Plant chemical defence: a partner control mechanism stabilising plant - seed-eating pollinator mutualisms

<p>Abstract</p> <p>Background</p> <p>Mutualisms are inherently conflictual as one partner always benefits from reducing the costs imposed by the other. Despite the widespread recognition that mutualisms are essentially reciprocal exploitation, there are few documented examples of traits that limit the costs of mutualism. In plant/seed-eating pollinator interactions the only mechanisms reported so far are those specific to one particular system, such as the selective abortion of over-exploited fruits.</p> <p>Results</p> <p>This study shows that plant chemical defence against developing larvae constitutes another partner sanction mechanism in nursery mutualisms. It documents the chemical defence used by globeflower <it>Trollius europaeus </it>L. (Ranunculaceae) against the seed-eating larvae of six pollinating species of the genus <it>Chiastocheta </it>Pokorny (Anthomyiidae). The correlative field study carried out shows that the severity of damage caused by <it>Chiastocheta </it>larvae to globeflower fruits is linked to the accumulation in the carpel walls of a C-glycosyl-flavone (adonivernith), which reduces the larval seed predation ability per damaged carpel. The different <it>Chiastocheta </it>species do not exploit the fruit in the same way and their interaction with the plant chemical defence is variable, both in terms of induction intensity and larval sensitivity to adonivernith.</p> <p>Conclusion</p> <p>Adonivernith accumulation and larval predation intensity appear to be both the reciprocal cause and effect. Adonivernith not only constitutes an effective chemical means of partner control, but may also play a key role in the sympatric diversification of the <it>Chiastocheta </it>genus.</p

Evaluation Method for Automotive Stereo-Vision Systems

International audienceSafe vehicle guidance under human or computer control requires a thorough understanding of the traversed environment. Consequently if perception systems are to be introduced into mass market vehicles as part of driving assistance systems, their proper operation throughout the vehicle working life is needed. Onboard stereo-vision systems can provide rich information in terms of range, feature recognition, etc., hence the interest by car OEMs. System performance depends on multiple factors like light conditions, algorithms and the mechanical apparatus. Due to inaccuracies produced by changes in the system physical properties due to vibrations, misalignment of fixtures, etc. through the vehicle operational life a reduction in performance will occur. In this paper, an evaluation framework to estimate the performance of a vehicle onboard stereo-vision system in terms of 3D measurements and re-projection errors is presented. The approach considers changes that might occur in the system during the vehicle working life. It includes means to evaluate the self-calibration process often used to correct the effects of physical changes in the stereo-vision system. The results provide key information for the design and geometrical specification of automotive stereo-vision systems. As the potential physical changes in the geometric configuration of the camera-pair over the vehicle life time are difficult to predict, it was necessary to simulate them to generate families of errors that these might trigger on the system performance

Vibrational signature of broken chemical order in a GeS2 glass: a molecular dynamics simulation

Using density functional molecular dynamics simulations, we analyze the broken chemical order in a GeS$_2$ glass and its impact on the dynamical properties of the glass through the in-depth study of the vibrational eigenvectors. We find homopolar bonds and the frequencies of the corresponding modes are in agreement with experimental data. Localized S-S modes and 3-fold coordinated sulfur atoms are found to be at the origin of specific Raman peaks whose origin was not previously clear. Through the ring size statistics we find, during the glass formation, a conversion of 3-membered rings into larger units but also into 2-membered rings whose vibrational signature is in agreement with experiments.Comment: 11 pages, 8 figures; to appear in Phys. Rev.

Research trends in ecosystem services provided by insects

Insects play a key role in the regulation and dynamics of many ecosystem services (ES). However, this role is often assumed, with limited or no experimental quantification of its real value. We examined publication trends in the research on ES provided by insects, ascertaining which ES and taxa have been more intensively investigated, and which methodologies have been used, with particular emphasis on experimental approaches. We first performed a systematic literature search to identify which ES have been attributed to insects. Then we classified the references retrieved according to the ES, taxonomic group and ecosystem studied, as well as to the method applied to quantify each ES (in four categories: no quantification, proxies, direct quantification and experiments). Pollination, biological control, food provisioning, and recycling organic matter are the most studied ES. However, the majority of papers do not specify the ES under consideration, and from those that do, most do not quantify the ES provided. From the rest, a large number of publications use proxies as indicators for ES, assuming or inferring their provision through indirect measurements such as species abundances, species density, species richness, diversity indices, or the number of functional groups. Pollinators, predators, parasitoids, herbivores, and decomposers are the most commonly studied functional groups, while Hymenoptera, Coleoptera, and Diptera are the most studied taxa. Experimental studies are relatively scarce and they mainly focus on biological control, pollination, and decomposition performed in agroecosystems. These results suggest that our current knowledge on the ES provided by insects is relatively scarce and biased, and show gaps in the least-studied functional and taxonomic groups. An ambitious research agenda to improve the empirical and experimental evidence of the role played by insects in ES provision is essential to fully assess synergies between functional ecology, community ecology, and biodiversity conservation under current global changes

A multi-country test of brief reappraisal interventions on emotions during the COVID-19 pandemic.

The COVID-19 pandemic has increased negative emotions and decreased positive emotions globally. Left unchecked, these emotional changes might have a wide array of adverse impacts. To reduce negative emotions and increase positive emotions, we tested the effectiveness of reappraisal, an emotion-regulation strategy that modifies how one thinks about a situation. Participants from 87 countries and regions (n = 21,644) were randomly assigned to one of two brief reappraisal interventions (reconstrual or repurposing) or one of two control conditions (active or passive). Results revealed that both reappraisal interventions (vesus both control conditions) consistently reduced negative emotions and increased positive emotions across different measures. Reconstrual and repurposing interventions had similar effects. Importantly, planned exploratory analyses indicated that reappraisal interventions did not reduce intentions to practice preventive health behaviours. The findings demonstrate the viability of creating scalable, low-cost interventions for use around the world

Traits morphologiques et biochimiques impliqués dans la spécialisation de Trollius europaeus sur les pollinisateurs prédateurs de graines Chiastocheta spp.

Interactions between species are a major driving force in evolution. We show here which morphological and biochemical traits evolved during the specialisation of the European globeflower (Trollius europaeus) on seed-eating pollinator flies (Chiastocheta spp). The globular shape is a key factor in the specific attraction of chiastochetes. Globular flowers produce more seeds (4%, they suffer higher predation but are better pollinated) and moreover export more pollen (85%) than artificially open flowers. An adaptive dynamics model shows that the evolution of the globular shape requires a minimal pollination efficiency by chiastochetes relatively to alternative pollinators that do not eat seeds, but also a maximal efficiency: if the chiastochetes are “too” efficient, to attract a lot of them rather than a few confers no advantage. The attraction of pollinators is also mediated by olfactive signals. Several volatile compounds emitted by the globeflower trigger an electrophysiological response in chiastochetes (methyl salicylate, Z-jasmone, β-caryophyllene, germacrene D, E,E-α-farnesene, linalool). Field behavioural observations of chiastochetes visits have shown that the variability of the volatile compounds inside the flowers explains a part of the variability of the visits, together with morphological and pigmentation traits. Interactions between plants and seed predators are conflictual: the plants tend to reduce predation costs. A flavonoid close to luteolin, adonivernith, accumulates in the carpel walls when the damages caused by the larvae increase, leading to a reduction of predation intensity. The six Chiastocheta studied species have different exploitation patterns in the fruit, they induce and are affected by adonivernith in specific ways: this chemical defence could be involved in the sympatric speciation of the genus. The traits involved in the globeflower specialisation on chiastochetes are simultaneously mutualistic (globular floral morphology, floral colour and volatile compounds) and antagonistic (chemical defence against the larvae). The contradictions of this trait mosaic are a factor of evolution.Les interactions entre espèces sont un moteur d'évolution. Nous montrons ici quels sont les traits morphologiques et biochimiques du trolle d'Europe qui ont évolué au cours de sa spécialisation (Trollius europaeus) vis-à-vis des mouches pollinisatrices et prédatrices de graines (Chiastocheta spp.). La forme globulaire de la fleur est décisive dans l'attraction spécifique des chiastochètes. En comparaison avec une forme artificiellement ouverte, les fleurs globulaires, bien que souffrant plus de la prédation produisent plus de graines (4%), mais surtout elles exportent plus de pollen (85%). Un modèle de dynamique adaptative montre que l'évolution de la forme globulaire requiert non seulement une efficacité minimale de la pollinisation par les chiastochètes, par rapport à des pollinisateurs alternatifs qui ne consomment pas de graines, mais également une efficacité maximale : si les chiastochètes sont « trop » efficaces, en attirer beaucoup plutôt que quelques uns ne confère pas d'avantage. L'attraction des pollinisateurs se fait également par des signaux olfactifs. Plusieurs composés volatils émis par le trolle déclenchent une réponse électrophysiologique chez les chiastochètes (methyl salicylate, Z-jasmone, b-caryophyllene, germacrene D, E,E-a-farnesene, linalool). Des observations de visites de chiastochètes en conditions naturelles ont montré que la variabilité des composés volatils présents dans les fleurs expliquait une part de la variabilité des visites reçues par ces fleurs, en comparaison avec des traits morphologiques et pigmentaires. Les interactions entre une plante et des prédateurs de graines sont conflictuelles : la plante à intérêt à soustraire les graines de l'appétit des larves. Un glycoside du flavonoïde lutéoline, l'adonivernith, s'accumule dans les parois des carpelles lorsque les dégâts causés par les larves augmentent, avec comme conséquence une baisse de l'intensité de prédation. Les six espèces du genre Chiastocheta étudiées induisent et réagissent différemment à l'adonivernith, cette molécule pourrait donc être impliquée dans la radiation sympatrique du genre. Les traits impliqués dans la spécialisation du trolle sur les chiastochètes sont donc à la fois mutualistes (morphologie globulaire et composés volatils de la fleur) et antagonistes (défense chimique contre les larves). Les contradictions de cette mosaïque de traits sont un moteur d'évolution

Biophysicalchemical caracterisation of cell membrane during carcinogenesis : application to cell plasticity

Le tissu mammaire est intrinsèquement hétérogène et son développement ainsi que son homéostasie impliquent des mécanismes génétiques et épigénétiques permettant des modifications contrôlées de l’identité cellulaire tout au long de la vie d’une femme. Dans un contexte tumoral, les mécanismes liés à cette modulation de l’identité cellulaire peuvent être en revanche perturbés. Ceci facilite une grande dynamique épigénétique et l’acquisition d’une plasticité phénotypique située au cœur du développement et de la progression tumorale. La plasticité phénotypique décrit la capacité d’un système biologique à s’adapter et exprimer différents phénotypes en réponse à des conditions environnementales changeantes. Les cellules perdent dans ce contexte leur identité cellulaire et subissent des modifications profondes de leur métabolisme. L’une des conséquences de ces dérégulations métaboliques est le remodelage des lipides lors de l’acquisition d’un phénotype plastique. Nous avons pu corréler ce remodelage lipidique à une modification de la fluidité membranaire des membranes cellulaires. Cette mesure de fluidité membranaire s’effectue à l’aide d’une sonde de fluorescence ratiométrique synthétisée pour la première fois dans notre équipe. La première partie de cette thèse a concerné la validation dans un contexte biologique de la capacité de cette sonde fluorescente, le Dioll, à rendre compte de l’alignement des chaînes lipidiques directement au sein des membranes d’une cellule. L’analyse des propriétés physicochimiques de la sonde de fluorescence lors du marquage des membranes cellulaires a mis en avant les avantages de cette molécule par rapport aux sondes préexistantes, notamment un meilleur rapport quantique, une meilleure répartition au sein des phases liquides désordonnées permettant ainsi une meilleure discrimination des endomembranes et un marquage des membranes cellulaires avec une résolution sans précédent. Lors de la deuxième partie de cette thèse, nous avons utilisé les propriétés du Dioll pour mettre en évidence la corrélation existant entre fluidité membranaire et des variations phénotypiques à l’origine de la plasticité cellulaire. L’analyse d’un ensemble de lignées cellulaires cancéreuses mammaires a montré que nous pouvions discriminer les différents sous-types cellulaires à partir de ces mesures corrélées le plus souvent à une plus grande fluidité membranaire. Dans un second temps, nous avons utilisé un modèle isogénique de modulation de la plasticité cellulaire par induction d’un processus de perte des caractéristiques épithéliales au sein de cellules mammaires humaines immortalisées initialement épithéliales (HMEC). À partir de ce modèle, nous avons pu observer une diminution de l’alignement des chaînes lipidiques membranaires lors de l’acquisition d’un phénotype plus indifférencié. Finalement en modulant l’environnement hormono-nutritif de la cellule, il a été possible de créer un modèle permettant l’acquisition et la stabilisation d’un phénotype très indifférencié, hybride en termes de composante épithéliale et mésenchymateuse et multipotent. Ce phénotype dit « métastable » permet de rediriger de façon très efficace ces cellules dans les différentes voies de différenciation mammaire luminale ou myoépithéliale. Nous avons pu ainsi corréler les variations phénotypiques dans ce modèle à des variations biophysiques associées à une plus grande fluidité membranaire, les cellules métastables possédant un désordre très important au niveau de leurs chaînes lipidiques membranaires en comparaison de leur descendance ayant acquis une identité cellulaire luminale ou myoépithéliale. L’ensemble de ces résultats est discuté dans la perspective d’utiliser ces mesures indirectes de fluidité membranaire pour déterminer un indice de plasticité phénotypique ou de dynamique épigénétique qui servirait alors d’outil diagnostic et d’aide à la mise en place de stratégies thérapeutiques plus efficaces et personnalisées.The mammary tissue is inherently heterogeneous and its development as well as homeostasis involve genetic and epigenetic mechanism allowing controlled switches of cell identity during woman’s lifetime. During tumoral context, the mechanisms linked to this cell identity modulation can be disturbed. This facilitates a large epigenetic dynamic and the acquisition of phenotypic plasticity essential for tumour development and progression. Phenotypic plasticity describes the ability of a biological system to adapt and express different phenotypes in response to variations of environmental conditions. In this context, the cells lose their cell identity and undergo profound changes in their metabolism. One of the consequences of these metabolic dysregulation is the remodelling of cell lipid composition during the acquisition of a plastic phenotype. We were able to correlate this lipid remodelling with a change in lipid chains arrangement within cell membranes, a phenomenon known to modify the membrane fluidity. The membrane fluidity is measured by a ratiometric fluorescent probe synthesized for the first time in our team. The first part of this thesis concerned the validation in a biological context of this probe, Dioll, to report its capacity of following the membrane fluidity of cell membranes. The analysis of the physicochemical properties of the fluorescent probe during the labeling of cell membranes has highlighted the advantages of this molecule compared to pre-existing probes (better quantum ratio, better distribution within disordered liquid phase and better discrimination of endomembranes). The second part of this thesis, we used the properties of Dioll to highlight the correlation between membrane fluidity and phenotypic variations at the origin of cell plasticity. Analysis of a set of breast cancer cell lines showed that we could discriminate different cell subtypes. Secondly, we used an isogenic model of modulation of cellular plasticity by inducing a process of loss of epithelial characteristics within initially epithelial immortalized human mammary cells (HMEC). From this model, we were able to observe an increase of membrane fluidity during the acquisition of a more undifferentiated phenotype. Finally, by modulating the hormonal-nutritive environment of the cell, it was possible to create a model allowing the acquisition and stabilization of a much undifferentiated phenotype, hybrid in terms of epithelial and mesenchymal component and multipotent. This so-called “metastable” phenotype makes it possible to redirect these cells into the various luminal or myoepithelial mammary differentiation pathways. We were thus able to correlate the phenotypic variations in this model with biophysical variations associated with greater membrane fluidity, the metastable cells having a very significant disorder at the level of their membrane lipid chains in comparison with their progeny having acquired a luminal cell identity or myoepithelial. All of these results are discussed with a view to using these measurements of membrane fluidity to determine an index of phenotypic plasticity or epigenetic dynamics which would then serve as a diagnostic tool and aid in the implementation of therapeutic strategies more efficient and personalized

How do emotional states Impact monetary donation to environmental NGOs?

International audienceThe aim of this paper is to study the impact of emotional states on monetary donations to environmentally friendly causes regarding Environmental Non-Governmental Organisation (ENGOs) fundraising. We design a three-stage laboratory experiment. In the first stage, we ask participants to reveal their ecological and environmental preferences through the New Environmental Paradigm (NEP) Scale. In the second stage, emotions are induced in the participants. In the third stage, participants play a dictator game in which the recipient is an ENGO. We show that emotional states do not prompt donations themselves, but that certain negative emotional states (“Shame”) can decrease the amount donated