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International audience; The wild grass Brachypodium distachyon has been proposed as an alternative model species for temperate cereals. The present paper reports on the characterization of B. distachyon grain, placing emphasis on endosperm cell walls. Brachypodium distachyon is notable for its high cell wall polysaccharide content that accounts for approximately 52% (w/w) of the endosperm in comparison with 2-7% (w/w) in other cereals. Starch, the typical storage polysaccharide, is low [

International audience; Seed storage proteins are of great importance in nutrition and in industrial transformation because of their functional properties. Brachypodium distachyon has been proposed as a new model plant to study temperate cereals. The protein composition of Brachypodium grain was investigated by separating the proteins on the basis of their solubility combined with a proteomic approach. Salt-soluble proteins as well as salt-insoluble proteins separated by two-dimensional gel electrophoresis revealed 284 and 120 spots, respectively. Proteins from the major spots were sequenced by mass spectrometry and identified by searching against a Brachypodium putative protein database. Our analysis detected globulins and prolamins but no albumins. Globulins were represented mainly by the 11S type and their solubility properties corresponded to the glutelin found in rice. An in silico search for storage proteins returned more translated genes than expressed products identified by mass spectrometry, particularly in the case of prolamin type proteins, reflecting a strong expression of globulins at the expense of prolamins. Microscopic examination of endosperm cells revealed scarce small-size starch granules surrounded by protein bodies containing 11S globulins. The presence of protein bodies containing glutelins makes B. distachyon closer to rice or oat than to wheat endosperm

Micro-scale enzymatic fingerprinting and FT-IR microspectroscopy were used to investigate changes of polysaccharide structure and composition in cell walls from wheat endosperm. These methods were applied to transverse and longitudinal sections of wheat grains harvested at maturity and 270°D. Principal component analysis treatment of the data revealed marked differences in the (1,3)-(1,4)-beta-glucans (BG)/arabinoxylans (AX) ratio and in the structure of AX depending on both cell position in the grain and stage of development. Cell walls close to the germ were enriched in BG in both developing and mature grain. AX in developing grain were characterized by a higher proportion of di-substitution by arabinose as compared to mature grain AX. In addition, AX in mature grains exhibited a different structure depending on prismatic or central origin of cell walls in the grain. These results indicated a high spatial and temporal control of the biosynthesis of AX and BG in wheat endosperm.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; Apple texture is one of the critical quality features for the consumer. Texture depends on several factors that are difficult to control and which change with freezing. To better understand the mechanisms involved in the texture degradation of apple tissues following freezing/thawing, our approach was to combine mechanical properties, cellular structure and cell wall composition measurements on fresh and thawed apples (Granny Smith) after three different freezing protocols (at -20 degrees C, -80 degrees C and -196 degrees C). This work highlighted the interest of applying macrovision and image texture analysis to quantify the freezing effects on cellular structure and ice crystal size. Freezing at -20 degrees C and after immersion into liquid nitrogen were the protocols affecting the most fruit texture leading to cell membrane breakage resulting in cell wall collapse and tissue breakage, respectively, which accounted for the mechanical behaviour of the samples. All freezing ! protocols induced vacuole burst showing that the turgor pressure preservation remains critical during the freezing process.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; It has previously been shown that down-regulation of an auxin response factor gene (DR12) results in pleiotropic phenotypes including enhanced fruit firmness in antisense transgenic tomato (AS-DR12). To uncover the nature of the ripening-associated modifications affecting fruit texture, comparative analyses were performed of pectin composition and structure in cell wall pericarp tissue of wild-type and AS-DR12 fruit at mature green (MG) and red-ripe (RR) stages. Throughout ripening, pectin showed a decrease in methyl esterification and in the content of galactan side chains in both genotypes. At mature green stage, pectin content in methyl ester groups was slightly higher in AS-DR12 fruit than in wild type, but this ratio was reversed at the red-ripe stage. The amount of water- and oxalate-soluble pectins increased at the red-ripe stage in the wild type, but decreased in AS-DR12. The distribution of methyl ester groups on the homogalaturonan backbone differed between the two! genotypes. There was no evidence of more calcium cross-linked homogalacturan involved in cell-to-cell adhesion in AS-DR12 compared with wild-type fruit. Furthermore, the outer pericarp contains higher proportion of small cells in AS-DR12 fruit than in wild type and higher occurrence of (1 -> 5) alpha-L-arabinan epitope at the RR stage. It is concluded that the increased firmness of transgenic fruit does not result from a major impairment of ripening-related pectin metabolism, but rather involves differences in pectin fine structure associated with changes in tissue architecture.

International audience; Retting is an important step in traditional cassava processing that involves tissue softening of the roots to transform the cassava into flour and various food products. The tissue softening that occurs during retting was attributed to the degradation of cell wall pectins through the action of pectin-methylesterase and pectate-lyase that possibly originated from a microbial source or the cassava plant itself. Changes in cell wall composition were investigated during retting using chemical analysis, specific glycanase degradation and immuno-labelling of cell wall polysaccharides. Pectic 1,4-beta-D-galactan was the main cell wall polysaccharide affected during the retting of cassava roots. This result suggested that better control of pectic galactan degradation and a better understanding of the degradation mechanism by endogenous endo-galactanase and/or exogenous microbial enzymes might contribute to improve the texture properties of cassava products.

Highlight The first evaluation of lignification in Brachypodium distachyon grain is reported. Moderately down-regulated BdCOMT6 alters grain and stem lignification, which improves stem saccharification without major detrimental effects on grain development and composition., Cereal crop by-products are a promising source of renewable raw material for the production of biofuel from lignocellulose. However, their enzymatic conversion to fermentable sugars is detrimentally affected by lignins. Here the characterization of the Brachypodium Bd5139 mutant provided with a single nucleotide mutation in the caffeic acid O-methyltransferase BdCOMT6 gene is reported. This BdCOMT6-deficient mutant displayed a moderately altered lignification in mature stems. The lignin-related BdCOMT6 gene was also found to be expressed in grains, and the alterations of Bd5139 grain lignins were found to mirror nicely those evidenced in stem lignins. The Bd5139 grains displayed similar size and composition to the control. Complementation experiments carried out by introducing the mutated gene into the AtCOMT1-deficient Arabidopsis mutant demonstrated that the mutated BdCOMT6 protein was still functional. Such a moderate down-regulation of lignin-related COMT enzyme reduced the straw recalcitrance to saccharification, without compromising the vegetative or reproductive development of the plant.

Plant cell walls are the earth's most abundant source of terrestrial biomass. When potatoes are processed for starch production, a low-value, cell wall-rich byproduct known as potato pulp is produced. The huge amounts of pulp available have motivated the reemergence of research devoted to potato cell wall polysaccharide extraction and use.

Wheat tissues had specific reproducible autofluorescence profiles using macro imaging.Wheat pericarp and aleurone layer fluoresce differently in air or water.Autofluorescence of wheat tissues is similar before and after grinding.Multispectral fluorescence imaging can help identifying the histological origins. Many plant tissues can be observed thanks to the autofluorescence of their cell wall components. Multispectral autofluorescence imaging at the macroscopic scale is a rapid efficient way of observing samples with a large field of view (>1cm2) and a nice resolution (

International audience

International audience; The objective of the present work was to relate the physical evolution quantified by image analysis to the chemical transformation of beet pulp particles during enzymatic degradation. Beet pulps were degraded into a torus reactor equipped for visualisation. Pectinolytic and cellulolytic enzymes were used separately or in combination. Two global image analysis techniques were tested to characterise the size distribution of overlapping particles. Granulometric curves were extracted by mathematical morphology and a regularisation dimension was assessed by fractal analysis. Both techniques proved efficient to follow particle size evolution during degradation. When using cellulolytic enzymes alone, no chemical or physical evolution was observed. When using pectinolytic enzymes, a chemical modification occurred without any physical evolution. Particles physically disappeared when both enzymes were used. The chemical and physical evolutions of particles during degradation were interpreted taking into account the current model of molecular arrangement of primary cell walls.

International audience; The time course and pattern of arabinoxylan deposition in the wheat (Triticum aestivum) endosperm during grain development were studied using Raman spectroscopy. The presence of arabinoxylans (AX) is detected at the beginning of grain filling. At this stage, AX appear more substituted than at the later stages. Feruloylation of AX increases during the grain-filling stage, especially in the case of the aleurone layer. Whatever the stage of grain development, four populations of cells could be defined according to Raman arabinoxylan signatures. In the walls of the aleurone cells, AX appeared to be little substituted and highly esterified with phenolic acids. In the walls of prismatic cells, AX were found to be highly substituted and poorly esterified. Apart from aleurone and prismatic cells, the substitution degree of AX in endosperm was in the same range. Cells in the crease region were distinguished from cells in the starchy endosperm by their lower amount of esterified phenolic compounds.

The time course and pattern deposition of the cell wall polysaccharides in the starchy endosperm of wheat (Triticum aestivum cv. Recital) during grain development was studied using Fourier transform infrared microspectroscopy (micro-FTIR). Three stages of grain development identified as key stages for cell wall construction were retained as follows: the end cellularization, the beginning of cell differentiation, and the beginning of maturation. Micro-FTIR revealed that beta-(1 -> 3),(1 -> 4) glucans and arabinoglactan proteins are the main cell wall components of enclosperm at the end of the cellularization stage, whereas arabinoxylans (AX) appeared only at the cell differentiation stage. Past the differentiation stage, FTIR spectra were dominated by AX features. Cell walls at the beginning of cell differentiation and at enclosperm maturation could be distinguished by spectral features that were ascribed to AX substitution. AX appeared more substituted at the beginning of cell differentiation. Moreover, a difference in the degree of AX substitution was found between peripheral and central parts of the grain at the cell differentiation stage; AX in central cells was less substituted. Thus, dramatic changes in enclosperm cell wall composition were detected during wheat grain development with respect to both the relative occurrence of individual constituents and the fine structure of the AX.

� Background and Aims The efficiency and safety functions of xylem hydraulics are strongly dependent on the pits that connect the xylem vessels. However, little is known about their biochemical composition and thus about their hydraulic properties. In this study, the distribution of the epitopes of different wall components (cellulose, hemicelluloses, pectins and lignins) was analysed in intervessel pits of hybrid poplar (Populus tremulaalba). � Methods Immunogold labelling with transmission electron microscopy was carried out with a set of antibodies raised against different epitopes for each wall polysaccharide type and for lignins. Analyses were performed on both immature and mature vessels. The effect of sap ionic strength on xylem conductance was also tested. � Key Results In mature vessels, the pit membrane (PM) was composed of crystalline cellulose and lignins. None of the hemicellulose epitopes were found in the PM. Pectin epitopes in mature vessels were highly concentrated in the annulus, a restricted area of the PM, whereas they were initially found in the whole PM in immature vessels. The pit border also showed a specific labelling pattern, with higher cellulose labelling compared with the secondary wall of the vessel. Ion-mediated variation of 24 % was found for hydraulic conductance. � Conclusions Cellulose microfibrils, lignins and annulus-restricted pectins have different physicochemical proper- ties (rigidity, hydrophobicity, porosity) that have different effects on the hydraulic functions of the PM, and these in- fluence both the hydraulic efficiency and vulnerability to cavitation of the pits, including ion-mediated control of hydraulic conductance. Impregnation of the cellulose microfibrils of the PM with lignins, which have low wettabil- ity, may result in lower cavitation pressure for a given pore size and thus help to explain the vulnerability of this species to cavitation.

Plant lignocellulosic biomass, mostly composed of cell walls, is one of the largest, mostly untapped, reserves of renewable carbon feedstock on the planet. Energy-rich polysaccharide polymers of plant cell walls can be broken down to produce fermentable sugars used to produce bioethanol. However, the complex structure of plant cell walls, and in particular, the presence of lignin, makes them recalcitrant to enzymatic degradation. Reducing this recalcitrance represents a major technological challenge. Brachypodium distachyon is an excellent model to identify parameters underlying biomass quality of energy grasses. In this work, we identified a mutant line spa1 with a so far undescribed phenotype combining brittleness with increased elasticity of the internodes. Mutant cell walls contain less crystalline cellulose and changes in hemicellulose and lignin quality and quantity. Using a dedicated reactor to follow in real-time, the evolution of straw particle size and sugar release during enzymatic digestion, we show that, despite the increased lignin content, the spa1 mutant has a dramatic reduced recalcitrance to saccharification compared to the WT. These observations demonstrate that other parameters besides lignin content are relevant for the improvement of biomass recalcitrance in energy grasses.

Cell walls play key roles during plant development. Following their deposition into the cell wall, polysaccharides are continually remodeled according to the growth stage and stress environment to accommodate cell growth and differentiation. To date, little is known concerning the enzymes involved in cell wall remodeling, especially in gramineous and particularly in the grain during development. Here, we investigated the cell wall proteome of the grain of Brachypodium distachyon. This plant is a suitable model for temperate cereal crops. Among the 601 proteins identified, 299 were predicted to be secreted. These proteins were distributed into eight functional classes; the class of proteins that act on carbohydrates was the most highly represented. Among these proteins, numerous glycoside hydrolases were found. Expansins and peroxidases, which are assumed to be involved in cell wall polysaccharide remodeling, were also identified. Approximately half of the proteins identified in this study were newly discovered in grain and were not identified in the previous proteome analysis conducted using the culms and leaves of B. distachyon. Therefore, the data obtained from all organs of B. distachyon infer a global cell wall proteome consisting of 460 proteins. At present, this is the most extensive cell wall proteome of a monocot species.

Highlight Wheat grain outer layers, decisive for development, protection and end-uses, comprise several specialized layers. Cell wall heterogeneity is highlighted and correlated to probable differences in composition of wall machineries., Cereal grain outer layers fulfil essential functions for the developing seed such as supplying energy and providing protection. In the food industry, the grain outer layers called ‘the bran’ is valuable since it is rich in dietary fibre and other beneficial nutriments. The outer layers comprise several tissues with a high content in cell wall material. The cell wall composition of the grain peripheral tissues was investigated with specific probes at a stage of active cell wall synthesis. Considerable wall diversity between cell types was revealed. To identify the cellular machinery involved in cell wall synthesis, a subcellular proteomic approach was used targeting the Golgi apparatus where most cell wall polysaccharides are synthesized. The tissues were dissected into outer pericarp and intermediate layers where 822 and 1304 proteins were identified respectively. Many carbohydrate-active enzymes were revealed: some in the two peripheral grain fractions, others only in one tissue. Several protein families specific to one fraction and with characterized homologs in other species might be related to the specific detection of a polysaccharide in a particular cell layer. This report provides new information on grain cell walls and its biosynthesis in the valuable outer tissues, which are poorly studied so far. A better understanding of the mechanisms controlling cell wall composition could help to improve several quality traits of cereal products (e.g. dietary fibre content, biomass conversion to biofuel).

Starch and fibre can be extracted, using wet or dry processes, from a variety of grain legumes and used as ingredients for food. a-Galactosides can be isolated during wet processes from the soluble extract. Starch isolates or concentrates are mostly produced from peas, whereas dietary fibre fractions from peas and soyabean are commercially available. The physico-chemical characteristics of fibre fractions very much depend on their origin, outer fibres being very cellulosic whereas inner fibres contain a majority of pectic substances. Inner fibres are often used as texturing agents whereas outer fibres find their main uses in bakery and extruded products, where they can be introduced to increase the fibre content of the food. Most investigations on impacts on health have been performed on soyabean fibres. When positive observations were made on lipaemia, glucose tolerance or faecal excretion, they were unfortunately often obtained after non-realistic daily doses of fibres. Legume starches contain a higher amount of amylose than most cereal or tuber starches. This confers these starches a lower bioavailability than that of most starches, when raw or retrograded. Their low glycaemic index can be considered as beneficial for health and especially for the prevention of diseases related to insulin resistance. When partly retrograded, these starches can provide significant amount of butyrate to the colonic epithelium and may help in colon cancer prevention. a-Galactosides are usually considered as responsible for flatus but their apparent prebiotic effects may be an opportunity to valorize these oligosaccharides.

International audience; Arabinoxylans (AX) and (1→3),(1→4)-β-glucans (BG) are the major components of wheat grain cell walls. Although incompletely described at the molecular level, it is known that the chemical and distributional heterogeneity of these compounds impacts the quality and use of wheat. In this work, an emerging technique based on MALDI mass spectrometry imaging (MSI) was employed to map variations in the quantity, localization, and structure of these polysaccharides in the endosperm during wheat maturation. MALDI MSI couples detailed structural information with the spatial localization observed at the micrometer scale. The enzymic hydrolysis of AX and BG was performed directly on the grain sections, resulting in the efficient formation of smaller oligosaccharides that are easily measurable through MS, with no relocation across the grain. The relative quantification of the generated oligosaccharides was achieved. The method was validated by confirming data previously obtained using other analytical techniques. Furthermore, in situ analysis of grain cell walls through MSI revealed previously undetectable intense acetylation of AX in young compared to mature grains, together with findings concerning the feruloylation of AX and different structural features of BG. These results provide new insights into the physiological roles of these polysaccharides in cell walls and the specificity of the hydrolytic enzymes involved.

Dietary fibre encompasses very diverse macromolecules exhibiting a large variety of physico-chemical properties. They might be naturally present in the food (in cell walls of vegetables and fruits, for instance) or introduced in the food to improve their nutritional properties (e.g. bran in bread products) or their physical characteristics (e.g. gelling agents or improved resistance to storage). The properties that are nutritionally relevant are mainly the particle size and bulk volume, the surface area characteristics, the hydration and rheological properties, and the adsorption or entrapment of minerals and organic molecules. Amongst these properties, the viscosity and ion exchange capacity are the main contributors to metabolic effects (glucose and lipid metabolisms) whereas fermentation pattern, bulking effect and particle size are strongly involved in effects on colonic function. Technological treatments can modify the physico-chemical properties of the fibre. This can be further exploited to optimise both their techno-functional and physiological properties.

Hydration properties related to the fibre matrix have been defined and measured in 19 European laboratories using common methods and the substrates: resistant starches, pea hull, citrus pulp and apple pulp. Swelling and water retention capacity (WRC) were the major hydration properties studied. The objective was to derive standardized methods with an included estimate of experimental variation or statistical tolerance. Measurement of swelling and WRC were complemented by measurement of water absorption and porosity. Swelling (∼7 mL/g) and WRC (∼4 g/g) were relatively low for resistant starches and pea hull. Swelling and WRC of citrus (∼11 mL/g: ∼11 g/g) and apple pulp (∼7 mL/g: ∼5g/g) were lower than expected, probably reflecting effects of processing on matrix structure. Coefficient of variation was higher between laboratories than within laboratory. The relationship between swelling, WRC, absorption and porosity, as well as matrix effects, are discussed.

Seaweed extracts, because of their physicochemical characteristics and potential nutritional value, could provide a new source of dietary fibre. This study investigated changes in seaweed fibres (physicochemical and fermentative properties) in different digestive sites and their effects on digesta (viscosity and hydration properties). Sixteen pigs were adapted to a test diet supplemented with 5% algal fibre (either Palmaria palmata (PP), a poorly viscous soluble xylan; or Eucheuma cottonii (EC), a partly insoluble carrageenan; or Laminaria digitata (LD), a highly viscous soluble alginate) or 5% cellulose (reference fibre). PP did not modify the characteristics of digesta and was fermented in the caecum (pH 6.1 ± 0.4; short-chain fatty acids measured in digesta, 1409 ± 691 µmol g−1 dry matter). EC and LD were mainly insoluble in the stomach, becoming soluble in the intestine; EC was slightly fermented in the colon, giving a low concentration of short-chain fatty acids (303 ± 122 µmol g−1 dry matter). Supplementation of the diet with alginate (LD) increased 3.5-fold the ileal viscosity of digesta and their hydration capacity in the ileum and colon. Thus the physicochemical properties of pig digesta largely depend on the physicochemical properties of the ingested seaweed fibre, the pH and ionic conditions prevailing in the gut, and their fermentability. © 2000 Society of Chemical Industry

To determine the role of physico-chemical characteristics (gross porosity, microporosity, particle size, crystallinity) of dietary fibres rich in primary cell walls in their degradability by human flora, two sources of sugar beet fibres were submitted to various chemical and then dehydration treatments. Chemical extraction involving hot dilute acid followed by cold dilute alkali treatments resulted mainly in the removal of pectic polysaccharides (9–49% recovery) at the expense of cellulose (80–100% recovery). Harsh drying, when applied to simply hydrated fibre, did not result in dramatic changes of the pore volume (from 14.9 to 12.7 ml g −1 for the total pore volume, and from 10.4 to 7.8 ml g −1 for the pore volume accessible to bacteria). The presence of pectins in such materials may prevent pore changes at high drying temperatures. In contrast, when following chemical extraction, harsh drying induced a noticeable decrease in the total pore volume (from 14.9 to 6.1 ml g −1 ) and especially in the pore volume accessible to bacteria (from 10.4 to 3.2 ml g −1 ). This dramactic changes was ascribed to the distortion and shrinking of cells during drying. Harsh drying conditions following chemical extraction did not affect the crystallinity of cellulose in the fibre. Neither the particle size, nor the crystallinity of cellulose were major determinant factors in degradability of sugar-beet fibres. In contrast, pore volume accessible to bacteria in sugar beet fibres was highly correlated ( R =0.88) with its fermentability. This was consistent with polysaccharides degrading enzymes being closely associated with bacteria and illustrates the importance of matrix physical structure in the control of the physicochemical behaviour of fibre.

Lignins and their cross-linking to hemicelluloses detrimentally affect the cellulose-to-ethanol conversion of grass lignocelluloses. Screening appropriate grass cell walls and their compositional changes during the various steps of the process calls for a high-throughput analytical technique. Such a performance can be fulfilled by Fourier transform mid-infrared (FT-MIR) spectroscopy. In the present paper, a set of maize cell walls from mature stems were selected, including brown midrib samples. Lignin fractions were isolated by mild acidolysis to obtain a set of purified maize lignin standards. The lignin content and the percentage of lignin-derived p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) thioacidolysis monomers were determined. In addition, the composition of cell wall polysaccharides, as well as the amount of ester-linked p-coumaric (CA) and ferulic (FA) acids, was measured by wet chemistry. Partial least square (PLS) analyses were applied to infrared and chemical data of cell walls. The resulting models showed a good predictive ability with regard to the lignin content, to the frequency of S (or G) thioacidolysis monomers, and to the level of ester-linked CA of maize cell walls. The loading plots and regression coefficients revealed relevant infrared absorption bands.

International audience; Background and Aims Rhamnogalacturonan II (RGII) is a structurally complex pectic sub-domain composed of more than 12 different sugars and 20 different linkages distributed in five side chains along a homogalacturonan backbone. Although RGII has long been described as highly conserved over plant evolution, recent studies have revealed variations in the structure of the polysaccharide. This study examines the fine structure variability of RGII in wine, focusing on the side chains A and B obtained after sequential mild acid hydrolysis. Specifically, this study aims to differentiate intrinsic structural variations in these RGII side chains from structural variations due to acid hydrolysis. Methods RGII from wine (Vitis vinifera Merlot) was sequentially hydrolysed with trifluoroacetic acid (TFA) and the hydrolysis products were separated by anion-exchange chromatography (AEC). AEC fractions or total hydrolysates were analysed by MALDI-TOF mass spectrometry. Key Results The optimal conditions to recover non-degraded side chain B, side chain A and RGII backbone were 0.1 M TFA at 40 degrees C for 16 h, 0.48 M TFA at 40 degrees C for 16 h (or 0.1 M TFA at 60 degrees C for 8 h) and 0.1 M TFA at 60 degrees C for 16 h, respectively. Side chain B was particularly prone to acid degradation. Side chain A and the RGII GalA backbone were partly degraded by 0.1 M TFA at 80 degrees C for 1-4 h. AEC allowed separation of side chain B, methyl-esterified side chain A and non-methyl-esterified side chain A. The structure of side chain A and the GalA backbone were highly variable. Conclusions Several modifications to the RGII structure of wine were identified. The observed dearabinosylation and deacetylation were primarily the consequence of acidic treatment, while variation in methyl-esterification, methyl-ether linkages and oxidation reflect natural diversity. The physiological significance of this variability, however, remains to be determined.

The dietary fibres of the seaweed Ulva sp (sea-lettuce) consist of water-soluble ulvan, alkali-soluble β(1,4)-D-glucuronan and β(1,4)-D-glucoxylan, and an insoluble α-cellulose containing xylose residues. They are poorly degraded by human colonic bacteria particularly when associated within the intact plant cell wall. In order to better understand this resistance to microbial attack, their organisation in the cell-wall has been investigated by light and electron microscopy after sequential chemical extractions. Their susceptibility to enzymatic degradation and their accessibility to bacteria and enzyme were also studied. Microscopic localisation in native and sequentially extracted Ulva sp demonstrated that ulvan is in all the cell-walls of the algae and particularly between the two cell layers constituting the thallus. Glucuronan is close to the cytoplasmic membrane facing the outside of the seaweed and between adjacent cells. The xylose and glucose containing polysaccharides form packed layers surrounding the cells. A model of the spatial distribution of the different polysaccharides within the algae is proposed. Ulvan and glucuronan did not limit the xyloglucan and α-cellulose degradation by an endo-xylanase in the whole seaweed and its insoluble dietary fibre but the α-cellulose was not affected by a cellulase. The cell-wall of Ulva sp was accessible to enzymes but poorly to bacteria as assessed from porosity measurements. These results established that the poor fermentation of sea-lettuce by human colonic flora is primarily due to the ubiquitous presence of the degradation-resistant ulvan in the cell wall of Ulva sp. ©1997 SCI

The enzymatic saccharification of lignocelluloses depends on their physical state and chemical composition, which is related to tissue properties. The objective of the present work was to study the enzymatic degradation pattern of particles isolated through a dry separation process from maize plant. Whole plants without ears were ground and fractionated by turbo-separation. The fine- and medium-size particles were submitted to electrostatic sorting. The IMATORE reactor [1] allowed us to monitor the compositional changes and size evolution of the particles during saccharification. In all fractions, glucose and xylose were the major sugars. However, minor sugars displayed distinct distributions, fine particles being richer in arabinose and uronic acids. While the large particles were found to be lignin-richer, the fine ones exhibited the lowest lignin amount and a higher ratio of syringyl over guaiacyl units. The enzymatic degradation patterns differed between fractions. Not unexpectedly, large and fine particles were respectively the less and the more degraded, as revealed by their compositional and size changes. Interestingly, positive-deviated medium size particles had a particular behaviour with most of the sugar released during the first 30 min without any noticeable change in particle size. The negative-deviated medium size particles behaved like the large ones. The present work confirms that plant heterogeneity should be considered in the biorefinery chain. Next steps will be (i) to find the relationships of particles degradation pattern to stem histology and (ii) to improve the dry separation process in order to increase the saccharification yield.

The present in vitro study was designed to test the hypothesis that soluble dietary fibers can alter the process of lipid emulsification, and possibly, subsequent triglyceride lipolysis. Three guar gums, two pectins, and gum arabic were dissolved in reconstituted duodenal medium in the range 0.3 to 2.0% ( w v ). Viscosities of solutions were measured. Emulsification of a lipid mixture (triolein/phospholipids/cholesterol) was performed under mild conditions in the presence of increasing concentrations of soluble fibers. The amount of emulsifled lipids was reduced and the size of emulsified droplets was increased by raising the concentration of viscous fibers only. The extent of emulsification (r = −0.79), the droplet size (r = 0.88), and the overall droplet surface area (r = −0.59) were strongly correlated to the medium viscosity in the range 0–20 mPa.s. Addition of solutions of viscous fibers to a preformed standard emulsion did not change the lag time and initial velocity of pancreatic lipase reaction. Conversely, when incubating emulsions prepared in the presence of fibers (with different droplet sizes) with excess enzyme for 2 hours, the high- and medium-viscosity guar gums significantly reduced the extent of triglyceride lipolysis only. Thus, reducing emulsification of dietary lipids is a mechanisms by which soluble viscous fibers can alter lipid assimilation.

Polysaccharides of the xylan family are the cell wall polymers most abundant after cellulose in the majority of higher plants. They are mainly present in the lignified secondary walls, where they account for 20–30% of the mass of tissues. This chapter focuses on xylan-type polysaccharides, frequently called arabinoxylans (AXs) found in cereal grains. Xylans are also found in other grains (pea, rapeseed, etc.) or other storage organs (potato tubers, beet roots, etc.) but their role in food is very limited or poorly understood and the literature is scarce.

International audience; Brachypodium distachyon is a suitable plant model for studying temperate cereal crops, such as wheat, barley or rice, and helpful in the study of the grain cell wall. Indeed, the most abundant hemicelluloses that are in the B. distachyon cell wall of grain are (1-3)(1-4)- -glucans and arabinoxylans, in a ratio similar to those of cereals such as barley or oat. Conversely, these cell walls contain few pectins and xyloglucans. Cell walls play an important role in grain physiology. The modifications of cell wall polysaccharides that occur during grain development and filling are key in the determination of the size and weight of the cereal grains. The mechanisms required for cell wall assembly and remodelling are poorly understood, especially in cereals. To provide a better understanding of these processes, we purified the cell wall at three developmental stages of the B. distachyon grain. The proteins were then extracted, and a quantitative and comparative LC-MS/MS analysis was performed to investigate the protein profile changes during grain development. Over 466 cell wall proteins (CWPs) were identified and classified according to their predicted functions. This work highlights the different proteome profiles that we could relate to the main phases of grain development and to the reorganization of cell wall polysaccharides that occurs during these different developmental stages. These results provide a good springboard to pursue functional validation to better understand the role of CWPs in the assembly and remodelling of the grain cell wall of cereals.

Allouche, F. Hanafi, M. Jamme, F. Robert, P. Guillon, F. Devaux, M. F.25ELSEVIER SCIENCE BVSI[Allouche, F.; Robert, P.; Guillon, F.; Devaux, M. F.] INRA, Biopolymeres Interact Assemblages UR1268, F-44300 Nantes, France. [Hanafi, M.] ONIRIS, Unite Mixte Rech Sensometrie & Chimiometrie, F-44322 Nantes 03, France. [Jamme, F.] Synchrotron SOLEIL, F-91192 Gif Sur Yvette, France.fallouche@nantes.inra.fr; mohamed.hanafi@oniris-nantes.fr; frederic.jamme@synchrotron-soleil.fr; International audience; Hyperspectral imaging in various spectral domains is used to perform in situ biochemical analysis of biological material. In the present work, two complementary microspectroscopies-mid-infrared and fluorescence-were coupled to characterise maize stem cell walls. In practice, each microspectroscopy operates with its own resolution, infrared pixels covering a 5 x 5 mu m(2) surface and fluorescence pixels a 1 x 1 mu m(2) area, making the coupling of both spectral ranges through unfolding the spectral images not straightforward. A data structure that preserved the spatial resolution in the two domains was built resulting in a two-way data table with a spatial way and a spectral way, paired to a three-way data table with two spatial ways and a spectral way. The multivariate inter-battery Tucker analysis was investigated in order to give each spectral domain a symmetric role. First, the inter-battery Tucker analysis was applied after averaging the three-way data table under the third mode to obtain a classical two-way data table. This led to work at the lowest resolution. Second, the method has been extended for coupling the three-way data table with the two-way data table. The spectral loadings were similar in both cases showing that phloem cell walls were rich in hydroxycinnamic acids and sclerenchyma cell walls in lignins. The extended version provided with fluorescence scores that preserved the spatial resolution showing more fluorescence intensity in cell junctions. The strong point of the extended inter-battery Tucker analysis is to allow the joint analysis of the two tables without altering their qualities. (c) 2011 Elsevier B.V. All rights reserved.

Article Dubreucq, B (reprint author), *INRA* AgroParisTech, UMR1318, F-78026 Versailles, France bertrand.dubreucq@versailles.inra.fr; A detailed and comprehensive understanding of seed reserve accumulation is of great importance for agriculture and crop improvement strategies. This work is part of a research programme aimed at using Brachypodium distachyon as a model plant for cereal grain development and filling. The focus was on the Bd21-3 accession, gathering morphological, cytological, and biochemical data, including protein, lipid, sugars, starch, and cell-wall analyses during grain development. This study highlighted the existence of three main developmental phases in Brachypodium caryopsis and provided an extensive description of Brachypodium grain development. In the first phase, namely morphogenesis, the embryo developed rapidly reaching its final morphology about 18 d after fertilization (DAF). Over the same period the endosperm enlarged, finally to occupy 80% of the grain volume. During the maturation phase, carbohydrates were continuously stored, mainly in the endosperm, switching from sucrose ! to starch accumulation. Large quantities of beta-glucans accumulated in the endosperm with local variations in the deposition pattern. Interestingly, new beta-glucans were found in Brachypodium compared with other cereals. Proteins (i.e. globulins and prolamins) were found in large quantities from 15 DAF onwards. These proteins were stored in two different sub-cellular structures which are also found in rice, but are unusual for the Pooideae. During the late stage of development, the grain desiccated while the dry matter remained fairly constant. Brachypodium exhibits some significant differences with domesticated cereals. Beta-glucan accumulates during grain development and this cell wall polysaccharide is the main storage carbohydrate at the expense of starch.

Document Type : Proceedings Paper Conference Date : SEP 20-24, 2010 Conference Location : Rabat, MOROCCO Conference Host : Min Sch Rabat; Coupling different techniques in spectroscopy is an efficient approach to characterise complex biological material. This work is carried out to characterise maize stem cell wall composition in the context of biofuel production. In this research, we propose to couple infrared, fluorescence and Raman hyperspectral images. Investigations have been attempted in coupling spectral data by means of multiblock methods. Multiblock techniques have been assumed to be equally applicable and effective in the analysis of biological samples with complex chemical composition and structure. The most commonly used methods are based on sequential approaches. In this article, we propose 1) to condition the data to be analysed towards multiblock analysis in term of pre-processing and organising the blocks from the initial hyperspectral images, 2) to apply Multiple Co-inertia Analysis (MCoA) a symmetrical method providing orthogonal loadings for spectral interpretation and score images for spatial analysis, and 3) to interpret and to analyse in one hand the common structure revealed by the three modalities and in the other hand the independent contribution to explain the variability under each block. (C) 2012 Elsevier B.V. All rights reserved.

Grain dietary fiber content in wheat not only affects its end use and technological properties including milling, baking and animal feed but is also of great importance for health benefits. In this study, integration of association genetics (seven detected loci on chromosomes 1B, 3A, 3D, 5B, 6B, 7A, 7B) and meta-QTL (three consensus QTL on chromosomes 1B, 3D and 6B) analyses allowed the identification of seven chromosomal regions underlying grain dietary fiber content in bread wheat. Based either on a diversity panel or on bi-parental populations, we clearly demonstrate that this trait is mainly driven by a major locus located on chromosome 1B associated with a log of p value >13 and a LOD score >8, respectively. In parallel, we identified 73 genes differentially expressed during the grain development and between genotypes with contrasting grain fiber contents. Integration of quantitative genetics and transcriptomic data allowed us to propose a short list of candidate genes that are conserved in the rice, sorghum and Brachypodium chromosome regions orthologous to the seven wheat grain fiber content QTL and that can be considered as major candidate genes for future improvement of the grain dietary fiber content in bread wheat breeding programs.

International audience; In addition to the starchy endosperm, a specialized tissue accumulating storage material, the endosperm of wheat grain, comprises the aleurone layer and the transfer cells next to the crease. The transfer cells, located at the ventral region of the grain, are involved in nutrient transfer from the maternal tissues to the developing endosperm. Immunolabeling techniques, Raman spectroscopy, and synchrotron infrared micro-spectroscopy were used to study the chemistry of the transfer cell walls during wheat grain development. The kinetic depositions of the main cell wall polysaccharides of wheat grain endosperm, arabinoxylan, and (1-3)(1-4)-beta-glucan in transfer cell walls were different from kinetics previously observed in the aleurone cell walls. While (1-3)(1-4)-beta-glucan appeared first in the aleurone cell walls at 90 degrees D, arabinoxylan predominated in the transfer cell walls from 90 to 445 degrees D. Both aleurone and transfer cell walls were enriched in (1-3)(1-4)-beta-glucan at the mature stage of wheat grain development. Arabinoxylan was more substituted in the transfer cell walls than in the aleurone walls. However, arabinoxylan was more feruloylated in the aleurone than in the transfer cell walls, whatever the stage of grain development. In the transfer cells, the ferulic acid was less abundant in the outer periclinal walls while para-coumarate was absent. Possible implications of such differences are discussed

Mention d'édition : 2. ed.; International audience; The dietary fibre hypothesis has been based upon pioneering observations of physicians and epidemiologists. They pointed out relationships between diet and chronic diseases such as cardiovascular diseases, diabetes and cancer. Since then, the definition of dietary fibre has been a matter of controversy and today is not fully agreed upon by experts in the field. Most recent definitions encompass all polysaccharides and lignin that resist digestion in the upper gut. Some definitions also include lower molecular weight carbohydrates. Dietary fibres include a wide array of compounds that vary in chemical structures and properties and they might be naturally present in food or incorporated in food to improve nutritional or technological properties. The physicochemical properties of dietary fibre play a key role in the actions on gut function, including fermentation. These properties depend on the source, the processing history of the plant material, as well as the form under which it is ingested. The concept of dietary fibres has stimulated a great deal of research and thrown new insight into the understanding of their metabolic and physiological effects while consumer interest in healthy foods has encouraged technologists in developing enriched food products and new fibre additives as supplements for food. However, there is still a need to bring dietary fibres into more appealing and healthy foods to increase the fibre intake.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; The cellular structure of fleshy fruits is of interest to study fruit shape, size, mechanical behaviour or sensory texture. The cellular structure is usually not observed in the whole fruit but, instead, in a sample of limited size and volume. It is therefore difficult to extend measurements to the whole fruit and/or to a specific genotype, or to describe the cellular structure heterogeneity within the fruit. An integrated method is presented to describe the cellular structure of the whole fruit from partial three-dimensional (3D) observations, involving the following steps: (1) fruit sampling, (2) 3D image acquisition and processing and (3) measurement and estimation of relevant 3D morphological parameters. This method was applied to characterize DR12 mutant and wild-type tomatoes (Solanum lycopersicum). The cellular structure was described using the total volume of the pericarp, the surface area of the cell walls and the ratio of cell-wall surface area to pericarp volume, referred to as the cell-wall surface density. The heterogeneity of cellular structure within the fruit was investigated by estimating variations in the cell-wall surface density with distance to the epidermis.

International audience; Monoclonal antibodies were raised against rhamnogalacturonan I backbone, a pectin domain, using Arabidopsis thaliana seed mucilage-derived rhamnogalacturonan I oligosaccharides-BSA conjugates. Two monoclonal antibodies, designated INRA-RU1 and INRA-RU2, selected for further characterization, were specific for the backbone of rhamnogalacturonan I, displaying no binding activity against the other pectin domains i.e. homogalacturonans, galactans or arabinans. A range of oligosaccharides was prepared by enzymatic digestion of rhamnogalacturonan I isolated from Arabidopsis thaliana seed mucilage and from sugar beet pectin, purified by low-pressure chromatography and characterized by high-performance anion-exchange chromatography and mass spectrometry. These rhamnogalacturonan I oligomers were used to characterize the binding site of the two monoclonal antibodies by competitive inhibition. Both INRA-RU1 and INRA-RU2 showed maximal binding to the [-> 2)-alpha-l-rhamnosep-(1 -> 4)-alpha-d-galacturonic acid p-(1 ->](7) structural motif but differed in their minimum binding requirement. INRA-RU2 required at least two disaccharide (rhamnose-galacturonic acid) repeats for the antibody to bind, while INRA-RU1 required a minimum of six disaccharide repeats. Furthermore, the binding capacity of INRA-RU1 decreased steeply as the number of disaccharide repeats go beyond seven. Each of these antibodies reacted with hairy regions isolated from sugar beet pectin. Immunofluorescence microscopy indicated that both antibodies can be readily used to detect rhamnogalacturonan I epitopes in various cell wall samples

L'article original est publié par The American Society of Plant Biologists; International audience; 1,3;1,4)-(bêta-d-Glucan ((bêta-glucan) accounts for 20% of the total cell walls in the starchy endosperm of wheat (Triticum aestivum) and is an important source of dietary fiber for human nutrition with potential health benefits. Bioinformatic and array analyses of gene expression profiles in developing caryopses identified the CELLULOSE SYNTHASE-LIKE F6 (CSLF6) gene as encoding a putative (bêta-glucan synthase. RNA interference constructs were therefore designed to down-regulate CSLF6 gene expression and expressed in transgenic wheat under the control of a starchy endosperm-specific HMW subunit gene promoter. Analysis of wholemeal flours using an enzyme-based kit and by high-performance anion-exchange chromatography after digestion with lichenase showed decreases in total (bêta-glucan of between 30% and 52% and between 36% and 53%, respectively, in five transgenic lines compared to three control lines. The content of water-extractable (bêta-glucan was also reduced by about 50% in the transgenic lines, and the Mr distribution of the fraction was decreased from an average of 79 to 85 × 104 g/mol in the controls and 36 to 57 × 104 g/mol in the transgenics. Immunolocalization of (bêta-glucan in semithin sections of mature and developing grains confirmed that the impact of the transgene was confined to the starchy endosperm with little or no effect on the aleurone or outer layers of the grain. The results confirm that the CSLF6 gene of wheat encodes a (bêta-glucan synthase and indicate that transgenic manipulation can be used to enhance the health benefits of wheat products.

The effect of structure and properties of sugar-beet fibre on its degradability by human faecal bacteria was investigated by an in-vitro fermentation test. The composition and physico-chemical properties of sugar-beet fibre were changed by autoclaving. Autoclaving at 122°C and 136°C for I h increased the solubility mainly of pectins and arabinans and caused increased swelling. The form of the fibre influenced the water-binding capacity, the ionic form giving lowest values. Increasing the ionic strength of the medium reduced the water-binding capacity, especially for the raw fibres and fibres autoclaved at 122°C. The composition of the fibre did not entirely explain these differences and the three-dimensional arrangement of the different polymers in the cell wall was apparently involved. Galacturonic acid and arabinose were extensively depleted by human faecal bacteria and after 24h more than 80% of the initial carbohydrates had been degraded. However, the time course measurement of residual polysaccharides, production of short-chain fatty acids and values of pH showed differences in the rate of fermentation; the presence of solubilised material stimulated bacterial proliferation. The removal of pectic polysaccharides increased the degradability of cellulose and this fact suggested that accessibility is mainly responsible for the slow attack of cellulose in sugar-beet fibre.

O.20; To improve the freezing process applied to vegetable and fruit, a better understanding of degradation mechanisms, strongly linked to the texture of the tissue during freezing is needed.Several studies described global texture modifications after freezing on vegetable and fruit(Marti and Aguilera,1991; Khan and Vincent, 1996; Delgado and Rubiolo, 2005), but none applied multi-scales qualitative and quantitative approach from macroscopic to microscopic level. In this work, different methodologies have been applied to the tissue as mechanical (rheometer), spectral (NMR), thermal (DSC), histological, cytological and chemical measurements, as well as the visualisation of micro-structural modification. As a complementary tool to quantify mechanisms, a mathematical model for the prediction of the water evolution during freezing of vegetable tissue has also been established.

International audience; Glycosyltransferases (GTs) constitute a very large multi-gene superfamily, containing several thousand members identified in sequenced organisms especially in plants. GTs are key enzymes involved in various biological processes such as cell wall formation, storage polysaccharides biosynthesis, and glycosylation of various metabolites. GTs have been identified in rice (Oryza sativa) and Arabidopsis thaliana, but their precise function has been demonstrated biochemically for only a few. In this work we have established a repertoire of virtually all the wheat (Triticum aestivum) GT sequences, using the large publicly available banks of expressed sequences. Based on sequence similarity with Arabidopsis and rice GTs compiled in the carbohydrate active enzyme database (CAZY), we have identified and classified these wheat sequences. The results were used to feed a searchable database available on the web (http://wwwappli.nantes.inra.fr:8180/GTIDB http://wwwappli.nantes.inra.fr:8180/GTIDB" ) that can be used for initiating an exhaustive candidate gene survey in wheat applied to a particular biological process. This is illustrated through the identification of GT families which are expressed during cell wall formation in wheat grain maturation.

Mention d'édition : 1. ed.; International audience

p -Coumaric acid is one of the predominant phenolic acids acylating the cell walls of grasses; p -coumarates are mainly esterified by lignins and arabinoxylans. Here we describe the production and characterisation of two monoclonal antibodies against p -coumarates. The 5- O - p Cou-Ara(1 → 4)Xyl was chemically synthesized and conjugated to a carrier protein. Two interesting antibodies were obtained, hereinafter named INRA-COU1 and INRA-COU2. The specificity of these monoclonal antibodies has been evaluated using competitive-inhibition assays with different oligosaccharides and phenolic compounds. INRA-COU1, recognized free p -coumaric acid or p -coumarate esters. INRA-COU1 did not react with any of the other hydroxycinnamic acids and related compounds found in plants. INRA-COU2, only recognizes esterified p -coumarate. These antibodies were used to study the localization of p -coumarates in the cell walls of grasses. Immunocytochemical analyses indicated noticeable amounts of p -coumarate in the cell walls of the aleurone layer of wheat grain, in the epiderm of cereal straw, and in the exoderm of wheat root. The use of these antibodies will contribute to a better understanding of the organisation and developmental dynamics of cell walls in Graminaceae.

Arabinoxylans (AX) are major components of cell walls in wheat endosperm. The water-extractable part, WEAX, is considered as dietary fibres with health promoting effects. AX exhibit large natural variations in their amount but few studies have been carried out on the genetics of WEAX content and structure in bread wheat. We first carried out a "forward'' quantitative genetic approach, using two recombinant populations derived from crosses between WEAX-high and WEAX-low parents and the viscosity of flour extract (WEAX-viscosity) as a predictor of WEAX content. This allowed us to identify two QTL regions, one of them, found on chromosome 6B in both populations, having a major effect with as much as 59% of the phenotypic variation explained by a single QTL. Then, we focused on key enzymes involved in the biosynthetic pathway of arabinoxylans. Out of 34 homoeologous candidate genes studied by sequencing a set of 46 lines, representing a worldwide diversity 179 show no polymorphi! sm. In the 16 polymorphic candidate genes, 80 SNP (in 15 genes) and 16 indels (in 4 genes) were detected. Then 27 SNP (in 13 genes) were genotyped in a larger collection of 156 lines (Healthgrain diversity screen). Eight associations were significant at an indicative 5% threshold, but only one, between COMT (Caffeic acid O methyltransferase) on chromosome 7A and A/X in WEAX was significant at a 1% level. The usefulness of these approaches and preliminary results for breeding is discussed.

Apple pieces were vacuum-impregnated with either a pectin methylesterase (PME) and calcium solution or with water prior to pasteurization. Pasteurized apple pieces impregnated with PME and calcium showed a significantly higher firmness. Moreover, solid state C-13 NMR spectroscopy of apple cell wall residues revealed an increase of their molecular rigidity. Exogenous PME addition involved a decrease from 82% to 45% of apple pectin degree of methyl-esterification. Microscopic observations of apple slices immunolabelled with antibodies specific for pectins showed that (i) demethyl-esterification was more intense in the cell wall region lining intercellular spaces (demonstrating a key role for these intercellular channels in the enzyme penetration in the tissue during vacuum-infusion) and that (ii) the number of calcium-dimerized deesterified homogalacturonan chains increased. The results corroborate the hypothesis that vacuum-impregnated PME action liberates free carboxyl groups along pectin chains that could interact with calcium, increasing the rigidity of pectins and finally the mechanical rigidity of apple tissue. (C) 2007 Elsevier Ltd. All rights reserved.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Histological assessment of plant material can be tedious by conventional microscopy. One reason is that plant parenchyma cells can be very large, and only a few cells are visible per field. Two macro-vision devices are proposed to visualise about 1 cm(2) of sample from whole organ halves and 100-500 mu m thick microtome sections, respectively. In images, the structure observed can be described in terms of image texture. Morphological grey level granulometries using erosion, dilation and closing are proposed to extract size information from these textures. Methods were applied to characterise tomato (Lycopersicon esculentum) fruit pericarp tissue. In images acquired from tomato halves, various amounts of cell walls and translucent areas were visible depending on regions in the pericarp. Erosion-dilation curves were assessed and compared using multidimensional data analysis. Pericarp texture was found to depend on fruit varieties, although a huge variability within varieties w! as observed. In images acquired from 200 mu m thick microtome sections, cells were clearly visible. Cell elongation in the direction perpendicular to the epidermis was quantified by assessing closing curves using vertical linear structuring elements. Two parental tomato varieties and two of their lines were compared. Average cell lengths ranged from 100 to 600 mu m, the longest cells being as large as 1000 mu m. For the two lines issued from the parental varieties, cell elongation was reduced. Cell length heterogeneity was found to depend on parental genetic background. Macro-vision and grey level granulometries were found useful to compare large areas of tomato pericarps. The two methods bring complementary information and are faster than usual microscopic techniques making the statistical characterisation of histological variability possible.

Hot acid-soluble pectins from sugar-beet pulp which do not gel in the presence of persulfate were submitted to hydrolysis with acid under different conditions of concentration, temperature and time, or with different combinations of enzymes. All the modified pectins have been chemically characterised and tested for their gelling capacity with persulfate ions. They varied primarily in the structure of the side-chains and only those obtained from cold acid hydrolysis and from degradation by arabino-furanosidase were able to gel. Accessibility of the feruloyl groups carried by the arabinose side-chains appeared essential for the gelling of beet pectins with persulfate.