Talc

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Jannick Duchet-rumeau - One of the best experts on this subject based on the ideXlab platform.

  • Chemical modification routes of synthetic Talc: Influence on its nucleating power and on its dispersion state
    Applied Clay Science, 2015
    Co-Authors: Brice Fiorentino, Jérome Crépin Leblond, René Fulchiron, Véronique Bounor-legaré, Jean-charles Majesté, Jannick Duchet-rumeau
    Abstract:

    New synthetic Talcs were incorporated into a polyolefin matrix to prepare synthetic Talc polypropylene (PP) nanocomposites via melt mixing. Different routes of physicochemical modifications of short range (cation exchange or silane grafting) or long range (compatibilizer) order were carried out to achieve an optimized dispersion state. A statistical TEM image analysis methodology was developed to evaluate more quantitatively the dispersion state of the Talc particles within the PP matrix. Natural Talc was taken as a reference in order to compare its nucleating power and its dispersion capacity with that of the synthetic Talcs in the same grade of PP. Even though natural Talc acts as the most efficient nucleating agent, the organophilic surface treatment enhances significantly the nucleating effect of the synthetic Talcs. By coupling the incorporation of a compatibilizer with a suitable organophilic surface treatment, the synthetic Talcs can be also better dispersed than their natural counterpart, giving rise to the formation of a heat shield that delays the thermal degradation of the filled matrix.

  • Use of new synthetic Talc as reinforcing nanofillers for polypropylene and polyamide 6 systems: thermal and mechanical properties.
    Journal of Colloid and Interface Science, 2013
    Co-Authors: M. Yousfi, Christophe Roux, Angela Dumas, Mike Greenhill Hooper, Sébastien Livi, Jérôme Crépin-leblond, Jannick Duchet-rumeau
    Abstract:

    New layered synthetic nanoTalc prepared at a lab-scale by a conventional hydrothermal process and commercial natural fine Talc were used in order to establish a comparative study in terms of their contributions on the improvement of the final properties of two different polymers: a nonpolar polyolefin matrix and a polyamide. All samples were prepared by melt extrusion in a co-rotating micro compounder. The surface properties of Talc -surface energy and isoelectric point- were probed. The particles crystalline structure and the distribution/dispersion within the polymer matrix were performed using transmission electron microscopy and X-ray diffraction. The effect of Talc particles on the cristallinity, the thermal and mechanical properties was highlighted as a function of the surface properties of Talc. In the case of Talc filled PP systems, it seems that the incorporation of both natural and synthetic Talc greatly improves the thermal stability of polypropylene matrix. The highest elastic modulus was obtained in presence of highly nucleating natural Talc. Oppositely the best ductility was observed for the synthetic Talc filled PP systems. For PA6/Talc nanocomposites, a remarkable improvement in the dispersion of Talc layers was shown and a significant increase in Young's modulus was determined due to the closer affinity between the hydrophilic nanoTalc lamellae and the polar PA6 matrix.

  • Controlled shear-induced molecular orientation and crystallization in polypropylene/Talc microcomposites - Effects of the Talc nature
    Polymer, 2013
    Co-Authors: Brice Fiorentino, René Fulchiron, Véronique Bounor-legaré, Jannick Duchet-rumeau, Jean-charles Majesté
    Abstract:

    Nowadays, innovation in the materials field, particularly for polymer materials undoubtedly requires the control of their structure at the nanoscale. Moreover, in the polymer processing tools, the material generally undergoes high strains. In our case, the goal is to determine the interactions between the filler and the matrix on the crystallization processes, especially for a high aspect ratio nucleating filler embedded in a semi-crystalline matrix submitted to a controlled strain field. In this study, PP/Talc blends were developed by compounding in the melt state using a mini-extruder. Several Talcs, different in morphology and particles size, have been studied to determine the influence of their dispersion and of their aspect ratio on the matrix crystallization kinetics. Particularly, one is natural Talc and the other is synthetic. The dispersion and orientation of the Talc lamellae were characterized by scanning electron microscopy (SEM) and Wide Angle X-Ray Scattering (WAXS). Moreover, the crystallization of the microcomposites polypropylene matrix was thoroughly analyzed in terms of kinetics and crystalline orientation. Experiments were performed using both a rheometer and a shearing hot stage mounted on a polarized light microscope or in a synchrotron X-ray beam. They revealed the influence of the nucleating effect depending on the filler, as well as of the shear conditions on both crystallization kinetics and crystalline orientation. Particularly, it was shown that there are two possible crystalline orientations with mother-daughter lamellar structure: one orientation is promoted by the nucleating effect of the aligned Talc platelets and the other is directly due to the shear.

Boris Szurek - One of the best experts on this subject based on the ideXlab platform.

  • targeted promoter editing for rice resistance to xanthomonas oryzae pv oryzae reveals differential activities for sweet14 inducing tal effectors
    Plant Biotechnology Journal, 2017
    Co-Authors: Servane Blanvillainbaufume, Maik Reschke, Montserrat Sole, Florence Auguy, Hinda Doucoure, Boris Szurek, Donaldo Meynard, Murielle Portefaix, Sebastien Cunnac, Emmanuel Guiderdoni
    Abstract:

    Summary As a key virulence strategy to cause bacterial leaf blight, Xanthomonas oryzae pv. oryzae (Xoo) injects into the plant cell DNA-binding proteins called transcription activator-like effectors (TALEs) that bind to effector-binding elements (EBEs) in a sequence-specific manner, resulting in host gene induction. TALEs AvrXa7, PthXo3, Talc and Tal5, found in geographically distant Xoo strains, all target OsSWEET14, thus considered as a pivotal TALE target acting as major susceptibility factor during rice–Xoo interactions. Here, we report the generation of an allele library of the OsSWEET14 promoter through stable expression of TALE-nuclease (TALEN) constructs in rice. The susceptibility level of lines carrying mutations in AvrXa7, Tal5 or Talc EBEs was assessed. Plants edited in AvrXa7 or Tal5 EBEs were resistant to bacterial strains relying on the corresponding TALE. Surprisingly, although indels within Talc EBE prevented OsSWEET14 induction in response to BAI3 wild-type bacteria relying on Talc, loss of Talc responsiveness failed to confer resistance to this strain. The Talc EBE mutant line was, however, resistant to a strain expressing an artificial SWEET14-inducing TALE whose EBE was also edited in this line. This work offers the first set of alleles edited in Talc EBE and uncovers a distinct, broader range of activities for Talc compared to AvrXa7 or Tal5. We propose the existence of additional targets for Talc beyond SWEET14, suggesting that TALE-mediated plant susceptibility may result from induction of several, genetically redundant, host susceptibility genes by a single effector.

  • five phylogenetically close rice sweet genes confer tal effector mediated susceptibility to xanthomonas oryzae pv oryzae
    New Phytologist, 2013
    Co-Authors: Jana Streubel, Celine Pesce, Mathilde Hutin, Ralf Koebnik, Jens Boch, Boris Szurek
    Abstract:

    Bacterial plant-pathogenic Xanthomonas strains translocate transcription activator-like (TAL) effectors into plant cells to function as specific transcription factors. Only a few plant target genes of TAL effectors have been identified, so far. Three plant SWEET genes encoding putative sugar transporters are known to be induced by TAL effectors from rice-pathogenic Xanthomonas oryzae pv. oryzae (Xoo). We predict and validate that expression of OsSWEET14 is induced by a novel TAL effector, Tal5, from an African Xoo strain. Artificial TAL effectors (ArtTALs) were constructed to individually target 20 SWEET orthologs in rice. They were used as designer virulence factors to study which rice SWEET genes can support Xoo virulence. The Tal5 target box differs from those of the already known TAL effectors Talc, AvrXa7 and PthXo3, which also induce expression of OsSWEET14, suggesting evolutionary convergence on key targets. ArtTALs efficiently complemented an Xoo Talc mutant, demonstrating that specific induction of OsSWEET14 is the key target of Talc. ArtTALs that specifically target individual members of the rice SWEET family revealed three known and two novel SWEET genes to support bacterial virulence. Our results demonstrate that five phylogenetically close SWEET proteins, which presumably act as sucrose transporters, can support Xoo virulence. © 2013 No claim to French Government works. © 2013 New Phytologist Trust.

Brice Fiorentino - One of the best experts on this subject based on the ideXlab platform.

  • Chemical modification routes of synthetic Talc: Influence on its nucleating power and on its dispersion state
    Applied Clay Science, 2015
    Co-Authors: Brice Fiorentino, Jérome Crépin Leblond, René Fulchiron, Véronique Bounor-legaré, Jean-charles Majesté, Jannick Duchet-rumeau
    Abstract:

    New synthetic Talcs were incorporated into a polyolefin matrix to prepare synthetic Talc polypropylene (PP) nanocomposites via melt mixing. Different routes of physicochemical modifications of short range (cation exchange or silane grafting) or long range (compatibilizer) order were carried out to achieve an optimized dispersion state. A statistical TEM image analysis methodology was developed to evaluate more quantitatively the dispersion state of the Talc particles within the PP matrix. Natural Talc was taken as a reference in order to compare its nucleating power and its dispersion capacity with that of the synthetic Talcs in the same grade of PP. Even though natural Talc acts as the most efficient nucleating agent, the organophilic surface treatment enhances significantly the nucleating effect of the synthetic Talcs. By coupling the incorporation of a compatibilizer with a suitable organophilic surface treatment, the synthetic Talcs can be also better dispersed than their natural counterpart, giving rise to the formation of a heat shield that delays the thermal degradation of the filled matrix.

  • Controlled shear-induced molecular orientation and crystallization in polypropylene/Talc microcomposites - Effects of the Talc nature
    Polymer, 2013
    Co-Authors: Brice Fiorentino, René Fulchiron, Véronique Bounor-legaré, Jannick Duchet-rumeau, Jean-charles Majesté
    Abstract:

    Nowadays, innovation in the materials field, particularly for polymer materials undoubtedly requires the control of their structure at the nanoscale. Moreover, in the polymer processing tools, the material generally undergoes high strains. In our case, the goal is to determine the interactions between the filler and the matrix on the crystallization processes, especially for a high aspect ratio nucleating filler embedded in a semi-crystalline matrix submitted to a controlled strain field. In this study, PP/Talc blends were developed by compounding in the melt state using a mini-extruder. Several Talcs, different in morphology and particles size, have been studied to determine the influence of their dispersion and of their aspect ratio on the matrix crystallization kinetics. Particularly, one is natural Talc and the other is synthetic. The dispersion and orientation of the Talc lamellae were characterized by scanning electron microscopy (SEM) and Wide Angle X-Ray Scattering (WAXS). Moreover, the crystallization of the microcomposites polypropylene matrix was thoroughly analyzed in terms of kinetics and crystalline orientation. Experiments were performed using both a rheometer and a shearing hot stage mounted on a polarized light microscope or in a synchrotron X-ray beam. They revealed the influence of the nucleating effect depending on the filler, as well as of the shear conditions on both crystallization kinetics and crystalline orientation. Particularly, it was shown that there are two possible crystalline orientations with mother-daughter lamellar structure: one orientation is promoted by the nucleating effect of the aligned Talc platelets and the other is directly due to the shear.

Emmanuel Guiderdoni - One of the best experts on this subject based on the ideXlab platform.

  • targeted promoter editing for rice resistance to xanthomonas oryzae pv oryzae reveals differential activities for sweet14 inducing tal effectors
    Plant Biotechnology Journal, 2017
    Co-Authors: Servane Blanvillainbaufume, Maik Reschke, Montserrat Sole, Florence Auguy, Hinda Doucoure, Boris Szurek, Donaldo Meynard, Murielle Portefaix, Sebastien Cunnac, Emmanuel Guiderdoni
    Abstract:

    Summary As a key virulence strategy to cause bacterial leaf blight, Xanthomonas oryzae pv. oryzae (Xoo) injects into the plant cell DNA-binding proteins called transcription activator-like effectors (TALEs) that bind to effector-binding elements (EBEs) in a sequence-specific manner, resulting in host gene induction. TALEs AvrXa7, PthXo3, Talc and Tal5, found in geographically distant Xoo strains, all target OsSWEET14, thus considered as a pivotal TALE target acting as major susceptibility factor during rice–Xoo interactions. Here, we report the generation of an allele library of the OsSWEET14 promoter through stable expression of TALE-nuclease (TALEN) constructs in rice. The susceptibility level of lines carrying mutations in AvrXa7, Tal5 or Talc EBEs was assessed. Plants edited in AvrXa7 or Tal5 EBEs were resistant to bacterial strains relying on the corresponding TALE. Surprisingly, although indels within Talc EBE prevented OsSWEET14 induction in response to BAI3 wild-type bacteria relying on Talc, loss of Talc responsiveness failed to confer resistance to this strain. The Talc EBE mutant line was, however, resistant to a strain expressing an artificial SWEET14-inducing TALE whose EBE was also edited in this line. This work offers the first set of alleles edited in Talc EBE and uncovers a distinct, broader range of activities for Talc compared to AvrXa7 or Tal5. We propose the existence of additional targets for Talc beyond SWEET14, suggesting that TALE-mediated plant susceptibility may result from induction of several, genetically redundant, host susceptibility genes by a single effector.

Jana Streubel - One of the best experts on this subject based on the ideXlab platform.

  • five phylogenetically close rice sweet genes confer tal effector mediated susceptibility to xanthomonas oryzae pv oryzae
    New Phytologist, 2013
    Co-Authors: Jana Streubel, Celine Pesce, Mathilde Hutin, Ralf Koebnik, Jens Boch, Boris Szurek
    Abstract:

    Bacterial plant-pathogenic Xanthomonas strains translocate transcription activator-like (TAL) effectors into plant cells to function as specific transcription factors. Only a few plant target genes of TAL effectors have been identified, so far. Three plant SWEET genes encoding putative sugar transporters are known to be induced by TAL effectors from rice-pathogenic Xanthomonas oryzae pv. oryzae (Xoo). We predict and validate that expression of OsSWEET14 is induced by a novel TAL effector, Tal5, from an African Xoo strain. Artificial TAL effectors (ArtTALs) were constructed to individually target 20 SWEET orthologs in rice. They were used as designer virulence factors to study which rice SWEET genes can support Xoo virulence. The Tal5 target box differs from those of the already known TAL effectors Talc, AvrXa7 and PthXo3, which also induce expression of OsSWEET14, suggesting evolutionary convergence on key targets. ArtTALs efficiently complemented an Xoo Talc mutant, demonstrating that specific induction of OsSWEET14 is the key target of Talc. ArtTALs that specifically target individual members of the rice SWEET family revealed three known and two novel SWEET genes to support bacterial virulence. Our results demonstrate that five phylogenetically close SWEET proteins, which presumably act as sucrose transporters, can support Xoo virulence. © 2013 No claim to French Government works. © 2013 New Phytologist Trust.