Antagonistic Regulation of Circadian Output and Synaptic Development by JETLAG and the DYSCHRONIC-SLOWPOKE Complex

Circadian output genes act downstream of the clock to promote rhythmic changes in behavior and physiology, yet their molecular and cellular functions are not well understood. Here we characterize an interaction between regulators of circadian entrainment, output, and synaptic development in Drosophila that influences clock-driven anticipatory increases in morning and evening activity. We previously showed the JETLAG (JET) E3 ubiquitin ligase resets the clock upon light exposure, whereas the PDZ protein DYSCHRONIC (DYSC) regulates circadian locomotor output and synaptic development. Surprisingly, we find that JET and DYSC antagonistically regulate synaptic development at the larval neuromuscular junction, and reduced JET activity rescues arrhythmicity of dysc mutants. Consistent with our prior finding that DYSC regulates SLOWPOKE (SLO) potassium channel expression, jet mutations also rescue circadian and synaptic phenotypes in slo mutants. Collectively, our data suggest that JET, DYSC, and SLO promote circadian output in part by regulating synaptic morphology

Photosynthetic traits of freshwater lichens are consistent with the submersion conditions of their habitat

In this study, we compared the photosynthetic performance of epilithic freshwater lichens on siliceous stream rock submerged for: more than 9 (hyper-), 6–9 (meso-) or 3–6 months (sub-hydrophilic lichens). In the dry state, neither variable fluorescence nor respiration activity could be detected. In the wet state, rates of dark respiration (O2 uptake and CO2 production for immerged and in-air samples) were in the lower range of that reported for non-aquatic lichens. With 200 (under water) or 500 mmol.mx2.sx1 photosyntheticallly active photon flux density (PPFD) (aerial), photosynthesis was positive but rates were lower than that published for non-aquatic species. Under intense PPFD (2000 mmol.mx2.sx1, aerial), photo- synthesis increased in sub- but became negative in hyper-hydrophilic species. After hydration, dry samples increased photosystem II (PSII) efficiency, which reached near steady state in <6–7 min. Hyper-hydrophilic lichen took longer than sub-hydrophilic species. A long period of desiccation (4 months) had a negative effect on subsequent PSII photochemistry of hyper- but not of sub-hydrophilic hydrated lichens. When thalli were allowed to dehydrate, all types of lichens lost PSII activity after about 15–20 min. Deactivation was faster in the hyper- than in the sub-hydrophilic species. The metabolic traits presented here are thus consistent with the ecological amplitude of the freshwater lichens studied

Syntaxin 16 and syntaxin 5 are required for efficient retrograde transport of several exogenous and endogenous cargo proteins

Retrograde transport allows proteins and lipids to leave the endocytic pathway to reach other intracellular compartments, such as trans-Golgi network (TGN)/Golgi membranes, the endoplasmic reticulum and, in some instances, the cytosol. Here, we have used RNA interference against the SNARE proteins syntaxin 5 and syntaxin 16, combined with recently developed quantitative trafficking assays, morphological approaches and cell intoxication analysis to show that these SNARE proteins are not only required for efficient retrograde transport of Shiga toxin, but also for that of an endogenous cargo protein - the mannose 6-phosphate receptor - and for the productive trafficking into cells of cholera toxin and ricin. We have found that the function of syntaxin 16 was specifically required for, and restricted to, the retrograde pathway. Strikingly, syntaxin 5 RNA interference protected cells particularly strongly against Shiga toxin. Since our trafficking analysis showed that apart from inhibiting retrograde endosome-to-TGN transport, the silencing of syntaxin 5 had no additional effect on Shiga toxin endocytosis or trafficking from TGN/Golgi membranes to the endoplasmic reticulum, we hypothesize that syntaxin 5 also has trafficking-independent functions. In summary, our data demonstrate that several cellular and exogenous cargo proteins use elements of the same SNARE machinery for efficient retrograde transport between early/recycling endosomes and TGN/Golgi membranes

High temperature oxidation of a Cu-Ni – based cermet: kinetic and microstructural study

International audienceThe oxidation of a cermet composed of nickel ferrite (NixFe3-xO4), nickel oxide (NiyFe1-yO) and Ni-Cu alloy (CuzNi1-z) (with x=0.8, y=0.84 and z=0.44) has been studied by thermogravimetry, at 960°C, under controlled oxygen partial pressure. The rate of oxidation increases with the oxygen partial pressure up to 5.1 103 Pa, then it becomes independent of the oxygen pressure. This is due to the presence of the two copper oxides, CuO and Cu2O, above this oxygen pressure. SEM observation of oxidized samples has shown that the oxidation mechanism involves both external and internal oxidation

Application d'un modèle de réaction en phase gazeuse à l'oxydation d'un alliage liquide Al-Mg 5% sous faible pression d'oxygène

National audienceApplication of a model of reaction in the gaseous phase to the oxidation of a liquid Al-5%Mg alloy at low oxygen pressure. The oxidation of a liquid Al-5%Mg alloy was studied by isothermal (700°C) and isobaric thermogravimetry, under controlled oxygen partial pressure (lower than 50hPa). At low oxygen pressure, the reaction proceeds in the gaseous phase, due to the evaporation of magnesium from the alloy. A model exists in the literature to describe such reactions ; we verified experimentally that the assumptions of this model could be made for our reacting system; consequently, the variations of the oxidation rate with oxygen partial pressure were accounted for.L'oxydation d'un alliage Al-Mg5% à l'état liquide a été étudiée par thermogravimétrie isotherme (700°C) et isobare, sous pression d'oxygène contrôlée, inférieure à 50 hPa. En effet, à faible pression d'oxygène, la réaction se déroule en phase gazeuse, du fait de l'évaporation du magnésium de l'alliage. L'utilisation d'un modèle proposé dans la littérature, dont nous avons vérifié expérimentalement la validité des hypothèses, a permis d'interpréter les variations de la vitesse d'oxydation avec la pression d'oxygèn

Tilt Texture Domains on a Membrane and Chirality induced Budding

We study the equilibrium conformations of a lipid domain on a planar fluid membrane where the domain is decorated by a vector field representing the tilt of the stiff fatty acid chains of the lipid molecules, while the surrounding membrane is fluid and structureless. The inclusion of chirality in the bulk of the domain induces a novel budding of the membrane, which preempts the budding induced by a decrease in interfacial tension.Comment: 5 pages, 3 figure

Leaf Carbon Isotope Discrimination as an Accurate Indicator of Water-Use Efficiency in Sunflower Genotypes Subjected to Five Stable Soil Water Contents

Leaf carbon isotope discrimination (CID ) has been suggested as an indirect tool for breeding for water‐use efficiency (WUE ) in various crops. This work focused on assessing phenotypic correlations between WUE and leaf CID and analysing genotypic variability in four sunflower genotypes grown in a greenhouse in pots with five different stable levels of soil water content (SWC ). We measured WUE at whole plant and leaf (intrinsic) level. At whole plant level, WUE was derived from the ratio of total dry aerial biomass (BM ) to cumulative water transpired (CWT ). At leaf level, intrinsic WUE was calculated as the ratio of light‐saturated CO 2 assimilation to stomatal conductance (A /gs) in younger expanded leaves. Significant differences among the four genotypes and the five SWC s were observed for whole plant and leaf WUE and CID . Strong negative correlations were observed between whole plant WUE and CID as well as between intrinsic WUE and CID with decreasing water availability. No relationships appeared between BM production and WUE or CID . Our results can help agronomists and breeders to evaluate sunflower lines with high WUE for adaptation to drought conditions and for reducing water consumption and crop water needs. Leaf CID appears to be a pertinent and valuable trait to select sunflower genotypes with high WUE

A continuous loop of bioreactors to provide for life support in space

MELiSSA project is developing Life Support technologies for long-term Space missions. The goals of the MELiSSA loop are the recovery of food, water and oxygen from wastes, i.e. CO2 and organic wastes, using light as a source of energy. It is conceived as a series of compartments, each one performing a specific function within this cycle, inspired in the terrestrial ecological systems. Each one of the compartments is colonized with specific bacteria or higher plants depending on its dedicated function. The MELiSSA Pilot Plant is a facility conceived for the demonstration of this technology, the development of the MELiSSA compartments and its integration to build the complete MELiSSA loop. It uses laboratory rats as a demonstrator of the crew. The experimental results from the connection of a 100L air-lift photobioreactor culturing the cyanobacteria Arthrospira platensis, producing oxygen with an isolator with rats as the mock crew, as oxygen consumers, is presented. Several experiments of continuous connection with duration of 4-5 weeks have shown the robustness of the system and the ability of the control system to adjust the dynamics of the oxygen production compartment to that of the oxygen consumption compartment, while maintaining a desired percentage of oxygen in the gas phase of the animal compartment. The key variable used to adjust the production of the photosynthetic compartment to the consumer’s compartment is the illumination intensity in the photobioreactor, governed by the control system of the MELiSSA Pilot Plant. To note, the demand of oxygen by the consumers is changing following 12 hours day/night periods. The results show a very precise adjustment of the operation of the integrated system and a fast capacity of the control system to drive the oxygen level to a given set point. The evolution and mathematical modeling of the different variables of the integration, such as oxygen production and CO2 consumption in the photobioreactor, the oxygen consumption and CO2 production in the animal compartment, the illumination intensity, percentage of oxygen in the gas phase and operational conditions of the system at several experimental conditions will be discusse