide components in the cell wall were studied during cell division, cell enlargmement and softening in Japanese pear fruit. Wall polysaccharides were fractionated into water soluble carbohydrate, NaClO2 soluble carbohydrate, EDTA soluble carbohydrate, acid soluble hemicellulose, alkali soluble hemicellulose and cellulose. These polysaccharides were composed of glucose, uronic acid, xylose, arabinose, galactose, rhamnose, mannose and fucose.The total polysaccharide content of the cell wall per cell (DNA content basis) remained constant during the cell division period (S1). But during the pre-enlargement period (S2) it began to increase rapidly in spite of the slightness of cell enlargement. Thereafter, during the enlargement period (S3) the polysaccharides remained almost constant although the fruits enlarged dramatically, and the polysaccharides increased somewhat with ripening. The quality of the polysaccharides, however, seemed to change actively at each stage. This suggested that the extensive fruit enlargement did not require an increase in polysaccharide content, and was rather accompanied by the partial breakdown or partial interconversion of polysaccharide components already present.The loss of arabinose and galactose in acid soluble hemicellulose was prominant in fruit softening occurring in the ripening stage. The cellulose component decreased with overripening. Water soluble pectin increased parallel to the increase in total pectin with ripening. On the other hand, xylose and non-cellulosic glucose residues did not alter with ripening or overripening. Non-cellulosic glucose continued to accumulate during cell enlargement. Changes in polysaccharide and monosaccharide components in the cell wall were studied during cell division, cell enlargmement and softening in Japanese pear fruit. Wall polysaccharides were fractionated into water soluble carbohydrate, NaClO2 soluble carbohydrate, EDTA soluble carbohydrate, acid soluble hemicellulose, alkali soluble hemicellulose and cellulose. These polysaccharides were composed of glucose, uronic acid, xylose, arabinose, galactose, rhamnose, mannose and fucose. The total polysaccharide content of the cell wall per cell (DNA content basis) remained constant during the cell division period (S1). But during the pre-enlargement period (S2) it began to increase rapidly in spite of the slightness of cell enlargement. Thereafter, during the enlargement period (S3) the polysaccharides remained almost constant although the fruits enlarged dramatically, and the polysaccharides increased somewhat with ripening. The quality of the polysaccharides, however, seemed to change actively at each stage. This suggested that the extensive fruit enlargement did not require an increase in polysaccharide content, and was rather accompanied by the partial breakdown or partial interconversion of polysaccharide components already present. The loss of arabinose and galactose in acid soluble hemicellulose was prominant in fruit softening occurring in the ripening stage. The cellulose component decreased with overripening. Water soluble pectin increased parallel to the increase in total pectin with ripening. On the other hand, xylose and non-cellulosic glucose residues did not alter with ripening or overripening. Non-cellulosic glucose continued to accumulate during cell enlargement.