18 results on '"Clément, Gilles"'
Search Results
2. Carbon and nitrogen remobilization during seed filling in Arabidopsis is strongly impaired in the pyrroline-5-carboxylate dehydrogenase mutant.
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Dourmap, Corentin, Marmagne, Anne, Lebreton, Sandrine, Clément, Gilles, Guivarc'h, Anne, Savouré, Arnould, and Masclaux-Daubresse, Céline
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SEED development ,SEED yield ,SUPPLY & demand ,NITROGEN ,AMINO acids ,GERMINATION - Abstract
Proline is an amino acid that is degraded in the mitochondria by the sequential action of proline dehydrogenase (ProDH) and pyrroline-5-carboxylate dehydrogenase (P5CDH) to form glutamate. We investigated the phenotypes of Arabidopsis wild-type plants, the knockout prodh1 prodh2 double-mutant, and knockout p5cdh allelic mutants grown at low and high nitrate supplies. Surprisingly, only p5cdh presented lower seed yield and produced lighter seeds. Analyses of elements in above-ground organs revealed lower C concentrations in the p5cdh seeds. Determination of C, N, and dry matter partitioning among the above-ground organs revealed a major defect in stem-to-seed resource allocations in this mutant. Again surprisingly, defects in C, N, and biomass allocation to seeds dramatically increased in high-N conditions.
15 N-labelling consistently confirmed the defect in N remobilization from the rosette and stem to seeds in p5cdh. Consequently, the p5cdh mutants produced morphologically abnormal, C-depleted seeds that displayed very low germination rates. The most striking result was the strong amplification of the N-remobilization defects in p5cdh under high nitrate supply, and interestingly this phenotype was not observed in the prodh1 prodh 2 double-mutant irrespective of nitrate supply. This study reveals an essential role of P5CDH in carbon and nitrogen remobilization for reserve accumulation during seed development in Arabidopsis. [ABSTRACT FROM AUTHOR]- Published
- 2023
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3. Outgrowth of the axillary bud in rose is controlled by sugar metabolism and signalling.
- Author
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Wang, Ming, Pérez-Garcia, Maria-Dolores, Davière, Jean-Michel, Barbier, François, Ogé, Laurent, Gentilhomme, José, Voisine, Linda, Péron, Thomas, Launay-Avon, Alexandra, Clément, Gilles, Baumberger, Nicolas, Balzergue, Sandrine, Macherel, David, Grappin, Philippe, Bertheloot, Jessica, Achard, Patrick, Hamama, Latifa, and Sakr, Soulaiman
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METABOLIC regulation ,PENTOSE phosphate pathway ,GLYCOLYSIS ,BUDS ,ROSES ,TRICARBOXYLIC acids ,PLANT growth - Abstract
Shoot branching is a pivotal process during plant growth and development, and is antagonistically orchestrated by auxin and sugars. In contrast to extensive investigations on hormonal regulatory networks, our current knowledge on the role of sugar signalling pathways in bud outgrowth is scarce. Based on a comprehensive stepwise strategy, we investigated the role of glycolysis/the tricarboxylic acid (TCA) cycle and the oxidative pentose phosphate pathway (OPPP) in the control of bud outgrowth. We demonstrated that these pathways are necessary for bud outgrowth promotion upon plant decapitation and in response to sugar availability. They are also targets of the antagonistic crosstalk between auxin and sugar availability. The two pathways act synergistically to down-regulate the expression of BRC1 , a conserved inhibitor of shoot branching. Using Rosa calluses stably transformed with GFP-fused promoter sequences of RhBRC1 (pRhBRC1), glycolysis/TCA cycle and the OPPP were found to repress the transcriptional activity of pRhBRC1 cooperatively. Glycolysis/TCA cycle- and OPPP-dependent regulations involve the –1973/–1611 bp and –1206/–709 bp regions of pRhBRC1 , respectively. Our findings indicate that glycolysis/TCA cycle and the OPPP are integrative parts of shoot branching control and can link endogenous factors to the developmental programme of bud outgrowth, likely through two distinct mechanisms. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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4. Integrating multiple omics to identify common and specific molecular changes occurring in Arabidopsis under chronic nitrate and sulfate limitations.
- Author
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Luo, Jie, Havé, Marien, Clément, Gilles, Tellier, Frédérique, Balliau, Thierry, Launay-Avon, Alexandra, Guérard, Florence, Zivy, Michel, and Masclaux-Daubresse, Céline
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PLANT metabolism ,METABOLIC regulation ,DNA replication ,RIBOSOMAL proteins ,ARABIDOPSIS ,NITRATE reductase - Abstract
Plants have fundamental dependences on nitrogen and sulfur and frequently have to cope with chronic limitations when their supply is sub-optimal. This study aimed at characterizing the metabolomic, proteomic, and transcriptomic changes occurring in Arabidopsis leaves under chronic nitrate (Low-N) and chronic sulfate (Low-S) limitations in order to compare their effects, determine interconnections, and examine strategies of adaptation. Metabolite profiling globally revealed opposite effects of Low-S and Low-N on carbohydrate and amino acid accumulations, whilst proteomic data showed that both treatments resulted in increases in catabolic processes, stimulation of mitochondrial and cytosolic metabolism, and decreases in chloroplast metabolism. Lower abundances of ribosomal proteins and translation factors under Low-N and Low-S corresponded with growth limitation. At the transcript level, the major and specific effect of Low-N was the enhancement of expression of defence and immunity genes. The main effect of chronic Low-S was a decrease in transcripts of genes involved in cell division, DNA replication, and cytoskeleton, and an increase in the expression of autophagy genes. This was consistent with a role of target-of-rapamycin kinase in the control of plant metabolism and cell growth and division under chronic Low-S. In addition, Low-S decreased the expression of several NLP transcription factors, which are master actors in nitrate sensing. Finally, both the transcriptome and proteome data indicated that Low-S repressed glucosinolate synthesis, and that Low-N exacerbated glucosinolate degradation. This showed the importance of glucosinolate as buffering molecules for N and S management. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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5. Responses of mature symbiotic nodules to the whole-plant systemic nitrogen signaling.
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Lambert, Ilana, Pervent, Marjorie, Queré, Antoine Le, Clément, Gilles, Tauzin, Marc, Severac, Dany, Benezech, Claire, Tillard, Pascal, Martin-Magniette, Marie-Laure, Colella, Stefano, and Lepetit, Marc
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LEGUMES ,PLANT capacity ,ROOT-tubercles ,SUGAR ,MEDICAGO truncatula ,PLANT defenses ,NITROGEN - Abstract
In symbiotic root nodules of legumes, terminally differentiated rhizobia fix atmospheric N
2 producing an NH4 + influx that is assimilated by the plant. The plant, in return, provides photosynthates that fuel the symbiotic nitrogen acquisition. Mechanisms responsible for the adjustment of the symbiotic capacity to the plant N demand remain poorly understood. We have investigated the role of systemic signaling of whole-plant N demand on the mature N2 -fixing nodules of the model symbiotic association Medicago truncatula / Sinorhizobium using split-root systems. The whole-plant N-satiety signaling rapidly triggers reductions of both N2 fixation and allocation of sugars to the nodule. These responses are associated with the induction of nodule senescence and the activation of plant defenses against microbes, as well as variations in sugars transport and nodule metabolism. The whole-plant N-deficit responses mirror these changes: a rapid increase of sucrose allocation in response to N-deficit is associated with a stimulation of nodule functioning and development resulting in nodule expansion in the long term. Physiological, transcriptomic, and metabolomic data together provide evidence for strong integration of symbiotic nodules into whole-plant nitrogen demand by systemic signaling and suggest roles for sugar allocation and hormones in the signaling mechanisms. [ABSTRACT FROM AUTHOR]- Published
- 2020
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6. Proline oxidation fuels mitochondrial respiration during dark-induced leaf senescence in Arabidopsis thaliana.
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Launay, Alban, Cabassa-Hourton, Cécile, Eubel, Holger, Maldiney, Régis, Guivarc'h, Anne, Crilat, Emilie, Planchais, Séverine, Lacoste, Jérôme, Bordenave-Jacquemin, Marianne, Clément, Gilles, Richard, Luc, Carol, Pierre, Braun, Hans-Peter, Lebreton, Sandrine, and Savouré, Arnould
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AMINO acid metabolism ,ARABIDOPSIS thaliana ,PROLINE ,KREBS cycle ,LEAF aging ,PLANT mitochondria ,RESPIRATION in plants ,APOPTOSIS - Abstract
Leaf senescence is a form of developmentally programmed cell death that allows the remobilization of nutrients and cellular materials from leaves to sink tissues and organs. Among the catabolic reactions that occur upon senescence, little is known about the role of proline catabolism. In this study, the involvement in dark-induced senescence of proline dehydrogenases (ProDHs), which catalyse the first and rate-limiting step of proline oxidation in mitochondria, was investigated using prodh single- and double-mutants with the help of biochemical, proteomic, and metabolomic approaches. The presence of ProDH2 in mitochondria was confirmed by mass spectrometry and immunogold labelling in dark-induced leaves of Arabidopsis. The prodh1 prodh2 mutant exhibited enhanced levels of most tricarboxylic acid cycle intermediates and free amino acids, demonstrating a role of ProDH in mitochondrial metabolism. We also found evidence of the involvement and the importance of ProDH in respiration, with proline as an alternative substrate, and in remobilization of proline during senescence to generate glutamate and energy that can then be exported to sink tissues and organs. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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7. Multi-omics Analysis Reveals Sequential Roles for ABA during Seed Maturation.
- Author
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Chauffour, Frédéric, Bailly, Marlène, Perreau, François, Cueff, Gwendal, Suzuki, Hiromi, Collet, Boris, Frey, Anne, Clément, Gilles, Soubigou-Taconnat, Ludivine, Balliau, Thierry, Krieger-Liszkay, Anja, Rajjou, Loïc, and Marion-Poll, Annie
- Published
- 2019
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8. Metabolomics of laminae and midvein during leaf senescence and source-sink metabolite management in Brassica napus L. leaves.
- Author
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Clément, Gilles, Moison, Michaël, Soulay, Fabienne, Reisdorf-Cren, Michèle, and Masclaux-Daubresse, Céline
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PLANT growth , *RUTABAGA , *PLANT physiology , *PHOTOSYNTHESIS , *ARABIDOPSIS , *METABOLOMICS - Abstract
Leaf senescence is a long developmental process important for nutrient management and for source to sink remobilization. Constituents of the mesophyll cells are progressively degraded to provide nutrients to the rest of the plant. Up to now, studies on leaf senescence have not paid much attention to the role of the different leaf tissues. In the present study, we dissected leaf laminae from the midvein to perform metabolite profiling. The laminae mesophyll cells are the source of nutrients, and in C3 plants they contain Rubisco as the most important nitrogen storage pool. Veins, rich in vasculature, are the place where all the nutrients are translocated, and sometimes interconverted, before being exported through the phloem or the xylem. The different metabolic changes we observed in laminae and midvein with ageing support the idea that the senescence programme in these two tissues is different. Important accumulations of metabolites in the midvein suggest that nutrient translocations from source leaves to sinks are mainly controlled at this level. Carbon and nitrogen long-distance molecules such as fructose, glucose, aspartate, and asparagine were more abundant in the midvein than in laminae. In contrast, sucrose, glutamate, and aspartate were more abundant in laminae. The concentrations of tricarboxylic acid (TCA) compounds were also lower in the midvein than in laminae. Since nitrogen remobilization increased under low nitrate supply, plants were grown under two nitrate concentrations. The results revealed that the senescence-related differences were mostly similar under low and high nitrate conditions except for some pathways such as the TCA cycle. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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9. Resolving the Role of Plant NAD-Glutamate Dehydrogenase: III. Overexpressing Individually or Simultaneously the Two Enzyme Subunits Under Salt Stress Induces Changes in the Leaf Metabolic Profile and Increases Plant Biomass Production.
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Tercé-Laforgue, Thérèse, Clément, Gilles, Marchi, Laura, Restivo, Francesco M., Lea, Peter J., and Hirel, Bertrand
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GLUTAMATE dehydrogenase , *OXIDOREDUCTASES , *PLANT biomass , *PLANT enzymes , *PLANT proteins - Abstract
NAD-dependent glutamate dehydrogenase (NAD-GDH) of higher plants has a central position at the interface between carbon and nitrogen metabolism due to its ability to carry out the deamination of glutamate. In order to obtain a better understanding of the physiological function of NAD-GDH under salt stress conditions, transgenic tobacco (Nicotiana tabacum L.) plants that overexpress two genes from Nicotiana plumbaginifolia individually (GDHA and GDHB) or simultaneously (GDHA/B) were grown in the presence of 50 mM NaCl. In the different GDH overexpressors, the NaCl treatment induced an additional increase in GDH enzyme activity, indicating that a post-transcriptional mechanism regulates the final enzyme activity under salt stress conditions. A greater shoot and root biomass production was observed in the three types of GDH overexpressors following growth in 50 mM NaCl, when compared with the untransformed plants subjected to the same salinity stress. Changes in metabolites representative of the plant carbon and nitrogen status were also observed. They were mainly characterized by an increased amount of starch present in the leaves of the GDH overexpressors as compared with the wild type when plants were grown in 50mM NaCl. Metabolomic analysis revealed that overexpressing the two genes GDHA and GDHB, individually or simultaneously, induced a differential accumulation of several carbon- and nitrogen-containing molecules involved in a variety of metabolic, developmental and stress-responsive processes. An accumulation of digalactosylglycerol, erythronate and porphyrin was found in the GDHA, GDHB and GDHA/B overexpressors, suggesting that these molecules could contribute to the improved performance of the transgenic plants under salinity stress conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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10. Assessing the Metabolic Impact of Nitrogen Availability Using a Compartmentalized Maize Leaf Genome-Scale Model.
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Simons, Margaret, Saha, Rajib, Amiour, Nardjis, Kumar, Akhil, Guillard, Lenaïg, Clément, Gilles, Miquel, Martine, Zhenni Li, Mouille, Gregory, Lea, Peter J., Hirel, Bertrand, and Maranas, Costas D.
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EFFECT of nitrogen on plants ,CORN genetics ,PLANT genomes ,CARBON fixation ,MESOPHYLL tissue - Abstract
Maize (Zea mays) is an important C
4 plant due to its widespread use as a cereal and energy crop. A second-generation genome-scale metabolic model for the maize leaf was created to capture C4 carbon fixation and investigate nitrogen (N) assimilation by modeling the interactions between the bundle sheath and mesophyll cells. The model contains gene-protein-reaction relationships, elemental and charge-balanced reactions, and incorporates experimental evidence pertaining to the biomass composition, compartmentalization, and flux constraints. Condition-specific biomass descriptions were introduced that account for amino acids, fatty acids, soluble sugars, proteins, chlorophyll, lignocellulose, and nucleic acids as experimentally measured biomass constituents. Compartmentalization of the model is based on proteomic/transcriptomic data and literature evidence. With the incorporation of information from the MetaCrop and MaizeCyc databases, this updated model spans 5,824 genes, 8,525 reactions, and 9,153 metabolites, an increase of approximately 4 times the size of the earlier iRS1563 model. Transcriptomic and proteomic data have also been used to introduce regulatory constraints in the model to simulate an N-limited condition and mutants deficient in glutamine synthetase, gln1-3 and gln1-4. Model-predicted results achieved 90% accuracy when comparing the wild type grown under an N-complete condition with the wild type grown under an N-deficient condition. [ABSTRACT FROM AUTHOR]- Published
- 2014
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11. Nitrogen-use efficiency in maize (Zea mays L.): from ‘omics’ studies to metabolic modelling.
- Author
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Simons, Margaret, Saha, Rajib, Guillard, Lenaïg, Clément, Gilles, Armengaud, Patrick, Cañas, Rafael, Maranas, Costas D., Lea, Peter J., and Hirel, Bertrand
- Abstract
Improving nitrogen-use efficiency in crops requires integrating information from multiple sources and techniques. This review highlights recent nitrogen regulation findings inferred from ‘omics’ data and predictions from metabolic models.In this review, we will present the latest developments in systems biology with particular emphasis on improving nitrogen-use efficiency (NUE) in crops such as maize and demonstrating the application of metabolic models. The review highlights the importance of improving NUE in crops and provides an overview of the transcriptome, proteome, and metabolome datasets available, focusing on a comprehensive understanding of nitrogen regulation. ‘Omics’ data are hard to interpret in the absence of metabolic flux information within genome-scale models. These models, when integrated with ‘omics’ data, can serve as a basis for generating predictions that focus and guide further experimental studies. By simulating different nitrogen (N) conditions at a pseudo-steady state, the reactions affecting NUE and additional gene regulations can be determined. Such models thus provide a framework for improving our understanding of the metabolic processes underlying the more efficient use of N-based fertilizers. [ABSTRACT FROM PUBLISHER]
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- 2014
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12. Nitrogen metabolism meets phytopathology.
- Author
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Fagard, Mathilde, Launay, Alban, Clément, Gilles, Courtial, Julia, Dellagi, Alia, Farjad, Mahsa, Krapp, Anne, Soulié, Marie-Christine, and Masclaux-Daubresse, Céline
- Abstract
Nitrogen fertilizers, essential for plant growth, affect disease severity through an impact on both pathogen virulence and plant defence, linking plant nitrogen metabolism and disease infection processes.Nitrogen (N) is essential for life and is a major limiting factor of plant growth. Because soils frequently lack sufficient N, large quantities of inorganic N fertilizers are added to soils for crop production. However, nitrate, urea, and ammonium are a major source of global pollution, because much of the N that is not taken up by plants enters streams, groundwater, and lakes, where it affects algal production and causes an imbalance in aquatic food webs. Many agronomical data indicate that the higher use of N fertilizers during the green revolution had an impact on the incidence of crop diseases. In contrast, examples in which a decrease in N fertilization increases disease severity are also reported, indicating that there is a complex relationship linking N uptake and metabolism and the disease infection processes. Thus, although it is clear that N availability affects disease, the underlying mechanisms remain unclear. The aim of this review is to describe current knowledge of the mechanisms that link plant N status to the plant’s response to pathogen infection and to the virulence and nutritional status of phytopathogens. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
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13. Stitching together the Multiple Dimensions of Autophagy Using Metabolomics and Transcriptomics Reveals Impacts on Metabolism, Development, and Plant Responses to the Environment in Arabidopsis.
- Author
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Masclaux-Daubresse, Céline, Clément, Gilles, Anne, Pauline, Routaboul, Jean-Marc, Guiboileau, Anne, Soulay, Fabienne, Shirasu, Ken, and Yoshimoto, Kohki
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TRANSCRIPTOMES , *ANTHOCYANINS , *AUTOPHAGY , *TRANSCRIPTION factors , *METABOLOMICS , *FLAVONOIDS , *IMMUNOSENESCENCE , *METABOLISM - Abstract
Autophagy is a fundamental process in the plant life story, playing a key role in immunity, senescence, nutrient recycling, and adaptation to the environment. Transcriptomics and metabolomics of the rosette leaves of Arabidopsis thaliana autophagy mutants (atg) show that autophagy is essential for cell homeostasis and stress responses and that several metabolic pathways are affected. Depletion of hexoses, quercetins, and anthocyanins parallel the overaccumulation of several amino acids and related compounds, such as glutamate, methionine, glutathione, pipecolate, and 2-aminoadipate. Transcriptomic data show that the pathways for glutathione, methionine, raffinose, galacturonate, and anthocyanin are perturbed. Anthocyanin depletion in atg mutants, which was previously reported as a possible defect in flavonoid trafficking to the vacuole, appears due to the downregulation of the master genes encoding the enzymes and regulatory proteins involved in flavonoid biosynthesis. Overexpression of the PRODUCTION OF ANTHOCYANIN PIGMENT1 transcription factor restores anthocyanin accumulation in vacuoles of atg mutants. Transcriptome analyses reveal connections between autophagy and (1) salicylic acid biosynthesis and response, (2) cytokinin perception, (3) oxidative stress and plant defense, and possible interactions between autophagy and the COP9 signalosome machinery. The metabolic and transcriptomic signatures identified for the autophagy mutants are discussed and show consistencies with the observed phenotypes. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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14. Increased Expression of a Phloem Membrane Protein Encoded by NHL26 Alters Phloem Export and Sugar Partitioning in Arabidopsis.
- Author
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Vilaine, Françoise, Kerchev, Pavel, Clément, Gilles, Batailler, Brigitte, Cayla, Thibaud, Bill, Laurence, Gissot, Lionel, and Dinant, Sylvie
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MEMBRANE proteins ,PHLOEM ,PLANT exudates ,SUGAR ,ORGANIC acids - Abstract
The complex process of phloem sugar transport involves symplasmic and apoplasmic events. We characterized Arabidopsis thaliana lines ectopically expressing a phloem-specific gene encoding NDR1/HIN1-like26 (NHL26), a putative membrane protein. NHL26 overexpressor plants grew more slowly than wild-type plants, accumulated high levels of carbohydrates in mature leaves, and had a higher shoot biomass, contrasting with slower root growth and a lower seed yield. Similar effects were observed when NHL26 was overexpressed in companion cells, under the control of a companion cell–specific promoter. The soluble sugar content of the phloem sap and sink organs was lower than that in the wild type, providing evidence of a sugar export defect. This was confirmed in a phloem-export assay with the symplastic tracer carboxyfluorescein diacetate. Leaf sugar accumulation was accompanied by higher organic acid, amino acid, and protein contents, whereas analysis of the metabolite profile of phloem sap exudate revealed no change in amino acid or organic acid content, indicating a specific effect on sugar export. NHL26 was found to be located in the phloem plasmodesmata and the endoplasmic reticulum. These findings reveal that NHL26 accumulation affects either the permeability of plasmodesmata or sugar signaling in companion cells, with a specific effect on sugar export. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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15. The use of metabolomics integrated with transcriptomic and proteomic studies for identifying key steps involved in the control of nitrogen metabolism in crops such as maize.
- Author
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Amiour, Nardjis, Imbaud, Sandrine, Clément, Gilles, Agier, Nicolas, Zivy, Michel, Valot, Benoît, Balliau, Thierry, Armengaud, Patrick, Quilleré, Isabelle, Cañas, Rafael, Tercet-Laforgue, Thérèse, and Hirel, Bertrand
- Abstract
Linking plant phenotype to gene and protein expression and also to metabolite synthesis and accumulation is one of the main challenges for improving agricultural production worldwide. Such a challenge is particularly relevant to crop nitrogen use efficiency (NUE). Here, the differences in leaf gene transcript, protein, and metabolite accumulation in maize subjected to long-term nitrogen (N)-deficient growth conditions at two important stages of plant development have been studied. The impact of N deficiency was examined at the transcriptomic, proteomic, and metabolomic levels. It was found that a number of key plant biological functions were either up- or down-regulated when N was limiting, including major alterations to photosynthesis, carbon (C) metabolism, and, to a lesser extent, downstream metabolic pathways. It was also found that the impact of the N deficiency stress resembled the response of plants to a number of other biotic and abiotic stresses, in terms of transcript, protein, and metabolite accumulation. The genetic and metabolic alterations were different during the N assimilation and the grain-filling period, indicating that plant development is an important component for identifying the key elements involved in the control of plant NUE. It was also found that integration of the three ‘omics’ studies is not straightforward, since different levels of regulation seem to occur in a stepwise manner from gene expression to metabolite accumulation. The potential use of these ‘omics’ studies is discussed with a view to improve our understanding of whole plant nitrogen economics, which should have applications in breeding and agronomy. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
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16. Characterization of a NADH-Dependent Glutamate Dehydrogenase Mutant of Arabidopsis Demonstrates the Key Role of this Enzyme in Root Carbon and Nitrogen Metabolism.
- Author
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Fontaine, Jean-Xavier, Tercé-Laforgue, Thérèse, Armengaud, Patrick, Clément, Gilles, Renou, Jean-Pierre, Pelletier, Sandra, Catterou, Manuella, Azzopardi, Marianne, Gibon, Yves, Lea, Peter J., Hirel, Bertrand, and Dubois, Frédéric
- Subjects
GLUTAMATE dehydrogenase ,CARBON metabolism ,KREBS cycle ,NAD (Coenzyme) ,BUTYRATES ,METABOLISM ,ENZYMES ,ARABIDOPSIS - Abstract
The role of NADH-dependent glutamate dehydrogenase (GDH) was investigated by studying the physiological impact of a complete lack of enzyme activity in an Arabidopsis thaliana plant deficient in three genes encoding the enzyme. This study was conducted following the discovery that a third GDH gene is expressed in the mitochondria of the root companion cells, where all three active GDH enzyme proteins were shown to be present. A gdh1-2-3 triple mutant was constructed and exhibited major differences from the wild type in gene transcription and metabolite concentrations, and these differences appeared to originate in the roots. By placing the gdh triple mutant under continuous darkness for several days and comparing it to the wild type, the evidence strongly suggested that the main physiological function of NADH- GDH is to provide 2-oxoglutarate for the tricarboxylic acid cycle. The differences in key metabolites of the tricarboxylic acid cycle in the triple mutant versus the wild type indicated that, through metabolic processes operating mainly in roots, there was a strong impact on amino acid accumulation, in particular alanine, γ-aminobutyrate, and aspartate in both roots and leaves. These results are discussed in relation to the possible signaling and physiological functions of the enzyme at the interface of carbon and nitrogen metabolism. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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17. Mutations in the Arabidopsis Homolog of LST8/GβL, a Partner of the Target of Rapamycin Kinase, Impair Plant Growth, Flowering, and Metabolic Adaptation to Long Days.
- Author
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Moreau, Manon, Azzopardi, Marianne, Clément, Gilles, Dobrenel, Thomas, Marchive, Chloé, Renne, Charlotte, Martin-Magniette, Marie-Laure, Taconnat, Ludivine, Renou, Jean-Pierre, Robaglia, Christophe, and Meyer, Christian
- Subjects
GLUTAMINE synthetase ,RNA interference ,PLANT growth ,SMALL interfering RNA ,AMINO acid synthesis ,NITRATE reductase ,RAPAMYCIN ,G protein coupled receptors - Abstract
The conserved Target of Rapamycin (TOR) kinase forms high molecular mass complexes and is a major regulator of cellular adaptations to environmental cues. The Lethal with Sec Thirteen 8/G protein β subunit-like (LST8/GβL) protein is a member of the TOR complexes, and two putative LST8 genes are present in Arabidopsis thaliana , of which only one (LST8-1) is significantly expressed. The Arabidopsis LST8-1 protein is able to complement yeast lst8 mutations and interacts with the TOR kinase. Mutations in the LST8-1 gene resulted in reduced vegetative growth and apical dominance with abnormal development of flowers. Mutant plants were also highly sensitive to long days and accumulated, like TOR RNA interference lines, higher amounts of starch and amino acids, including proline and glutamine, while showing reduced concentrations of inositol and raffinose. Accordingly, transcriptomic and enzymatic analyses revealed a higher expression of genes involved in nitrate assimilation when lst8-1 mutants were shifted to long days. The transcriptome of lst8-1 mutants in long days was found to share similarities with that of a myo-inositol 1 phosphate synthase mutant that is also sensitive to the extension of the light period. It thus appears that the LST8-1 protein has an important role in regulating amino acid accumulation and the synthesis of myo-inositol and raffinose during plant adaptation to long days. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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18. Peptide mass-assisted antibody cloning strategy for accurate characterization of potential therapeutic monoclonal antibodies against neurodegenerative diseases.
- Author
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Essono, Sosthene, Clément, Gilles, Padiolleau-Lefevre, Severine, Créminon, Christophe, Grassi, Jacques, and Boquet, Didier
- Subjects
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PEPTIDES , *IMMUNOGLOBULINS , *CLONING , *THERAPEUTIC use of monoclonal antibodies , *NEURODEGENERATION - Abstract
The development of therapeutic recombinant antibodies involves accurate characterization of immunoglobulin variable light (VL) and heavy (VH) chains. However, it has been reported that the use of subgroup or isotype-specific primers for the amplification of monoclonal antibody (mAb) variable domains introduces heterogeneities within the variable domains, or amplifies aberrant productive Ig domains. To address these issues, we have combined the rapid amplification of cDNA ends PCR (RACE-PCR) for the full-length VL and VH amplification, with peptide mass fingerprinting of the corresponding Ig chain. Using this strategy, we amplified full-length cDNA chains of SAF34 and SAF32, two potential therapeutic mAbs against neurodegenerative diseases directed to the prion protein (PrP). We report an unambiguous correlation between hybridoma cDNA sequences and protein fingerprints of the variable domains of each mAb, indicating the discrimination between mutated, pseudo-genes and functional Ig genes. As a proof of principle for this dual strategy of full-length PCR amplification of variable domains and their characterization by MALDI-TOF, we show that the corresponding scFvs recognize the native PrP and retain full capacity to bind to human PrP, as does the parental mAb. This finding addresses the need for reliable light and heavy chain characterization, a key factor for humanization of mouse antibodies and for its use in passive immunotherapy applications. [ABSTRACT FROM PUBLISHER]
- Published
- 2010
- Full Text
- View/download PDF
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