References of "Tocquin, Pierre"
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See detailInflorescence development in tomato: gene functions within a zigzag model.
Périlleux, Claire ULg; Lobet, Guillaume ULg; Tocquin, Pierre ULg

in Frontiers in Plant Science (2014), 5

Tomato is a major crop plant and several mutants have been selected for breeding but also for isolating important genes that regulate flowering and sympodial growth. Besides, current research in ... [more ▼]

Tomato is a major crop plant and several mutants have been selected for breeding but also for isolating important genes that regulate flowering and sympodial growth. Besides, current research in developmental biology aims at revealing mechanisms that account for diversity in inflorescence architectures. We therefore found timely to review the current knowledge of the genetic control of flowering in tomato and to integrate the emerging network into modeling attempts. We developped a kinetic model of the tomato inflorescence development where each meristem was represented by its ‘vegetativeness’ (V), reflecting its maturation state towards flower initiation. The model followed simple rules: maturation proceeded continuously at the same rate in every meristem (dV); floral transition and floral commitment occurred at threshold levels of V; lateral meristems were initiated with a gain of V (ΔV) relative to the V level of the meristem from which they derived. This last rule created a link between successive meristems and gave to the model its zigzag shape. We next exploited the model to explore the diversity of morphotypes that could be generated by varying dV and ΔV and matched them with existing mutant phenotypes. This approach, focused on the development of the primary inflorescence, allowed us to elaborate on the genetic regulation of the kinetic model of inflorescence development. We propose that the lateral inflorescence meristem fate in tomato is closer to an immature flower meristem than to the inflorescence meristem of Arabidopsis. In the last part of our paper, we extend our thought to spatial regulators that should be integrated in a next step for unraveling the relationships between the different meristems that participate to sympodial growth. [less ▲]

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See detailThe hidden half of flowering
Bouché, Frédéric ULg; Mistiaen, Kevin ULg; D'Aloia, Maria ULg et al

Poster (2013, June)

Flowering is one of the most important developmental steps in plant life cycle and is therefore tightly controlled by environmental cues. The involvement of the aerial part of the plant in the molecular ... [more ▼]

Flowering is one of the most important developmental steps in plant life cycle and is therefore tightly controlled by environmental cues. The involvement of the aerial part of the plant in the molecular mechanisms leading to floral transition is well documented while participation of the roots received less attention. Nevertheless, the induction of flowering by photoperiod is known to involve systemic signals that move in phloem sap towards sinks, throughout the plants, including the roots. Transcriptomic analysis of roots tissues during the floral induction of flowering by a single long day of in Arabidopsis thaliana by a single long day allowed us to identify a large number of differentially expressed genes. How mutations We subsequently selected in some candidate genes affect plant development - including root architecture and flowering time - is being to analyze their flowering timefurther analyzed. Further analysis of those genes will permit us to unravel their role in the flowering induction process. [less ▲]

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See detailTowards the improvement of a rhizosecretion-based recombinant protein production system: Developing protease-depleted lines of Arabidopsis thaliana.
Lallemand, Jérôme ULg; Désiron, Carole ULg; Périlleux, Claire ULg et al

Poster (2013, June)

Besides traditional production systems, such as bacteria, yeasts and mammal cells, plants can now be used to produce eukaryotic recombinant proteins. Their advantages as hosts for protein production ... [more ▼]

Besides traditional production systems, such as bacteria, yeasts and mammal cells, plants can now be used to produce eukaryotic recombinant proteins. Their advantages as hosts for protein production include correct post-translational modifications, low cost of maintenance and no risk of contamination by human pathogens. Targeting heterologous proteins to the extracellular space is required for the correct folding of complex proteins and makes harvesting and purification easier. However, the quantity and the quality of recombinant proteins have been proved to be reduced by the action of endogenous co-secreted proteases. In this study, we aimed at identifying active root-secreted (rhizosecreted) proteases in the model plant Arabidopsis thaliana. Their activity was assayed by in vitro degradation of a target protein (Bovine Serum Albumine, BSA) in a range of pH. The protease classes involved in BSA degradation were evaluated by inhibitor-based assays that revealed serine proteases as the major class involved in this degradation in any tested conditions. As a first step towards identification, and subsequent silencing, of the most active members of this class, rhizosecreted proteases are being analyzed by the “Activity-Based Protein Profiling” approach. [less ▲]

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See detailTowards identification of active root-secreted proteases of Arabidopsis thaliana.
Lallemand, Jérôme ULg; Désiron, Carole ULg; Périlleux, Claire ULg et al

Poster (2013, April 18)

Besides traditional production systems, such as bacteria, yeasts and mammal cells, plants can now be used to produce eukaryotic recombinant proteins. Their advantages as hosts for proteins production ... [more ▼]

Besides traditional production systems, such as bacteria, yeasts and mammal cells, plants can now be used to produce eukaryotic recombinant proteins. Their advantages as hosts for proteins production include correct post-translational modifications, low cost of maintenance and no risk of contamination by human pathogens. Targeting heterologous proteins to the extracellular space is required for the correct folding of complex proteins and makes harvesting and purification easier. However, the quantity and the quality of recombinant proteins have been proved to be reduced by the action of endogenous co-secreted proteases. In this study, we characterized root-secreted proteases in the model plant Arabidopsis thaliana, at the activity and expression levels. Their activity was analyzed by in vitro degradation of a target protein (Bovine Serum Albumine, BSA) in a range of pH and in the presence of several proteases inhibitors. Serine proteases were identified as the major protease class involved in the degradation of BSA under all tested conditions. As a first step towards the identification of the key players, the expression level of selected members of this class was analyzed by quantitative RT-PCR in roots and leaves. [less ▲]

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See detailMolecular analysis of root medium impact on Arabidopsis thaliana development
Bouché, Frédéric ULg; André, Julie; Tocquin, Pierre ULg et al

Poster (2013, April 18)

Hydroponics and soil are the most common media used for plant growth. Hydroponics has the main advantage of providing easy access to the root system and is therefore commonly used for gene expression ... [more ▼]

Hydroponics and soil are the most common media used for plant growth. Hydroponics has the main advantage of providing easy access to the root system and is therefore commonly used for gene expression analyses in molecular studies of the model plant Arabidopsis thaliana. However, the impact of root substrate on plant growth remains poorly documented. Here we show that hydroponics accelerates both shoot growth and developmental phases as compared with culture on soil. In order to identify molecular changes in the roots that could account for these medium effects, a transcriptomic comparison was performed by microarray analysis. This experiment revealed that more than 20% of the genes were differentially expressed in hydroponics vs soil. Among them, the flowering time gene FLOWERING LOCUS C and two clades of microRNA targeted genes. To further assess the role of these genes in roots, artificial microRNAs were designed for root specific expression in transgenic Arabidopsis plants. [less ▲]

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See detailA root chicory MADS-box sequence and the Arabidopsis flowering repressor FLC share common features that suggest conserved function in vernalization and devernalization responses
Périlleux, Claire ULg; Pieltain, Alexandra; Jacquemin, Guillaume et al

in Plant Journal (The) (2013), 75

Root chicory (Cichorium intybus var. sativum) is a biennial crop, but is harvested for root inulin at the end of the first growing season before flowering. However, cold temperatures might vernalize seeds ... [more ▼]

Root chicory (Cichorium intybus var. sativum) is a biennial crop, but is harvested for root inulin at the end of the first growing season before flowering. However, cold temperatures might vernalize seeds or plantlets, leading to incidental early flowering and hence understanding the molecular basis of vernalization is important. A MADS-box sequence was isolated by RT-PCR and named FLC-LIKE1 (CiFL1) because of its phylogenetic positioning within the same clade as the floral repressor Arabidopsis FLOWERING LOCUS C (AtFLC). Moreover, overexpression of CiFL1 in Arabidopsis caused late flowering and prevented up-regulation of the AtFLC target FLOWERING LOCUS T gene by photoperiod, suggesting functional conservation between root chicory and Arabidopsis. Like AtFLC in Arabidopsis, CiFL1 was repressed during vernalization of seeds or plantlets of chicory, but repression of CiFL1 was unstable whether the post-vernalization temperature was favorable to flowering or whether it devernalized the plants. Instability of CiFL1 repression might be linked to bienniality of root chicory versus the annual life cycle of Arabidopsis. However, reactivation of AtFLC was also observed in Arabidopsis when a high temperature treatment was given straight after seed vernalization, erasing the promotive effect of cold on flowering. Cold-induced downregulation of a MADS-box floral repressor and its reactivation by high temperature thus appear as conserved features of the vernalization and devernalization responses in distant species.This article is protected by copyright. All rights reserved. [less ▲]

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See detailOptimization of an Haematococcus pluvialis medium by a Genetic Algorithm-based strategy
Fratamico, Anthony ULg; Tocquin, Pierre ULg; Franck, Fabrice ULg

Poster (2012, June 14)

The successful use of living organisms for the production of biomass or metabolites requires a careful control and optimization over growing conditions. However the range of interacting parameters makes ... [more ▼]

The successful use of living organisms for the production of biomass or metabolites requires a careful control and optimization over growing conditions. However the range of interacting parameters makes full optimization difficult and time-consuming. In this context, Genetic Algorithm-based (GA) methods emerge as promising strategies for optimization of biotechnological processes. However, the potential of GA in the microalgae field remains, today, poorly explored. As a proof-of-concept, we evaluated how GA could be applied for the optimization of a medium for high yield photoautotrophic growth of Haematoccocus pluvialis. [less ▲]

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See detailRooting the flowering process
D'Aloia, Maria ULg; Bouché, Frédéric ULg; Tamseddak, Karim et al

Poster (2012, May)

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See detailDegradation of recombinant IgG by root-secreted proteases of Arabidopsis thaliana and Nicotiana tabacum
Désiron, Carole ULg; Lallemand, Jérôme ULg; Périlleux, Claire ULg et al

Poster (2012, April 18)

Plants are promising hosts for the production of complex recombinant pharmaceuticals, such as antibodies (mAbs), because they offer an inexpensive and safer alternative to traditional production systems ... [more ▼]

Plants are promising hosts for the production of complex recombinant pharmaceuticals, such as antibodies (mAbs), because they offer an inexpensive and safer alternative to traditional production systems. The plant-based production of mAbs, which are multimeric glycoproteins, require their targeting to the secretory pathaway where they are properly folded and matured. However, co-secretion of endogenous proteases, which can represent up to 10% of the extracellular proteins (secretome), is known to significantly alter the yield and quality of secreted mAbs. In this study, we analyzed the proteolytic activities in root-secretome of Arabidopsis thaliana and Nicotiana tabacum. Root-secretomes were recovered by salt extraction and the protease activity was assayed in vitro or by zymography, in a range of pH. The relative contribution of protease classes was evaluated with specific inhibitors. [less ▲]

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See detailOptimization of recombinant root-secreted IgGs production in Arabidopsis thaliana by screening cell wall mutants
Boulanger, Benoit ULg; Périlleux, Claire ULg; Tocquin, Pierre ULg

Poster (2012, April 18)

The production of complex heterologous proteins (e.g. monoclonal antibodies, mAbs) in plants has several advantages animal based systems such as low cost, scalability and limited risk of contamination by ... [more ▼]

The production of complex heterologous proteins (e.g. monoclonal antibodies, mAbs) in plants has several advantages animal based systems such as low cost, scalability and limited risk of contamination by human pathogens. mAbs are glycoproteins that require to be targeted to the plant secretory pathway in order to be properly folded and matured. They are ultimately delivered in the cell wall and are expected to be freely released in the extracellular space and the external medium, which would greatly simplify downstream processing. However, a significant part of plant produced and secreted mAbs remains bound to the cell wall, therefore hindering recovery. In this study, we evaluated the extra-cellular release of root-secreted proteins of wild-type plants and cell wall mutants of Arabidopsis thaliana. Recovered protein were either analyzed by SDS-PAGE for full proteome profiling or by gelatin zymography to reveal the activity of cell wall-bound proteases. The production, secretion and release of recombinant IgG will be eventually studied in transgenic hairy-roots generated from selected mutants. [less ▲]

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See detailScreening for a low-cost Haematococcus pluvialis medium reveals an unexpected impact of a low N:P ratio on vegetative growth
Tocquin, Pierre ULg; Fratamico, Anthony ULg; Franck, Fabrice ULg

in Journal of Applied Phycology (2012), 24(3), 365-373

Haematococcus pluvialis is the current better source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system ... [more ▼]

Haematococcus pluvialis is the current better source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system: during the first stage, vegetative “green” cells are produced and then converted, in the second stage, into cysts that accumulate astaxanthin. In this work, a medium screening strategy based on the mixing of a 3-component hydroponic fertilizer was applied to identify a new formulation optimized for the vegetative stage. A maximal and high cell density of 2 x 106 cells mL−1 was obtained in a medium containing a high level of phosphate relative to nitrate, resulting in a N:P ratio much lower than commonly used media for H. pluvialis. In this medium, cells remained at the vegetative and motile stage during a prolonged period of time. Both high cell density culture and motile stage persistence was proved to be related to the N:P feature of this medium. We conclude that the macrozoid stage of H. pluvialis is favored under high-P and low-N supply and that low-cost hydroponic fertilizers can be successfully used for achieving high density cultures of vegetative cells of H. pluvialis. [less ▲]

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See detailAnalysis of Root Secreted Proteases in Arabidopsis thaliana and Nicotiana tabacum
Désiron, Carole ULg; De Lemos Esteves, Frédéric ULg; Natalis, Lucie et al

Poster (2011, June 09)

Plants are promising tools to produce complex recombinant proteins like antibodies. When host plants are grown on hydroponics, the production of recombinant proteins that are secreted by the roots ... [more ▼]

Plants are promising tools to produce complex recombinant proteins like antibodies. When host plants are grown on hydroponics, the production of recombinant proteins that are secreted by the roots ('rhizosecretion') greatly simplifies harvest and purification of the product, during whole plant life. However, proteases represent up to 10% of the naturally secreted proteins and are known to significantly decrease the yield of production by rhizosecretion. In this study, we analyzed the rhizosecreted proteases of Arabidopsis thaliana and Nicotiana tabacum. Total rhizosecreted proteins were recovered by salt extraction and the protease activity was assayed in vitro or by zymography. The relative contribution of major protease families to total activity was evaluated with specific inhibitors and revealed significant differences between the two species. The degradation capacity of the root-secreted proteases was further characterized against selected target proteins: BSA and human IgGs. [less ▲]

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See detailTranscriptomic analysis of Arabidopsis roots during floral induction by photoperiod
D'Aloia, Maria ULg; Lamoureux, Thibaut ULg; Tocquin, Pierre ULg et al

Poster (2011, June)

Contribution of the root system to the flowering process remains poorly studied. Part of the problem resides in its difficult isolation from the substrate, especially on adult plants. We used an ... [more ▼]

Contribution of the root system to the flowering process remains poorly studied. Part of the problem resides in its difficult isolation from the substrate, especially on adult plants. We used an hydroponic device that allows synchronous growth and flowering of Arabidopsis and performed global transcript profiling of roots. Samples were harvested during the extension period of a single long day (LD), and in non inductive short day. Microarray data were validated by real-time RT-PCR, and the expression patterns of selected probes were further analyzed in shoots and roots. Some of the genes that were differentially expressed in the roots during the inductive LD did not show the same variations in the shoot, indicating that root transcriptome undergoes specific changes at floral transition. These genes include, for example, GIGANTEA. T-DNA mutants from selected candidate genes are being studied. Both the expression analysis and the reverse genetic approach provide new insights into the contribution of the roots to the flowering process. [less ▲]

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See detailTranscriptomic analysis of Arabidopsis roots during flowering
D'Aloia, Maria ULg; Tocquin, Pierre ULg; Périlleux, Claire ULg

Poster (2010, February)

Contribution of the root system to the flowering process remains poorly studied. Part of the problem resides in its difficult isolation from the substrate, especially on adult plants. Taking advantage of ... [more ▼]

Contribution of the root system to the flowering process remains poorly studied. Part of the problem resides in its difficult isolation from the substrate, especially on adult plants. Taking advantage of an hydroponic device that allows synchronous growth and flowering of Arabidopsis thaliana (Tocquin et al., 2003), we performed global transcript profiling of roots during induction of flowering by a single long day (LD). Results were validated by real-time RT-PCR, and the expression patterns of selected probes were further analyzed in shoots and roots. Some of the genes that were identified in the microarray experiment were already known to be involved in the photoperiodic pathway of flowering in Arabidopsis, and hence were activated in both roots and shoots during the LD. These genes include, for example, components of light signaling or circadian machinery (e.g. GIGANTEA). Other genes providing new insights into the control of flowering at the whole plant level will be presented. Tocquin et al., (2003). BMC Plant Biology, 3: 2. [less ▲]

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See detailOptimization of the Production of the Amyloidogenic Variants of Human Lysozyme
Menzer, Linda ULg; Tocquin, Pierre ULg; Dony, Nicolas et al

Poster (2008, February 16)

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See detailVernalization-induced repression of FLOWERING LOCUS C stimulates flowering in Sinapis alba and enhances plant responsiveness to photoperiod.
D'Aloia, Maria ULg; Tocquin, Pierre ULg; Périlleux, Claire ULg

in New Phytologist (2008), 178(4), 755-65

Of the Brassicaceae, Sinapis alba has been intensively studied as a physiological model of induction of flowering by a single long day (LD), while molecular-genetic analyses of Arabidopsis thaliana have ... [more ▼]

Of the Brassicaceae, Sinapis alba has been intensively studied as a physiological model of induction of flowering by a single long day (LD), while molecular-genetic analyses of Arabidopsis thaliana have disclosed complex interactions between pathways controlling flowering in response to different environmental cues, such as photoperiod and vernalization. The vernalization process in S. alba was therefore analysed here. The coding sequence of S. alba SaFLC, which is orthologous to the A. thaliana floral repressor FLOWERING LOCUS C, was isolated and the transcript levels quantified in different conditions. Two-week-old seedlings grown in noninductive short days (SDs) were vernalized for 1-6 wk. Down-regulation of SaFLC was already marked after 1 wk of cold but 2 wk was needed for a significant acceleration of flowering. Flower buds were initiated during vernalization. When vernalization was stopped after 1 wk, repression of SaFLC was not stable but a significant increase in plant responsiveness to 16-h LDs was observed when LDs followed immediately after the cold treatment. These results suggest that vernalization does not only work when plants experience long exposure to cold during the winter: shorter cold periods might stimulate flowering of LD plants if they occur when photoperiod is increasing, such as in spring. [less ▲]

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