Lepidimoide is a naturally occurring disaccharide reported to be an oligosaccharin, i.e. to exhibit ‘hormone-like’ biological activity. It was found in cress (Lepidium sativum) root exudates and exerts apparently allelopathic effects on neighbouring Amaranthus seedlings. In the present study the effect of cress root exudates on hypocotyl and root length of Amaranthus caudatus and Lactuca sativa was studied. The seedlings of both species grown with Lepidium sativum seedlings had longer hypocotyls and shorter roots as compared to the control. In this study I found an active principle with biological effects similar to those of lepidimoide to be more abundant in cress seed-coat mucilage than in root exudates. The active principle peaked 24 hours after seed soaking, and thereafter plateaued. I also for the first time confidently proved that the bioactive compound(s) were exuded by cress and were not microbial digestion products or seed treatment chemicals. Quantitative tests of cress root exudates and cress seed-coat mucilage showed the presence of hexoses, pentoses, uronic acids and unsaturated uronic acid. The presence of unsaturated uronic acid might be of interest because the known structure of lepidimoide includes an unsaturated uronic acid. Active principle from mucilage was partitioned into the aqueous phase when shaken with ethyl acetate at pH 2, 6.5 and 12, showing it to be hydrophilic, unlike auxins and gibberellins. The mucilage was also heated at 130°C for 48 h and severe heating did not affect its biological activity, suggesting that if the compound is lepidimoide then it is heat-resistant. In an attempt to test whether the compound is of high or low Mr, the mucilage was partitioned into 75% ethanol-precipitated and non-precipitated fractions. The biological activity in the non-precipitated fraction was very high, and was further separated by gel-permeation chromatography (GPC). GPC on Bio-Gel P-10 and P-2 suggested that the active principle had Mr ~500–750, compatible with oligosaccharide(s), suggesting that a particular oligosaccharide may be the active principle. TLC separation of bioactive fractions from P-2 showed that the bioactive compound migrated between GalA and Gal but co-migrated with sucrose; however, paper chromatography separation proved that the compound is not sucrose and might be a different disaccharide (lepidimoide). From the structure of lepidimoide, Fry et al. (1993) proposed that lepidimoide is formed by the lyase-catalysed cleavage of a pectic polysaccharide, rhamnogalacturonan-I (RG-I). So I tried to prepare lepidimoide or lepidimoide-like compounds by the action of RG-I lyase from Pichia pastoris on purified potato RG-I. The lyase showed its activity but the digest did not demonstrate biological activity, which might be due to presence of tris-HCl buffer in the solution. An attempt was also made to prepare lepidimoide by methyl esterification and -elimination of purified potato RG-I but again the product did not show any biological activity, which might be due to presence of borate buffer in the solution. This part of research might be useful for future work on preparation of lepidimoide and lepidimoide-like compounds.

Seedbanks provide many ecosystem services that support wildlife and regulate soil function. The fate of arable seeds is vital in shaping the aboveground composition of plant communities in agroecosystems. Understanding seed fate informs seedbank dynamics with multi-species interactions, as well as safeguarding arable biodiversity and food security. While many seed fate pathways are well known, the role of myxospermy in temperate agricultural soils is rarely addressed. Mucilage released by myxospermous seeds can modify the soil physical, hydraulic and microbial environment surrounding the seed. The principle biophysical mechanisms underlying the redistribution of weed seeds in eroded soils are unknown. It is possible that myxospermy delivers crucial services at the field scale, such as soil stability and water retention. However, modifications of the soil physical environment have been investigated using only a single-species approach and are often tested with extracted mucilage rather than seeds in-situ. As multiple taxa produce myxospermous seeds, the effects of a single species cannot be generalised. As seeds co-exist in the soil as multi-species communities, a multi-species approach is needed to further understand the functionality of seed mucilage and their implications for soil, relative to the wider seedbank. This thesis focussed on examining the mechanisms responsible for the adhesive interactions between soil and myxospermous seeds and discusses the ecological function and behaviour at the soil particle scale.

No description available.

INDETERMINATE DOMAIN (IDD) genes encode a large family of putative transcription factors characterized by four different zinc finger motifs in a conserved arrangement. In Arabidopsis thaliana there are 16 IDD genes designated AtIDD1-AtIDD16. Microarray database expression resources show that AtIDD1 transcripts are present at high levels in dry seed and in response to abscisic acid. Transcripts present in dry seed at high levels have previously been shown to play roles in later stages of seed development or as provisions necessary for the resumption of metabolic activity following seed dormancy. Here I show that lines with constitutive expression of AtIDD1 have decreased and increased sensitivity to the phytohormones abscisic acid and gibberellic acid, respectively, when applied exogenously. Additionally, plants overexpressing AtIDD1 have altered mucilage extrusion and seed coat morphology. Altered seed coat morphology was also observed In constitutive AtIDD1 knock down lines. Therefore, these phenotypes could indicate that AtIDD1 plays a regulatory role in seeds during seed development and/or germination.

Physcomitrella patens, a haploid-dominant land plant, has increasingly become useful in molecular genetic studies and is a model for early land plant evolution. This thesis work explores the mucilage secretory hair ontology, development, and ultrastructure with microscopic methods. Axillary hair development parallels that of secretory tissues found in other mosses and ultrastructure shares important similarities with liverwort mucilage papillae. These mucilage secretory structures cover the developing apex and young leaves with mucilage for protection. Changes in the hair cell wall and mucilage secretion are mediated by pectin and wall modification. Using bioinformatic methods, this thesis also investigates protein-protein interactions in Physcomitrella to understand the molecular mechanisms governing pectin biosynthesis and modification.

Made available in DSpace on 2014-06-11T19:31:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-08Bitstream added on 2014-06-13T20:22:36Z : No. of bitstreams: 1 leite_ra_dr_botfca.pdf: 2500405 bytes, checksum: 55b4922dcb1ec7fc7e7e25a07c362a62 (MD5) / O Café Cereja Descascado vem fazendo história ao ganhar a maioria dos prêmios de qualidade nos concursos de Cafés Especiais promovidos pelas empresas e associações do ramo. Semelhante ao Café Despolpado, difere deste no entanto, por ter bebida mais encorpada devido sua tecnologia de produção que mantém a mucilagem natural que envolve o pergaminho. A necessidade da secagem imediata e a dificuldade dos secadores operarem com o produto úmido e impregnado de mucilagem, levou ao desenvolvimento dos Desmuciladores que fazem uma desmucilagem parcial do produto úmido, encurtam o tempo de escorrimento no terreiro e facilitam a operação do secador. Tendo em vista as ponderações anteriores, formulou-se como principal objetivo deste trabalho a análise da relação entre o teor de mucilagem residual do CD® e a bebida e o corpo resultantes. Paralelamente a isso analisou-se a relação entre o perfil do café da roça e o teor de mucilagem no café cereja. As variações nos teores de mucilagem, que resultaram em 4 diferentes combinações de lotes processados, foram obtidas com a variação da altura percorrida pelo café no Desmucilador Vertical e da injeção de água na câmara de desmucilagem. Como testemunhas obteve-se uma amostra despolpada do mesmo café e outra produzida com mucilagem natural do Cereja Descascado. Os cafés assim tratados foram submetidos às provas de xícara por três provadores que analisaram as características: bebida, corpo, acidez, aroma, e sabor. Os resultados obtidos permitiram concluir entre outras coisas, que é possível controlar os teores de mucilagem desejados produzindo diferentes características de corpo sem afetar a qualidade da bebida. / The pulped ripe red coffee berry has become prominent for the most quality prizes it has taken in competitions of the special coffees promoted by companies and associations in the sector. It is similar to the pulped coffee, but differs from this one because it produces a more consistent beverage, since its production technology keeps the natural mucilage involving the pulped coffee. The need for immediate drying and the operational difficult of the dryers when the product is moistened and impregnated with mucilage led to the development of demucilators that partially demucilate the humid product, as well as shorten the time of the water flowing on the ground and facilitate the operation of the dryer. Taking the previous aspects into account, the main objective of this study is to analyze the relationship between the content of the residual mucilage in CD® and the resulting beverage consistence. At the same time, the relationship between the natural rough coffee profile and the mucilage content in the ripe red coffee berry. The variation in mucilage contents resulting into four different combinations of the processed lots were obtained, by varying either the height from which the coffee berries run down the vertical demucilator and the water injection in the demucilaging chamber. A pulped sample of the same coffee and another one produced with natural mucilage of the pulped ripe red coffee cherry were used as control. The treated coffee cherries were submitted to “cupping”, and three tasters analyzed their characteristics: beverage, consistence, acidity , odor, and flavor . According to the results, it may be concluded that it is possible to control the desired mucilage contents, therefore obtaining different consistence characteristics without affecting the quality of the beverage.

Sweet basil (Ocimum basilicum L.) is a warm season herb usually propagated from seeds. Establishment of basil is difficult as seed germination may be limited, particularly during field seeding at cold soil temperatures. The germination of six cultivars (\'Italian Large Leaf\', \'Italian Large Leaf\' 35X, \'Nufar\', \'Genovese\', \'Genovese Compact Improved\' and \'Aroma 2\') of sweet basil seeds were tested on a one dimensional thermo-gradient table over temperatures ranging from 0 to 50"C. At temperatures below 20"C, germination among cultivars was more variable and the mean time to germination (MTG) increased to greater than 25 days for some cultivars. Germination declined sharply and had a sudden termination at high temperatures above 40"C for all six cultivars.  There were statistical differences among the cultivar base temperatures, which ranged between 10.1 and 13.3"C. The optimal and ceiling temperatures for germination were similar and did not differ statistically among the cultivars compared in this study. The average optimal temperature for all cultivars was 35 ± 0"C, while the average ceiling temperature was 43 ± 1.3"C. Stored seeds (> 5 years) had lower seed vigor and lower germination percentage, also lower ceiling temperature compared with the fresh seeds of the same cultivar (\'Italian Large Leaf\'), but the base temperatures were the same for both new and old seeds. Sweet basil (Ocimum basilicum L.) seeds produce a thick layer of mucilage around the pericarp within minutes after hydration. Mucilage is most prevalent among plant species adapted to surviving in arid sandy soils, though its significance in determining ecological fitness is unclear. The mucilage produced by seeds is reported to be composed of cell-wall polysaccharides that are deposited in testa pericarp cells during development. In this study, sweet basil seeds were examined using light and environmental scanning electron microscopy. The mucilage of basil seeds is held together by columnar structures that unfolded from the pericarp and helped hold and stabilize the mucilage to the outer surface. The mucilage was removed using diluted hydrochloric acid to compare performance of seeds with and without mucilage. Mucilage removal did not inhibit seed germination under ideal laboratory conditions but decreased the water content of seeds significantly. The water content of intact seeds was almost 4 times greater than seeds without mucilage. Mucilage enabled seeds cling to an incline board set to a steeper angle than seeds without mucilage. The fully hydrated seeds approached zero water potential, so the mucilage did not prevent seeds from fully hydrating. Soil (media) germination testing showed the seeds with mucilage had higher germination percentage than the seed without mucilage on several different types of media. Seeds with mucilage also had higher survival percentages after 10 days on different types of media. Basil seeds mucilage acts as a reservoir to hold loosely bound water at high water potential so it is available for seed germination and early seedling development. / Master of Science

Les cellules épidermiques des téguments des graines d’Arabidopsis thaliana, espèce myxospermique, libèrent un halo de mucilage polysaccharidique lors de leur imbibition. Les polysaccharides du mucilage sont produits et accumulés au cours du développement de la graine, selon un processus de différenciation déjà largement décrit (Western et al. 2006). Au laboratoire, une mutation naturelle a été mise en évidence chez l’accession Djarly, dont les graines ne libèrent pas de mucilage au cours de leur imbibition. Le clonage positionnel a démontré que le locus affecté chez Djarly code pour un inhibiteur de pectine méthylestérase (PMEI6). Les PMEIs exercent un contrôle négatif sur l’activité des pectines méthylestérases (PME), enzymes qui déméthylestérifient les homogalacturonanes, par la formation d’un complexe PME-PMEI (Di Matteo et al., 2005 ; Hothorn et al., 2004). Des études génétiques, cytologiques et biochimiques ont prouvé que PMEI6 régule la méthylestérification des homogalacturonanes du mucilage et des parois cellulaires distales des cellules épidermiques de la graine retardant la libération du mucilage séminal. L’expression de PMEI6 dépend des régulateurs de transcription GLABRA2 et MUM1. L’activité PME dans les cellules épidermiques des graines est aussi modulée par la subtilisine serine protéase AtSBT1.7, et le phénotype additif du mutant pmei6 atsbt1.7 indique que PMEI6 régule d’autres PMEs. Djarly fait partie d’un groupe de vingt accessions, dont les graines flottent à cause de modifications des propriétés du mucilage séminal. Ces accessions portent au moins dix mutations indépendantes, qui affectent au moins 4 locus différents. Cette étude nous a permis de proposer que la modification des propriétés du mucilage est impliquée dans l’adaptation à l’environnement local, permettant la dispersion à longue distance des graines par l’eau. / Upon imbibition, the myxospermous seeds of Arabidopsis thaliana, form a mucilage from hydrated polysaccharides released from the epidermal cells of the seed coat. These polysaccharides are produced and accumulated during seed development in a differentiation process that has been described in detail (Western et al. 2006). A screen of Arabidopsis accessions identified Djarly as a natural mucilage mutant affected in mucilage release on imbibition. The locus defective in Djarly was identified by map-based cloning as encoding a pectin methylesterase inhibitor (PMEI6). Theseproteinaceous inhibitors negatively control the activity of pectin methylesterases (PME), enzymes that demethylesterify HG, through the formation of a PME-PMEI complex (Di Matteo et al., 2005; Hothorn et al, 2004). Genetic, cytological and biochemical studies demonstrated that PMEI6 regulates methylesterification of homogalacturonans present in mucilage and the outer cell wall of seed coat epidermal cells. Delayed seed mucilage release in pmei6 mutants results, therefore, from the reduced level of homogalacturonan methylesterification. Expression of PMEI6 required the transcription regulators GLABRA2 and MUM1. PME activity in seed coat epidermal cells is also modulated by the subtilisin serine protease AtSBT1.7, and the additive phenotype of pmei6 atsbt1.7 mutants indicates that PMEI6 regulates different PMEs. Djarly is one of twenty accessions where seeds float due to modifications of mucilage properties. At least ten independent mutations are responsible for the mucilage modifications in these accessions, affecting at least 4 different loci. This study has led us to propose that these mucilage modifications are local adaptations that allow longdistance seed disperal on water.

Les travux de thèse ont été menés dans un contexte de développement et de valorisation de la filière lin au travers de l'élaboration de nouveaux matériaux composites biosourcés à base de mucilage et de fibres de lin. Ces travaux ont conduit dans un premier temps à la synthèse de précurseurs d'isosorbide époxy et polyuréthanes comme alternative aux précurseurs toxiques conventionnels. Pour cela nous avons proposé une voie originale d'optimisation de la synthèse de diglycidyle éther d'isosorbide (DGEI) en utilisant un procédé ultrasonique. Par la suite, la comparaison des méthodes de transformation des époxys en carbonates cycliques par l'inclusion de CO₂ nous a servi de base dans l'élaboration d'un protocole efficace de conversion des DGEI en cyclocarbonates d'isosorbide (CCI) dans des conditions douces de pression et de température. Dans une seconde partie, l'extraction de composés hydrosolubles de la graine de lin a permis d'identifier la structure complexe du mucilage et les effets des paramètres d'extraction sur les propriétés physico-chimiques et thermiques du mucilage. Ensuite, pour la première fois, l'oxydation du mucilage au 2,2,6,6-tétraméthylpipéridine-1-oxyle (TEMPO) a été réalisée avec succès. Puis, nous avons pu mettre en évidence l'efficience de l'oxydation assistée par ultrasons comparée à la méthode classique lors de la montée en échelle du procédé. En vue d'améliorer la compatibilité fibre/matrice des composites à fibres végétales, des traitements appliqués sur des fibres courtes de lin ont été effectués amenant à l'individualisation des fibres et à l'amélioration de l'oxydation appliquée sur des fibres sonifiées. Ces différents matériaux ont permis de formuler un panel de nouveaux biocomposites. Les DGEI ont été valorisés par la confection d'une résine réticulée par une amine renforcée par des fibres longues de lin dont les performances sont identiques aux composites pétro-sourcés. Par la suite, la sonicationdes fibres courtes de lin a mené à l'amélioration des propriétés mécaniques de composite PLA/Lin. L'utilisation de mucilage oxydé a démontré les aspects positifs de l'incorporation du mucilage de lin dans les composites légers et résistants en compression. / The thesis was carried out in a context of development and valorisation of the flax through the conception of new bio-based composite materials made of mucilage and flax fibres. This work initially led to the synthesis of isosorbide epoxy and polyurethane precursors as an alternative to the conventional toxic precursors. For this, we proposed an original route for optimizing the synthesis of isosorbide diglycidyl ether (DGEI) using an ultrasonic process. Subsequently, the comparison of the conversion methods of epoxies into cyclic carbonates by the inclusion of CO₂ served as a basis for the development of an efficient protocol for converting DGEI into isosorbide cyclic carbonates (CCI) under moderate conditions of temperature and pressure. In the second part, the extraction of water-soluble compounds from the flaxseed allowed us to identify the complex structure of the mucilage and the effects of the extraction parameters on its physicochemical and thermal properties. Then, for the first time, oxidation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mucilage was successfully performed. After that, we have highlighted the enhanced efficiency of ultrasonic assisted oxidation over the conventional method when scaling up the process. In order to improve the fibre/matrix compatibility of natural fibre-based composites, different treatments of short flax fibres led to the individualizationof the fibres and to the improvement of the oxidation of sonicated fibres.These new materials allowed to formulate a series of novel biocomposites. The DGEI have been enhanced by making an amine-crosslinked resin reinforced with long flax fibres which have a comparable performance to oil-based composites. Additionally, the sonication of short flax fibres led to the improvement of the mechanical properties of PLA/Flax composite. The use of oxidized mucilage has demonstrated the beneficial aspects of flax mucilage incorporation into lightweight, compression-resistant composites.

Les polysaccharides sont des composants majeurs des parois cellulaires ayant une structure dynamique et jouant un rôle essentiel dans la croissance des plantes. Les cellules épidermiques du tégument des graines d’Arabidopsis libèrent un halo de mucilage polysaccharidique lors de leur imbibition. Le mucilage séminal s'est avéré être un excellent système modèle pour l’étude de la production, des propriétés des polysaccharides et de leurs interactions. Le premier objectif de ma thèse était de valoriser la variabilité naturelle existant entre accessions d’Arabidopsis pour identifier de nouveaux gènes contrôlant la production de mucilage. Une analyse de génétique d’association a permis l’identification d’une amine oxidase et d’une glycosyltransferase putatives dont j’ai confirmé l’implication dans la biosynthèse des pectines du mucilage.J’ai également associé une famille de protéines aux interactions entre polysaccharides. De part ses propriétés d’hydrogel, le mucilage joue un rôle adaptatif et influence la physiologie de la graine. Il permet la rétention d’eau autour de celle-ci et pourrait ainsi influencer sa longévité. Le deuxième objectif de ma thèse était d’utiliser des mutants impactés dans la production de mucilage pour déterminer si ce dernier influence la longévité des graines après un traitement d’hydratation contrôlée appelé ‘priming’. Les graines ne libérant pas de halo de mucilage à l’imbibition ont une meilleure longévité en lien avec une diminution réduite d’acide salicylique. Mes résultats participent à une compréhension intégrée de la production de mucilage à plusieurs niveaux : écologiques, génétiques et physicochimiques. / Polysaccharides are the major component of cell walls that are dynamic structures playing a fundamental role in plant growth. On imbibition, the epidermal cells of the Arabidopsis seed coat release a mucilage hydrogel formed of polysaccharides. This has proved to be an excellent model system for the study of cell wall polysaccharide production, properties and interactions. The first objective of my thesis was to exploit natural variation between Arabidopsis accessions to identify genes controlling mucilage polysaccharide production. A genome wide association study identified genes encoding proteins with putative functions as either an amine oxidase or glycosyltransferase and these were confirmed to contribute to the synthesis of mucilage pectin. I also found that a family of small proteins, whose function is undetermined, are likely to modulate the interaction of mucilage polymers. Mucilage is also an adaptive trait that may influence various aspects of seed physiology. Recent results indicate that this hydrogel plays a role in the retention of water around the seed and could influence their lifespan. A second objective of my thesis was to use mutants showing altered mucilage production to determine its contribution to seed lifespan after a controlled hydration treatment called ‘priming’. Seeds that do not release mucilage on imbibition retained longevity better after priming. I highlighted that the steady state levels of salicylic acid in primed seeds were influenced by mucilage and correlated negatively with their longevity. My results contribute to our genetic, physicochemical and ecophysiological understanding of mucilage production by seeds.