Oscillatory nucleocytoplasmic shuttling of the general stress response transcriptional activators Msn2 and Msn4 in Saccharomyces cerevisiae

Msn2 and Msn4 are two related transcriptional activators that mediate a general response to stress in yeast Saccharomyces cerevisiae by eliciting the expression of specific sets of genes. In response to stress or nutritional limitation, Msn2 and Msn4 migrate from the cytoplasm to the nucleus. Using GFP-tagged constructs and high-resolution time-lapse video microscopy on single cells, we show that light emitted by the microscope also triggers this migration. Unexpectedly, the population of Msn2 or Msn4 molecules shuttles repetitively into and out of the nucleus with a periodicity of a few minutes. A large heterogeneity in the oscillatory response to stress is observed between individual cells. This periodic behavior, which can be induced by various types of stress, at intermediate stress levels, is not dependent upon protein synthesis and persists when the DNA-binding domain of Msn2 is removed. The cAMP–PKA pathway controls the sensitivity of the oscillatory nucleocytoplasmic shuttling. In the absence of PKA, Msn4 continues to oscillate while Msn2 is maintained in the nucleus. We show that a computational model based on the possibility that Msn2 and Msn4 participate in autoregulatory loops controlling their subcellular localization can account for the oscillatory behavior of the two transcription factors

Moderate conformational impact of citrate on ovotransferrin considerably increases its capacity to self-assemble at the interface

International audienceWe have compared the behavior of ovotransferrin at the air-solution interface in the presence of a monovalention (acetate), or a divalent ion (citrate), the latter being known to induce conformational changesof this protein upon interaction with its iron-binding sites. We have characterised the adsorption layer atthe air–water interface in terms of homogeneity, surface concentration excess and rheological propertiesat pH 4.0. Besides we have investigated the bulk conformation in the presence of the two anions. In thepresence of citrate only, interfacial layers display well-defined domains of higher overall surface concentrationsuggesting multilayers adsorption. Citrate also induces higher helical content and stabilizes theprotein against thermal denaturation. Hence we propose that these changes are involved in the propensityof ovotransferrin to self-assemble at the air–water interface resulting in thick and heterogeneousinterfacial layer

Native spider silk as a biological optical fiber.

International audienceIn this study, we demonstrate the use of eco-friendly native spider silk as an efficient optical fiber in air, highly bent fibers, and physiological liquid. We also integrated the silk filament in a photonic chip made of polymer microstructures fabricated by UV lithography. The molding process is non-destructive for silk and leads to an efficient micro-optical coupling between silk and synthetic optical structures. These optical performances combined with the unique biocompatibility, bioresorbability, flexibility, and tensile strength of silk filaments pave the way for new applications in biological media and for original biophotonic purposes

Ostreid herpesvirus 1 detection and relationship with Crassostrea gigas spat mortality in France between 1998 and 2006

Since its molecular characterisation, Ostreid herpesvirus 1 (OsHV-1) has been regularly detected in Crassostrea gigas in France. Although its pathogenicity was demonstrated on larval stages, its involvement during mortality outbreaks at the juvenile stage was highly suspected but not evidenced. To investigate mortality outbreaks, the French National Network for Surveillance and Monitoring of Mollusc Health (REPAMO) carried out two surveys in juvenile C. gigas. The first survey lasted from 1998 to 2006 and was an epidemiological inquiry occurring when oyster farmers reported mortality outbreaks. The second survey, a longitudinal one, was set up in 1998 to complete the network observations on OsHV-1. Data analysis showed a specific pattern of mortality outbreaks associated with OsHV-1 detection. Ostreid herpesvirus 1 detection mainly appeared during the summer, suggesting the influence of the seawater temperature on its occurrence. It mostly presented a patchy distribution in the field in contrast to the nursery. Significant relationship between OsHV-1 detection and spat mortality was found, preferentially in sheltered and closed environments. The longitudinal survey confirmed most of the network observations. Although subsequent works particularly epidemiological surveys would be useful to confirm the causal link between the detection of OsHV-1 and the mortality outbreaks in juvenile C. gigas, the role of OsHV-1 in oyster mortality is progressing

Nose-only inhalations of high-dose alumina nanoparticles/hydrogen chloride gas mixtures induce strong pulmonary pro-inflammatory response: a pilot study

Objective Solid composite propellants combustion, in aerospace and defense fields, can lead to complex aerosols emission containing high concentrations of alumina nanoparticles (Al2O3 NPs) and hydrogen chloride gas (HClg). Exposure to these mixtures by inhalation is thus possible but literature data toward their pulmonary toxicity are missing. To specify hazards resulting from these combustion aerosols, a pilot study was implemented. Materials and methods Male Wistar rats were nose-only exposed to Al2O3 NPs (primary size 13 nm, 10 g/L suspension leading to 20.0–22.1 mg/m3 aerosol) and/or to HClg aerosols (5 ppm target concentration) following two exposure scenarios (single exposures (SE) or repeated exposures (RE)). Bronchoalveolar lavage fluids (BALF) content and lungs histopathology were analyzed 24 h after exposures. Results Repeated co-exposures increased total proteins and LDH concentrations in BALF indicating alveolar–capillary barrier permeabilization and cytolysis. Early pulmonary inflammation was induced after RE to Al2O3 NPs ± HClg resulting in PMN, TNF-α, IL-1β, and GRO/KC increases in BALF. Both exposure scenarios resulted in pulmonary histopathological lesions (vascular congestions, bronchial pre-exfoliations, vascular and interalveolar septum edemas). Lung oxidative damages were observed in situ following SE. Conclusion Observed biological effects are dependent on both aerosol content and exposure scenario. Results showed an important pro-inflammatory effect of Al2O3 NPs/HClg mixtures on the lungs of rat 24 h after exposure. This pilot study raises concerns toward potential long-term pulmonary toxicity of combustion aerosols and highlights the importance for further studies to be led in order to define dose limitations and exposure thresholds for risk management at the work place

Proprietes et mecanismes des echanges de nutriments entre le gametophyte et le sporophyte chez Polytrichum formosum. Le role des cellules de transfert

SIGLEINIST T 76294 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Les apports de la génétique dans la filière ostréicole française

The most known and certainly the most important contribution of genetics to the oyster indus try is the development of the triploid cupped oyster. Released for the first time in the 1980s, the triploid oyster has triplets of  chromosomes instead of pairs. Currently, triploid oysters are obtained by crossing diploid and tetraploid oysters. These oysters are characterized by a near lack of milt in summer, which makes them generally popular with consumers, and by a faster growth, allowing a shorter production cycle. In parallel, the exploitation of natural resistance in the diversity of French oysters has been considered to improve the health of farmed populations which is a  major challenge for the sustainability of aquaculture farms. Currently, the knowledge acquired and the tools developed make it possible to propose the first of selection methods to the shellfish sectorL’apport le plus connu et certainement le plus important de la génétique à la filière ostréicole est le développement de l’huître creuse triploïde. Le caryotype de l’huître triploïde, produite pour la première fois dans les années 1980,  st composé de triplets de chromosomes (3n) et non de paires (2n) comme chez l’huître « commune ». Actuellement, les huîtres triploïdes sont obtenues par croisement d’huîtres diploïdes et tétraploïdes. Ces huîtres se caractérisent par une quasi absence de laitance qui les fait apprécier d’une majorité de consommateurs, et par une croissance plus rapide, permettant un cycle de production plus court. En parallèle, l'exploitation de résistances naturellement présentes dans la diversité des huîtres françaises a été envisagée pour améliorer la santé des cheptels qui est un enjeur majeur de la durabiltié des élevages aquacoles. Actuellement, les connaissances acquises et les outils développés permettent de proposer les premiers transferts de méthodes de sélection vers le secteur ostréicole

Une théorie sociale est-elle encore possible?

International audienceno abstrac