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Polysaccharides in Germination. Physical Characterization of the Pectic Araban of White Mustard Cotyledons *
Abstract
The molecular weight of mustard seed araban, determined by sedimentation equilibrium and vapor pressure osmometry, corresponds to a molecule containing about 45 sugar units. Arabans extracted at different pH values, extracted from different batches of resting seeds, and extracted from cotyledons after germination are all homogeneous and similar in the ultracentrifuge and on free solution electrophoresis in borate. These findings confirm that mustard seed araban is not a degradation artifact of a large heteropolysaccharide, and show that the change in araban structure which occurs with germination cannot take place by the simple addition or simple partial removal of arabinose units from a polysaccharide subfraction.
... 47 The object of our investigation of seed germination is to obtain information about the structure and biological changes of cell-wall polysaccharides to correlate with parallel investigations of chain conformation and interactions (Rees & Skerrett, 1968Rees, 1969;Rees & Wight, 1971;Rees & Scott, 1971; Anderson, Campbell, Harding, Rees & Samuel, 1969;Rees, Steele & Williamson, 1969; McKinnon, , hoping to work towards an understanding of polysaccharide function in molecular terms. In earlier papers (Rees & Wight, 1969;Rees & Richardson, 1966;Rees & Steele, 1966;Gould & Rees, 1965;Hirst, Rees & Richardson, 1965) we have described the chemical composition of the cotyledons of white mustard and the way this changes with germination, with special reference to the carbohydrate components. The major polysaccharides of the cell wall are cellulose, pectic materials (Rees & Richardson, 1966;Rees & Steele, 1966 Wight, 1969) and substances which give xylose, glucose, and smaller amounts of other sugars, on acid hydrolysis. ...
... In earlier papers (Rees & Wight, 1969;Rees & Richardson, 1966;Rees & Steele, 1966;Gould & Rees, 1965;Hirst, Rees & Richardson, 1965) we have described the chemical composition of the cotyledons of white mustard and the way this changes with germination, with special reference to the carbohydrate components. The major polysaccharides of the cell wall are cellulose, pectic materials (Rees & Richardson, 1966;Rees & Steele, 1966 Wight, 1969) and substances which give xylose, glucose, and smaller amounts of other sugars, on acid hydrolysis. More information is now given about the latter polysaccharides, which, following Aspinall (1969), we propose to call 'xyloglucans'. ...
Two xyloglucan fractions have been isolated from the cotyledons of resting white-mustard seeds, the first by extraction with hot EDTA, and the second by subsequent extraction with alkali or lithium thiocyanate. Although both appear to have the ;amyloid' type of structure in which chains of (1-->4)-linked beta-d-glucopyranose residues carry d-xylose-rich side chains through position 6, these side chains are rather different in structure in the two polysaccharide fractions, and the second or ;insoluble' xyloglucan has fewer of them. The side chains in both polysaccharides are also different from those in other seed amyloids, especially in having xylose linked through positions 3 and 4 (instead of through position 2 as usual) and in containing fucose residues. Both polysaccharides show the characteristic blue ;amyloid' colour with iodine in the presence of sodium sulphate, and it is suggested that this arises by the interaction of iodine molecules and possibly iodide ions within the interstices between aggregated xyloglucan chains. ;Soluble' xyloglucan is metabolized during germination and is presumed to have a reserve function. ;Insoluble' xyloglucan is metabolized less completely over the period studied but its lack of turnover during cell-wall differentiation indicates that it also is a reserve. These and other beta-(1-->4)-linked reserve polysaccharides of seeds might also have a structural function which is of particular value for the survival of the dormant seed.
... Water-soluble yellow mustard mucilage is a heterogeneous mixture of neutral and acidic polysaccharides [1][2][3][4]. Recent interest in the mucilage of yellow mustard seed is attributed to its unique rheological behaviour in solutions/dispersions and its ability to interact with galactomannans synergistically, which may have commercial potential in the food hydrocolloids industry [3][4][5]. ...
Plant polysaccharides comprise the major portion of organic matter in the biosphere. The cell wall built on the basis of polysaccharides is the key feature of a plant organism largely determining its biology. All together, around 10 types of polysaccharide backbones, which can be decorated by different substituents giving rise to endless diversity of carbohydrate structures, are present in cell walls of higher plants. Each of the numerous cell types present in plants has cell wall with specific parameters, the features of which mostly arise from the structure of polymeric components. The structure of polysaccharides is not directly encoded by the genome and has variability in many parameters (molecular weight, length, and location of side chains, presence of modifying groups, etc.). The extent of such variability is limited by the "functional fitting" of the polymer, which is largely based on spatial organization of the polysaccharide and its ability to form supramolecular complexes of an appropriate type. Consequently, the carrier of the functional specificity is not the certain molecular structure but the certain type of the molecules having a certain degree of heterogeneity. This review summarizes the data on structural features of plant cell wall polysaccharides, considers formation of supramolecular complexes, gives examples of tissue- and stage-specific polysaccharides and functionally significant carbohydrate-carbohydrate interactions in plant cell wall, and presents approaches to analyze the spatial structure of polysaccharides and their complexes.
Schizolobium amazonicum and S. parahybae galactomannans yielded the same pattern of oligosaccharides on partial acid hydrolysis. Seed coats of both species furnished unusual linear arabinans providing chemotyping evidence supporting the suggestion that they are not different species.Schizolobium parahybae and S. amazonicum seeds yielded galactomannans with identical 3.0:1 Man:Gal ratios and with the same d-galactose distribution along the main chain. Although the galactomannan from seeds of Cassia fastuosa showed the same Man:Gal ratio, its fine structure differed significantly from that of the two Schizolobium species as shown by the analysis of oligosaccharides (DP 2 to 6) obtained by partial acid hydrolysis. Seed coasts of S. parahybae and S. amazonicum furnished similar unusual neutral linear α-l-arabinofuranan (1 → 5) linked, as determined by methylation analysis, optical rotation and 13C NMR spectroscopy. On the other hand, C. fastuosa seed coats furnished two acidic arabinans. These results in terms of using galactomannans and arabinans in chemotyping, support the suggestion of Rizzini that S. parahybae and S. amazonicum are not different species.
In germinating lupin cotyledons, there was a rapid depletion of raffinose series oligosaccharides, a temporary increase in sucrose and constant low levels of reducing monosaccharides. The major polysaccharide fraction was extracted with hot NH4 oxalate—EDTA solution and had the constitution of intercellular/cell wall polysaccharide. GLC examination of component sugars showed that as cotyledons expanded this fraction was depleted and that there was selective hydrolysis of arabinose and galactose, so that the uronic acid proportion increased. Gel and DEAE-cellulose chromatography showed that this fraction became more heterogeneous. The neutral and acidic fractions were separated and the component sugars, viscosities, gel chromatographic behaviour and sedimentation constants of these determined. The results indicated that in the later phase of plant cell wall expansion in germinating lupin cotyledons the arabinogalactan side chains of the pectic polysaccharide fraction are selectively hydrolysed leaving a primary wall with a high uronic acid content.
An arabinan and the previously characterized arabinogalactan and acidic polysaccharide complex have been isolated by extraction of defatted and deproteinized soybean cotyledon meal with water. Methylation analysis involving gas chromatography – mass spectrometry of methylated alditol acetates formed from the methylated arabinan has shown that the parent polysaccharide is highly branched and of the same structural type as other arabinans associated with pectins. Methylated derivatives of mustard seed and lemon-peel arabinans and of soybean arabinogalactan have been similarly analyzed.
An arabinan isolated from parsnip was shown by sedimentation studies to be homogeneous, and methylation revealed a highly branched structure. Hydrolysis of the fully methylated polysaccharide yielded 2,3,5-tri-O-methyl-L-arabinose (11 mol), 2,3-di-O-methyl-L-arabinose (20 mol), 3-0-methyl-L-arabinose (trace), 2-O-methyl-L-arabinose (7 mol), and L-arabinose (2 mol). The general structural features of the arabinan are discussed.
The occurrence, isolation, chemistry and physico-chemistry of plant arabino-3,6-galactans and arabino-3,6-galactan-proteins is reviewed. The structural relationships between arabino-3,6-galactans from gymnosperm wood, gum exudates of Acacia and other trees, and from plant callus cells and whole tissues are discussed. The nature of these proteoglycans is compared with the arabinose and galactose containing cell wall glycoproteins. Interactions of the arabino-3,6-galactan proteoglycans with carbohydrate binding proteins and with Yariv antigens are described. The utility of these reactions for both cellular and subcellular localization of the proteoglycans is discussed. The possible biological roles of the arabinogalactans and the arabinogalactan-proteins are reviewed.
Graded extraction of oil-free, dehulled, rapeseed cotyledon meal with boiling aqueous ethanol, hot water, hot ammonium oxalate and finally sodium hydroxide yielded a series of fractions. The composition, identification and structural evaluation of the various products is presented and the results compared with those obtained from other seeds.
An arabinan isolated from rapeseed was shown by sedimentation studies to be essentially homogeneous, and methylation analysis revealed a highly branched structure. Hydrolysis of the methylated polysaccharide yielded 2,3,5-tri-O-methyl-L-arabinose (11 mol.), 2,3-di-O-methyl-L-arabinose (7 mol.), 3-O-methyl-L-arabinose (trace), 2-O-methyl-L-arabinose (7 mol.), and L-arabinose (2 mol.). Periodate-oxidation data substantiate the methylation results. The general, structural features of the arabinan are discussed.
Methylation analysis was used to characterize the pectic polysaccharides from mustard cotyledons, a tissue with potential for rapid biological change involving the walls. The methylated sugars were identified by g.l.c. and paper chromatography after conversion of uronic acid derivatives into [(3)H]hexoses, and confirmed by the formation of crystalline derivatives of most of the main products, which were: 2,3-di-O-methyl-d-[6-(3)H]galactose, 2-O-methyl-d-[6-(3)H]galactose, 3,4-di-O-methylrhamnose, 3-O-methylrhamnose, 2,3,5-tri-O-methyl-l-arabinose, 2,3-di-O-methyl-l-arabinose, 2-O-methyl-l-arabinose, 2,3,4-tri-O-methyl-d-xylose and 2,3,4,6-tetra-O-methyl-d-galactose in the molar proportions 1.00:1.14:0.54:0.74:2.86:2.50:2.24:1.88:0.32. The structural units present are similar to those in wellknown polysaccharides from mature tissues, but their proportions are strikingly different. Uninterrupted and unbranched galacturonan segments can therefore contribute little cohesion to these walls, and it is suggested that this correlates with a function of the wall matrix to hydrate and permit readjustment, during germination, of structural elements or wall surfaces or both.
1. d-Glucose and l-arabinose serve as precursors of the pectic polysaccharides of sycamore suspension-callus tissue. 2. The rates and characteristics of the incorporation of radioactive sucrose, glucose and mesoinositol by sycamore callus tissue have been compared and shown to be different. 3. The time-course of the incorporation of radioactive glucose into the major fractions within the cells has been determined. Approx. 7-10% of the radioactivity incorporated is present in the whole pectin of the cells. 4. A study of the continuous incorporation of radioactive glucose showed that the neutral arabinan-galactan fraction of the pectin quickly became saturated with the radioactive label. During the incorporation of radioactivity from a pulse of radioactive glucose the neutral fraction became progressively less labelled, with a corresponding increase in the radioactivity of the weakly acidic pectinic acid, which is known to contain neutral sugars. 5. When the cells were exposed to a pulse of radioactive l-arabinose, the label accumulated first in the neutral fraction and then after 4hr. it passed to the weakly acidic pectinic acid with a corresponding decrease in the radioactivity of the neutral fraction. 6. The product that was initially labelled during the first hour of exposure of the cells in the stationary phase to radioactive glucose was identified as an incompletely methylated galacturonan in which the radioactivity was present in the anhydrogalacturonide residues. This polysaccharide probably acts as the precursor of the polyuronide portions of both the strongly acidic and weakly acidic pectinic acids. 7. The observations are discussed in relation to the structure of the pectic substances and their function in cell growth and development. A tentative model for their metabolic relationship is put forward.
The polysaccharide isolated by extracting sugar-beet chips with hot lime-water was found to contain L-arabinose, D-galactose, L-rhamnose, and galacturonic acid, in the approximate proportions of 74, 10, 3.5, and 5% respectively, and smaller quantities of 2-O-methyl-D-xylose, 2-O-methyl-L-fucose, mannose, fucose, and an aldobiouronic acid composed of galacturonic acid and 2-O-methylxylose. The polysaccharide preparation had an average molecular weight of about 12,500 and attempts to fractionate the material were unsuccessful. It is suggested therefore that the "araban" component of pectin exists in combination with a variety of monosaccharide units.
95,453. sota, St. Paul, Minn. Corp. I, 179; Chem. Abstr. 39, 5525. try 5, 3009 (this issue; preceding paper)
- Y Tomimatsu
- K J J Palmer
- Polymer
- R L Whistler
- J N Bemiller
Tomimatsu, Y., and Palmer, K. J. (1963), J. Polymer Whistler, R. L., and BeMiller, J. N. (1958), Adoan. Yphantis, D. A. (1960), Ann. N. Y. Acad. Sei. 88, 586. M. (1959), J. Chem. Soc., 774. 94,617. Steele, I. W. (1965), Nature 208, 876. Biochem J. 95,453. sota, St. Paul, Minn. Corp. I, 179; Chem. Abstr. 39, 5525. try 5, 3009 (this issue; preceding paper). (1965), Australian J. Chem. 18, 851. Sei. AI, 1005. Carbohydrate Chem. 13, 289.