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International audience; Two aspects of isospin breaking in the decay K±→π0π0e±νe(−) are studied and discussed. The first addresses the possible influence of the phenomenological description of the unitarity cusp on the extraction of the normalization of the form factor from data. Using the scalar form factor of the pion as a theoretical laboratory, we find that this determination is robust under variations of the phenomenological parameterizations of the form factor. The second aspect concerns the issue of radiative corrections. We compute the radiative corrections to the total decay rate for K±→π0π0e±νe(−) in a setting that allows comparison with the way radiative corrections were handled in the channel K±→π+π−e±νe(−). We find that, once radiative corrections are included, the normalizations of the form factor as determined experimentally from data in the two decay channels come to a better agreement. The remaining discrepancy can easily be accounted for by other isospin-breaking corrections, mainly those due to the difference between the masses of the up and down quarks.

Omics data are very valuable for researchers in biology, but the work required to develop a solid expertise in their analysis contrasts with the rapidity with which the omics technologies evolve. Data accumulate in public databases, and despite significant advances in bioinformatics softwares to integrate them, data analysis remains a burden for those who perform experiments. Beyond the issue of dealing with a very large number of results, we believe that working with omics data requires a change in the way scientific problems are solved. In this chapter, we explain pitfalls and tips we found during our functional genomics projects in yeasts. Our main lesson is that, if applying a protocol does not guarantee a successful project, following simple rules can help to become strategic and intentional, thus avoiding an endless drift into an ocean of possibilities.

International audience; We present a general formalism to model and calculate linear and nonlinear optical processes in composite systems,based on a graphical representation of light-matter interactions by loop diagrams associated with Feynmanrules. Through this formalism, we recover the usual second-order response of a simple system by drawing fourtimes fewer loop diagrams than doubled-sided ones. For composite systems, we introduce coupling Hamiltoniansbetween subsystems (for example, a molecule and a substrate), graphically represented by virtual bosons. In thisway, we enumerate all the diagrams describing the second-order response of the system and show how to selectthose relevant for the calculation of the molecular second-order hyperpolarizabilities under the influence of thesubstrate, including effective second-order contributions from the molecular third-order response. As it appliesto all nonlinear processes and an arbitrary number of interacting partners, this representation provides a generalframe for the calculation of the nonlinear response of arbitrarily complex systems.

International audience; The purpose of this work is to develop an integrated imaging approach to characterize without labeling at the sub-cellular level the formation of lipid body droplets (LBs) in microalgae undergoing nitrogen starvation. First conventional optical microscopy approaches, gas chromatography, and turbidimetry measurements allowed to monitor the biomass and the total lipid content in the oleaginous microalgae Parachlorella kesslerii during the starvation process. Then a local analysis of the LBs was proposed using an innovative infrared nanospectroscopy technique called atomic force microscopy-based infrared spectroscopy (AFM-IR). This label-free technique assessed the formation of LBs and allowed to look into the LB composition thanks to the acquisition of local infrared spectra. Last correlative measurements using fluorescence microscopy and AFM-IR were performed to investigate the subcellular reorganization of LB and the chloroplasts.

The plasmonic amplification of non-linear vibrational sum frequency spectroscopy (SFG) at the surfaces of gold nanoparticles is systematically investigated by tuning the incident visible wavelength. The SFG spectra of dodecanethiol-coated gold nanoparticles chemically deposited on silicon are recorded for twenty visible wavelengths. The vibrational intensities of thiol methyl stretches extracted from the experimental measurements vary with the visible color of the SFG process and show amplification by coupling to plasmonics. Since the enhancement is maximal in the orange-red region rather than in the green, as expected from the dipolar model for surface plasmon resonances, it is attributed mostly to hotspots created in particle multimers, in spite of their low surface densities., Comment: 17 pages, 3 figures, includes 12 pages SI

Legume-rhizobium symbiosis is a major ecological process in the nitrogen cycle, responsible for the main input of fixed nitrogen into the biosphere. The efficiency of this symbiosis relies on the coevolution of the partners., Legume plants can form root organs called nodules where they house intracellular symbiotic rhizobium bacteria. Within nodule cells, rhizobia differentiate into bacteroids, which fix nitrogen for the benefit of the plant. Depending on the combination of host plants and rhizobial strains, the output of rhizobium-legume interactions varies from nonfixing associations to symbioses that are highly beneficial for the plant. Bradyrhizobium diazoefficiens USDA110 was isolated as a soybean symbiont, but it can also establish a functional symbiotic interaction with Aeschynomene afraspera. In contrast to soybean, A. afraspera triggers terminal bacteroid differentiation, a process involving bacterial cell elongation, polyploidy, and increased membrane permeability, leading to a loss of bacterial viability while plants increase their symbiotic benefit. A combination of plant metabolomics, bacterial proteomics, and transcriptomics along with cytological analyses were used to study the physiology of USDA110 bacteroids in these two host plants. We show that USDA110 establishes a poorly efficient symbiosis with A. afraspera despite the full activation of the bacterial symbiotic program. We found molecular signatures of high levels of stress in A. afraspera bacteroids, whereas those of terminal bacteroid differentiation were only partially activated. Finally, we show that in A. afraspera, USDA110 bacteroids undergo atypical terminal differentiation hallmarked by the disconnection of the canonical features of this process. This study pinpoints how a rhizobium strain can adapt its physiology to a new host and cope with terminal differentiation when it did not coevolve with such a host. IMPORTANCE Legume-rhizobium symbiosis is a major ecological process in the nitrogen cycle, responsible for the main input of fixed nitrogen into the biosphere. The efficiency of this symbiosis relies on the coevolution of the partners. Some, but not all, legume plants optimize their return on investment in the symbiosis by imposing on their microsymbionts a terminal differentiation program that increases their symbiotic efficiency but imposes a high level of stress and drastically reduces their viability. We combined multi-omics with physiological analyses to show that the symbiotic couple formed by Bradyrhizobium diazoefficiens USDA110 and Aeschynomene afraspera, in which the host and symbiont did not evolve together, is functional but displays a low symbiotic efficiency associated with a disconnection of terminal bacteroid differentiation features.

International audience; Photosynthesis has to work efficiently in contrasting environments such as in shade and full sun. Rapid changes in light intensity and over-reduction of the photosynthetic electron transport chain cause production of reactive oxygen species, which can potentially damage the photosynthetic apparatus. Thus, to avoid such damage, photosynthetic electron transport is regulated on many levels, including light absorption in antenna, electron transfer reactions in the reaction centers, and consumption of ATP and NADPH in different metabolic pathways. Many regulatory mechanisms involve the movement of protein-pigment complexes within the thylakoid membrane. Furthermore, a certain number of chloroplast proteins exist in different oligomerization states, which temporally associate to the thylakoid membrane and modulate their activity. This review starts by giving a short overview of the lipid composition of the chloroplast membranes, followed by describing supercomplex formation in cyclic electron flow. Protein movements involved in the various mechanisms of non-photochemical quenching, including thermal dissipation, state transitions and the photosystem II damage–repair cycle are detailed. We highlight the importance of changes in the oligomerization state of VIPP and of the plastid terminal oxidase PTOX and discuss the factors that may be responsible for these changes. Photosynthesis-related protein movements and organization states of certain proteins all play a role in acclimation of the photosynthetic organism to the environment.

International audience; This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BYCyanobacteria are widely-diverse, environmentally crucial photosynthetic prokaryotes of great interests for basic and applied science. Work to date has focused mostly on the three non-nitrogen fixing unicellular species Synechocystis PCC 6803, Synechococcus PCC 7942, and Synechococcus PCC 7002, which have been selected for their genetic and physiological interests summarized in this review. Extensive “omics” data sets have been generated, and genome-scale models (GSM) have been developed for the rational engineering of these cyanobacteria for biotechnological purposes. We presently discuss what should be done to improve our understanding of the genotype-phenotype relationships of these models and generate robust and predictive models of their metabolism. Furthermore, we also emphasize that because Synechocystis PCC 6803, Synechococcus PCC 7942, and Synechococcus PCC 7002 represent only a limited part of the wide biodiversity of cyanobacteria, other species distantly related to these three models, should be studied. Finally, we highlight the need to strengthen the communication between academic researchers, who know well cyanobacteria and can engineer them for biotechnological purposes, but have a limited access to large photobioreactors, and industrial partners who attempt to use natural or engineered cyanobacteria to produce interesting chemicals at reasonable costs, but may lack knowledge on cyanobacterial physiology and metabolism. View Full-TextKeywords: Synechocystis PCC 6803; Synechococcus PCC 7942; Synechococcus PCC 7002; biodiversity; genotype-phenotype relationships; conjugation; transformation; RSF1010 plasmid; neutral cloning sites

Summary Photobiocatalysis uses light to perform specific chemical transformations in a selective and efficient way. The intention is to couple a photoredox cycle with an enzyme performing multielectronic catalytic activities. Laccase, a robust multicopper oxidase, can be envisioned to use dioxygen as a clean electron sink when coupled to an oxidation photocatalyst. Here, we provide a detailed study of the coupling of a [Ru(bpy)3]2+ photosensitizer to laccase. We demonstrate that efficient laccase reduction requires an electron relay like methyl viologen. In the presence of dioxygen, electrons transiently stored in superoxide ions are scavenged by laccase to form water instead of H2O2. The net result is the photo accumulation of highly oxidizing [Ru(bpy)3]3+. This study provides ground for the use of laccase in tandem with a light-driven oxidative process and O2 as one-electron transfer relay and as four-electron substrate to be a sustainable final electron acceptor in a photocatalytic process., Graphical abstract, Highlights • An electron relay boosts photoreduction of laccase • Superoxide is efficiently captured by laccase preventing formation of H2O2 • Light activation reveals information on elementary steps inside the enzyme • Laccase enables O2 as terminal electron acceptor for oxidative photocatalysis, Chemistry ; Catalysis ; Biomolecules

International audience; LppX is an important virulence factor essential for surface localization of phthiocerol dimycocerosates (DIM) in Mycobacterium tuberculosis. Based on Concanavalin A recognition, M. tuberculosis LppX (LppX-tb) was initially proposed to be glycosylated in M. tuberculosis and more recently this glycosylation was characterized by mass spectrometry analysis on LppX-tb expressed and purified from Corynebacterium glutamicum. Here, using this model organism and Mycobacterium smegmatis, we show that S16 and T18 residues of LppX-tb are indeed glycosylated with several hexoses units. Interestingly this glycosylation is strictly dependent on the mannosyl transferase PMT which, in M. tuberculosis, has been reported to be crucial for virulence. Using a site directed mutagenesis approach, we were able to show that the absence of S16 and T18 glycosylation does not alter phthiocerol dimycocerosates (DIM) localization in M. tuberculosis.

International audience; Gene targeting approaches have demonstrated the essential role for the malaria parasite of membrane transport proteins involved in lipid transport and in the maintenance of membrane lipid asymmetry, representing emerging oportunites for therapeutical intervention. This is the case of ATP2, a Plasmodium-encoded 4 P-type ATPase (P4-ATPase or lipid flippase), whose activity is completely irreplaceable during the asexual stages of the parasite. Moreover, a recent chemogenomic study has situated ATP2 as the possible target of two antimalarial drug candidates. In eukaryotes, P4-ATPases assure the asymmetric phospholipid distribution in membranes by translocating phospholipids from the outer to the inner leaflet. In this work, we have used a recombinantly-produced P. chabaudi ATP2 (PcATP2), to gain insights into the function and structural organization of this essential transporter. Our work demonstrates that PcATP2 associates with two of the three Plasmodium-encoded Cdc50 proteins: PcCdc50B and PcCdc50A. Purified PcATP2/PcCdc50B complex displays ATPase activity in the presence of either phosphatidylserine or phosphatidylethanolamine. In addition, this activity is upregulated by phosphatidylinositol 4-phosphate. Overall, our work describes the first biochemical characterization of a Plasmodium lipid flippase, a first step towards the understanding of the essential physiological role of this transporter and towards its validation as a potential antimalarial drug target.

International audience; The influence of vibration mode distortion and mode mixing in the vibronic structure of molecules on the doubly resonant sum and difference frequency generation spec-troscopies is systematically studied on several examples. These phenomena modify the spectral overlap function at the heart of the modeling of the doubly resonant processes. When the visible beam is tuned, under the Franck-Condon approximation , each vibration mode generates two main peaks corresponding to the resonance of the molecular electronic transition with the visible and SFG energies, together with higher order ones driven by the amplitudes of the vibronic displacements. For a single mode system, mode distortion modifies the positions of the main peaks and the excitations of the higher order ones. For a two-mode system, mode mixing induces in addition a deep change in the balance between the intensities of the mixed modes. It also changes the phases of the vibrations, which makes curve fitting difficult. For multimode systems, mode mixing may greatly enhance intensity of a poorly active mode. For all these reasons, it seems mandatory to take mode distortion and mode mixing into account for an accurate analysis of second-order nonlinear spectroscopic experimental data.

In most organisms, methylglyoxal (MG), a toxic metabolite by-product that causes diabetes in humans, is predominantly detoxified by the glyoxalase enzymes. This process begins with the so-called “spontaneous” conjugation of MG with the cytoprotectant metabolite glutathione (GSH). In this study, we unravel a logical, but as yet unsuspected, link between MG detoxification and a (prokaryotic) representative of the ubiquitous glutathione transferase (GST) enzymes. We show that a GST of a model cyanobacterium plays a prominent role in the detoxification of MG in catalyzing its conjugation with GSH. This finding is important because this reaction, always regarded as nonenzymatic, could exist in plants and/or human and thus have an impact on agriculture and/or human health., Methylglyoxal (MG) is a detrimental metabolic by-product that threatens most organisms (in humans MG causes diabetes). MG is predominantly detoxified by the glyoxalase pathway. This process begins with the conjugation of MG with glutathione (GSH), yielding a hemithioacetal product that is subsequently transformed by the glyoxalase enzymes into d-lactate and GSH. MG has been overlooked in photosynthetic organisms, although they inevitably produce it not only by the catabolism of sugars, lipids, and amino acids, as do heterotrophic organisms, but also by their active photoautotrophic metabolism. This is especially true for cyanobacteria that are regarded as having developed photosynthesis and GSH-dependent enzymes to detoxify the reactive oxygen species produced by their photosynthesis (CO2 assimilation) and respiration (glucose catabolism), which they perform in the same cell compartment. In this study, we used a combination of in vivo and in vitro approaches to characterize a logical, but as yet never described, link between MG detoxification and a (prokaryotic) representative of the evolutionarily conserved glutathione transferase (GST) detoxification enzymes. We show that the Sll0067 GST of the model cyanobacterium Synechocystis sp. strain PCC 6803 plays a prominent role in MG tolerance and detoxification, unlike the other five GSTs of this organism. Sll0067 catalyzes the conjugation of MG with GSH to initiate its elimination driven by glyoxalases. These results are novel because the conjugation of MG with GSH is always described as nonenzymatic. They will certainly stimulate the analysis of Sll0067 orthologs from other organisms with possible impacts on human health (development of biomarkers or drugs) and/or agriculture.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the ongoing COVID-19 pandemic, like many other viruses, uses programmed ribosomal frameshifting (PRF) to enable synthesis of multiple proteins from its compact genome. In independent analyses, we evaluated the PRF regions of all SARS-CoV-2 sequences available in GenBank and from the Global Initiative on Sharing All Influenza Data for variations. Of the 5,156 and 27,153 sequences analyzed, respectively, the PRF regions were identical in 95.7% and 97.2% of isolates. The most common change from the reference sequence was from C to U at position 13,536, which lies in the three-stemmed pseudoknot known to stimulate frameshifting. With the conversion of the G 13493 -C 13536 Watson-Crick pair to G-U, the SARS-CoV-2 PRF closely resembles its counterpart in the Middle East respiratory syndrome coronavirus. The occurrence of this change increased from 0.5 to 3% during the period of March to May 2020.; The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the ongoing COVID-19 pandemic, like many other viruses, uses programmed ribosomal frameshifting (PRF) to enable synthesis of multiple proteins from its compact genome. In independent analyses, we evaluated the PRF regions of all SARS-CoV-2 sequences available in GenBank and from the Global Initiative on Sharing All Influenza Data for variations. Of the 5,156 and 27,153 sequences analyzed, respectively, the PRF regions were identical in 95.7% and 97.2% of isolates. The most common change from the reference sequence was from C to U at position 13,536, which lies in the three-stemmed pseudoknot known to stimulate frameshifting. With the conversion of the G 13493-C 13536 Watson-Crick pair to G-U, the SARS-CoV-2 PRF closely resembles its counterpart in the Middle East respiratory syndrome coronavirus. The occurrence of this change increased from 0.5 to 3% during the period of March to May 2020.

Place: Basel Publisher: Mdpi WOS:000540843800016; International audience; Cyanobacteria constitute the only phylum of oxygen-evolving photosynthetic prokaryotes that shaped the oxygenic atmosphere of our planet. Over time, cyanobacteria have evolved as a widely diverse group of organisms that have colonized most aquatic and soil ecosystems of our planet and constitute a large proportion of the biomass that sustains the biosphere. Cyanobacteria synthesize a vast array of biologically active metabolites that are of great interest for human health and industry, and several model cyanobacteria can be genetically manipulated. Hence, cyanobacteria are regarded as promising microbial factories for the production of chemicals from highly abundant natural resources, e.g., solar energy, CO2, minerals, and waters, eventually coupled to wastewater treatment to save costs. In this review, we summarize new important discoveries on the plasticity of the photoautotrophic metabolism of cyanobacteria, emphasizing the coordinated partitioning of carbon and nitrogen towards growth or compound storage, and the importance of these processes for biotechnological perspectives. We also emphasize the importance of redox regulation (including glutathionylation) on these processes, a subject which has often been overlooked.

The glycolytic/lipogenic axis promotes the synthesis of energetic molecules and building blocks necessary to support cell growth, although the absolute requirement of this metabolic axis must be deeply investigated. Here, we used Drosophila genetics and focus on the mTOR signaling network that controls cell growth and homeostasis. mTOR is present in two distinct complexes, mTORC1 and mTORC2. The former directly responds to amino acids and energetic levels, whereas the latter is required to sustain the signaling response downstream of insulin-like-peptide (Ilp) stimulation. Either signaling branch can be independently modulated in most Drosophila tissues. We confirm this independency in the fat tissue. We show that ubiquitous over-activation of mTORC1 or Ilp signaling affects carbohydrate and lipid metabolism, supporting the use of Drosophila as a powerful model to study the link between growth and metabolism. We show that cell-autonomous restriction of glycolysis or lipogenesis in fat cells impedes overgrowth dependent on Ilp-but not mTORC1-signaling. Additionally, ubiquitous deficiency of lipogenesis (FASN mutants) results in a drop in mTORC1 but not Ilp signaling, whereas, at the cell-autonomous level, lipogenesis deficiency affects none of these signals in fat cells. These findings thus, reveal differential metabolic sensitivity of mTORC1- and Ilp-dependent overgrowth. Furthermore, they suggest that local metabolic defects may elicit compensatory pathways between neighboring cells, whereas enzyme knockdown in the whole organism results in animal death. Importantly, our study weakens the use of single inhibitors to fight mTOR-related diseases and strengthens the use of drug combination and selective tissue-targeting.

We introduce valence bond fluctuations, or bipartite fluctuations associated to bond-bond correlation functions, to characterize quantum spin liquids and their entanglement properties. Using analytical and numerical approaches, we find an identical scaling law between valence bond fluctuations and entanglement entropy in the two-dimensional Kitaev spin model and in one-dimensional chain analogues. We also show how these valence bond fluctuations can locate quantum phase transitions between the three gapped and the gapless Majorana semi-metal phases in the honeycomb model. We then study the effect of a uniform magnetic field along the 111 direction opening a gap in the intermediate phase which becomes topological. We still obtain a robust signal to characterize the transitions towards the three gapped phases. The linear scaling behavior of such bipartite fluctuations in two dimensions is also distinguishable from the one in the Neel magnetic state., Comment: 21 pages, Version as Accepted for Physical Review Research

International audience; Cyanobacteria, the largest phylum of prokaryotes, perform oxygenic photosynthesis and are regarded as the ancestors of the plant chloroplast and the purveyors of the oxygen and biomass that shaped the biosphere. Nowadays, cyanobacteria are attracting a growing interest in being able to use solar energy, H2O, CO2 and minerals to produce biotechnologically interesting chemicals. This often requires the introduction and expression of heterologous genes encoding the enzymes that are not present in natural cyanobacteria. However, only a handful of model strains with a well-established genetic system are being studied so far, leaving the vast biodiversity of cyanobacteria poorly understood and exploited. In this study, we focused on the robust unicellular cyanobacterium Cyanothece PCC 7425 that has many interesting attributes, such as large cell size; capacity to fix atmospheric nitrogen (under anaerobiosis) and to grow not only on nitrate but also on urea (a frequent pollutant) as the sole nitrogen source; capacity to form CO2-sequestrating intracellular calcium carbonate granules and to produce various biotechnologically interesting products. We demonstrate for the first time that RSF1010-derived plasmid vectors can be used for promoter analysis, as well as constitutive or temperature-controlled overproduction of proteins and analysis of their sub-cellular localization in Cyanothece PCC 7425. These findings are important because no gene manipulation system had been developed for Cyanothece PCC 7425, yet, handicapping its potential to serve as a model host. Furthermore, using this toolbox, we engineered Cyanothece PCC 7425 to produce the high-value terpene, limonene which has applications in biofuels, bioplastics, cosmetics, food and pharmaceutical industries. This is the first report of the engineering of a Cyanothece strain for the production of a chemical and the first demonstration that terpene can be produced by an engineered cyanobacterium growing on urea as the sole nitrogen source.

The infrared–visible sum-frequency generation (SFG) spectroscopy response of a composite interface comprising molecules, spherical nanoparticles, and a substrate is modeled in the dipolar approximation. The spheres modify the local electric fields felt by the molecules grafted on either the surfaces of the particles or the substrate below the spheres. In the case of plasmonic spheres, the excitation of their surface plasmons leads to amplifications of the molecular SFG signals at the incoming visible and SFG frequencies for both types of molecules. The spectral evolutions of these amplifications are described as a function of the natures of the metal, the molecules, and the substrate; the chemical groups involved; and the surface density of nanoparticles on the substrate and their surface coverage. The latter parameter is shown to be the main source of SFG from molecules adsorbed on these highly centrosymmetric objects. Models are compared to experimental data, and excellent agreement is found for the amp...

International audience; The MAPEG2 sub-family of glutathione-S-transferase proteins (GST) has been poorly investigated in vivo, even in prokaryotes such as cyanobacteria the organisms that are regarded as having developed glutathione-dependent enzymes to protect themselves against the reactive oxygen species (ROS) often produced by their powerful photosynthesis. We report the first in vivo analysis of a cyanobacterial MAPEG2-like protein (Sll1147) in the model cyanobacterium Synechocystis PCC 6803. While Sll1147 is dispensable to cell growth in standard photo-autotrophic conditions, it plays an important role in the resistance to heat and cold, and to n-tertbutyl hydroperoxide (n-tBOOH) that induces lipid peroxidation. These findings suggest that Sll1147 could be involved in membrane fluidity, which is critical for photosynthesis. Attesting its sensitivity to these stresses, the Delta sll1147 mutant lacking Sll1147 challenged by heat, cold, or n-tBOOH undergoes transient accumulation of peroxidized lipids and then of reduced and oxidized glutathione. These results are welcome because little is known concerning the signaling and/or protection mechanisms used by cyanobacteria to cope with heat and cold, two inevitable environmental stresses that limit their growth, and thus their production of biomass for our food chain and of biotechnologically interesting chemicals. Also interestingly, the decreased resistance to heat, cold and n-tBOOH of the Delta sll1147 mutant could be rescued back to normal (wild-type) levels upon the expression of synthetic MAPEG2-encoding human genes adapted to the cyanobacterial codon usage. These synthetic hmGST2 and hmGST3 genes were also able to increase the Escherichia coli tolerance to heat and n-tBOOH. Collectively, these finding indicate that the activity of the MAPEG2 proteins have been conserved, at least in part, during evolution from (cyano)bacteria to human.

International audience

International audience; Despite therapeutic advances, heart failure is the major cause of morbidity and mortality worldwide, but why cardiac regenerative capacity is lost in adult humans remains an enigma. Cardiac regenerative capacity widely varies across vertebrates. Zebrafish and newt hearts regenerate throughout life. In mice, this ability is lost in the first postnatal week, a period physiologically similar to thyroid hormone (TH)-regulated metamorphosis in anuran amphibians. We thus assessed heart regeneration in Xenopus laevis before, during, and after TH-dependent metamorphosis. We found that tadpoles display efficient cardiac regeneration, but this capacity is abrogated during the metamorphic larval-to-adult switch. Therefore, we examined the consequence of TH excess and deprivation on the efficiently regenerating tadpole heart. We found that either acute TH treatment or blocking TH production before resection significantly but differentially altered gene expression and kinetics of extracellular matrix components deposition, and negatively impacted myocardial wall closure, both resulting in an impeded regenerative process. However, neither treatment significantly influenced DNA synthesis or mitosis in cardiac tissue after amputation. Overall, our data highlight an unexplored role of TH availability in modulating the cardiac regenerative outcome, and present X. laevis as an alternative model to decipher the developmental switches underlying stage-dependent constraint on cardiac regeneration.

The influence of vibration mode distortion and mode mixing in the vibronic structure of molecules on the doubly resonant sum (SFG) and difference frequency generation spectroscopies is systematically studied in several examples. These phenomena modify the spectral overlap function at the heart of the modeling of the doubly resonant processes. When the visible beam is tuned, under the Franck–Condon approximation, each vibration mode generates two main peaks corresponding to the resonance of the molecular electronic transition with the visible and SFG energies, together with higher order ones driven by the amplitudes of the vibronic displacements. For a single mode system, mode distortion modifies the positions of the main peaks and the excitations of the higher order ones. For a two-mode system, mode mixing induces in addition a deep change in the balance between the intensities of the mixed modes. It also changes the phases of the vibrations, which makes curve fitting difficult. For multimode systems, mode mixing may greatly enhance intensity of a poorly active mode. For all these reasons, it seems mandatory to take mode distortion and mode mixing into account for an accurate analysis of second-order nonlinear spectroscopic experimental data.

International audience; Cyanobacteria are widely-diverse prokaryotes that colonize our planet. They use solar energy to assimilates huge amounts of atmospheric CO2 and produce a large part of the biomass and oxygen that sustain most life forms. Hence cyanobacteria are increasingly studied for basic research objective, as well as for the photosynthetic production of chemicals of industrial interests. One potential approach to reduce the cost of the future bioproduction processes will be to couple them with the treatment of wastewaters that are often polluted with urea, which in any case is cheaper than nitrate. As yet, however, research has mostly focused on a very small number of model cyanobacteria growing on nitrate. Thus, the genetic inventory of the cyanobacterial phylum is still insufficiently employed to meaningfully select the right host for the right purpose. This review reports what is known about urea transport and catabolism in cyanobacteria, and what can be inferred from the comparative analysis of the publicly available genome sequence of 308 cyanobacteria. We found that most cyanobacteria harbor the genes encoding the urea catabolytic enzymes urease (ureABCDEFG) mostly, but not systematically, together with the urea transport (urtABCDE). These findings are consistent with the capacity of the few tested cyanobacteria to grow on urea as the sole nitrogen source. They also indicate that urease is important for the detoxification of internally generated urea (re-cycling its carbon and nitrogen). In contrast, several cyanobacteria have urtABCDE but not ureABCDEFG, suggesting that urtABCDE could operate in the transport of not only urea but also of other nutrients. Only four cyanobacteria appeared to have the genes encoding the urea carboxylase (uc) and allophanate hydrolase (ah) enzymes that sequentially catabolize urea. Three of these cyanobacteria belongs to the genera Gloeobacter and Gloeomargarita that have likely diverged early from other cyanobacteria, suggesting that the urea carboxylase and allophanate hydrolase enzymes appeared in cyanobacteria before urease.

review article; The deformation and flow of disordered solids, such as metallic glasses and concentrated emulsions, involves swift localized rearrangements of particles that induce a long-range deformation field. To describe these heterogeneous processes, elastoplastic models handle the material as a collection of 'mesoscopic' blocks alternating between an elastic behavior and plastic relaxation, when they are too loaded. Plastic relaxation events redistribute stresses in the system in a very anisotropic way. We review not only the physical insight provided by these models into practical issues such as strain localization, creep and steady-state rheology, but also the fundamental questions that they address with respect to criticality at the yielding point and the statistics of avalanches of plastic events. Furthermore, we discuss connections with concurrent mean-field approaches and with related problems such as the plasticity of crystals and the depinning of an elastic line.; L'écoulement et la déformation de solides désordonnés comme les verres métalliques et les émulsions concentrées mettent en jeu des réarrangements rapides et localisés de particules, qui génèrent un champ de déformation à longue portée. Dans l'optique de décrire ces processus hétérogènes, les modèles élasto-plastiques traitent le matériau comme un ensemble de blocs "mésoscopiques" qui alternent entre un comportement élastique et une relaxation plastique, lorsqu'ils sont trop chargés. Les événements de relaxation plastique redistribuent les contraintes au sein du système de manière très anisotrope. Nous passons en revue les avancées réalisées à l'aide de ces modèles non seulement dans la compréhension physique de problèmes pratiques comme la localisation de la déformation, le fluage et la rhéologie stationnaire, mais aussi pour des questions de nature fondamentale sur le comportement critique au voisinage du point de rupture et sur les statistiques des avalanches d'événements plastiques. De plus, nous étendons la discussions aux approches de champ moyen de même finalité ainsi qu'à des problèmes connexes, comme la plasticité des cristaux et le dépiégeage de lignes élastiques.

In this review, we provide an introduction and overview to some more recent advances in real-time dynamics of quantum impurity models and their realizations in quantum devices. We focus on the Ohmic spin-boson and related models, which describes a single spin-1/2 coupled to an infinite collection of harmonic oscillators. The topics are largely drawn from our efforts over the past years, but we also present a few novel results. In the first part of this review, we begin with a pedagogical introduction to the real-time dynamics of a dissipative spin at both high and low temperatures. We then focus on the driven dynamics in the quantum regime beyond the limit of weak spin-bath coupling. In these situations, the non-perturbative stochastic Schroedinger equation method is ideally suited to numerically obtain the spin dynamics as it can incorporate bias fields h$_z$(t) of arbitrary time-dependence in the Hamiltonian. We present different recent applications of this method: (i) how topological properties of the spin such as the Berry curvature and the Chern number can be measured dynamically, and how dissipation affects the topology and the measurement protocol, (ii) how quantum spin chains can experience synchronization dynamics via coupling to a common bath. In the second part of this review, we discuss quantum engineering of spin-boson and related models in circuit quantum electrodynamics (cQED), quantum electrical circuits and cold-atoms architectures. In different realizations, the Ohmic environment can be represented by a long (microwave) transmission line, a Luttinger liquid, a one-dimensional Bose-Einstein condensate, a chain of superconducting Josephson junctions. We show that the quantum impurity can be used as a quantum sensor to detect properties of a bath at minimal coupling, and how dissipative spin dynamics can lead to new insight in the Mott-Superfluid transition.

International audience; A novel series of tubulin polymerization inhibitors, based on fluorinated derivatives of isocombretastatin A-4 was synthesized with the goal of evaluating the effect of these compounds on the proliferative activity. The introduction of fluorine atom was performed on the phenyl ring or at the linker between the two aromatic rings. The modification of isoCA-4 by introduction of difluoromethoxy group at the para-position (3i) and substitution of the two protons of the linker by two fluorine atoms (3m), produced the most active compounds in the series, with IC50 values of 0.15 -2.2 nM (3i) and 0.1-2 nM (3m) respectively, against a panel of six cancer cell lines. Compounds 3i and 3m had greater antiproliferative activity in comparison with references CA-4 or isoCA-4, the presence of fluorine group leads to a significant enhancement of the antiproliferative activity. Molecular docking studies indicated that compounds 3i and 3m occupy the colchicine binding site of tubulin. Evaluation of cytotoxicity in Human noncancer cells indicated that the compounds 3i and 3m were practically ineffective in quiescent peripheral blood lymphocytes, and may have a selective antiproliferative activity against cancer cells. Analyses of cell cycle distribution, and morphological microtubules organization showed that compound 3m induced G(2)/M phase arrest and, dramatically disrupted the microtubule network.

The deformation and flow of disordered solids, such as metallic glasses and concentrated emulsions, involves swift localized rearrangements of particles that induce a long-range deformation field. To describe these heterogeneous processes, elastoplastic models handle the material as a collection of 'mesoscopic' blocks alternating between an elastic behavior and plastic relaxation, when they are too loaded. Plastic relaxation events redistribute stresses in the system in a very anisotropic way. We review not only the physical insight provided by these models into practical issues such as strain localization, creep and steady-state rheology, but also the fundamental questions that they address with respect to criticality at the yielding point and the statistics of avalanches of plastic events. Furthermore, we discuss connections with concurrent mean-field approaches and with related problems such as the plasticity of crystals and the depinning of an elastic line., review article

International audience; In this paper, we demonstrate the feasibility of in situ non-linear IR-Vis Sum Frequency Generation (SFG) Spec-troscopy investigations at zinc surfaces in electrochemical ambient. We investigated both zinc electrodeposition onto an extraneous electrode and adsorption on polycrystalline zinc. Electrodeposition studies were carried out onto a polycrystalline gold cathode in contact with a Zn-cyanocomplex solution containing free CN − , while ad-sorption studies were carried out on a polycrystalline zinc electrode in contact with a free-CN − solution. In both experiments, we monitored the spectroscopic features associated with the internal stretching of the adsorbed cyanide (ca. 2100 cm −1) that we exploited as local Au and Zn site probes. Spectroelectrochemical results were complemented by cyclic voltammetric measurements. This proof-of-principle study is encouraging in the view of more concrete applications regarding additive adsorption at zinc electrodes, aiming at a fundamental understanding of the cycling stability of zinc battery anodes.

International audience

International audience; Préface : L’analyse des sentiments est un domaine de recherche extrêmement actif en traitement automatique des langues. En effet, ces dernières années ont vu se multiplier les sources de données textuelles porteuses d’opinion disponibles sur le web. Devant cette abondance de données et de sources, l’automatisation de la synthèse des multiples avis devient cruciale pour obtenir efficacement une vue d’ensemble des opinions sur un sujet donné. Globalement, les systèmes actuels ont obtenu de bons résultats sur la classification automatique du caractère subjectif ou objectif d’un document (Liu, 2015) En revanche, les résultats sur la tâche d’analyse de polarité restent encore peu concluants. La raison principale de cet échec est l’incapacité des algorithmes actuels à comprendre toutes les subtilités du langage humain. Parmi ces subtilités, nous nous focalisons sur le langage figuratif. Contrairement au langage littéral, le langage figuratif détourne le sens propre pour lui conférer un sens dit figuré ou imagé, comme l’ironie, le sarcasme, l’humour, la métaphore ou encore les jeux de mots. La détection automatique du langage figuratif est un sujet de recherche extrêmement actif principalement en raison de son importance pour améliorer les performances des systèmes d’analyse d’opinions (Maynard and Greenwood 2014 ; Ghosh et al. 2015, Benamara et al, 2017). Pour ce défi,nous nous intéressons en particulier à l’ironie, au sarcasme et à l’humour.L’ironie est un phénomène complexe largement étudié en philosophie et en linguistique (Grice 1975 ; Sperber and Wilson 1981 ; Utsumi 1996). Globalement, l’ironie est définie comme une figure de rhétorique par laquelle on dit le contraire de ce qu’on veut faire comprendre. Par exemple, pour exprimer une opinion négative envers son téléphone portable, on peut utiliser une forme littérale ("Ce téléphone est un désastre") ou alors une forme imagée ("Quel super téléphone !"). En linguistique computationnelle, l’ironie est un terme générique employé pour désigner un ensemble de phénomènes figuratifs incluant le sarcasme, même si ce dernier s’exprime avec plus d’aigreur et d’agressivité (Clift 1999). La détection du langage figuratif et son rôle dans l’analyse de sentiment a fait l’objet de plusieurs campagnes d’évaluation ces dernières années. Citons notamment la campagne SemEval 2015 Task11 (Ghosh et al. 2015) sur des tweets anglais et les campagnes SENTIPOLC@Evalita dans leurs éditions de 2014 et 2016 sur des tweets italiens (Basile et al., 2014 ; Barbieri et al., 2016). Grâce à cette édition de DEFT, nous mettons en place une 1ère campagne d’évaluation autour de ces thèmes pour le français. La tâche est ouverte aux équipes de recherche académiques et industrielles.