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Accueil > Départements > Biologie Cellulaire > Sébastien THOMINE : Approches Intégratives du Transport des Ions

Financements

Le laboratoire reçoit le soutien de :

- l’Agence Nationale de la Recherche pour les projets ISISTOR "Improving Seed Iron STORage", MOBIFER "Dynamics of coumarin secretion by plant roots into the soil to improve iron nutrition", et VACTION "Studies of vacuolar transporters controlling nutrient storage and ion detoxification in Arabidopsis thaliana"
- ARIMNet “Agricultural Research In the Mediterranean Network” pour le projet BEST "BarlEy Stress Tolerance"
- Labex Saclay Plant Sciences pour le projet DYNANO "Dynamic in vivo imaging of cellular parameters in plants combining fluorescent nanosensors and microfluidic platforms"
- La Mission Interdisciplinaire du CNRS pour le projet X-TrEM "Ionomique et transcriptomique X-espèces au service de l’étude des espèces végétales hyperaccumulatrices d’Eléments Traces Métalliques"


ISISTOR : Improving Seed Iron STORage
Contract type : PRC ANR
Period : 01/2017-12/2019
Coordinator : Stéphane MARI (BPMP, Montpellier, France)
Participant : Sébastien THOMINE (P2)

Abstract : Iron (Fe) is (...)

Abstract : Iron (Fe) is an essential element for all living organisms. Plants and seeds in particular represent the main dietary source of micronutrients (iron and zinc) for humans. The consumption of grains with low quantities of micronutrients is considered as the main cause of mineral deficiencies in humans. In particular, dietary iron deficiencies account for 90% anemia worldwide and are still prevalent in developed countries. The concept of biofortification, namely the development of plants with more concentrated and bioavailable micronutrients is widely recognized as the most sustainable solution to cope with these nutritional disorders. Controlling the Fe content in grains, quantitatively as well as qualitatively, is thus a major challenge. The identification of genes involved in this process is an indispensable step to implement future strategies of biofortification aimed at improving the nutritional value of seeds.
The objective of the proposed project is to identify, in the model plant species Arabidopsis thaliana, the genes controlling the processes of Fe loading, storage and remobilization, based on the expertise and results previously obtained by the three partners (P1, BPMP, Montpellier ; P2, I2BC, Gif-sur-Yvette, P3, UPMC, Paris). Indeed, we have recently shown in Arabidopsis and pea seeds that Fe is delivered to the embryo as ferric complexes with citrate and malate and that a reduction activity, catalyzed by ascorbic acid is an obligatory step for the transport of Fe to the embryo (P1). Moreover, thanks to the use of complementary elemental imaging techniques, partners 1 and 2 have shown that in the mature embryo Fe is stored in the vacuoles of endodermal cells, a specific cell layer surrounding the vascular system. Finally, the pioneering work of partner 2 has established the central role of two vacuolar efflux transporters, NRAMP3 and NRAMP4, in the remobilization process of Fe from vacuoles during germination. Based on these data and preliminary results, we propose a new project, ISISTOR, that will aim at identifying (i) the genes that control Fe import into seeds, with a focus on the ascorbic acid efflux transporters, (ii) the genes controlling the process of Fe remobilization from the vacuoles during germination, (iii) the interactions between Fe homeostasis and seed biology. The project proposed will combine the functional analysis of candidate genes previously isolated as well as untargeted genetic approaches including screens and genome wide association studies (GWAS) with Fe imaging techniques in cells to identify new molecular players. If successful, this project will provide new tools for the manipulation of the concentration and bioavailability of Fe in seeds that could be implemented, eventually, to crops and identify new roles of Fe in the physiology of seeds (dormancy and germination).
The three partners of the project are well recognized for their work on the biochemical and molecular characterization of Fe transport mechanisms on the one hand (P1+P2) and on seed biology on the other hand (P3). P1 and P2 have recently acquired an expertise on the use of complementary techniques for elemental imaging and analyses of Fe chemical environment in cells and organelles (histochemistry, synchrotron imaging, electron microscopy, X-ray absorption).



BEST : BarlEy Stress Tolerance

Contract type : ARIMNet “Agricultural Research In the Mediterranean Network”
Period : 01/2017-12/2020
Coordinator : Chedly ABDELLI (CBBC, Borj Cedria, Tunisia)
Participant : Sébastien THOMINE

Abstract : Mediterranean (...)

Abstract : Mediterranean climate and soils impose drastic constraints to agriculture. Barley (Hordeum vulgare) is one of the best adapted species to Mediterranean conditions. Climate change and growing Mediterranean population will further increase environmental and anthropic constraints on barley culture in a near future. An urgent objective is therefore to obtain barley varieties with high yield under stress conditions, while maintaining high nutritional quality of edible parts, associating high protein, mineral and fiber content with low contamination. In this context, the use of biostimulants of plant growth may help improving stress tolerance as well as nutritional quality, while limiting the use of classical chemical fertilizers that contribute to soil pollution.
Our proposal is based on exploring the genetic diversity of a collection of Mediterranean barley accessions subjected to combined environmental constraints : heavy metals (HM), salinity, drought and pathogens. A collection of representative H. vulgare cultivars from Morocco, Algeria, Tunisia and Egypt as well as a wild barley accession will be screened in the frame of this project. The project will therefore make use of local biodiversity to identify ideotypes maintaining high nutritional quality and low contaminant content even when grown under combinations of biotic and abiotic stresses. Nutritional quality and mineral content of grain and straw of these accessions will be analyzed under combinations of different abiotic (drought, salinity, Cd) and biotic (the fungal pathogen Rynchosporium commune) stresses. Physiological and molecular characterization of genotypes with contrasting phenotypes will shed light on the mechanisms underlying their adaptation to multiple stresses. Biostimulants provided by the private partner Roullier will be tested to evaluate their ability to increase stress tolerance and nutritional quality.
This project will bring together the expertise of 9 partners from 5 European and North African Mediterranean countries. It is expected to provide key information on the resilience and quality traits of Mediterranean barley germplasm under stress conditions, which can be used by breeders and farmers to choose their variety depending on a particular agricultural environment. We will identify potential ideotypes for entering breeding programs to reach resilience objectives while preserving nutritional quality. An important scientific output of this project will be a better understanding of the molecular and physiological mechanisms involved in barley nutritional quality and tolerance to combined stresses that will be of great relevance for agronomical and scientific communities.



DYNANO : Dynamic in vivo imaging of cellular parameters in plants combining fluorescent nanosensors and microfluidic platforms

Contract type : Labex Saclay Plant Sciences SPS2020
Period : 01/2017-12/2019
Coordinator : Sébastien THOMINE

Abstract : Systems biology

Abstract : Systems biology approaches in cell biology require a combination of computational modelling with the measurement of cellular processes with a high spatiotemporal resolution in individual cells. This is greatly facilitated with the recent development of genetically encoded nanosensors, which are potentially applicable to many research themes of the SPS. Two main bottlenecks for the adoption of these technologies by SPS scientists are the lack of efficient experimental systems for the observation of rapid changes in cellular parameters and the absence of data analysis procedures to obtain quantitative information on cellular processes in 3D or 4D. DYNANO is a 42 months project addressing these bottlenecks. The project will be carried out by a multidisciplinary team bringing together more than 15 scientists from the three SPS institutes, the hydrodynamics laboratory of the Ecole Polytechnique (LadHyX) and the Elvesys microfluidics company. DYNANO will develop microfluidic chips for the analysis of response kinetics in parallel in multiple roots and will master developing biosensors technologies. Moreover, DYNANO will develop methodologies for the acquisition and analysis of the data. DYNANO partners will use the technologies for the analysis of cytosolic and apoplastic Ca2+, ROS and pH, anion fluxes and heavy metal concentrations, cytoskeleton dynamics, ubiquitination, autophagosome formation, MAP kinase activity, mechanosensing, lipid domain formation and plant microbe interactions. DYNANO is expected to reinforce links with the private sector through the development of new generations of microfluidic chips that can be patented and commercialized and the possibility to develop platforms for the screening of cellular responses to molecules. Finally, the concerted effort around DYNANO is expected to position SPS as a leader in the field of quantitative live cell imaging in plants, which not only should enhance the attractiveness and competitiveness of the SPS teams but also may lead to new scientific breakthroughs leading to innovation.



MOBIFER : Dynamic in vivo imaging of cellular parameters in plants combining fluorescent nanosensors and microfluidic platforms

Contract type : PRC ANR
Period : 01/2018-12/2020
Coordinator : Christian DUBOS (BPMP, Montpellier, France)
Participant : Sébastien THOMINE (P2)

Abstract : Iron (Fe) is (...)

Abstract : Iron (Fe) is an essential micronutrient for plant productivity as well as for the quality of their derived products. However Fe is generally poorly available to plants because it is mainly present in the soil in the form of insoluble chelates. We and others have recently identified a novel mechanism involved in plant Fe acquisition that relies on the secretion in the soil of coumarin compounds (secondary metabolites) through the PDR9 transporter in order to improve the Fe mining capacity of the plants. Results we have recently obtained allowed us to pinpoint that the coumarin secretion process follows a complex and yet undescribed pathway involving various cell types and proteins involved in their transport. Understanding the whole dynamics of coumarin transport and secretion into the soil is therefore the next challenge we need to tackle. Hence, addressing this issue is of primary importance if one aims at improving food crop production as well as providing better food for the growing population without the use of Fe fertilizers that is expensive and can be questioned in term of sustainability in modern agriculture.
The aim of the MOBIFER project is to decrypt the molecular mechanisms that govern coumarin transport, partitioning and storage within and between the root cells prior to their secretion into the rizhosphere, a key molecular mechanism that non-grass species have evolved to cope with Fe deficiency. We will identify and characterize the proteins involved in coumarin transport. The completion of this project relies first on the molecular and physiological characterization of Arabidopsis mutant lines for several selected candidate genes (i.e. mainly transporters and GSTUs selected from large-scale expression studies), alone or in combination with described mutants associated to this pathway (e.g. pdr9).
The complementary of the methods that are routinely used by each partner (P) will ensure reaching all the goals of the MOBIFER project. It includes genetics, molecular biology and bioinformatics approaches (P1, 2 & 3), protein biochemistry including in vitro and in vivo analysis of protein activities (P2 & 3), proteomics (P1) and protein and metabolite imaging (P1 & 3).



X-TrEM : Ionomic and X-species transcriptomic for the study of metal hyperaccumulator plants

Contract type : MI-CNRS
Period : 01/2018-12/2019
Coordinator : Sylvain MERLOT (I2BC)
Participants : I2BC, IRD, UL, MNHN

Abstract : Plants that (...)

Abstract : Plants that are able to hyperaccumulate metals (0,2% of angiosperms) is still a group of plants that is very little known in terms of diversity and biological mechanisms. The X-TrEM projet aims to develop a large scale screen of herbarium specimens based on X-Ray fluorescence to identify new hyperaccumulator species. This project also aims to develop a cross-species transcriptomic method to be able to compare distantly related species and identify genes whose expression is linked to the metal hyperaccumulation trait. We believe that X-TrEM will help to better understand the mechanisms involved in metal hyperaccumulation and therefore support the use of these plants in sustainable biotechnologies.



VACTION : Studies of vacuolar transporters controlling nutrient storage and ion detoxification in Arabidopsis thaliana

Contract type : ANR-DFG
Period : 11/2016-10/2020
Coordinator : Sophie Filleur
Participant : Alexis de Angeli (I2BC), Karin Schumacher, Melanie Krebs (University of Heidelberg)

Abstract : The vacuole (...)

Abstract : The vacuole and TGN/EE (trans-Golgi network/early endosome) are intracellular compartments essential for nutrient accumulation and cytosolic ion detoxification by compartmentalizing the different cellular components. The multiple roles of these compartments are tightly linked to the activities of transporters present in their membranes. It is assumed that transporters use the energy of the electrochemical gradient generated by proton pumps such as the V-type H+-Adenosintriphosphatases (V-ATPase). The studies on V-ATPase suggest a specificity of action : a vha-a2 vha-a3 knock-out Arabidopsis mutant affected in vacuolar V-ATPase activity specifically reduces the vacuolar storage of nitrate but not the sequestration of chloride whereas the sensitivity to NaCl salt stress increases in a knock-down mutant of vha-a1, a mutant with reduced V-ATPase activity at the TGN/EE. The project aims at understanding the molecular basis of this functional specification through the analysis of interaction between V-ATPase and CLC anion transporters in Arabidopsis. This latter protein family is characterized by interesting features : (1) they can be channel (passive transporter) or anion/proton exchangers (active transporter) although all the members are structurally very close, (2) they can be either more selective for chloride or nitrate depending of a presence of a serine/proline in their selectivity filter and, (3) members are present on both TGN/EE and vacuolar membranes. The project will be divided in three Tasks : Task 1 will investigate the specificities/redundancies of AtCLCs localised in the vacuole and the TGN/EE. The two other Tasks will analyze the co-regulation between V-ATPase and AtCLCs in the vacuolar (Task 2) and TGN/EE membrane (Task 3).
The project will take advantage of the expertise of two expert groups in the field of primary and secondary transport in Arabidopsis thaliana. The French partner will provide knowledge in molecular physiology and electrophysiology which will be complemented by cell biological and ‘omics’ approaches of the German partner. The cooperation between the two laboratories will allow an in-depth analyses of the interaction between V-ATPase and AtCLC at the molecular, cellular and whole-plant level, taking different environmental fluctuations (nitrate concentrations, drought and NaCl stress) into account. Overall, this project will gain new insights into the coordination of primary and secondary transport processes at the tonoplast and TGN/EE and holds the potential for developing future strategies to improve crops for nutrient assimilation and tolerance to abiotic stress.



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