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

NEW : Projets de Thèse 2018

Nous proposons pour 2018 les projets de thèse suivants à l’Ecole Doctorale Sciences du Végétal, Université Paris-Sud :

- Role of the phosphatidylinositol 3-phosphate binding protein AtPH1/2 in trafficking of metal transporters and in metal homeostasis (Michele W. Bianchi) click to read

- Metal transport mechanisms involved in nickel hyperaccumulation in Noccaea caerulescens (Sylvain Merlot) click to read

- Deciphering the molecular and cellular mechanisms of iron storage and remobilization in seeds (Sebastien Thomine) click to read


You are encouraged to contact the corresponding investigator and visit the ADUM database for additional information.


Role of the phosphatidylinositol 3-phosphate binding protein AtPH1/2 in trafficking of metal transporters and in metal homeostasis
The precise control of metal concentration and compartmentalization within the plant cell is crucial for many important physiological functions. To achieve metal homeostasis, plants therefore seem to regulate activity of metal transporters but also their trafficking across cell compartments to achieve correct subcellular localization. Details of underlying mechanisms are however still poorly known. We have recently identified the evolutionary conserved protein AtPH1 as a regulator of the cellular trafficking of the NRAMP1 Mn2+ and Fe2+ transporter in Arabidopsis (PNAS, 2017). AtPH1 specifically binds phosphatidylinositol 3-phosphate, an important lipid in cell compartments of the endocytic and vacuolar degradation pathways, where its precise role is still little understood. The aim of this project is to investigate the molecular and cellular mechanism by which AtPH1 controls the fate of AtNRAMP1 and the physiological importance of AtPH1 in metal homeostasis. The student will start by exploiting available mutants and fluorescent reporter lines, but also contribute to the generation of new molecular tools and genotypes. Experimental approaches include analysis of mutant phenotypes in response to different metal availability, molecular cloning, subcellular colocalization studies by confocal microscopy (and subsequent image analysis) exploiting microfluidics devices, pharmacological approaches, search for molecular partners of AtPH1, reverse genetics of candidate genes.

Local context : MWB (Plant Cell 2010 ; Nature Comm 2014), collaborates closely on this topic with Sylvain Merlot and Sebastien Thomine within the « Integrative Approaches to Ion Transport » group at I2BC.

Keywords : Metal Homeostasis, Arabidopsis, Cell Biology, Endosomal pathway, Vacuole, Confocal Microscopy, Microfluidics, Genetics, Protein-protein interactions, Metal Transporters, Phosphatidylinositol 3- phosphate, Pleckstrin Homology Domain, Natural Resistance Associated Macrophage Protein


Metal transport mechanisms involved in nickel hyperaccumulation in Noccaea caerulescens

Transition metals such as iron, zinc or nickel (Ni) are essential for living organisms but become toxic at high concentration. Nevertheless, 500 plant species are able to accumulate tremendous amount of metals including 400 species accumulating more than 0,1% Ni in leaves and are so called Ni hyperaccumulators. Ni hyper accumulation involves 3 main steps : metal uptake by roots, root-to-shoot translocation, detoxification of metals and sequestration in vacuoles. The molecular mechanisms involved in metal hyperaccumulation, and in particular in the uptake of Ni and its translocation to the shoot, remain mostly unknown. This project aims to take advantage of recent RNA-Seq data obtained from the hyperaccumulator species Noccaea caerulescens (Brassicaceae) to identify genes, acting in roots, involved in Ni hyperaccumulation. Comparative transcriptomic analyses between ecotypes hyperaccumulating Ni and ecotypes or closely related species not accumulating or accumulating other metals (Zn) will reveal candidate genes coding for metal transporters whose expression or particular sequence is linked to the Ni hyperaccumulation trait. The activity and specificity of these transporters towards Ni will be tested using expression in heterologous systems. Then the role of these transporters in Ni hyperaccumulation will be confirmed in N. caerulescens combining cellular and genetic approaches. This validation step will require to develop or implement protocols for the transformation of N. caerulescens. A better knowledge of the molecular mechanisms involved in Ni hyperaccumulation will favor the development of sustainable technologies such as phytoremediation and green chemistry.

Keywords : nickel, phytoextraction, hyperaccumulator, metal transporter, RNA-Seq


Deciphering the molecular and cellular mechanisms of iron storage and remobilization in seeds

Seeds contain all the nutrients required for the development of a new organism, including iron which is often limiting in the human diet. Seeds are most often the edible part of crops. The germination of the nramp3nramp4 Arabidopsis thaliana mutant is arrested on iron deficient medium, because this mutant is unable to mobilize the iron stored in the vacuoles of its embryo. The objective of the thesis project is to identify novel genes involved in the control of iron storage and remobilisation in seeds by characterizing mutations that suppress the phenotype of the nramp3nramp4 mutant. The PhD candidate will characterize the genes affected in several confirmed suppressor mutants. Moreover, he/she will analyze the modifications in iron content, localization or speciation in the mutant seeds. The goal of this research is to identify candidate genes to improve iron availability in crop seeds. Through this project, the PhD candidate will receive training in molecular genetics. He/she will have the opportunity to use new generation sequencing and microscopic techniques to map iron distribution in seeds.

Keywords : seed, genetics, nutrition, iron, micronutrients, biofortification

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