Robert Selvendran

... and Molecular Plant Pathology (1988) 33, 377384 The wound response of tomato plants can be inhibited by aspirin and related hydroxybenzoic acids HELEN M. DOHERTY ... 9 . HILDER, VA, GATEHOUSE, A. M . R., SHEERMAN, S . E., BARKER, R. F . BOUTLER, D. (1987) . ...

... The presence of addi-tional ether linkages between pectic polysaccharides and ferulic acid is indicated by the failure of alkaline saponification to release all the hound ferulic acid from sugar beet cell walls (BJ H. Stevens and RR Selvendran. unpublished resuhs1. ...

ABSTRACT Changes in the cell wall composition of stems of asparagus (Asparagus officinalis L. cv. Connovor Collossus) during maturation and during storage in modified atmospheres were investigated. Alcohol-insoluble residues from portions of stems were analysed for changes in alkali-soluble phenolics and in the constituent sugars and their glycosidic linkages. Maturation-related changes down the stem involved increased levels of (l–4)-linked xylosyl residues from xylans, cellulose and phenolics, which arise from the lignified vascular and sclerenchyma tissues, and a decrease in the levels of (l–5)-linked arabinosyl residues from pectic arabinans from the parenchy-matous tissues. Storage under aerobic conditions permitted stem elongation in the apical sections and secondary thickening in the basal sections. This was due to continued tissue maturation. Storage under anaerobic conditions inhibited such changes. In accordance with these effects of storage on stem physiology, maturation-related changes in cell wall components were enhanced by storage only under aerobic conditions. However, levels of (1–4)-linked galactosyl residues which remained relatively constant during maturation, decreased substantially (ca 50%) in all stem sections during both aerobic and anaerobic storage.

1. Methylation analysis of potato (Solanum tuberosum) lectin and thorn-apple (Datura stramonium) lectin confirmed previous conclusions that both glycoproteins contained high proportions of l-arabinofuranosides and lesser amounts of d-galactopyranosides. The arabinofuranosides are present in both lectins as short unbranched chains containing 1-->2- and 1-->3-linkages, which are known to be linked to hydroxyproline. Galactopyranosides are present as monosaccharides, which are known to be attached to serine, in potato lectin and as both the monosaccharide and the 1-->3-linked disaccharide in Datura lectin. 2. Alkaline digestion of potato lectin and subsequent separation of the components by gel filtration led to the isolation of four fractions corresponding to the mono-, di-, tri- and tetra-arabinosides of hydroxyproline. The latter two fractions accounted for over 70% of the total hydroxyproline. 3. Methylation analysis was used to show that the triarabinoside contained only ...

Cell wall material (CWM) was prepared from sections of fresh and aerobically-stored asparagus (Asparagus officinalis, L. cv. Connovor Collossus) stems. Polymers were solubilized from the CWM by successive extraction with cyclohexane-trans-1,2-diamine-N N N' N'-tetraacetate (CDTA), Na2CO3 and KOH to leave the alpha-cellulose residue which contained a significant amount of cross-linked pectic polysaccharides. The polymers were fractionated by anion-exchange chromatography and selected fractions were subjected to methylation analysis. The storage-related decrease in (1-4)-linked Galp was detected in all the fractions rich in pectic polysaccharides, particularly in the CDTA, Na2CO3, 0.5 M KOH fractions and alpha-cellulose residue. A smaller decrease in Araf was also observed. This was mainly due to a decrease in (1-5)-linked Araf in the Na2CO3-1-soluble polymers, and terminal Araf in the alpha-cellulose residue. There was evidence for the occurrence of significant amounts of complexes containing pectic polysaccharides and xylans having a relatively low degree of polymerization in the dilute alkali-soluble polymers, and some of these contained phenolic compounds; the storage-induced increase in (1-4)-linked Xylp was confined to these polymers. Interestingly, no free acidic xylans could be detected in the 1 M and 4 M KOH-soluble polymers; instead, the bulk of the hemicellulosic polysaccharides appeared to be mixtures of xyloglucans and xylans in which the ratio of xyloglucan to xylan increased with increasing strength of alkali used for extraction of the polymers. The non-degradative extraction and fractionation procedures revealed heterogeneity in pectic polysaccharides, pectic polysaccharide-xylan complexes and xyloglucans in close association with xylans. The possible relationship between pectic polysaccharide-xylan-phenolic complexes and the onset of lignification in maturing tissues is discussed.

The alcohol-insoluble residue (AIR) of immature and mature runner beans contains co-precipitated cytoplasmic proteins, nucleic acids, starch and polyphenols, which contaminate the isolated polysaccharide fractions and their binding is sufficiently tenacious to resist complete ...

ABSTRACT Changes in the cell wall composition of stems of asparagus (Asparagus officinalis L. cv. Connovor Collossus) during maturation and during storage in modified atmospheres were investigated. Alcohol-insoluble residues from portions of stems were analysed for changes in alkali-soluble phenolics and in the constituent sugars and their glycosidic linkages. Maturation-related changes down the stem involved increased levels of (l–4)-linked xylosyl residues from xylans, cellulose and phenolics, which arise from the lignified vascular and sclerenchyma tissues, and a decrease in the levels of (l–5)-linked arabinosyl residues from pectic arabinans from the parenchy-matous tissues. Storage under aerobic conditions permitted stem elongation in the apical sections and secondary thickening in the basal sections. This was due to continued tissue maturation. Storage under anaerobic conditions inhibited such changes. In accordance with these effects of storage on stem physiology, maturation-related changes in cell wall components were enhanced by storage only under aerobic conditions. However, levels of (1–4)-linked galactosyl residues which remained relatively constant during maturation, decreased substantially (ca 50%) in all stem sections during both aerobic and anaerobic storage.

Portions of stems from the base of asparagus spears (Asparagus officinalis L. cv. Connovor Collossus) were dissected to give the following tissues:(1) pith, which was free of vascular bundles,(2) two surrounding layers, parenchyma and fibre I and II (PFI and PFII), ...

ABSTRACT Unripe Spanish pears (Pyrus communis, c.v. Blanquille) were allowed to ripen at 18°C for 1 week. Cell walls were prepared as alcohol-insoluble residues (AIRS) which were free of starch. On a fresh weight basis, ripening was accompanied by a decrease in cell wall arabinose and uronic acid, a proportion of which were metabolised, and an increase in xylose and glucose. To investigate the origin of the changes in cell wall polymers, the AIRS of unripe and ripe fruit were extracted sequentially with water, cyclohexanetrans-1,2-diamine-N, N, N', N'-tetraacetate (CDTA), Na2CO3 at 1°C and 20°C, 0.5, 1 and 4M KOH to leave a cellulose-rich residue. The extracts and residues were analysed for their carbohydrate composition and, where appropriate, degree of pectin-methyl esterification. The water, CDTA and Na2C03 extracted polymers were rich in pectic polysaccharides. These exhibited heterogeneity in the ratios of neutral and acidic components and contained small quantities of xylose. The KOH-extracted polymers were rich in hemicelluloses, particularly xylans, but also contained sugars common to pectic polysaccharides. The cellulose-rich residues were rich in cellulosic glucose and xylose which probably originated from the highlylignified sclereids. Ripening resulted in an increase in water- and CDTA-soluble pectic polysaccharides which exhibited a lower degree of pectin-methyl esterification. These results and the changes in carbohydrate composition are discussed in the light of corresponding decreases in the yields of pectic polysaccharides of the Na2CO3 extracts and cellulose-rich residues during ripening.

ABSTRACT The Na2CO3-soluble pectic polysaccharides of mature onions were separated by anion-exchange chromatography, and the structural features of two of the pectic polysaccharides were examined by methylation analysis and 13C-n.m.r. spectroscopy. The oligosaccharide side-chains containing β-d-galactose were (1→4)-linked and were shown to have an average, d.p. of 7–8 by methylation analysis and 8–9 by n.m.r. spectroscopy. The α-l-arabinose side-chains were (1→5)-linked and had an average d.p. of 3, as shown by methylation analysis, but it was not possible to obtain a value from the n.m.r. data.

Selected fractions of cauliflower stem, obtained after ethanol graded precipitation of 0.5M KOH cell wall extractions, were further purified by anion-exchange and gel-permeation chromatographic methods. Pure xyloglucans and various xylan-rich polysaccharide complexes were obtained, particularly from the most mature section of the stem. A pectic-xylan–xyloglucan complex, tentatively characterised by methylation analysis, was digested separately with purified and highly specific endo-xylanase

... 1 Dept Biochemistry, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK. 2 ... Correspondence: James A Robertson, Dept Biochemistry, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK. Publication History. ...

... APPLES HELEN D. CHAPMAN, VICTOR J. MORRIS*, ROBERT R. SELVENDRAN, AFRC Institute of Food Research, Norwich Laboratory, Colney Lane, Norwich NR4 7UA (Great Britain) AND MALCOLM A. O'NEILL Complex Carbohydrate ... Cider apples were a gift from Drs. ...

We have identified a family of abundant peripheral plasma membrane glycoproteins that is unique to flowering plants. They are identified by a monoclonal antibody, MAC 207, that recognizes an epitope containing L-arabinose and D-glucuronic acid. Immunofluorescence and immunogold labeling studies locate the MAC 207 epitope to the outer surface of the plasma membrane both in protoplasts and in intact tissues. In some cells MAC 207 also binds to the vacuolar membrane, probably reflecting the movement of the plasma membrane glycoproteins in the endocytic pathway. The epitope recognized by MAC 207 is also present on a distinct soluble proteoglycan secreted into the growth medium by carrot (Daucus carota) suspension culture cells. Biochemical evidence identifies this neutral proteoglycan as a member of the large class of arabinogalactan proteins (AGPs), and suggests a structural relationship between it and the plasma membrane glycoproteins. AGPs have the property of binding to beta-glycans, and we therefore propose that one function of the AGP-related, plasma membrane-associated glycoproteins may be to act as cell surface attachment sites for cell wall matrix polysaccharides.

Pectic substances are a major component of cell walls in vegetable plants and have an important influence on plant food texture. Cauliflower (Brassica oleracea L. var. botrytis) stem sections at different regions of the mature plant stem have been monitored for tissue-related changes in the native pectic polysaccharides. Chemical analysis detected appreciable differences in the degree of methyl-esterification (ME) of pectic polysaccharides. About 65% of galacturonic acid (GalpA) residues were methyl-esterified in floret tissues. Relative ME showed a basipetal decrease, from 94% in the upper stem to 51% in the lower-stem vascular tissues. The decrease was not related to a basipetal increase in glucuronic acid (GlcpA) residues. The monoclonal antibodies, JIM 5 and JIM 7, produced distinct labelling patterns for the relatively low-methylesterified and high-methyl-esterified pectin epitopes, respectively. Labelling was related to cell type and tissue location in the stem. Floret cell walls contained epitopes for both JIM 5 and JIM 7 throughout the wall. Stem vascular tissues labelled more strongly with JIM 5. Whereas pith parenchyma in the upper stem labelled more strongly with JIM 7, in the lower-stem pith parenchyma, JIM 5 labelling predominated. Localization of pectic polysaccharide epitopes in cell walls provides an insight into how structural modifications might relate to the textural and nutritional properties of cell walls.

Page 1. PHY.S1OLOGIA PLANTARUM 91: 671-679. 1994 /*;v''ilf(/ CI iii'imiurk - nil yi,i,'lil\ rc^ti'm'd hysiohtiiia Planmrum Ripening-related changes in the cell walls of Spanish pear (Pyrus communis) Maria A, Martin-Cabrejas, Keith ...

... 1 Dept Biochemistry, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK. 2 ... Correspondence: James A Robertson, Dept Biochemistry, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK. Publication History. ...

ABSTRACT Cell wall material (CWM) was prepared from green olive pulp processed according to the ''Sevillian Style'', Polymers were solubilized from the CWM by the sequential extraction with trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid, sodium salt (CDTA); Na2CO3; 1 M KOH; 4 M KOH; and 4 M KOH + berate to leave a cellulosic residue (CR). The polymers from the various extracts were fractionated and selected fractions were subjected to methylation analysis. This study showed that the softening of the olive pulp with the processing was due to a partial degradation of the pectic polysaccharides. Part of the degraded polymers were solubilized during the preparation of the CWM and the majority were solubilized after CDTA treatment. The CWM also showed coprecipitation with intracellular proteins and phenolic compounds that originated a material that was insoluble in aqueous solutions. The hemicellulosic polymers were not significantly affected by the processing.

The effects of heat treatment and dehydration on fiber structure and hydration properties, using cauliflower floret/curd and stem tissues, have been investigated. No major changes in fiber composition resulted from sample treatments, but the degree of esterification of pectic polysaccharides, approximately 60% in fresh cauliflower, decreased by approximately 12% in samples heated at temperatures >40 degrees C. Enzymic activity was considered to be responsible, through pectin methyl esterase activity. De-esterification was temperature and moisture sensitive. Hydration properties were also affected by processing conditions. The solubility of nonstarch polysaccharides in fresh, freeze-dried, and 40 degrees C dried samples was approximately 6% but increased to 12% in boiled samples and decreased in samples dried at 75 degrees C. Similar behavior occurred for swelling and water retention capacity (WRC), with swelling and WRC highest for boiled samples and lowest for samples dried at 75 degrees C. Hence, a decrease in de-esterification was not directly responsible for changes in hydration properties. The results demonstrate the importance of processing history on functional properties and on the preparation of fiber-rich ingredients for successful incorporation into foods.

... Research, 135 (1984) 155166 Elsevier Science Publishers BV, Amsterdam Printed in The Netherlands STRUCTURAL FEATURES OF CELLWALL POLYMERS OF THE APPLE BARRY JH STEVENS ... 31 C. VERSTEEG, Ph D Thesis. ... 34 B JH STEVENS AND RR SELVENDRAN. ...