Tesis sobre el tema "Plant secondary cell walls"
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1
Escamez, Sacha. "Xylem cells cooperate in the control of lignification and cell death during plant vascular development". Doctoral thesis, Umeå universitet, Institutionen för fysiologisk botanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-115787.
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The evolutionary success of land plants was fostered by the acquisition of the xylem vascular tissue which conducts water and minerals upwards from the roots. The xylem tissue of flowering plants is composed of three main types of cells: the sap-conducting tracheary elements (TE), the fibres which provide mechanical support and the parenchyma cells which provide metabolic support to the tissue. Both the TEs and the fibres deposit thick polysaccharidic secondary cell walls (SCWs), reinforced by a rigid phenolic polymer called lignin. The cell walls of TEs form efficient water conducting hollow tubes after the TEs have undergone programmed cell death (PCD) and complete protoplast degradation as a part of their differentiation. The work presented in this thesis studied the regulation of TE PCD by characterizing the function of the candidate PCD regulator METACASPASE 9 (MC9) in Arabidopsis thaliana xylogenic cell suspensions. These cell suspensions can be externally induced to differentiate into a mix of TEs and parenchymatic non-TE cells, thus representing an ideal system to study the cellular processes of TE PCD. In this system, TEs with reduced expression of MC9 were shown to have increased levels of autophagy and to trigger the ectopic death of the non-TE cells. The viability of the non-TE cells could be restored by down-regulating autophagy specifically in the TEs with reduced MC9 expression. Therefore, this work showed that MC9 must tightly regulate the level of autophagy during TE PCD in order to prevent the TEs from becoming harmful to the non-TEs. Hence, this work demonstrated the existence of a cellular cooperation between the TEs and the surrounding parenchymatic cells during TE PCD. The potential cooperation between the TEs and the neighbouring parenchyma during the biosynthesis of lignin was also investigated. The cupin domain containing protein PIRIN2 was found to regulate TE lignification in a non-cell autonomous manner in Arabidopsis thaliana. More precisely, PIRIN2 was shown to function as an antagonist of positive transcriptional regulators of lignin biosynthetic genes in xylem parenchyma cells. Part of the transcriptional regulation by PIRIN2 involves chromatin modifications, which represent a new type of regulation of lignin biosynthesis. Because xylem constitutes the wood in tree species, this newly discovered regulation of non-cell autonomous lignification represents a potential target to modify lignin biosynthesis in order to overcome the recalcitrance of the woody biomass for the production of biofuels.
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Karlsson, Marlene. "Molecular factors involved in the formation of secondary vascular tissues and lignification in higher plants : studies of CuZn-SOD and members of MYB and zinc-finger transcription factor families /". Umeå : Dept. of Forest Genetics and Plant Physiology, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/s280.pdf.
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Bonham, Victoria Anne. "Secondary cell wall specific proteins in plants". Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312839.
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Islam, Azharul. "Cell-walls of growing plant cells". Thesis, University of Westminster, 2013. https://westminsterresearch.westminster.ac.uk/item/8z033/cell-walls-of-growing-plant-cells.
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The plant primary cell wall is a three-dimensional interwoven network of cellulose microfibrils, cross-linked by xyloglucan and dispersed in a pectin matrix. It has been suggested that in the wall of growing plant cells, xyloglucan is bound to the rigid cellulose microfibrils by hydrogen bonds and holds the microfibrils together by forming molecular tethers, which is referred to as the ‘sticky network’ model. Plant growth occurs when these tethers are peeled from the microfibrils by expansins or broken by glycosidases or transglycosylases. A number of researchers have presented theoretical difficulties and observations inconsistent with this model and a new hypothesis has been proposed, claiming that the cellulose – xyloglucan cross-links may act as ‘scaffolds’ holding the microfibrils apart. Analogies with synthetic polymers suggests that the spacing between the cellulose microfibrils may be an important determinant of the mechanical properties of the cell wall and the results presented in this thesis support this hypothesis. Water contents of Acetobacter xylinus synthesized cellulose based cell wall analogues (as a mimic of primary cell wall) and sunflower hypocotyl cell walls were altered using high molecular weight polyethylene glycol (PEG) solution, and their extension under a constant load was measured using a creep extensiometer and showed that there were clear reduction (30-35%) in extensibility suggesting that water content of the wall and therefore the cell wall free volume directly influence wall extensibility. When hydration of A. xylinus cellulose composite pellicles was reduced using PEG 6000 solution and re-hydrated in buffer solution, followed by treatment with α-expansin or snail acetone powder extract, it was found that expansin and snail powder extracts caused a rapid rehydration of the composites and that the pellicles only returned to their original weights after these treatments, suggesting that expansin and snail powder can increase the free volume of the wall perhaps contributing to the increases in extensibility that they cause. Assays on cell wall fragments also indicated that expansin increased the cell wall free volume, demonstrated by changes of the turbidity of fragment suspensions. The role of pectic polysaccharide, RG-II, in cell wall biomechanics was also investigated using mechanical and biochemical testing of available Arabidopsis thaliana cell wall mutants and by incorporating RG-II (purified from red wine) with Acetobacter cellulose. It was demonstrated that RG-II significantly increased the hydration of cellulose composite; hydration rate was 15 -16% more than the composite without RG-II and thus increased the pellicle extensibility. From the results, it is evidenced that cell wall extension is not only the consequences of breaking hydrogen bonds between cellulose microfibrils and xyloglucan by expansins or glycosidases and transglycosylases, but also a wider range of factors are involved including cell wall water content, cell wall free volume and the pectic polymers, especially RG-II.
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Cuello, Clément. "Vers l'élaboration d'un modèle de construction des parois secondaires des fibres de bois chez le peuplier". Electronic Thesis or Diss., Orléans, 2021. https://theses.univ-orleans.fr/prive/accesESR/2021ORLE3118_va.pdf.
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Les arbres atteignent des hauteurs et des durées de vie considérables grâce aux propriétés remarquables de leur bois. En effet, le bois remplit trois fonctions principales : (i) la conduction de la sève brute de la racine au houppier, (ii) le soutien mécanique de la masse toujours en augmentation de l'arbre en croissance et (iii) le stockage de réserves temporaires, capitales pour la pérennité de l'arbre. Chez les angiospermes, les vaisseaux, les fibres et les rayons parenchymateux sont, respectivement, affiliés à ces fonctions. Chacune de ces cellules possède son propre schéma de développement. Par ailleurs, la composition et la structure des parois de ces cellules varient considérablement en fonction des stades de développement et des conditions environnementales. Cette complexité représente donc un frein à l’étude des mécanismes moléculaires de la formation du bois. Cette difficulté peut être contournée par le développement d’approches à l’échelle cellulaire.La thèse présentée ici vise à une caractérisation du développement des fibres, plus particulièrement de leurs parois secondaires, par le déploiement d’outils de caractérisation à l’échelle cellulaire et d’une analyse intégrative à cette échelle. Le développement d’une méthode de caractérisation des parois à l’échelle cellulaire, l’imagerie hyperspectrale en ATR-FTIR, a permis une analyse fine des différences entre types cellulaires au sein d’un arbre et entre types de bois pour un même type cellulaire. L’étude de données transcriptomiques obtenues par RNA-Seq de fibres et rayons micro disséqués a, elle, permis d’identifier des différences transcriptionnelles entre ces deux types cellulaires. La combinaison de ces deux résultats a permis d’identifier des acteurs semblant majeurs dans le développement des fibres de bois. Ce travail de thèse ouvre donc des perspectives de recherche permettant de mieux comprendre les mécanismes moléculaires associés à la formation des fibres de boisTrees are able to grow high et survive many years thanks to their wood properties. Wood delivers three major functions in trees : (i) water conduction, (ii) mechanical support et (iii) nutrient storage. In Angiosperm trees, vessels, fibers et parenchyma rays are respectively assigned to these functions, each of them following their own development scheme. Cell wall composition et structure varies greatly depending on cell type, developmental stage et environmental conditions. This complexity therefore represents a hindrance to study the molecular mechanisms of wood formation. However, this can be circumvented by the development of cell-specific approaches.This work aims at characterizing fiber development, focusing on their secondary cell wall, developing cell-specific methods et integrative analysis at the cell level. Development of ATR-FTIR hyperspectral imaging enabled to finely characterize differences in cell wall composition between cell types in a tree et within cell types in different types of wood. Transcriptomics data obtained by RNA-Seq of microdissected fibers et rays gave rise to major differences in the transcriptome of these two cell types. Combining both kind of result led to the identification of key players in fibers development. Hence, this work opens up new research hypothesis, which could lead to a better understanding of the molecular mechanisms underlying wood fiber development, including from a dynamic perspective
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Murugesan, Yogesh Kumar. "Anisotropic soft matter models for plant cell walls". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117093.
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This thesis uses theory and simulation to elucidate the principles and mechanisms that govern the thermodynamics, material science, and rheology of biological anisotropic soft matter that are involved in growth/self-assembly/material processing in plant cell walls, a multi-functional biological fibrous composite. The plant cell wall can be considered as a reinforced biological membrane consisting of cellulose microfibrils (CMFs) of high tensile strength embedded in a polysaccharide matrix. These CMFs in the extracellular matrix are oriented instrategic directions and generate commonly observed textures such as line, ring, helix, crossed helix and helicoids. The orientation of CMFs governs the physical properties of wood, controls the shape of the cell and contributes to themorphology at the tissue and organ level. Two models are used in this thesis, depending on the concentration of CMFs.At concentration of CMFs below Onsager critical limit, we develop an integrated mechanical model that describes nematic liquid crystalline self-assembly of rigid fibers on an arbitrarily curved 2D fluid membrane to demonstrate the possibility of the CMF orientation imparted by the interaction between membrane curvature and embedded fiber order. This curvature driven planar self assembly model can predict and explain the observed line, ring and helical cell wall textures. These predictions are partially validated through available experimental observations. An integrated shape and nematic order equation developed in this thesis gives a complete model whose solution describes the coupled membraneshape and fiber order state. The validated model is then used to analyze the structure and mechanics of biological and biomimetic fiber-laden membranes of variable curvature. The statics of anisotropic fiber-laden membranes developed inthis model is integrated with the planar nematodynamics of fibers and the dynamics of isotropic membranes to formulate a viscoelastic model to study dynamic remodeling of plant cell wall during growth and morphogenesis. The novel coupling between in-plane fiber orientation and order and membrane curvature formulated this thesis has the potential to open up a novel venue to control two dimensional anisotropic soft matter with tailored functionalities. When the concentration of the CMFs exceeds Onsager's critical fiber concentration threshold, the interaction between these CMFs results in theiralignment in a specific direction as an attempt to minimize the excluded volume of the CMFs. A mathematical model based on the Landau–de Gennes theory of liquid crystals is used to simulate defect textures arising in the domain of chiralself-assembly due to the presence of secondary phases such as pit canal and cell lumens. In addition to providing information on material properties and length scales that cannot be experimentally measured in vivo, the simulated transient defect pattern confirms for first time the long postulated formation mechanism of helicoidal plywoods through liquid crystalline self-assembly. The model is further extended to investigate defect textures and liquid crystalline (LC) phases observed in polygonal arrangement of cylindrical particles embedded in a cholesteric liquid crystal matrix. These validated findings provide a comprehensive set of trends and mechanisms that contribute to the evolving understanding of biological plywoods and serve as a platform for future biomimetic applications.The integration of soft matter physics theories and models with actual biological data for plant cell walls provides a foundation for understanding growth, form, and function and a platform for biomimetic innovation.Cette thèse utilise la théorie et la simulation pour élucider les principes et mécanismes qui gouverne la hermodynamique, la science des matériaux, et la rhéologie de la matière biologique molle anisotropique qui est impliquée dans ledéveloppement/auto-assemblage/la transformation des parois cellulaires de plantes, un composite biologique fibreux multifonctionnel. Les parois cellulaires de plantes peuvent être considérées comme des membranes biologiques renforcées consistant en des microfibres de cellulose (CMFs) de hautes ténacités contenues dans une matrice de polysaccaride. Ces CMFs dans la matrice extracellulaire sont orientés dans une direction stratégique hélices et des hélicoïdes. L'orientation des CMFs gouverne les propriétés physiques du bois et contrôle la forme des cellules. Deux modèles sont employés dans cette thèse dépendamment de la concentration en CMFs. A la concentration de CMFs dessous la limite critique de Onsager, nous développons un modèle mécanique intégré qui décrit un auto-assemblage de fibres rigides de type cristal liquide nématique sur une membrane courbée bidimensionnelle arbitraire afin de démontrer la possibilité de l'orientation des CMFs indue par les interactions entre la courbature de la membrane et l'organisation fibrillaire intrinsèque. Cette auto-assemblage planaire indus par la courbature peut prédire et expliquer les lignes, annaux et textures hélicoïdales observées dans les parois cellulaires. Ces prédictions sont partiellement validées au travers d'observations expérimentales publiés. Une équation décrivant l'ordre nématique et la forme intégrée qui a été développé dans cette thèse fournis un modèle complet dont la solution décrit le couplage entre l'alignement des fibres et la forme de la membrane. Le model validé est par la suite utilisé à fin d'analyser la structure et la mécanique de membrane fibreuses biologiques et biomimétiques de courbatures variables. La statique des membranes fibreuses anisotropes développés dans ce modèle est intégrée avec la némato-dynamique planaire des fibres et la dynamique des membranes isotropes afin de formuler un modèle viscoélastique pour étudier le remodelage dynamique des CMF durant leur développement et morphogénèse. Le nouveau couplage entre l'orientation fibrillaire planaire et l'ordre ainsi que la courbature de la membrane formulé dans cette thèse à le potentiel d'ouvrir de nouvelles avenues pour contrôler l'ordre bidimensionnel de matière molle selon des propriétés bien définies. Quand la concentration en CMFs excède la limite critique en fibre de Onsager, l'interaction entre les CMFs résulte en un alignement dans une direction spécifique qui tente de minimiser le volume exclu de CMFs. Un modèle mathématique basé sur la théorie de Landau de Gennes des cristaux liquides est utilisé pour simuler les textures de défauts survenant dans un chirale d'auto assemblage du à la présence de phases secondaires tel que les lumens cellulaires. En plus de fournir de l'information sur les propriétés matériels et les ordres de grandeurs qui ne peuvent être mesuré expérimentalement in vivo, les motifs des défauts transitoires simulés confirment pour la première fois le mécanisme de formation des assemblages hélicoïdaux. Le modèle est de plus étendu pour investiguer les textures de défauts et les phases liquides cristallines (LC) observées dans les arrangements polygonaux de particules cylindriques inclus dans des matrices de cristaux liquide cholestériques. Ces découvertes validées fournissent un ensemble de mécanismes qui contribues à faire évoluer la compréhension des assemblages lamellaires biologiques et servent de plateforme pour de futur développement d'applications biomimétiques. L'intégration des théories et des modèles de la matière molle avec des données biologique concrète pour les parois cellulaires fournissent des fondement pour la compréhension du développement, de formation et fonctionnalité ainsi qu'une plateforme pour l'innovation biomimétique
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Sene, Christophe F. B. "Infrared microspectroscopy and raman spectroscopy of plant cell walls". Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240996.
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Nunan, Kylie. "Cell wall metabolism in developing grape berries /". Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09APSP/09pspn972.pdf.
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John, Melford Apti. "Post-harvest changes in cell walls of mango fruits". Thesis, Royal Holloway, University of London, 1985. http://repository.royalholloway.ac.uk/items/e6f2ec32-7c86-4106-a945-0ac589c09f14/1/.
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Comparative work on the structure of the cell walls of red kidney bean hypocotyls and mesocarp from unripe and ripe mango fruits showed significant differences. Cell-wall fractions from each were obtained using solvent extraction (water, alkali and acid) and enzymic (endopolygalacturonase) degradation procedures. The monosaccharide composition of each fraction was determined after TFA-hydrolysis by TLC-analysis. Greatest variation in monosaccharide compositions was observed in the water-soluble fractions which accounted for 18%, 48% and 11% of the cell walls of the bean, unripe and ripe mango, respectively. Water-soluble carbohydrates present in the mango pulp were examined by TLC, gel-filtration and ion-exchange methods. Only sucrose, fructose, glucose and high-MW polysaccharides were detected. The ripe mango contained 8 times more soluble polysaccharide than the unripe. In the ripe fruit the approximate MW of the polysaccharide fraction, which was rich in uronic acid was 40,000. In the unripe fruitpolysaccharides with MW's ranging from 40,000 to > 300,000 were detected. These polymers contained much smaller proportions of uronic acid than those from the ripe mesocarp. A crude 3 M LiCl enzyme extract from the cell walls of the ripe mango was able to solubilize 14% of prepared cell walls from the unripe fruit. The mechanism of this process was investigated. Endo-enzymes involved could not be identified. The involvement of b-galactosidase in cell-wall degradation was examined. Using p-nitrophenyl-b-D-galactopyranoside as substrate, 3 wall-bound forms of the enzyme were found in the ripe fruit and 2 in the unripe. Four soluble forms which were different from the wall-bound forms were observed in the ripe fruit. Three of these were present in the unripe fruit. The action of the enzyme forms on mango pectin and cell walls was examined. There was no evidence that any were directly implicated in cell-wall degradation. Wall-bound exopolygalacturonase was detected for the first time in the mango fruit.
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McCann, Maureen C. "Architecture of the plant extracellular matrix". Thesis, University of East Anglia, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279709.
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Chou, Eva Yi. "Understanding the patterned deposition of lignin in secondary cell walls". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60228.
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Lignin, one of the three main components of the secondary cell wall, is an important phenolic biopolymer that provides strength and rigidity to the cell walls of tracheary elements and fibers in vascular plants. Lignin is composed of phenolic alcohol monomers called monolignols, which are synthesized in the cytoplasm. These monolignols are exported to the apoplast where they polymerize by random radical coupling following oxidation by laccases and peroxidases. Two laccases found in Arabidopsis thaliana, LAC4 and LAC17, were localized to secondary cell wall, and required for lignification of protoxylem tracheary elements. The localization of LAC4 and LAC17 to spiral secondary cell walls could be due to either: 1) the diffuse secretion of laccases followed by remobilization to the secondary wall, or 2) a reorientation of post-Golgi vesicle trafficking to secondary cell wall specific plasma membrane domains. Localization studies with LAC4-RFP driven by a constitutive promoter found laccases localized to all regions of the primary cell wall prior to differentiation, then the localization shifted into the helical secondary cell wall bands during protoxylem tracheary elements differentiation. This change in localization suggests there is a change in vesicle traffic during secretion of secondary cell wall components (such as laccases). Furthermore, Fluorescence Recovery After Photobleaching (FRAP) was used to determine if laccase localization in secondary cell walls was due to constraint by the secondary cell walls or exclusion from the primary cell wall. Laccases were also found to be immobile in secondary cell wall domains, but mobile when expressed ectopically in primary cell wall domains. Further drug and mutant FRAP studies found laccases remain immobile in the absence of secondary cell wall: cellulose, xylan, lignin and xylan/lignin. These results suggest laccases are not only anchored to secondary cell wall specific components but may be anchored to multiple components of the secondary cell wall or an unknown component of the secondary cell wall.Science, Faculty of
Graduate
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Musker, D. "Secondary product biosynthesis in plant cell cultures". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384335.
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Bekker, Jan P. I. "Genetic manipulation of the cell wall composition of sugarcane". Thesis, Link to online version, 2007. http://hdl.handle.net/10019/336.
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Kobayashi, Masaru. "Studies on the Boron-Polysaccharide Complex of Higher Plant Cell Walls". Kyoto University, 2000. http://hdl.handle.net/2433/59286.
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Grundy, Myriam Marie-Louise. "Plant cell walls as barriers to lipid bioaccesibility in model lipid-rich plant food (almond)". Thesis, King's College London (University of London), 2014. http://kclpure.kcl.ac.uk/portal/en/theses/plant-cell-walls-as-barriers-to-lipid-bioaccesibility-in-model-lipidrich-plant-food-almond(a48a63df-c061-4c5c-ad69-0036041079d5).html.
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It is generally assumed that most of the nutrients contained in a food are released (bioaccessible) during digestion and potentially available for absorption. However, the structure of plant food such as almonds, in particular the cell walls (‘dietary fibre’), may encapsulate intracellular nutrients, thereby limiting their bioaccessibility. The main aim of the studies described in this thesis was to investigate the role played by almond cell walls in the regulation of lipid bioaccessibility and digestion kinetics using a combination of in vivo, in vitro and in silico methods. The particle size distributions of masticated whole raw and roasted almonds collected from 15 volunteers were used to predict lipid bioaccessibility from a mathematical model. Predicted values were compared with experimental measurements of lipid release in the same almond samples. Samples of masticated almonds were then loaded into a dynamic gastric model followed by a static duodenal model to determine lipid loss in these compartments. The rate and extent of lipolysis were measured by pH-stat titration and gas liquid chromatography of released fatty acids on almond materials with different degrees of bioaccessibility under simulated duodenal digestion conditions. The effect of processing on lipid losses and almond microstructure was also determined in ileostomy subjects who consumed two almond meals varying in lipid bioaccessibility. Finally, the potential penetration of lipase(s) through the cell wall matrix was investigated using notably confocal microscopy. The findings of this project indicated that following mastication and gastrointestinal digestion of whole almonds, only a small proportion of lipid was released from ruptured cells. Depending on the almond structure and degree of processing, the amount of lipid released from the food matrix and fatty acids produced from lipolysis varied substantially. This work has provided further evidence that cell walls act as a physical barrier that limits nutrient digestion.
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Li, Xiaofei. "Development and application of a new method for analysing plant cell walls". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610338.
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Segura, Marcelo Patricio. "Identification of proteins involved in cell wall synthesis by integration of high-throughput technologies". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610582.
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Dong, Xiaoyun. "Functional investigation of arabidopsis callose synthases and the signal transduction pathway". Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1102297893.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xvi, 99 p.; also includes graphics (some col.) Includes bibliographical references (p. 87-99).
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Gray, Douglas Fraser. "The fermentation of 14C-plant cell walls in the rat gastrointestinal tract". Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/23952.
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Dietary fibre (DF) has become an increasingly important part of a healthy diet as its fate in the gastrointestinal (G.I.) tract becomes apparent. The heterogeneous nature of DF components makes the understanding of the overall beneficial effects confusing. The methodology has been limited and in this thesis a new approach to investigating the fate of a radioactive dietary fibre marker in the G.I. tract of rats is described. A U-14C-plant cell wall preparation produced from spinach cell cultures was analysed by various chemical and enzymic techniques. The 14C distribution in the plant cell wall was confined mainly to the major polysaccharide groups: pectins (48.4%), hemicelluloses (15.3%), cellulose (21.3%) and starch (2.6%). The pectins consisted of predominantly homogalacturonan and the major hemicellulose was xyloglucan. The analsyis confirmed that the suspension cultured spinach cell walls were a good comparison with other plant cell walls. Therefore the U-14C-plant cell wall preparation was used in animal studies as a marker for dietary fibre and its fate investigated. The pectic fraction of the cell walls was degraded completely in the rat G.I. tract but the hemicellulose/cellulose fraction was still detected in the colon. It is postulated that the chemical and physical properties of different plant cell wall polysaccharides will dictate their fate in the caecum and colon with respect to degradation by the bacterial microflora. The U-14C-plant cell wall preparation was over 85% degraded by the bacterial micorflora and the fermentation products were utilised by the host. The incorporation of 14C into host tissues was high (22% of the 14C dose) as was the production 14CO2 (26% of the 14C dose) in high fibre fed animals. In vitro fermentation, using a caecal inoculum, confirmed the production of short chain fatty acids (SCFAs) with reduced 14CO2 production (12% of 14C dose). These studies show that both bacterial fermentation of 14C-plant cell walls and host metabolism of 14C-SCFAs result in the production of 14CO2. Comparative studies using animals maintained on low fibre diets showed that both the 14CO2 production in vivo (16% of 14C dose) and in vitro (7% of 14C dose) were reduced. The level of SCFAs was also much lower in the low fibre fed animals suggesting that their caecal bacterial capacity to ferment polysaccharide was grossly reduced. By using the ratio of in vitro to in vivo production of 14CO2 as an indicator of the host capacity to absorb and metabolise SCFAs it was clear that there was no difference between a high and low fibre diet, despite the differences between the activities of the bacterial populations. To conclude, these U-14C-labelled spinach cell walls are a good marker to investigate the fate of DF in the G.I. tract. There is a potential to use the methods described to extend the available information on the biological effects of dietary fibre in our diets.
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Jackson, Owen David. "Cyanobacteria in symbiosis and their relationship with components of plant cell walls". Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555914.
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The cyanobacteria are a unique and important phylum of bacteria. They are photosynthetic, thought to be responsible for up to half of all atmospheric carbon dioxide fixation, and are capable of fixation of atmospheric nitrogen, thus contributing to the nitrogen cycle. Many species readily form symbiotic relationships with a variety of other organisms, from marine animals, through mosses and lichens, to large land plants. The precursor to the modern chloroplast is thought to have been a cyanobacterium. They have played, and continue to play, a huge part in the formation of the environment of the Earth. Using a wide array of monoclonal antibodies to a variety of plant cell wall components, along with a specific reagent (~-glucosyl Yariv reagent), this study has shown that free- living cyanobacteria have components expressed on the outer surfaces of cells with characteristics very much like those of arabinogalactan-proteins (AGPs). AGPs are a class of plant cell wall glycoproteins with a large number of proposed actions in plant growth, development and signalling (including symbiotic signalling). Bioinformatic analysis of the model symbiotic cyanobacterial proteome of Nostoc punctiforme 29133 has suggested that it contains several proteins which share critical characteristics with known plant AGPs. Wider bioinformatic analysis hints at the presence of AGP-like proteins in a wide variety of ; other cyanobacterial species. The study concludes that free-living cyanobacteria produce AGPs and proposes a role for these in extracellular signalling. The study also uses an array of plant cell wall-specific monoclonal antibodies to investigate the potential interactions between Nostoc, a symbiotic cyanobacterial genus, and two of their symbionts, the angiosperm Gunnera and the liverwort B/asia. The presence of AGP- specific epitopes, along with pectins and hemicelluloses at the symbiotic surface is demonstrated. Other than AGPs, analysis suggests that symbiotic cyanobacteria lack the genetic capability to produce these components, and hence it is hvpotheslsed that the plant produces these at the symbiotic surface. Potential roles for these are discussed, including roles in symbiotic signalling and helping the cyanobiont evade plant immune responses.
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Dodson, A. P. J. "The use of lignin peroxidases to degrade lignin in plant cell walls". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46747.
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Sharples, Sandra Christina. "Competing pathways of sugar-nucleotide synthesis during the biosynthesis of plant cell walls". Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/12919.
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The project aim was to determine which of the competing pathways predominate(s) in vivo in the formation of the UDP-GlcA, GDP-GalA and UDP-Man utilised for plant cell wall synthesis. The studies conducted on the 3H:14C ratios of plant cell wall residues at 8 h indicate that UDP-Gal is not a significant direct precursor of UDP-GalA. The 3H:14C ratios of the intermediary metabolites were studied over time. The results show that the 3H:14C ratio kinetics of UDP-GalA and UDP-Gal are vastly different from one another. These results also indicate that UDP-Gal is not a significant direct precursor of UDP-GalA. The 3H:14C ratios of the AIR (alcohol insoluble residue)-derived monosaccharides indicate that UDP-GlcA, UDP-GalA, UDP-Xyl, UDP-Ara and UDP-Api, like UDP-Rha, arose mainly from the UDP-Glc ‘core’ metabolite. The 3H:14C ratio kinetics of UDP-GalA, UDP-GlcA, UDP-Xyl and UDP-Ara are very distinct from the 3H:14C ratio kinetics of Glc 6-P but they are similar to the isotope ratio kinetics of UDP-Glc. The 3H:14C ratios of the AIR-derived monosaccharides and 3H:14C ratios of the intermediary metabolites give strong evidence that UDP-GalA and UDP-GlcA are predominantly formed by the UDP-Glc dehydrogenase pathway and not the myo-inositol pathway. The 3H:14C ratios kinetics of UDP-Glc are approximately equal to those of Glc 1-P. It is observed that the 3H:14C ratio of AIR-derived GalA residue is greater than for Man and Fuc. As UDP-GalA was determined to arise predominantly from UDP-Glc, GDP-Man and GDP-Fuc cannot also stem from Glc 1-P. The predominant pathway of GDP-Man synthesis must be via Gla 6-P or Fru 6-P. The 3H:14C ratio of Rib was similar to those of GalA, Ara, Xyl and Api. A pathway is known to exist that may convert to UDP-Xyl to the RNA precursor Rib 5-P. The results suggest that this is the predominant pathway of Rib synthesis for RNA.
23
Suzuki, Kiyoshi. "Ultrastructural Analysis of Plant Cell Walls by Using Deep-Etching and Immunolabeling Techniques". Kyoto University, 2000. http://hdl.handle.net/2433/151626.
Texto completoResumen
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第8631号
農博第1158号
新制||農||814(附属図書館)
学位論文||H12||N3476(農学部図書室)
UT51-2000-R37
京都大学大学院農学研究科森林科学専攻
(主査)教授 伊東 隆夫, 教授 藤田 稔, 教授 東 順一
学位規則第4条第1項該当
24
Mussa, Huda Jamal. "Elicitor-induced destabilization of PvPRP1 mRNA and characterization of its encoded protein /". Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Clarke, Jonathan H. "Molecular architecture of xylanases from two aerobic soil bacteria". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321447.
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Aliwan, Fraj O. "Mechanism, structure and specificity of a feruloyl esterase from Aspergillus niger". Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267727.
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Azencott, Harold R. "Influence of the cell wall on intracellular delivery by electroporation and acoustic cavitation". Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/11294.
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Desveaux, Darrell. "Xyloglucan (XG) in periplasmic spaces and primary cell walls of developing nasturtium fruits". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0007/MQ44155.pdf.
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Wang, Tuo Ph D. Massachusetts Institute of Technology. "Structure and dynamics of plant cell walls and membrane peptides from solid-state NMR". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103710.
Texto completoResumen
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Solid-state nuclear magnetic resonance (SSNMR) is a powerful technique to study the structure, dynamics and interactions of bio-macromolecules. This thesis mainly focuses on the characterization of the architecture and loosening of primary plant cell walls and the interactions between membrane and peptides. Plant cell wall is a complex system mainly comprising three types of insoluble polysaccharides: cellulose, hemicellulose and pectin. The spatial arrangement of these macromolecules has been largely elusive due to the lack of high-resolution and sitespecific characterization techniques. Here, we introduce SSNMR to investigate the interactions of macromolecules in ¹³C-labeled plant primary cell walls with minimal treatment. Our multidimensional ¹³C spectra show intense cellulose-pectin correlations, suggesting subnanometer contacts between these polymers. The cellulose-pectin interaction is found to be an inherent feature of primary cell walls because it is independent of the hydration history and is caused by site-specific interactions instead of molecular crowding. By measuring water to polysaccharide spin diffusion in intact and sequentially digested walls, we are able to examine the three-dimensional structure of cell walls. Our results suggest a single network model, where cellulose microfibrils make physical contacts with both pectin and hemicellulose. We also investigated how this network was unlocked by expansin, a wall-loosening protein. Using differential isotopic labeling and dynamic nuclear polarization, we determined the binding sites of 0.2 mg expansin in cell walls. Cellulose microfibrils with entrapped hemicellulose were found to be the targets of expansins, thus shedding light on the mechanisms of wall elongation and plant growth. These results have deepened our understanding of plant cell walls, a smart material with both high mechanical strength and extensibility. In addition, we also developed new approaches to investigate the interactions between membranes and peptides. By measuring heteronuclear correlation spectra and proton relaxation times, we determined the localization of the Influenza M2 peptide in distinctly curved membrane domains. Using a rigid-solid heteronuclear correlation experiment, we were able to determine the depth of insertion of dynamically invisible peptides in gel-phase membranes. These studies provide new strategies to study the functionally relevant membrane-curvature induction by proteins and the partitioning and insertion of proteins into lipid membranes.
by Tuo Wang.
Ph. D.
30
Wilson, Linda Georgina. "The effects of food processing on plant cell walls, with special reference to extensin". Thesis, Royal Holloway, University of London, 1987. http://repository.royalholloway.ac.uk/items/e64a8e77-377c-451e-a3e4-fba40b97b209/1/.
Texto completoResumen
Changes in plant cell wall composition caused by a variety of cooking and manufacturing processes have been investigated. These chemical changes have been compared with corresponding structural modifications which were assessed by light and electron microscopy. The different processing treatments have been applied to a single plant tissue, namely mung been seedlings, thus enabling comparisons to be made between the processes. Amino acid analysis was employed to assess changes in cell wall composition. The predominant amino acids in extensin, and isodityrosine, the critical cross-linking unit in this glycoprotein, were measured. Changes resulting from separate chemical extraction of pectin and glycoprotein wall components were also examined. An automated amino acid analysis method for isodityrosine has been established and a novel system for synthesising this dimer developed. The latter involves simple incubation of isolated cell walls with tyrosine, an arrangement which has achieved a six-fold increase in isodityrosine concentration. A reduction in the wall content of hydroxyproline and isodityrosine was observed in samples which had been stored in sulphite solution. It is suggested that this process may degrade pectin and glycoprotein. This idea is discussed with reference to the wall structure seen by microscopical examinations. The soluble extract resulting from boiling cell walls in dilute bicarbonate solution and the water-soluble pectin fraction were both found to contain significant quantities of isodityrosine. It is proposed that these two treatments may extract extensin glycopeptides or even cross-linked extensin oligomers from the wall. It is concluded that most of the processes damaged cell wall pectin to some extent while some also affected extensin. Results from the chemical fractionation experiments demonstrated that these two wall components tend to be co-extracted. This observation is discussed in relation to current models of cell wall structure.
31
Benske, Anika. "Laccase-dependent lignification of secondary cell walls of protoxylem tracheary elements in Arabidopsis thaliana". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50247.
Texto completoResumen
Lignin is a phenolic polymer that plays important roles in the structural integrity of
plants. Both peroxidases and laccases have been implicated in the polymerization of lignin, and
mutant analyses have conclusively demonstrated a role for laccases in lignification of
Arabidopsis thaliana stems. However, the oxidative enzymes that polymerize lignin in
protoxylem tracheary elements (TEs) have not been defined. Induction of the master
transcription factor VASCULAR RELATED NAC-DOMAIN 7 (VND7) causes systemic transdifferentiation
into protoxylem TEs, providing an inducible-experimental model system to study
protoxylem TE differentiation. The transcriptome of these lines has been well characterized, and
two laccases, LAC4 and LAC17, are strongly expressed following induction of protoxylem TE
development. To test if LAC4 and LAC17 are necessary for the lignification of protoxylem TEs,
the inducible VND7 construct was transformed into the lac4-2/lac17 double mutant background
and fluorescently labeled monolignols were exogenously applied to differentiating protoxylem
TEs. Labeled polymerized lignin was only detected in the wild-type protoxylem TEs, but not in
lac4-2/lac17 protoxylem TEs. To test if laccases alone are sufficient to promote lignification, the
constitutive 35S promoter was used to drive either LAC4 or LAC17 in wild-type plants, resulting
in strong ectopic lignification of primary cell walls upon application of fluorescently labeled
monolignols. Fluorescently tagged laccases were transformed into the inducible protoxylem TEs
system, where they specifically localize to the secondary, but not primary, cell walls of
protoxylem tracheary elements. This research shows that LAC4 and LAC17 are necessary and
sufficient for the lignification of secondary cell wall domains of protoxylem TEs and that they
are specifically localized to these domains.Science, Faculty of
Botany, Department of
Graduate
32
Subramanian, Senthil. "Short blue root (sbr), an arabidopsis mutant that ectopically over-expresses and ABA- and auxin-inducible transgene Dc3-GUS and has defects in the cell wall /". View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202002%20SUBRAM.
Texto completoResumen
Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 238-266). Also available in electronic version. Access restricted to campus users.
33
Nealey, Luke T. "The isolation, characterization, and biological testing of xyloglucan from suspension cultured lobloly pine cell spent medium". Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/5749.
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Horstmann, Carl Ulrich. "Manipulating cell wall biosynthesis in yeast and higher plants". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5288.
Texto completoResumen
Thesis (MSc (Genetics))--University of Stellenbosch, 2010.Includes bibliography.
Title page: Dept. of Genetics, Faculty of Science.
ENGLISH ABSTRACT: Undeniably, changes in the environment and dwindling traditional energy resources have resulted in the search for viable, renewable energy alternatives such as biofuels. Cellulose is one of the most abundant polymers on earth and can be converted to simple sugars and fermented to ethanol biofuel fairly easily. Cellulose rich biomass that can serve to supply ethanol biofuel production can be sourced from unexploited agricultural waste. The main drawback to using vegetative tissue as opposed to harvested food stocks from crops results from the structural properties of plant cell walls. Although cellulose is abundant, the contaminating hemicellulose and lignin fibres within the cell wall matrix have a negative impact on the digestibility of the cellulose present. Thus, an important step in creating an effective biofuel production system from agricultural excess is developing crops with improved cell wall polymer characteristics that can be converted to ethanol more efficiently. This project consisted of two parts. Firstly, the aim was to assess lignin production in transgenic sugarcane transformed with a construct aimed at down-regulating the 4- (hydroxyl) cinnamoyl CoA ligase (4CL) gene in the lignin biosynthesis pathway. The second part of the project revolved around discovering the mechanism of impared cell growth caused by expressing the gene encoding cellulose synthase from a marine invertebrate, Ciona savignyi, in the yeast Saccharomyces cerevisiae. Several sugarcane lines that had been previously transformed with a hairpin RNAi construct aimed at down-regulating the 4CL gene in the monolignol biosynthesis pathway were subjected to analysis to determine if lignification had been reduced. Although the presence of the hairpin construct in the genomic DNA had been confirmed for all of the transgenic lines, there was no significant decrease in the lignin levels in any of the transgenic lines. PCR analysis of the mRNA and enzyme assays also confirmed that the 4CL gene was still being expressed. Ongoing work will determine the cause of the unsuccessful down-regulation. Previously, it had been proven that the cellulose synthase gene from C. savignyi could be functionally expressed in S. cerevisiae. However, cellulose production resulted in extremely retarded growth of colonies and cultures, to the point of the apparent death of the cultures. The aim of this part of the project was to determine the mechanism (either metabolic or physical) that causes this effect. To generate enough cell mass to perform metabolic analysis, several strategies to impede cellulose production in transgenic yeast were explored. Attempts to stop cellulose production and induce better growth by introducing Isoxaben (a traditional weed killer that targets cellulose synthases) into the growth medium used for the transgenic yeast proved unsuccessful. To control the expression of the transgene, it was attempted to clone the cellulose synthase gene into an expression system containing an inducible promoter. The cloning exercise proved extremely difficult and multiple attempts with several strategies proved unsuccessful. This process is still ongoing as the growth retarding process induced by cellulose production in yeast remains to be identified.
AFRIKAAANSE OPSOMMING: Dit is onontkenbaar dat veranderinge in die omgewing en minderwordende tradisionele energiebronne veroorsaak dat lewensvatbare en hernubare energiebronne soos biobrandstof gevind moet word. Sellulose is een van die mees volop polimere op aarde en kan redelik maklik omgeskakel word na eenvoudige suikers en gefermenteer word tot etanol-biobrandstof. Sellulose-ryk biomassa wat etanol-biobrandstof kan verskaf, kan herwin word van tot op hede ongebruikte landbou-afval. Die komplekse struktuur van plantselwande is die hoofstruikelblok in die omskakeling van vegetatiewe weefsel tot biobrandstof. Hoewel sellulose volop is, het die kontaminerende hemisellulose- en lignienvesels binne die selwand-matriks ’n negatiewe impak op die verteerbaarheid van die sellulose teenwoordig in die selwand. Daarom is ’n belangrike stap in die ontwikkeling van effektiewe biobrandstof-produksiesisteme vanaf landbou-afval om gewasse te ontwikkel met verbeterde selwandpolimeer-eienskappe wat etanol-produksie kan vergemakilik. Hierdie projek het bestaan uit twee dele. Eerstens was die doel om vas te stel of die lignienproduksie geaffekteer is in transgeniese suikerriet getransformeer met ’n konstruk wat mik om die 4-(hidroksie)-cinnamoyl CoA ligase (4CL) geen te af-reguleer in die lignienbiosintese- padweg. Die tweede deel van die projek het daarop gefokus om die meganisme te ondek wat die belemmerde selgroei veroorsaak, as gevolg van die uitdrukking van die geen wat kodeer vir sellulose-sintase in ’n mariene ongewerwelde, Ciona savignyi, in Saccharomyces cerevisiae. Verskeie suikerriet-lyne, wat voorheen getransformeer is met ’n haarnaald-RNAi-konstruk om die 4CL-geen te af-reguleer in die monolignol-biosintese-padweg, is onderwerp aan analise om vas te stel of lignifikasie verminder is. Hoewel die teenwoordigheid van die haarnaald-konstruk in die genomiese DNA bevestig is vir al die transgeniese lyne, was daar geen beduidende vermindering in die lignienvlakke in die transgeniese lyne nie. PKRanalise van die mRNA en ensiem-aktiwiteitstoetse het ook bevestig dat die 4CL-geen steeds uitgedruk word. Verdere ondersoek sal kan vasstel wat die oorsaak van die onsuksesvolle af-regulering is. Voorheen is bewys dat die sellulose-sintase-geen van C. savignyi funksioneel uitgedruk kon word in Saccharomyces cerevisiae. Egter, selluloseproduksie het die gevolg gehad dat groei in die transgeniese kolonies en kulture erg gestrem is, tot die punt dat die kulture dood voorgekom het. Die doel van hierdie deel van die projek was om vas te stel wat die meganisme (òf metabolies òf fisies) is wat hierdie verskynsel veroorsaak het. Om genoeg selmassa te genereer om metaboliese analise uit te voer, is verskeie strategieë om selluloseproduksie in transgeniese gis te verhinder, ondersoek. Pogings om selluloseproduksie te stop en om groei te verbeter deur Isoxaben by te voeg in die groeimedium gebruik vir transgeniese gis, was onsuksesvol. Isoxaben is ’n tradisionele onkruiddoder wat sellulose-sintases teiken en inhibeer. Om die uitdrukking van die transgeen te beheer, is ’n poging aangewend om dié sellulose-sintase-geen in ’n uitdrukking-sisteem te kloon met ’n induseerbare promotor. Die kloneringsoefening was uiters moeilik en veelvoudige pogings met verskeie strategieë was onsuksesvol. Hierdie proses moet verder gevoer word aangesien die groeistremmingsmeganisme veroorsaak deur selluloseproduksie in gis nog geïdentifiseer moet word.
35
Merkouropoulos, Georgios. "Regulation and analysis of atExt1, a novel extensin gene from Arabidopsis thaliana". Thesis, Bangor University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341217.
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Eberhardt, Thomas Leonard. "Characterization of lignin deposition in Pinus taeda L. cell suspension cultures". Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07282008-134210/.
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Kiyoto, Shingo. "Immunolocalization of 8-5′ and 8-8′ linked structure of lignin in plant cell walls". Kyoto University, 2015. http://hdl.handle.net/2433/202813.
Texto completoResumen
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第19379号
農博第2149号
新制||農||1037(附属図書館)
学位論文||H28||N4959(農学部図書室)
32393
新制||農||1037
京都大学大学院農学研究科森林科学専攻
(主査)教授 髙部 圭司, 教授 髙野 俊幸, 教授 杉山 淳司
学位規則第4条第1項該当
38
Wu, Yajun. "Cell wall proteins and growth maintenance of the maize primary root at low water potentials /". free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9720531.
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Brändström, Jonas. "Morphology of Norway spruce tracheids with emphasis on cell wall organisation /". Uppsala : Swedish University of Agricultural Sciences, 2002. http://diss-epsilon.slu.se/archive/00000236/.
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Thesis (doctoral)--Swedish University of Agricultural Sciences, 2002.Thesis documentation sheet inserted. Appendix reprints four papers and manuscripts, three co-authored with others. Includes bibliographical references. Issued also electronically via World Wide Web in PDF format; online version lacks appendix.
40
McFarlane, Heather Elizabeth 1983. "Isolation and characterization of SOS5 in a novel screen for plasma membrane to cell wall adhesion genes in Arabidopsis thaliana". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116116.
Texto completoResumen
Although dynamic interactions between plant cells and their environment require adhesion between the cell wall (CW) and the plasma membrane (PM), few plant adhesion molecules have been identified. Therefore, the seed coat mucilage secretory cells (MSCs) of Arabidopsis thaliana (which undergo developmentally regulated changes in adhesion) were developed into a novel model system to study PM-CW adhesion. Twenty-seven candidate genes were identified using data from publicly available and seed-specific microarrays. Mutant plants for these genes were screened for defects in adhesion via plasmolysis, and for changes in MSC morphology that may result from defective adhesion (Chapter 1). Two fasciclin-like arabinogalactan proteins were isolated in this screen. One of these, SOS5, was characterized in detail (Chapter 2). sos5 mutants are sensitive to hyperosmotic conditions and show defects in PM-CW adhesion and MSC mucilage structure. Interestingly, these phenotypes may be attributed to defects in adhesion or to defects in cell wall deposition.
41
Temple, Max. "The role of enzymes and binding modules in the degradation of eukaryotic, microbial and plant cell walls". Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3327.
Texto completoResumen
The microbial enzymes that depolymerize complex carbohydrates are of industrial significance particularly in the biofuels and biorefinery sectors. In the human large bowel glycan utilization plays a critical role in defining the composition of the human gut microbial community (microbiota) which, in turn, has a significant impact on health. A central feature of these processes is the specificity of the enzymes and the non-catalytic carbohydrate binding modules (CBMs) that contribute to glycan degradation. This thesis describes research designed to understand the mechanisms by which CBMs and glycoside hydrolases contribute to glycan degradation and how this impacts on the structure of the microbiota. The first results chapter describes the biochemical properties and structural basis for the specificity displayed by two CBMs appended to the glucanase of a rumen bacterium. The sequence of the two CBMs are >75% identical and display essentially identical ligand specificities. Isothermal titration calorimetry revealed that the two proteins bound to a range of β1,4-glucans (cellulose) and, β1,3-β1,4-mixed linked glucans, displaying highest affinity for xyloglucan, a β1,4-glucan decorated with α1,6-xylose residues. The structures of the two CBMs reveal a β-sandwich fold. The ligand binding site comprises the β-sheet that forms the concave surface of the proteins. Binding to the backbone chains of β-glucans is mediated primarily by five aromatic residues that also make hydrophobic interactions with the xylose side chains of xyloglucan, conferring the distinctive specificity of the CBMs for the decorated polysaccharide. Significantly, and in contrast to other CBMs that recognize β-glucans, CBM65A utilizes different polar residues to bind cellulose and mixed linked glucans. Thus, Gln106 is central to cellulose recognition, but is not required for binding to mixed linked glucans. This chapter reveals the mechanism by which β-glucan-specific CBMs can distinguish between linear and mixed linked glucans, and show how these CBMs can exploit an extensive hydrophobic platform to target the side chains of decorated β-glucans. In the second chapter the enzymes that contribute to the degradation of α-mannan, a prominent component of yeast cell walls, were studied. These enzymes were derived from Bacteroides thetaiotaomicron, a member of the microbiota. The data showed that the GH76 endo-α1,6-mannanases presented on the bacterial surface displayed significantly less activity against small mannooligosaccharides compared to the equivalent periplasmic enzymes. All the endo-α1,6-mannanases were only active on the linear backbone of a-mannan, the enzymes were unable to accommodate any side chains. These decorations were partially removed by a poorly expressed and slow acting surface GH92 α-mannosidase. In contrast, in the periplasm a highly active GH38 α-mannosidase rapidly debranched the imported yeast mannan oligosaccharides. The manooligosaccharides generated by the GH76 enzymes were then depolymerized into mannose by a pair of periplasmic exo-acting α1,6-mannosidases that contained only two substrate binding subsites. The biochemical characterization of these enzymes led to the selfish hypothesis in which B. thetaiotaomicron maximises deconstruction of yeast mannan in the periplasm, ensuring that the mannose generated will not be available to other organisms in the microbiota. This hypothesis were verified by showing that B. thetaiotaomicron was unable to support the growth of other Bacteroides sp. (that were able to grow on mannose and, in the case of B. xylanisolvens, also on debranched α-mannan) on yeast α-mannan. In the final results chapter the mechanism by which B. thetaiotaomicron utilized β1,6-glucan, a component of the yeast wall, was analysed. Transcriptomic analysis identified a Polysaccharide Utilization Locus (PUL) that was transcribed in response to β1,6-glucan. The PUL encoded two enzymes and two surface glycan binding proteins (SGBPs), one of which was a SusD homologue. The two SGBPs displayed tight specificity for β1,6-glucan over other β-glucans, displaying a preference for ligands that contained >3 glucose units. The surface GH30 enzyme, BT3312, was shown to be an endo-β1,6-glucanase, while the periplasmic GH3 exo-acting β-glucosidase displayed a preference for β1,6-linkages. B. thetaiotaomicron accumulated β1,6-glucobiose, which was due to the low activity of the GH3 enzyme against the disaccharide and poor expression of the β-glucosidase. The crystal structure of BT3312 revealed a deep pocket that mirrored the U-shaped typology of β1,6-glucan, revealing the mechanism of substrate specificity. Finally the catalytic amino acids of both the GH30 and GH76 enzymes were identified by site-directed mutagenesis.
42
McDonnell, Lisa Marie. "Investigating the role of cellulose synthases in the biosynthesis and properties of cellulose in secondary cell walls". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/30534.
Texto completoResumen
Cellulose synthases are the enzymes responsible for the production of cellulose in plant cell walls. Mutations in any one of the Arabidopsis cellulose synthase (CesA) AtCesA4, AtCesA7, and AtCesA8 genes cause plants to develop collapsed xylem as a result of reduced cellulose content, demonstrating their critical role in secondary cell wall biosynthesis. A thorough characterization of the growth, cell wall properties, and cellulose ultrastructure of the AtCesA4irx⁵-¹, AtCesA7irx³-¹, and AtCesA8irx¹-¹ mutants, presented herein, is the first report of the changes to cellulose microfibril angle, cell wall crystallinity, and cellulose degree of polymerization (DP) in these mutants. This study suggests that the non-redundant functions of individual CesAs may be related to CesA-specific thresholds required for the formation of a cellulose synthesizing complex (CSC), and CesA-specific roles in regulating crystallinity and DP. Additionally, the results illustrate the importance of a fully formed CSC in regulating cellulose microfibril angle.
By identifying and characterizing three new CesA genes from spruce (Picea glauca), PgCesA1, PgCesA2, and PgCesA3, which are homologous to the Arabidopsis AtCesA8, A4, and A7 and the Populus trichocarpa PtiCesA8-A, A4, and A7-A genes, respectively, the degree of functional conservation among AtCesA homologs was explored. Expression of PgCesA1 or the PtiCesAs in AtCesAirx plants rescued the collapsed xylem phenotype, thus demonstrating for the first time that orthologs of AtCesA4, A7, and A8 have conserved functions.
Lastly, in planta techniques were used to measure interactions between AtCesAs to investigate if specific and consistent interactions exist. The results suggest that CesA8 and A4 can form homodimers in planta, and that there might be weak or transient interactions between AtCesA7-A4 and AtCesA7-A8.
Collectively, the results presented suggest, indirectly, an unequal ratio of CesA subunits (AtCesA4:A7:A8) is required for proper cellulose biosynthesis, and that each CesA likely has a unique function which ultimately affects cellulose properties such as cell wall crystallinity and DP. Our conclusions shed new light on the role of CesAs in cellulose biosynthesis in secondary cell walls and elicit questions about the current model of CSC form and function.
43
O'Rourke, Christina Margaret. "Cell wall polysaccharides in charophytic algae". Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/17868.
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Plants colonised land 460 million years ago and charophytes represent the closest living relatives of land plants. The ability to live on land may depend on the presence of certain cell wall polysaccharides such as xyloglucan, a hemicellulose exclusively found in land plants (Popper and Fry, 2003). The cell walls of charophytes are poorly characterised. The aim of this project was to use biochemical techniques to characterise the cell wall polysaccharides of charophytic algae in relation to early land plant phylogeny. Hydrolysis of Coleochaete scutata and Chara vulgaris cell walls in 2 M trifluoroacetic acid yielded predominantly GalA, Gal, Glc and Man residues and also some Ara, Xyl and traces of Fuc and Rha. In addition, hydrolysis of Chara pectin revealed an abundance of an unusual monosaccharide, 3-O-methyl-D-galactose, which was structurally identified by a series of 1-D and 2D NMR spectroscopy by COSY, TOCSY, NOESY and HSQC. 3-O-Methyl-D-galactose is more commonly found in lycophyte cell walls where its presence has been suggested to be related to lycophytes’ evolutionarily isolated position (Popper et al., 2001). The newly discovered presence of 3-O-methyl-D-galactose in charophyte pectin suggests that this polymer may be more complex than previously thought. Coleochaete and Chara hemicellulose extracts were fractionated by anion-exchange chromatography into five classes. A strongly anionic fraction from Chara hemicellulose was found to be rich in Glc, Xyl, Gal and Fuc suggestive of a xyloglucan-like polysaccharide. However, XEG was unable to produce diagnostic xyloglucan oligosaccharides in either Coleochaete or Chara hemicelluloses. Xylanase and mannanase digestion of Coleochaete and Chara hemicelluloses gave xylan- and mannan-oligosaccharides. Furthermore, lichenase digestion of Coleochaete hemicellulose yielded an unusual octasaccharide composed of approximately equimolar xylose and glucose. My work has shown that charophyte cell walls are a source of undiscovered monosaccharides and potentially novel pectic and hemicellulosic domains which may have important functions in enabling the successful colonisation of land by plants.
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Kuhlmann, Somruedee [Verfasser], Johann P. [Akademischer Betreuer] Plank, Johann P. [Gutachter] Plank y Cordt [Gutachter] Zollfrank. "Biomineralization: Nanocasting of Plant Cell Walls / Somruedee Kuhlmann ; Gutachter: Johann P. Plank, Cordt Zollfrank ; Betreuer: Johann P. Plank". München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1192441869/34.
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Parisi, Ann Margaret. "Investigation of Secondary Metabolite Production in Selected Australian Native Species via Plant Cell Suspension Culture". Thesis, Griffith University, 2006. http://hdl.handle.net/10072/366129.
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Natural products and natural-product-derived substances comprised about
35% of the total pharmaceuticals market volume of US$230 billion in 1996
(Wessjohann, 2000). The success of natural-based drugs can be attributed to
nature’s ability to induce effects by chemical means and many of these chemicals
are able to pass species boundaries to cause an effect. Since plant secondary
metabolites have evolved in the interaction with other organisms, many of them
have interesting biological or therapeutical activities that are useful to man. In
addition to their intriguing chemistry a number of these compounds are
economically important, serving as pharmaceuticals, aromatics, fragrances,
stimulants, colours and pesticides.
Plant cell culture is viewed as a potential means of producing useful plant
products without the inherent problems associated with conventional agriculture.
Undifferentiated cell suspension cultures have the potential to produce varied
secondary metabolites by the alteration of culture conditions or addition of
chemicals to elicit expression of different metabolic pathways. Suitable substrate
compounds may be biotransformed to a desired product using plant cell cultures.
Biotransformation can produce compounds that can then be replicated by
synthetic means or produce novel compounds that have previously not been
identified or recognised as important. This thesis describes the initiation of plant
suspension cultures for the purposes of examining the production of secondary
metabolites of selected Australian native rainforest species.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Biomedical Science
Science, Environment, Engineering and Technology
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Neubauer, Jonathan David. "Gene Expression Associated with Wound and Native Periderm Maturation in Potato Tubers". Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/29771.
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Potato (Solanum tuberosum L.) is the world's fourth largest food crop and large financial losses are incurred each year from wound and bruise related injuries. However, little is known about the coordinate induction of genes that may be associated with, or mark major wound-healing and periderm maturation
events. Also, one of the key defense mechanisms for potato tubers is the robust barrier provided by the phellem (skin) of the native periderm. Many biological processes are involved in the formation of this stout tissue. However, little is known about induction of genes that may be associated with this process.
The objectives of this research were to molecularly assess the processes of wound periderm development and maturation, and native periderm maturation in potato tubers. In this study, these processes were determined in coordination with expression profiles of selected genes. The cell cycle, cell wall protein, and pectin methyl esterase genes were determined from two diverse potato genotypes and two harvests NDTX4271-5R (ND) and Russet Burbank (RB) tubers; 2008 and 2009 harvests. Cell cycle genes encoding epidermal growth factor binding protein (StEBP), cyclin-dependent kinase B (StCDKB), and cyclin-dependent kinase regulatory subunit (StCKS1At) expression profiles were coordinated with related phellogen formation and the induction and cessation of phellem cell formation. Genes encoding the structural cell wall proteins extensin (StExt1) and extensin-like (StExtlk) expression profiles suggested involvement with closing layer formation and subsequent phellem cell layer formations. The coordinate induction and expression profile of StTLRP, a gene encoding a cell wall strengthening "tyrosine- and lysine-rich protein," suggested a role in the formation of the closing layer followed by phellem cell generation and lastly cell wall thickening in nonmeristematic phellogen cells. StPME and StPrePME expression increased during periderm development, implicating involvement in modifications for closing layer and phellem cell formation. Collectively, these results indicate that the genes monitored were involved in and their expression profiles markedly coordinated with periderm formation and the on-set of periderm maturation; results were more influenced by harvest than genotype. Importantly, StTLRP was the only gene examined that may be involved in phellogen cell wall strengthening or thickening after cessation of cell division.
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Keppler, Brian D. "IRX₁₄ and IRX₁₄-LIKE two glycosyl transferases involved in glucuronoxylan biosynthesis in Arabidopsis /". Ohio : Ohio University, 2010. http://www.ohiolink.edu/etd/view.cgi?ohiou1268243386.
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Guhl, Katherine Elizabeth. "Biochemical characterization of Medicago truncatula root knots induced by Meloidogyne incognita". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 7.41 Mb., 122 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1432288.
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Whitney, Sarah E. C. "The interaction of cellulose with xyloglucan and other glucan-binding polymers". Thesis, University of Stirling, 1996. http://hdl.handle.net/1893/2243.
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This thesis examines the interaction of xyloglucan, the major hemicellulosic component of type I primary plant cell walls, with cellulose. Initial attempts to form xyloglucan-cellulose complexes by in vitro association methods are described, which gave low levels of interaction, with features not similar to those found in primary wall networks. The majority of the work focusses on the use of the bacterium Acetobacter aceti ssp. xylinum (ATCC 53524), which synthesise highly pure, crystalline cellulose as an extracellular polysaccharide. Addition of xyloglucan to a cellulose-synthesising bacterial culture results in the formation of cellulose-xyloglucan networks with ultrastructural and molecular features similar to those of the networks of higher plants. Applicatioon of the bacterial fermentation system is extended to incorporate the polysaccharides glucomannan, galactomannan, xylan, mixed-linkage glucan, pectin and carboxymethylcellulose, all of which impart unique architectural and molecular effects on the composistes formed. Preliminary data on the mechanical properties of composite structures under large and small deformation conditions are also described.
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Crouch, Elke Monika. "Cell wall compositional differences between mealy and non-mealy ‘Forelle’ pear (Pyrus communis L.)". Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6746.
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Thesis (PhD(Agric) (Horticulture))--University of Stellenbosch, 2011.Includes bibliography.
ENGLISH ABSTRACT: Mealiness, a soft, dry textural disorder of ‘Forelle’ pear (Pyrus communis L.), is a problem for the South African fruit export industry. Soft, dry textural disorders seem to be related to changes in cell wall breakdown. The aim of this work was, therefore, to investigate the occurrence of mealiness‐associated changes in the cell wall and elucidate the mechanism by which mealiness occurs in ‘Forelle’ pear, as well as to characterise cell wall changes occurring during normal ripening. Mealy ‘Forelle’ tissues had significantly lower total galacturonic acids associated with the middle lamella (water‐ and CDTA‐soluble fractions). The water‐soluble pectin of mealy tissues was depolymerised at an earlier stage of ripening. The widespread disintegration of cell‐to‐cell adhesion in mealy cell walls only, suggests that the middle lamella and the plasmodesmata are more broken down. In mealy ‘Forelle’ tissues there was no indication of less broken down high molecular weight polyuronides in the CDTA fraction, normally associated with these dry, soft textures. The pectins from mealy tissues were more broken down and both mealy and non‐mealy tissue polyuronides depolymerised. Furthermore, there was a lack of light toluidine staining in the larger air spaces, which would indicate such water‐insoluble pectins. These data suggest that the formation of high molecular weight pectate gels is unlikely in mealy ‘Forelle’ pear. The slight increase in the galactose content in mealy tissues in CDTA‐ and Na2CO3‐soluble fractions and slight decrease in the 1 M KOH glycan fraction during later stages of ripening (6+11, 9+7, 9+11; weeks at ‐0.5°C plus days at 15°C) may indicate that galactose loosely interlinked into the glycan fraction broke down sooner for mealy tissues. This didn’t increase molecular size profiles in the CDTA fraction. Arabinose content was slightly higher in the 4 M KOH fraction and slightly lower in mealy tissues of water‐ and CDTA fractions. This did not influence the molecular weight of the glycans compared to those in the nonmealy tissues. ‘Forelle’ data therefore seem to be more congruent with a decrease in intercellular adhesion as the mechanism by which mealiness occurs, rather than the formation of high molecular weight pectins taking up the cellular fluid. ‘Forelle’ pear water‐soluble pectin content increases with increased ripening. High amounts of watersoluble pectin and low amounts of Na2CO3‐soluble pectin suggests that solubilisation of rhamnogalacturonan‐I pectins must have taken place during early ripening (at a fruit firmness of > 4.7 kg (7.9mm tip). Galactose and glucose in the pectin fraction dramatically decreased after fruit ripened to a firmness of 4.5 kg, whereafter they remained unchanged. This was also the period in which fruit softened the most and the biggest increase in pectin water‐solubility occurred. It is not known whether these events are coincidental, or linked causally. Rhamnose and arabinose extractability increased in the water fraction and xylose, fucose and mannose increased in glycan fractions with ripening. The biggest changes in polyuronide solubilisation and depolymerisation occurred in water‐ and CDTA fractions between storage and ripening durations of 3+7 (4.7 kg) and 6+4 (2.7 kg).
AFRIKAANSE OPSOMMING: Melerigheid, ʼn sagte droë tekstuur afwyking van ‘Forelle’ pere (Pyrus communis L.), is ʼn probleem vir die Suid Afrikaanse vrugte uitvoerbedryf. Sagte, droë tekstuur afwykings blyk betrekking te hê op selwandafbraak veranderinge. Die doel van die studie was dus om die melerigheid‐geassosieerde veranderinge in die selwand te ondersoek, sowel as om vas te stel wat die meganisme betrokke is by melerigheid ontwikkeling in ‘Forelle’ pere. Die selwand veranderinge gedurende normale rypwording is ook gekarakteriseer. Melerige ‘Forelle’ weefsel het betekenisvol laer totale galakturoonsuur wat geassosieer is met die middellamella (water‐ en CDTA‐oplosbare fraksies). Die water‐oplosbare pektien van melerige weefsel was op ʼn vroeër stadium van rypwording gedepolimeriseer. Die wydverspreide disintegrasie van sel‐tot‐sel adhesie, slegs in melerige selwande, dui aan dat die middellamella en die plasmodesmata meer afgebreek is. Daar is geen indikasie van hoë molekulêre massa poliuroniedes in die CDTA fraksie van melerige ‘Forelle’ weefsel, wat gewoonlik geassosieer word met droë, sagte teksture nie. Die pektiene van melerige weefsel was meer afgebreek en melerige en nie‐melerige weefsel se poliurone was gedepolimeriseer. Daar was ook geen ligte toluïdien verkleuring in die groter intersellulêre lugruimtes nie, wat ʼn aanduiding sou wees van wateronoplosbare pektiene. Hierdie data dui dus aan dat die vorming van hoë molekulêre pektien jel in melerige ‘Forelle’ pere onwaarskynlik is. Die klein toename in galaktose inhoud in die CDTA‐ en Na2CO3‐ oplosbare fraksies en ʼn klein afname in 1 M KOH glikaan fraksie tydens latere rypheidstadiums (6+11, 9+7, 9+11; weke by ‐0.5°C plus dae by 15°C), kan beteken dat los verweefde galaktose in die glikaan fraksie vroeër afgebreek het in melerige weefsels. Die molekulêre grootte profiel is nie verander in die CDTA fraksie nie. Arabinose inhoud was bietjie hoër in die 4 M KOH fraksie en bietjie laer in melerige weefsel van die water‐ en CDTA fraksies. Die molekulêre massa van die glikane was klaarblyklik onbeïnvloed hierdeur. ‘Forelle’ data blyk dus meer saam te stem met die meganisme waar ʼn vermindering in intersellulêre adhesie ʼn rol speel in melerigheid, eerder as die meganisme waar hoë molekulêre pektien selvloeistowwe bind. ‘Forelle’ peer water‐oplosbare pektieninhoud neem toe met toenemende rypheid. Hoë vlakke wateroplosbare pektien en lae vlakke Na2CO3‐oplosbare pektien stel voor dat die oplossing van rhamnogalakturonan‐I pektiene gedurende vroeë rypwording moes plaasgevind het (by ʼn fermheid van > 4.7 kg (7.9mm punt). Galaktose en glukose in die pektienfraksie het drasties verminder nadat vrugte tot ʼn fermheid van 4.5 kg ryp geword het, waarna hul onveranderd gebly het. Dit was ook die periode waarin vrugte die meeste sag geword het en die grootste toename in poliuronied wateroplosbaarheid gevind is. Dit is nie bekend of die gebeure toevallig of oorsaaklik verbind is nie. Rhamnose en arabinose ekstraheerbaarheid het vermeerder in die water fraksies, en xylose, fukose en mannose het vermeerder in die glikaan fraksies gedurende rypwording. Die grootste verandering in oplosbaarheid en depolimerisasie het plaasgevind in die water‐ en CDTA fraksies tussen opberging en rypwordingsperiodes van 3+7 (4.7 kg) en 6+4 (2.7 kg).