Phosphate Import in Plants: Focus on the PHT1 Transporters

The main source of phosphorus for plants is inorganic phosphate (Pi), which is characterized by its poor availability and low mobility. Uptake of this element from the soil relies heavily upon the PHT1 transporters, a specific family of plant plasma membrane proteins that were identified by homology with the yeast PHO84 Pi transporter. Since the discovery of PHT1 transporters in 1996, various studies have revealed that their function is controlled by a highly complex network of regulation. This review will summarize the current state of research on plant PHT1 multigenic families, including physiological, biochemical, molecular, cellular, and genetics studies

The Phosphate Fast-Responsive Genes <i>PECP1</i> and <i>PPsPase1</i> Affect Phosphocholine and Phosphoethanolamine Content

International audiencePhosphate starvation-mediated induction of the HAD-type phosphatases PPsPase1 (AT1G73010) and PECP1 (AT1G17710) has been reported in Arabidopsis (Arabidopsis thaliana). However, little is known about their in vivo function or impact on plant responses to nutrient deficiency. The preferences of PPsPase1 and PECP1 for different substrates have been studied in vitro but require confirmation in planta. Here, we examined the in vivo function of both enzymes using a reverse genetics approach. We demonstrated that PPsPase1 and PECP1 affect plant phosphocholine and phosphoethanolamine content, but not the pyrophosphate-related phenotypes. These observations suggest that the enzymes play a similar role in planta related to the recycling of polar heads from membrane lipids that is triggered during phosphate starvation. Altering the expression of the genes encoding these enzymes had no effect on lipid composition, possibly due to compensation by other lipid recycling pathways triggered during phosphate starvation. Furthermore, our results indicated that PPsPase1 and PECP1 do not influence phosphate homeostasis, since the inactivation of these genes had no effect on phosphate content or on the induction of molecular markers related to phosphate starvation. A combination of transcriptomics and imaging analyses revealed that PPsPase1 and PECP1 display a highly dynamic expression pattern that closely mirrors the phosphate status. This temporal dynamism, combined with the wide range of induction levels, broad expression, and lack of a direct effect on Pi content and regulation, makes PPsPase1 and PECP1 useful molecular markers of the phosphate starvation response

High-resolution laser system for the S3-Low Energy Branch

In this paper we present the first high-resolution laser spectroscopy results obtained at the GISELE laser laboratory of the GANIL-SPIRAL2 facility, in preparation for the first experiments with the S$^3$-Low Energy Branch. Studies of neutron-deficient radioactive isotopes of erbium and tin represent the first physics cases to be studied at S$^3$. The measured isotope-shift and hyperfine structure data are presented for stable isotopes of these elements. The erbium isotopes were studied using the $4f^{12}6s^2$ $^3H_6 \rightarrow 4f^{12}(^3 H)6s6p$ $J = 5$ atomic transition (415 nm) and the tin isotopes were studied by the $5s^25p^2 (^3P_0) \rightarrow 5s^25p6s (^3P_1)$ atomic transition (286.4 nm), and are used as a benchmark of the laser setup. Additionally, the tin isotopes were studied by the $5s^25p6s (^3P_1) \rightarrow 5s^25p6p (^3P_2)$ atomic transition (811.6 nm), for which new isotope-shift data was obtained and the corresponding field-shift $F_{812}$ and mass-shift $M_{812}$ factors are presented

Heterologous Expression of Membrane Proteins: Choosing the Appropriate Host

International audienceBACKGROUND: Membrane proteins are the targets of 50% of drugs, although they only represent 1% of total cellular proteins. The first major bottleneck on the route to their functional and structural characterisation is their overexpression; and simply choosing the right system can involve many months of trial and error. This work is intended as a guide to where to start when faced with heterologous expression of a membrane protein. METHODOLOGY/PRINCIPAL FINDINGS: The expression of 20 membrane proteins, both peripheral and integral, in three prokaryotic (E. coli, L. lactis, R. sphaeroides) and three eukaryotic (A. thaliana, N. benthamiana, Sf9 insect cells) hosts was tested. The proteins tested were of various origins (bacteria, plants and mammals), functions (transporters, receptors, enzymes) and topologies (between 0 and 13 transmembrane segments). The Gateway system was used to clone all 20 genes into appropriate vectors for the hosts to be tested. Culture conditions were optimised for each host, and specific strategies were tested, such as the use of Mistic fusions in E. coli. 17 of the 20 proteins were produced at adequate yields for functional and, in some cases, structural studies. We have formulated general recommendations to assist with choosing an appropriate system based on our observations of protein behaviour in the different hosts. CONCLUSIONS/SIGNIFICANCE: Most of the methods presented here can be quite easily implemented in other laboratories. The results highlight certain factors that should be considered when selecting an expression host. The decision aide provided should help both newcomers and old-hands to select the best system for their favourite membrane protein

La flexibilité des enseignants d’EPS dans la gestion d’imprévus relationnels et organisationnels

This article focuses on the professional gestures of two PE teachers working in the same REP+ establishment and when they face the unexpected (relational and organizational) lessons. Mobilizing a socio-didactic framework, the resultats show that the ways of adjusting to unforeseen events in the classroom respond to differentiated educational intentions. From the plural ressources mobilized by the two teachers, the survey shows that if the experiential dimension plays a role in the adjustments made in classe, this experiential judgment can be « wrong » sometimes and lead to limits of effectiveness in the adjustments adopted

Réaffectation d'une friche industrielle: les anciens abattoirs de la Chaux-de-Fonds (NE)

Les anciens abattoirs de La Chaux-de-Fonds furent réalisés en 1906 par l'architecte allemand G. UHLMANN. Conçu dans un esprit pragmatique et fonctionnaliste, l'équipement satisfait au principe rationnel du “mouvement en avant”, qui lui donna sa configuration particulière. Projeté sur le très long terme, le site fut pourtant progressivement abandonné. Classés monuments historiques en 1988, ses bâtiments se dégradent inexorablement. Construit à l'origine en périphérie de la ville, l'ensemble se trouve désormais au cœur de l'extension urbaine. Ses qualités intrinsèques telles son accessibilité, sa valeur esthétique, sa volumétrie, ses grandes ouvertures et sa rue couverte nous ont conduit à l'élaboration d'un programme de réaffectation à vocation publique. Alors que les bâtiments existants regroupent une variété d'équipement (restaurant, salle de représentation, crèche, ludothèque, locaux associatifs, musée, accueil extrascolaire), nous proposons de densifier le Nord du site par la construction de logements. Tout en prenant en compte les besoins réels et actuels de la ville, l'enjeu principal est de conserver l'identité, l'unité typologique et stylistique du site. Le projet propose ainsi de piétonniser l'espace délimité par le mur d'enceinte tout en conservant les tracés historiques, de restaurer les trois bâtiments périphériques ainsi que le bâtiment central, de valoriser la rue couverte comme espace public et d'ajouter des volumes dans la continuité des halles existantes