Papers by Arnould Savouré
Biologie Aujourd'hui, 2010
Plant molecular biology reporter, Feb 12, 2024
Journal of Experimental Botany
Proline dehydrogenase (ProDH) and pyrroline-5-carboxylate (P5C) dehydrogenase (P5CDH) catalyse th... more Proline dehydrogenase (ProDH) and pyrroline-5-carboxylate (P5C) dehydrogenase (P5CDH) catalyse the oxidation of proline into glutamate via the intermediates P5C and glutamate-semialdehyde (GSA), which spontaneously interconvert. P5C and GSA are also intermediates in the production of glutamate from ornithine and α-ketoglutarate catalysed by ornithine δ-aminotransferase (OAT). ProDH and P5CDH form a fused bifunctional PutA enzyme in Gram-negative bacteria and are associated in a bifunctional substrate-channelling complex in Thermus thermophilus; however, the physical proximity of ProDH and P5CDH in eukaryotes has not been described. Here, we report evidence of physical proximity and interactions between Arabidopsis ProDH, P5CDH, and OAT in the mitochondria of plants during dark-induced leaf senescence when all three enzymes are expressed. Pairwise interactions and localization of the three enzymes were investigated using bimolecular fluorescence complementation with confocal microsco...
Comptes Rendus Biologies, Jun 1, 2008
The interaction between soil drying and salinity was studied in the perennial halophyte, Sesuvium... more The interaction between soil drying and salinity was studied in the perennial halophyte, Sesuvium portulacastrum. Rooted cuttings were individually cultivated for three months in silty-sandy soil under two irrigation modes: 100 and 25% of field capacity (FC). The amount of the evapotranspirated water was replaced by a nutrient solution containing either 0 or 100 mM NaCl. Wholeplant growth, leaf water content, leaf water potential (Ψ w), and Na + , K + , and proline concentrations in the tissues were measured. When individually applied, both drought and salinity significantly restricted whole-plant growth, with a more marked effect of the former stress. However, the effects of the two stresses were not additive on whole-plant biomass or on leaf expansion. Root growth was more sensitive to salt than to soil drying, the latter being even magnified by the adverse impact of salinity. Leaf water content was significantly reduced following exposure to water-deficit stress, but was less affected in salt-treated plants. When simultaneously submitted to water-deficit stress and salinity, plants displayed higher values of water and potassium use efficiencies, leaf proline and Na + concentrations, associated with lower leaf water potential (−1.87 MPa), suggesting the ability of S. portulacastrum to use Na + and proline for osmotic adjustment. To cite this article: I.
Science of The Total Environment, 2023
Biologie Aujourd'hui, 2012
Reçu le 9 octobre 2012 Résumé-Outre son rôle dans le métabolisme primaire en tant que constituant... more Reçu le 9 octobre 2012 Résumé-Outre son rôle dans le métabolisme primaire en tant que constituant des protéines, la proline est l'un des solutés compatibles le plus fréquemment accumulé en réponseà des contraintes environnementales variées et joue un rôle important dans la tolérance des plantes. La proline aété proposée comme stabilisateur de protéines et de complexes macromoléculaires, piégeur de radicaux libres et régulateur du potentiel redox cellulaire. La concentration intracellulaire de la proline dépend d'une régulation fine entre sa biosynthèse et sa dégradation. Cependant le rôle exact de la proline et les voies de signalisation impliquées dans la régulation de son métabolisme ne sont pas encore complètementélucidés. L'étude du métabolisme de la proline chez les plantes modèles permettrait d'acquérir des informations quant aux mécanismes différentiels mis en oeuvre par les plantes pour faire face aux contraintes environnementales et d'établir des outils pertinents pouvantêtre utilisés dans l'amélioration des plantes cultivées. Mots clés : Contraintes environnementales / plantes / métabolisme de la proline / adaptation des plantes / signalisation cellulaire Abstract-Proline, a multifunctional amino-acid involved in plant adaptation to environmental constraints. In addition to its role in primary metabolism as a component of proteins, proline is one of the most widely distributed compatible solutes that accumulates in plants during adverse environmental constraints and plays an important role in plant stress tolerance. Proline was proposed to act as stabilizer for proteins and macromolecular complexes, scavenger of free radicals and regulator of cellular redox potential. Intracellular proline concentration depends on a tight regulation between its biosynthesis and catabolism. However the exact role of proline and the signaling pathways involved in the regulation of its metabolism are not completely known yet. Investigation of proline metabolism in model plants would allow to acquire information about the diversity of the mechanisms developed by plants to overcome environmental constraints and to establish some reliable tools for the improvement of crop tolerance.
Biologie Aujourd'hui, 2010
-Les plantes, organismes fixés, ont développé la capacité de détecter les variations de leur envi... more -Les plantes, organismes fixés, ont développé la capacité de détecter les variations de leur environnement. Cette propriété est liéeà la perception de ces signaux età leur transduction par des voies de signalisation pour les traduire en une réponse adaptative. Parmi ces voies, la signalisation lipidique joue un rôle considérable chez les végétaux, avec en particulier l'acide phosphatidique (PA) comme acteur clé. Ce second messager peutêtre synthétisé via deux voies impliquant soit des phospholipases D (PLD), soit des phospholipases C (PLC) et des diacylglycérol kinases (DAGK). La variation des niveaux de PA peutêtre modulée par sa conversion en diacylglycérolpyrophosphate (DGPP) par les PA kinases (PAK). Les PLCs,à travers la formation d'IP3 ou de ses dérivés, sont impliquées dans les variations des teneurs en Ca 2+ intracellulaire, autre second messager essentiel de la signalisation cellulaire. Les phosphoinositides, comme le PI3P, le PI4P et le PI(4,5)P2, sontégalement deś eléments importants de la signalisation lipidique. Ils sontà la fois les substrats des PLCs et des PLDs et des seconds messagers. Dans cet article nous nous sommes attachésà présenter l'état des connaissances sur ces voies de signalisation lipidique en mettant l'accent sur les spécificités de ces voies chez les végétaux par rapport aux autres règnes vivants. Mots clés : Acide phosphatidique / Arabidopsis thaliana / contraintes hydriques / phosphoinositides / phospholipases / signalisation lipidique Abstract-Lipid signaling pathways in plants and their roles in response to water constraints. Plants are sessile organisms that have developed the capacity to detect slight variations of their environment. They are able to perceive these environmental signals and to transduce them by signaling pathways in order to trigger adaptative responses. Lipid signaling elements play a central role in these pathways in plants. A key element is phosphatidic acid (PA), which can be produced by two pathways. In the first one, phospholipids are hydrolysed by phospholipase D (PLD) to release PA. In the second one, PA is produced through the activity of phospholipase C (PLC) to produce diacylglycerol (DAG) which is then phosphorylated by DAG kinase (DAGK). The amount of PA in the cell is regulated by PA kinase, which phosphorylates PA to produce diacylglycerolpyrophosphate (DGPP), considered as a second messenger as well. PLCs play a dual role in cell signaling by regulating the amount of intracellular Ca 2+ , another essential second messenger. Phosphoinositides, such as PI3P, PI4P and PI(4,5)P2, are substrates of PLCs and PLDs and are considered as second messengers also. In this review, we present recent data regarding the specific features of these lipid signaling pathways in plant compared with other eukaryotes.
Plant Physiology and Biochemistry, 1990
Les endoproteases, ayant l'azocoll pour substrat, ont ete extraites d'aiguilles de Picea ... more Les endoproteases, ayant l'azocoll pour substrat, ont ete extraites d'aiguilles de Picea abies, et partiellement purifiees. Six formes enzymatiques principales ont ete separees sur la base du point isoelectrique. Elles peuvent etre classees en deux groupes de masse moleculaire differente et de sensibilite differente a plusieurs inhibiteurs. La composition isozymique des endoproteases est modifiee de facon irreversible pendant l'assechement, en presence ou absence de pollution; elle devient semblable a celle presente dans les aiguilles âgees
Springer eBooks, 1993
We have shown that R. meliloti cells induced for their nod genes excrete a family of structurally... more We have shown that R. meliloti cells induced for their nod genes excrete a family of structurally related lipo-oligosaccharides, the Nod factors. These molecules evoke root hair deformation, cortical cell division, nodule induction and expression of an early nodulin gene, Nms-8b, to different extents. Using various approaches we have demonstrated that the NodRmIV(S) factor can act as plant growth regulator not only on Medicago root cells but also on cells grown in suspension. The factor was shown to stimulate the cell cycle; increased transition of cells from G1 to G2 phase was observed. In addition, perturbation of the hormonal balance in the plant cells was found to affect nodulation drastically, suggesting that the Nod factors may act in conjunction or via plant hormones to reprogram cells for nodule organogenesis.
Plant Molecular Biology, 1993
In a search for plant genes expressed during early symbiotic interactions between Medicago sativa... more In a search for plant genes expressed during early symbiotic interactions between Medicago sativa and Rhizobium meliloti, we have isolated and characterized two alfalfa genes which have strong sequence similarity to members of the Enodl2 gene family of Pisum sativum. The M. sativa genes, MsEnodl2A and B, encode putative protein products of 8066 Da and 12849 Da, respectively, each with a signal sequence at the N-terminus followed by a repetitive proline-rich region. Based on their expression during the initial period of nodule development, MsEnodl2A and B are alfalfa early nodulin genes.
Journal of Experimental Botany, Dec 18, 2022
Proline is an amino acid that is degraded in the mitochondria by the sequential action of proline... more 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. 15N-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 prodh2 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.
Functional Plant Biology, 2016
Nitric oxide (NO)an endogenous signalling molecule in plants and animalsmediates responses to bio... more Nitric oxide (NO)an endogenous signalling molecule in plants and animalsmediates responses to biotic and abiotic stresses. In the present study, we examined the role of exogenous application of NO in mediating stress responses in Cakile maritima Scop. seedlings under water deficit stress using sodium nitroprusside (SNP) as NO donor and as a pretreatment before the application of stress. Water deficit stress was applied by withholding water for 14 days. Growth, leaf water content (LWC), osmotic potential (ys), chlorophyll, malondialdehyde (MDA), electrolyte leakage (EL), proline and D 1-pyrroline-5-carboxylate synthetase (P5CS) and proline dehydrogenase (ProDH) protein levels were determined. Enzyme activities involved in antioxidant activities (superoxide dismutase (SOD) and catalase (CAT)) were measured upon withholding water. The results showed that shoot biomass production was significantly decreased in plants subjected to water deficit stress alone. However, in water deficit stressed plants pre-treated with SNP, growth activity was improved and proline accumulation was significantly increased. Proline accumulation was concomitant with the stimulation of its biosynthesis as shown by the accumulation of P5CS proteins. Nevertheless, no significant change in ProDH protein levels was observed. Besides plants showed lower water deficit-induced lipid membrane degradation and oxidative stress after the pretreatment with 100 mM SNP. This behaviour was related to the increased activity of SOD and CAT. Thus, we concluded that NO increased C. maritima drought tolerance and mitigated damage associated with water deficit stress by the regulation of proline metabolism and the reduction of oxidative damage.
Frontiers in Plant Science, Jan 12, 2015
Scholarly Research Exchange, 2008
The Arabidopsis genome contains 20 MPK, 10 MKK, 60 MAP3K, and 10 MAP4K genes, but the functions o... more The Arabidopsis genome contains 20 MPK, 10 MKK, 60 MAP3K, and 10 MAP4K genes, but the functions of the corresponding proteins are still poorly characterized. To research possible functional MAP kinase modules involved in water stress signalling, original macroarrays were developed for their sensitivity and specificity. The expression patterns of the MPK and MKK gene families, as well as selected key members of the MAP3K and MAP4K families, were studied in relation to organ specificity and to various water stresses. Several kinases of the scarcely studied MPK group containing a TDY activation motif were induced by water stresses. There are four different MPKs (MPK9, MPK11, MPK17, and MPK18), among which three contain the TDY activation motif, and MKK9 and MAP3K6 are induced at the transcriptional level by dehydration, salinity, and hyperosmolarity treatments. They probably constitute MAP kinase key elements involved in water stress signalling.
Journal of Soil Science and Plant Nutrition
South African Journal of Botany
Journal of Plant Growth Regulation, Sep 22, 2022
Rapid synchronized seed germination is desirable to ensure seedling establishment and improve cro... more Rapid synchronized seed germination is desirable to ensure seedling establishment and improve crop yield. However, abiotic stresses from drought, salinity, and heavy metals have a negative impact on seed germination. The application of silicon (Si) has emerged as a promising approach for improving seed germination, especially under unfavorable conditions. However, the mechanisms of Si action have not been systematically studied in germinating seeds under conditions of abiotic stress. Considering the potential importance of sustainable agriculture, here we review recent findings of how seeds of numerous species, including several important crops, respond to Si treatment under abiotic stress. Exogenous Si has multiple effects on embryo viability, reserve mobilization, hormone/enzyme activity, membrane integrity, antioxidant metabolism, and regulation of gene expression in seed germination.
� Background and Aims Osmolytes are low-molecular-weight organic solutes, a broad group that enco... more � Background and Aims Osmolytes are low-molecular-weight organic solutes, a broad group that encompasses a variety of compounds such as amino acids, tertiary sulphonium and quaternary ammonium compounds, sugars and polyhydric alcohols. Osmolytes are accumulated in the cytoplasm of halophytic species in order to balance the os- motic potential of the Na þ and Claccumulated in the vacuole. The advantages of the accumulation of osmolytes are that they keep the main physiological functions of the cell active, the induction of their biosynthesis is controlled by environmental cues, and they can be synthesized at all developmental stages. In addition to their role in osmoreg- ulation, osmolytes have crucial functions in protecting subcellular structures and in scavenging reactive oxygen species. � Scope This review discusses the diversity of osmolytes among halophytes and their distribution within taxonomic groups, the intrinsic and extrinsic factors that influence their accumulation, and...
Silicon, 2021
Silicon (Si) is a ubiquitous element and the second most abundant after oxygen in the Earth’s cru... more Silicon (Si) is a ubiquitous element and the second most abundant after oxygen in the Earth’s crust. Although silicon is not yet listed among the essential nutrients for higher plant growth, its beneficial impact on improving crop development and yield, especially under stressful environments such as iron deficiency, was well documented. Iron deficiency is a major concern for crop production mainly observed in calcareous soils all over the world. The objective of this study was to investigate the effects of silicon on sea barley (Hordeum marinum ssp. marinum) under iron deficiency. Twenty-six-day-old plants of H. marinum were exposed to three treatments, sufficient iron treatment (50 µM Fe), iron-deficient treatment (0.1 µM Fe), and iron-deficient treatment (0.1 µM Fe) combined with silicon application (0.5 mM Na2SiO3). Our results showed that iron deficiency negatively affects almost all measured parameters. However, these depressive effects were significantly mitigated under silicon treatment. Indeed, silicon addition alleviated stress effect on the morphological aspect of plants and enhanced their growth (between + 93 % and + 283 %), water status (between + 57 % and + 58 %), photosynthetic pigment concentrations (between + 129 % and + 200 %), photosynthetic gas exchange (between + 73 % and + 129 %), and both Photosystem I (PSI) and Photosystem II (PSII) functions. However, a greater beneficial effect of silicon was observed on PSI, by comparison with PSII. This was concomitant with a significant increase of iron quantities in both roots and shoots by 153 % and 236 %, respectively. Based on our findings, silicon is able to mitigate the adverse effects of iron deficiency, probably by enhancing iron remobilization. Therefore, silicon application seems to be an effective and successful solution to cope with iron deficiency.
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Papers by Arnould Savouré