Interaction of the N-terminal domain of the AMPA receptor GluR4 subunit with the neuronal pentraxin NP1 mediates GluR4 synaptic recruitment

Synaptogenesis requires recruitment of neurotransmitter receptors to developing postsynaptic specializations. We developed a coculture system reconstituting artificial synapses between neurons and nonneuronal cells to investigate the molecular components required for AMPA-receptor recruitment to synapses. With this system, we find that excitatory axons specifically express factors that recruit the AMPA receptor GluR4 subunit to sites of contact between axons and GluR4-transfected nonneuronal cells. Furthermore, the N-terminal domain (NTD) of GluR4 is necessary and sufficient for its recruitment to these artificial synapses and also for GluR4 recruitment to native synapses. Moreover, we show that axonally derived neuronal pentraxins NP1 and NPR are required for GluR4 recruitment to artificial and native synapses. RNAi knockdown and knockout of the neuronal pentraxins significantly decreases GluR4 targeting to synapses. Our results indicate that NP1 and NPR secreted from presynaptic neurons bind to the GluR4 NTD and are critical trans-synaptic factors for GluR4 recruitment to synapses.     

Salt impact on photosynthesis and leaf ultrastructure of <Emphasis Type="Italic">Aeluropus littoralis</Emphasis>

The effects of salinity (400 mM NaCl) on growth, biomass partitioning, photosynthesis, and leaf ultrastructure were studied in hydroponically grown plants of Aeluropus littoralis (Willd) Parl. NaCl produced a significant inhibition of the main growth parameters and a reduction in leaf gas exchange (e.g. decreased rates of photosynthesis and stomatal conductance). However, NaCl salinity affected neither the composition of photosynthesis pigments nor leaf water content. The reduction in leaf gas exchange seemed to correlate with a decrease in mesophyll thickness as well as a severe disorganisation of chloroplast structure, with misshapen chloroplasts and dilated thylakoid membranes. Conspicuously, mesophyll chloroplasts were more sensitive to salt treatment than those of bundle sheath cells. The effects of NaCl toxicity on leaf structure and ultrastructure and the associated physiological implications are discussed in relation to the degree of salt resistance of A. littoralis.     

Cylinder-shaped conducting polypyrrole for labelless electrochemical multidetection of DNA

A new multidetection biosensor has been developed using the electrochemical properties of cylinder-shaped conducting polypyrrole grown on miniaturized graphite electrodes. Our objective was to conceive a sensitive, labelless and real-time DNA sensor for biomedical diagnosis. In a first step, copolymers bearing both ferrocene redox markers and oligonucleotide probes were selectively electro-addressed on microchip electrodes. Then, the study of their voltammetric response upon the addition of DNA targets revealed that the hybridization was efficiently transduced through the variation of ferrocene oxidation intensity. Using this technique, a good selectivity between Human Immunodeficiency Virus and Hepatitis B Virus targets was obtained. It was indeed possible to directly follow the hybridization. Complementary DNA detection limit reached 100 pM (3 fmol in 30 microL), which represents a good performance for such a practical, labelless and real-time sensor.     

Cenp-F links kinetochores to Ndel1/Nde1/Lis1/dynein microtubule motor complexes

Cenp-F is a nuclear matrix component that localizes to kinetochores during mitosis and is then rapidly degraded after mitosis [1]. Unusually, both the localization and degradation of Cenp-F require it to be farnesylated [2]. Five studies recently demonstrated that Cenp-F is required for kinetochore-microtubule interactions and spindle checkpoint function [3-7]; however, the underlying molecular mechanisms have yet to be defined. Here, we show that Cenp-F interacts with Ndel1 and Nde1, two human NudE-related proteins implicated in regulating Lis1/Dynein motor complexes (reviewed in [8]). We show that Ndel1, Nde1, and Lis1 localize to kinetochores in a Cenp-F-dependent manner. In addition, Nde1, but not Ndel1, is required for kinetochore localization of Dynein. Accordingly, suppression of Nde1 inhibits metaphase chromosome alignment and activates the spindle checkpoint. By contrast, inhibition of Ndel1 results in malorientations that are not detected by the spindle checkpoint; Ndel1-deficient cells consequently enter anaphase in a timely manner but lagging chromosomes then manifest. A major function of Cenp-F, therefore, is to link the Ndel1/Nde1/Lis1/Dynein pathway to kinetochores. Furthermore, our data demonstrate that Ndel1 and Nde1 play distinct roles to ensure chromosome alignment and segregation.     

High quantitative and no molecular differentiation of a freshwater snail (Galba truncatula) between temporary and permanent water habitats

We investigate the variation in quantitative and molecular traits in the freshwater snail Galba truncatula, from permanent and temporary water habitats. Using a common garden experiment, we measured 20 quantitative traits and molecular variation using seven microsatellites in 17 populations belonging to these two habitats. We estimated trait means in each habitat. We also estimated the distributions of overall genetic quantitative variation (QST), and of molecular variation (FST), within and between habitats. Overall, we observed a lack of association between molecular and quantitative variance. Among habitats, we found QST>FST, an indication of selection for different optima. Individuals from temporary water habitat matured older, at a larger size and were less fecund than individuals from permanent water habitat. We discuss these findings in the light of several theories for life-history traits evolution.     

Ferritins, bacterial virulence and plant defence

The enterobacterial pathogen Erwinia chrysanthemi causes soft rot diseases on a wide range of plants, including the model plant Arabidopsis thaliana. This bacterium proliferates in the host by secreting a set of pectin degrading enzymes responsible for symptom development. In addition, survival of this bacterium in planta requires two high-affinity iron acquisition systems mediated by siderophores and protective systems against oxidative damages, suggesting the implication by both partners of accurate mechanisms controlling their iron homeostasis under conditions of infection. In this review, we address this question and we show that ferritins both from the pathogen and the host are subtly implicated in the control of this interplay.     

Communication of male quality in owl hoots

The evolution of communication through intrasexual selection is expected to lead signalers to transmit honest information on their fighting ability. Here we studied the information encoded in the acoustic structure of the territorial calls of a nocturnal raptor. During territorial contests, male scops owls give hoots composed of a downward frequency shift followed by a stable plateau. We found that the frequency of the hoot was negatively correlated with the body weight of the vocalizer. We shifted the frequency contour of natural hoots in order to create resynthesized calls corresponding to individuals of varying body weight and used these stimuli in playback experiments simulating an intrusion into the territory of established breeders. Territory owners responded less intensely when they heard hoots simulating heavier intruders, and males with heavier apparent weight tended to give hoots with a lower plateau in response to playbacks simulating heavier intruders.     

Study of hydration of cross-linked high amylose starch by solid state 13C NMR spectroscopy

Starch is subjected to chemical treatments such as cross-linking or hydroxypropylation to meet the material requirements for food uses or controlled release in the pharmaceutical industries. In this work, two types of cross-linking formulations have been employed for the preparation of high amylose starch for use as an excipient for sustained drug release. The structural differences and chain dynamics of the modified starches in the dry and hydrated states have been compared by the use of variable contact time cross polarization-magic angle spinning solid state (13)C NMR spectroscopy.