Katia Ruel

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (76)254.67 Total impact

  • American Wood Protection Association - 111th annual meeting "Preserving the past, protecting the future", Ashvill - USA; 04/2015
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    ABSTRACT: In the cell walls of higher plants, cellulose chains are present in crystalline microfibril, with an amorphous part at the surface, or present as amorphous material. To assess the distribution and relative occurrence of the two forms of cellulose in the inflorescence stem of Arabidopsis, we used two carbohydrate-binding modules, CBM3a and CBM28, specific for crystalline and amorphous cellulose, respectively, with immunogold detection in TEM. The binding of the two CBMs displayed specific patterns suggesting that the synthesis of cellulose leads to variable nanodomains of cellulose structures according to cell type. In developing cell walls, only CBM3a bound significantly to the incipient primary walls, indicating that at the onset of its deposition cellulose is in a crystalline structure. As the secondary wall develops, the labeling with both CBMs becomes more intense. The variation of the labeling pattern by CBM3a between transverse and longitudinal sections appeared related to microfibril orientation and differed between fibers and vessels. Although the two CBMs do not allow the description of the complete status of cellulose microstructures, they revealed the dynamics of the deposition of crystalline and amorphous forms of cellulose during wall formation and between cell types adapting cellulose microstructures to the cell function.
    Plant Science 09/2012; 193-194:48-61. DOI:10.1016/j.plantsci.2012.05.008 · 4.11 Impact Factor
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    ABSTRACT: Pycnoporus cinnabarinus laccase and a chimeric laccase-CBM were applied in softwood kraft pulp biobleaching in the presence of 1-hydroxybenzotriazole (HBT). The presence of CBM could enhance the laccase biobleaching potential as a decrease in the enzymatic charge and chlorine dioxide consumption, as well as an increase in pulp brightness were observed. Laccase/HBT treatment could be improved by increasing oxygen pressure from 1 to 3bar and pulp consistency from 5% to 10%. Conversely, under the same conditions, no improvement of laccase-CBM/HBT treatment was observed, indicating a different behavior of both systems. However, laccase-CBM/HBT treatment led to a better preservation of pulp properties. This effect was probably due to fiber surface modifications involving the action of the CBM. Transmission electron microscopy examination of pulp fibers indicated a retention of laccase-CBM inside the pulp fibers due to CBM binding and an increased external microfibrillation of the fibers due to enzymatic treatments.
    Bioresource Technology 07/2012; 121:68-75. DOI:10.1016/j.biortech.2012.06.077 · 5.04 Impact Factor
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    ABSTRACT: Due to the high potential of cellulose nanoparticles in composite materials and for both fundamental and technological considerations, we investigated the interaction between microfibrillar cellulose and fibers. The contribution to the paper properties of fines added to a pulp suspension was determined. The impact of various proportions of fines added to a softwood kraft pulp on the paper strength and how they affected porosity and density was evaluated. The respective effects of dried fines (dead fines), originating from paper or board degradation, and the newly formed secondary fines (fresh fines) generated during refining were examined. The nature of the bonding between the fines and the fibers versus physical retention was characterized in the pulp suspension. For the first time the respective parts in the interaction of hydrogen bonds and mechanical associations were demonstrated and quantified. The amount of H-bonded fresh fines exceeded that of dead fines by more than 30 %. The results revealed that, for both types, the amount of H-bonded fines reached a threshold, independently of the proportion of fines added to the fibers. Addition of fines significantly affected the porosity of papers, fresh fines decreasing porosity more readily than dead fines. All the results are convergent to indicate that fresh fines penetrate more evenly and more deeply into the fiber network and induce better bonding that produces a closure of the fiber mat structure. They also demonstrate that incorporating an optimal proportion of fresh cellulose fines in fiber networks can bring significant improvement to the final composite material.
    Cellulose 06/2012; 19(3). DOI:10.1007/s10570-012-9693-5 · 3.03 Impact Factor
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    IAWA journal / International Association of Wood Anatomists 01/2012; 33(3):269-286. DOI:10.1163/22941932-90000093 · 0.96 Impact Factor
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    ABSTRACT: Cinnamyl alcohol dehydrogenase (CAD) is a key enzyme involved in the last step of monolignol biosynthesis. The effect of CAD down-regulation on lignin production was investigated through a transgenic approach in maize. Transgenic CAD-RNAi plants show a different degree of enzymatic reduction depending on the analyzed tissue and show alterations in cell wall composition. Cell walls of CAD-RNAi stems contain a lignin polymer with a slight reduction in the S-to-G ratio without affecting the total lignin content. In addition, these cell walls accumulate higher levels of cellulose and arabinoxylans. In contrast, cell walls of CAD-RNAi midribs present a reduction in the total lignin content and of cell wall polysaccharides. In vitro degradability assays showed that, although to a different extent, the changes induced by the repression of CAD activity produced midribs and stems more degradable than wild-type plants. CAD-RNAi plants grown in the field presented a wild-type phenotype and produced higher amounts of dry biomass. Cellulosic bioethanol assays revealed that CAD-RNAi biomass produced higher levels of ethanol compared to wild-type, making CAD a good target to improve both the nutritional and energetic values of maize lignocellulosic biomass.
    Molecular Plant 12/2011; 5(4):817-30. DOI:10.1093/mp/ssr097 · 6.61 Impact Factor
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    ABSTRACT: During cell wall formation and degradation, it is possible to detect cellulose microfibrils assembled into thicker and thinner lamellar structures, respectively, following inverse parallel patterns. The aim of this study was to analyse such patterns of microfibril aggregation and cell wall delamination. The thickness of microfibrils and lamellae was measured on digital images of both growing and degrading cell walls viewed by means of transmission electron microscopy. To objectively detect, measure and classify microfibrils and lamellae into thickness classes, a method based on the application of computerized image analysis combined with graphical and statistical methods was developed. The method allowed common classes of microfibrils and lamellae in cell walls to be identified from different origins. During both the formation and degradation of cell walls, a preferential formation of structures with specific thickness was evidenced. The results obtained with the developed method allowed objective analysis of patterns of microfibril aggregation and evidenced a trend of doubling/halving lamellar structures, during cell wall formation/degradation in materials from different origin and which have undergone different treatments.
    Planta 08/2010; 232(3):621-7. DOI:10.1007/s00425-010-1202-1 · 3.38 Impact Factor
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    ABSTRACT: Tobacco plants expressing an antisense construct for a cationic peroxidase, which down-regulated lignin content at the presumed level of polymerisation, have been further analysed. T(1) plants were derived from a large-scale screen of T(0) mutant lines, previously published, which identified lines demonstrating consistent lignin down-regulation. Of these, line 1074 which had the most robust changes in lignin distribution through several generations was shown to have accompanying down-regulation of transcription of most lignin biosynthesis genes, except cinnamoyl-CoA reductase. The consistent 20% reduction in lignin was not accompanied by significant gross changes in vascular polysaccharide content and composition, despite a modest up-regulation of transcripts of genes involved in cellulose and hemicellulose synthesis. Morphologically, 1074 plants have under-developed xylem with both fibers and vessels having thin cell walls and limited secondary wall thickening with an abnormal S2 layer. However, they were not compromised in overall growth. Nevertheless, these and other lines showed improved potential industrial utility through a threefold increase in enzymic saccharification efficiency compared with wild-type (wt). Therefore, they were profiled for further un-intended effects of transgenesis that might compromise their value for industrial or biofuel processes. Other phenotypic changes included increased leaf thickness and bifurcation at the tip of the leaf. wt-Plants had smaller chloroplasts and higher stomatal numbers than mutants. Transgenic lines also showed a variable leaf pigment distribution with light-green areas that contained measurably less chlorophyll a, b, and carotenoids. Changes in epidermal pavement cells of mutant lines were also observed after exposure to various chemicals, while wt leaves retained their structural integrity. Despite these changes, the mutant plants grew and were viable indicating that lignification patterns can be manipulated considerably through targeting polymerisation without serious deleterious effects.
    Phytochemistry 02/2010; 71(5-6):531-42. DOI:10.1016/j.phytochem.2010.01.008 · 3.35 Impact Factor
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    New Biotechnology 09/2009; 25. DOI:10.1016/j.nbt.2009.06.632 · 2.11 Impact Factor
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    ABSTRACT: A cinnamoyl-CoA reductase 1 knockout mutant in Arabidopsis thaliana was investigated for the consequences of lignin synthesis perturbation on the assembly of the cell walls. The mutant displayed a dwarf phenotype and a strong collapse of its xylem vessels corresponding to lower lignin content and a loss of lignin units of the noncondensed type. Transmission electron microscopy revealed that the transformation considerably impaired the capacity of interfascicular fibers and vascular bundles to complete the assembly of cellulose microfibrils in the S(2) layer, the S(1) layer remaining unaltered. Such disorder in cellulose was correlated with X-ray diffraction showing altered organization. Semi-quantitative immunolabeling of lignins showed that the patterns of distribution were differentially affected in interfascicular fibers and vascular bundles, pointing to the importance of noncondensed lignin structures for the assembly of a coherent secondary wall. The use of laser capture microdissection combined with the microanalysis of lignins and polysaccharides allowed these polymers to be characterized into specific cell types. Wild-type A. thaliana displayed a two-fold higher syringyl to guaiacyl ratio in interfascicular fibers compared with vascular bundles, whereas this difference was less marked in the cinnamoyl-CoA reductase 1 knockout mutant.
    New Phytologist 08/2009; 184(1):99-113. DOI:10.1111/j.1469-8137.2009.02951.x · 6.55 Impact Factor
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    ABSTRACT: The involvement of the maize ZmMYB42 R2R3-MYB factor in the phenylpropanoid pathway and cell wall structure and composition was investigated by overexpression in Arabidopsis thaliana. ZmMYB42 down-regulates several genes of the lignin pathway and this effect reduces the lignin content in all lignified tissues. In addition, ZmMYB42 plants generate a lignin polymer with a decreased S to G ratio through the enrichment in H and G subunits and depletion in S subunits. This transcription factor also regulates other genes involved in the synthesis of sinapate esters and flavonoids. Furthermore, ZmMYB42 affects the cell wall structure and degradability, and its polysaccharide composition. Together, these results suggest that ZmMYB42 may be part of the regulatory network controlling the phenylpropanoid biosynthetic pathway.
    Plant Molecular Biology 03/2009; 70(3):283-96. DOI:10.1007/s11103-009-9473-2 · 4.07 Impact Factor
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    ABSTRACT: Lignified cell walls are widely considered to be key innovations in the evolution of terrestrial plants from aquatic ancestors some 475 million years ago. Lignins, complex aromatic heteropolymers, stiffen and fortify secondary cell walls within xylem tissues, creating a dense matrix that binds cellulose microfibrils and crosslinks other wall components, thereby preventing the collapse of conductive vessels, lending biomechanical support to stems, and allowing plants to adopt an erect-growth habit in air. Although "lignin-like" compounds have been identified in primitive green algae, the presence of true lignins in nonvascular organisms, such as aquatic algae, has not been confirmed. Here, we report the discovery of secondary walls and lignin within cells of the intertidal red alga Calliarthron cheilosporioides. Until now, such developmentally specialized cell walls have been described only in vascular plants. The finding of secondary walls and lignin in red algae raises many questions about the convergent or deeply conserved evolutionary history of these traits, given that red algae and vascular plants probably diverged more than 1 billion years ago.
    Current biology: CB 02/2009; 19(2):169-75. DOI:10.1016/j.cub.2008.12.031 · 9.92 Impact Factor
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    ABSTRACT: Cinnamoyl-CoA reductase 1 (CCR1, gene At1g15950) is the main CCR isoform implied in the constitutive lignification of Arabidopsis thaliana. In this work, we have identified and characterized two new knockout mutants for CCR1. Both have a dwarf phenotype and a delayed senescence. At complete maturity, their inflorescence stems display a 25-35% decreased lignin level, some alterations in lignin structure with a higher frequency of resistant interunit bonds and a higher content in cell wall-bound ferulic esters. Ferulic acid-coniferyl alcohol ether dimers were found for the first time in dicot cell walls and in similar levels in wild-type and mutant plants. The expression of CCR2, a CCR gene usually involved in plant defense, was increased in the mutants and could account for the biosynthesis of lignins in the CCR1-knockout plants. Mutant plantlets have three to four-times less sinapoyl malate (SM) than controls and accumulate some feruloyl malate. The same compositional changes occurred in the rosette leaves of greenhouse-grown plants. By contrast and relative to the control, their stems accumulated unusually high levels of both SM and feruloyl malate as well as more kaempferol glycosides. These findings suggest that, in their hypolignified stems, the mutant plants would avoid the feruloyl-CoA accumulation by its redirection to cell wall-bound ferulate esters, to feruloyl malate and to SM. The formation of feruloyl malate to an extent far exceeding the levels reported so far indicates that ferulic acid is a potential substrate for the enzymes involved in SM biosynthesis and emphasizes the remarkable plasticity of Arabidopsis phenylpropanoid metabolism.
    Planta 05/2008; 227(5):943-56. DOI:10.1007/s00425-007-0669-x · 3.38 Impact Factor
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    ABSTRACT: Plants growing in altered gravity conditions encounter changes in vascular development and cell wall deposition. The aim of this study was to investigate xylem anatomy and arrangement of cellulose microfibrils in vessel walls of different organs of soybean seedlings grown in Space. Seeds germinated and seedlings grew for 5 d in Space during the Foton-M2 mission. The environmental conditions, other than gravity, of the ground control repeated those experienced in orbit. The seedlings developed in space were compared with those of the control test on the basis of numerous anatomical and ultrastructural parameters such as number of veins, size and shape of vessel lumens, thickness of cell walls and deposition of cellulose microfibrils. Observations made with light, fluorescence and transmission electron microscopy, together with the quantification of the structural features through digital image analysis, showed that the alterations due to microgravity do not occur at the same level in the various organs of soybean seedlings. The modifications induced by microgravity or by the indirect effect of space-flight conditions, became conspicuous only in developing vessels at the ultrastructural level. The results suggested that the orientation of microfibrils and their assembly in developing vessels are perturbed by microgravity at the beginning of wall deposition, while they are still able to orient and arrange in thicker and ordered structures at later stages of secondary wall deposition. The process of proper cell-wall building, although not prevented, is perturbed in Space at the early stage of development. This would explain the almost unaltered anatomy of mature structures, accompanied by a slower growth observed in seedlings grown in Space than on Earth.
    Annals of Botany 05/2008; 101(5):661-9. DOI:10.1093/aob/mcn001 · 3.30 Impact Factor
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    ABSTRACT: In view of tracing the fate of cellulose fine elements added to a suspension of cellulose fibers, a novel method for specific labeling of polysaccharides in a composite material was developed. The purpose was to visualize a given cellulose material within a cellulose mixture. The method consists of generating aldehyde groups in the chain by mild periodic acid oxidation followed by biotinylation of the carbonyls. Once added to the composite, the biotinylated molecules are labeled with streptavidin conjugated to a fluorescent probe for confocal microscopy, or streptavidin-gold for electron microscopy observations. In the present work, the fate of fresh fines (never-dried) and dead fines (dried) when they were added to a purified suspension of fibers was followed by observation of the labeling in confocal and electron microscopy. The differential mode of interaction of fresh fines and dead fines with the fibers was correlated to the mechanical characteristics measured on the corresponding papers. The versatility of the new labeling method and its possible generalization to other polysaccharides incorporated to a polysaccharide or nonpolysaccharide material should be of potential interest for the study of composite microstructure.
    Biomacromolecules 04/2008; 9(3):767-71. DOI:10.1021/bm7011339 · 5.75 Impact Factor
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    ABSTRACT: Xyloglucan endotransglucosylase/hydrolases (XTHs; EC 2.4.1.207 and/or EC 3.2.1.151) are enzymes involved in the modification of cell wall structure by cleaving and, often, also re-joining xyloglucan molecules in primary plant cell walls. Using a pool of antibodies raised against an enriched cell wall protein fraction, a new XTH cDNA in maize, ZmXTH1, has been isolated from a cDNA expression library obtained from the elongation zone of the maize root. The predicted protein has a putative N-terminal signal peptide and possesses the typical domains of this enzyme family, such as a catalytic domain that is homologous to that of Bacillus macerans beta-glucanase, a putative N-glycosylation motif, and four cysteine residues in the central and C terminal regions of the ZmXTH1 protein. Phylogenetic analysis of ZmXTH1 reveals that it belongs to subgroup 4, so far only reported from Poaceae monocot species. ZmXTH1 has been expressed in Pichia pastoris (a methylotrophic yeast) and the recombinant enzyme showed xyloglucan endotransglucosylase but not xyloglucan endohydrolase activity, representing the first enzyme belonging to subgroup 4 characterized in maize so far. Expression data indicate that ZmXTH1 is expressed in elongating tissues, modulated by culture conditions, and induced by gibberellins. Transient expression assays in onion cells reveal that ZmXTH1 is directed to the cell wall, although weakly bound. Finally, Arabidopsis thaliana plants expressing ZmXTH1 show slightly increased xyloglucan endohydrolase activity and alterations in the cell wall structure and composition.
    Journal of Experimental Botany 02/2008; 59(4):875-89. DOI:10.1093/jxb/ern013 · 5.79 Impact Factor
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    ABSTRACT: Cellulose Binding Domains (CBD) were conjugated with fluorescein isothiocyanate (FITC). The surface concentration of the Binding Domains adsorbed on cellulose fibres was determined by fluorescence image analysis. For a CBD-FITC concentration of 60 mg/L, a coating fraction of 78% and 110% was estimated for Portucel and Whatman fibres, respectively. For a saturating CBD concentration, using Whatman CF11 fibres, a surface concentration of 25.2 x 10-13 mol/mm2 was estimated, the equivalent to 4 protein monolayers. This result does not imply the existence of several adsorbed protein layers. It was verified that CBDs were able to penetrate the fibres, according to confocal microscopy and TEM-immunolabelling analysis. The surface concentration of adsorbed CBDs was greater on amorphous fibres (phosphoric acid swollen) than on more crystalline ones (Whatman CF11 and Sigmacell 20).
    BMC Biotechnology 02/2008; 8:1. DOI:10.1186/1472-6750-8-1 · 2.59 Impact Factor
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    ABSTRACT: Lignins are complex phenolic heteropolymers present in xylem and sclerenchyma cell walls in tracheophytes. The occurrence of lignin-like polymers in bryophytes is controversial. In this study two polyclonal antibodies against homoguaiacyl (G) and guaiacyl/syringyl (GS) synthetic lignin-like polymers that selectively labelled lignified cell walls in tracheophytes also bound to cell walls in bryophytes, the GS antibody usually giving a stronger labelling than the G antibody. In contrast to tracheophytes, the antibody binding in liverworts and mosses was not tissue-specific. In the hornworts Megaceros flagellaris and M. fuegiensis the pseudoelaters and spores were labelled more intensely than the other cell types with the GS antibody. The cell walls in Nitella were labelled with both antibodies but no binding was observed in Coleochaete. The results suggest that the ability to incorporate G or GS moieties in cell walls is a plesiomorphy (primitive character) of the land plant clade.
    Plant Systematics and Evolution 02/2008; 270(3):257-272. DOI:10.1007/s00606-007-0617-z · 1.15 Impact Factor
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    ABSTRACT: Cinnamoyl-CoA reductase (CCR) catalyzes the penultimate step in monolignol biosynthesis. We show that downregulation of CCR in transgenic poplar (Populus tremula x Populus alba) was associated with up to 50% reduced lignin content and an orange-brown, often patchy, coloration of the outer xylem. Thioacidolysis, nuclear magnetic resonance (NMR), immunocytochemistry of lignin epitopes, and oligolignol profiling indicated that lignin was relatively more reduced in syringyl than in guaiacyl units. The cohesion of the walls was affected, particularly at sites that are generally richer in syringyl units in wild-type poplar. Ferulic acid was incorporated into the lignin via ether bonds, as evidenced independently by thioacidolysis and by NMR. A synthetic lignin incorporating ferulic acid had a red-brown coloration, suggesting that the xylem coloration was due to the presence of ferulic acid during lignification. Elevated ferulic acid levels were also observed in the form of esters. Transcript and metabolite profiling were used as comprehensive phenotyping tools to investigate how CCR downregulation impacted metabolism and the biosynthesis of other cell wall polymers. Both methods suggested reduced biosynthesis and increased breakdown or remodeling of noncellulosic cell wall polymers, which was further supported by Fourier transform infrared spectroscopy and wet chemistry analysis. The reduced levels of lignin and hemicellulose were associated with an increased proportion of cellulose. Furthermore, the transcript and metabolite profiling data pointed toward a stress response induced by the altered cell wall structure. Finally, chemical pulping of wood derived from 5-year-old, field-grown transgenic lines revealed improved pulping characteristics, but growth was affected in all transgenic lines tested.
    The Plant Cell 12/2007; 19(11):3669-91. DOI:10.1105/tpc.107.054148 · 9.58 Impact Factor

Publication Stats

2k Citations
254.67 Total Impact Points

Institutions

  • 1992–2012
    • French National Centre for Scientific Research
      • Centre de Recherches sur les Macromolécules Végétales
      Lutetia Parisorum, Île-de-France, France
  • 1993–2009
    • University Joseph Fourier - Grenoble 1
      • Centre de Recherche sur les MAcromolécules Végétales
      Grenoble, Rhone-Alpes, France