29 research outputs found
Modification des traits racinaires le long dâune succession secondaire sur des talus routiers: implications dans la dynamique des communautĂ©s et la protection des sols contre lâĂ©rosion
Les traits fonctionnels des plantes varient au cours des successions secondaires vĂ©gĂ©tales. Alors que certains traits ont Ă©tĂ© largement Ă©tudiĂ©s, les variations des traits racinaires au cours des successions restent relativement peu documentĂ©es. Lâobjectif de cette Ă©tude vise Ă mieux comprendre en quoi des variations de traits racinaires le long dâune succession secondaire contribuent Ă la dynamique de communautĂ©s vĂ©gĂ©tales mĂ©diterranĂ©ennes. Pour cela, quinze communautĂ©s vĂ©gĂ©tales, ĂągĂ©es de 0 Ă 69 ans, ont Ă©tĂ© repĂ©rĂ©es sur des talus en bordures de routes, dans le nord MontpelliĂ©rain. Sur cette chronosĂ©quence, nous nous intĂ©ressons Ă des traits racinaires morphologiques et architecturaux des espĂšces dominantes, reprĂ©sentant 70% de lâabondance vĂ©gĂ©tale. Nous faisons lâhypothĂšse que des traits morphologiques des racines fines (< 2 mm) permettent de mieux comprendre les modifications des stratĂ©gies dâacquisition et de conservation des ressources en nutriments et en eau. Des traits architecturaux, tels que la prĂ©sence dâun pivot, de racines traçantes et/ou adventives, permettent dâĂ©tudier le rĂŽle des racines dans lâancrage et la capacitĂ© des espĂšces Ă coloniser le milieu en rĂ©ponse aux contraintes topographiques liĂ©es Ă la pente des talus. Dans cette communication, nous prĂ©sentons (i) la mĂ©thode retenue pour lâĂ©tude des traits racinaires morphologiques et architecturaux sur des espĂšces de formes de croissance diverses (herbacĂ©es, buissons, arbres) et (ii) discutons des limites et atouts de ces mĂ©thodes. Enfin, nous discutons de lâimplication de ces traits racinaires dans la capacitĂ© des communautĂ©s Ă limiter lâĂ©rosion superficielle des talu
Negative regulation of EB1 turnover at microtubule plus ends by interaction with microtubule-associated protein ATIP3
International audienceThe regulation of microtubule dynamics is critical to ensure essential cell functions. End binding protein 1 (EB1) is a master regulator of microtubule dynamics that autonomously binds an extended GTP/GDP-Pi structure at growing microtubule ends and recruits regulatory proteins at this location. However, negative regulation of EB1 association with growing microtubule ends remains poorly understood. We show here that microtubule-associated tumor suppressor ATIP3 interacts with EB1 through direct binding of a non-canonical proline-rich motif. Results indicate that ATIP3 does not localize at growing microtubule ends and that in situ ATIP3-EB1 molecular complexes are mostly detected in the cytosol. We present evidence that a minimal EB1-interacting sequence of ATIP3 is both necessary and sufficient to prevent EB1 accumulation at growing microtubule ends in living cells and that EB1-interaction is involved in reducing cell polarity. By fluorescence recovery of EB1-GFP after photobleaching, we show that ATIP3 silencing accelerates EB1 turnover at microtubule ends with no modification of EB1 diffusion in the cytosol. We propose a novel mechanism by which ATIP3-EB1 interaction indirectly reduces the kinetics of EB1 exchange on its recognition site, thereby accounting for negative regulation of microtubule dynamic instability. Our findings provide a unique example of decreased EB1 turnover at growing microtubule ends by cytosolic interaction with a tumor suppressor. INTRODUCTION Microtubules (MTs) are polarized structures that continuously switch between periods of polymerization and depolymerization at their growing (plus) ends. This process, termed MT dynamic instability, allows rapid reorganization of the MT cytoskeleton during essential cell functions such as cell polarity and migration, mitosi
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.
RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 â„60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Ecological succession and influence of mowing in road slopes plant communities in Mediterranean southern France
Les mesures de vĂ©gĂ©talisation ou de restauration Ă©cologique nĂ©cessitent de comprendre les mĂ©canismes qui sous-tendent les changements de composition et de structure de la vĂ©gĂ©tation au cours de la succession Ă©cologique. Des perturbations, dâintensitĂ© et frĂ©quence variables, naturelles ou causĂ©es par lâHomme, agissent souvent en interaction sur la dynamique temporelle de la vĂ©gĂ©tation. Cependant, lâinfluence dâune perturbation rĂ©currente combinĂ©e aux changements Ă©cologiques au cours de la succession est restĂ©e peu Ă©tudiĂ©e jusquâĂ prĂ©sent.Les communautĂ©s vĂ©gĂ©tales de talus routiers reprĂ©sentent un modĂšle pertinent pour Ă©tudier cette problĂ©matique. Lâhistorique dâamĂ©nagement et de gestion des talus est particuliĂšrement bien renseignĂ© ; on a donc une connaissance prĂ©cise de lâĂąge des communautĂ©s et de leur rĂ©gime de perturbation par la fauche. Les talus routiers fournissent ainsi un plan quasi-expĂ©rimental in situ permettant lâĂ©tude des processus qui affectent lâassemblage des communautĂ©s au cours de la succession sous lâinfluence dâune perturbation rĂ©currente.Lâobjectif principal de cette Ă©tude est de caractĂ©riser la dynamique successionnelle initiĂ©e par la mise en place dâun talus routier en rĂ©gion mĂ©diterranĂ©enne et de dĂ©terminer les processus Ă©cologiques et les facteurs environnementaux influençant cette dynamique. On sâintĂ©resse en particulier Ă lâinfluence de la fauche rĂ©currente sur cette dynamique.Pour cela, nous avons Ă©tudiĂ© la composition floristique et la diversitĂ© des traits fonctionnels (traits foliaires et de phĂ©nologie de floraison principalement) de la vĂ©gĂ©tation de talus routiers de lâHĂ©rault (France). Chaque talus inclut une partie fauchĂ©e et une partie non fauchĂ©e, lâensemble formant une chronosĂ©quence sur prĂšs de 70 ans.Lâanalyse des variations taxonomiques entre les communautĂ©s vĂ©gĂ©tales de talus routiers montre un large remplacement des espĂšces au cours de la succession. Ce turnover floristique est associĂ© Ă des changements fonctionnels au sein des communautĂ©s. Ces derniers sont structurĂ©s par des filtres environnementaux qui influent (1) sur la synchronie de floraison entre espĂšces au sein des communautĂ©s au cours du temps et (2) sur la diversitĂ© de combinaisons de traits fonctionnels entre communautĂ©s dâĂąge similaire. Ces changements de filtres environnementaux au cours du temps semblent liĂ©s Ă des changements pĂ©dologiques et Ă lâaugmentation de lâhĂ©tĂ©rogĂ©nĂ©itĂ© spatiale des conditions de lumiĂšre et de tempĂ©rature (avec la fermeture progressive de canopĂ©e). La fauche altĂšre les trajectoires floristiques et fonctionnelles, notamment en provoquant un ralentissement du changement de stratĂ©gie dâutilisation des ressources au cours de la succession par rapport Ă la trajectoire naturelle, sans fauche. De plus, cette perturbation rĂ©currente induit une augmentation de la diversitĂ© taxonomique et fonctionnelle au sein des communautĂ©s alors quâelle la rĂ©duit entre communautĂ©s dâĂąge similaire. Finalement, la fauche agit comme un filtre environnemental supplĂ©mentaire sur lâassemblage des communautĂ©s au cours de la succession et induit une homogĂ©nĂ©isation de la vĂ©gĂ©tation entre communautĂ©s dâĂąge similaire.Les conclusions de cette Ă©tude contribuent Ă la connaissance Ă©cologique fondamentale. En termes dâimplications pour la gestion des communautĂ©s vĂ©gĂ©tales de talus routiers, nos conclusions suggĂšrent, entre autres, que lâassociation de vĂ©gĂ©tation fauchĂ©e et non fauchĂ©e au sein des mĂȘmes sites pourrait servir dâhabitat pour une plus grande diversitĂ© de faune associĂ©e. Cette association permettrait de plus dâavoir un rendu paysager agrĂ©able aux usagers de la route, tout en garantissant une bonne visibilitĂ© pour la sĂ©curitĂ© routiĂšre.The success of revegetation or ecological restauration highly depends on our knowledge of mechanisms underlying changes in composition and structure of the vegetation along the ecological succession. Natural or human-induced disturbances of varying intensity and frequency often occur simultaneously to influence vegetation temporal dynamics. However, the influence of a recurrent disturbance combined with ecological changes along plant succession remains poorly documented.Plant communities growing on road slopes are particularly appropriate to study this issue. Construction work and management history are well documented, so that the age of the vegetation and its disturbance regime by mowing can be precisely informed. Thus, road slopes plant communities represent an in situ quasi-experimental framework particularly adapted to study processes affecting community assembly along the ecological succession under the influence of a recurrent disturbance.The principal objective of this study is to characterise the successional dynamic initiated after road slope construction in the Mediterranean area, and to identify the ecological processes and environmental factors influencing this dynamic. We particularly focused on the influence of recurrent mowing on this dynamic.We studied the floristic composition and the diversity of functional traits (mainly leaf traits and flowering phenology traits) in a 70-year long chronosequence of French Mediterranean (HĂ©rault, France) road slopes, each including both mown and unmown vegetation.The analysis of taxonomical variations between road slopes plant communities reveals a large species turnover along the ecological succession. This floristic turnover relates with functional changes within communities. These functional changes are structured by environmental filters influencing flowering synchrony within communities on one hand, and the diversity of a combination of functional traits between communities of similar age on the other hand. These environmental filters changing along the succession relate with changing soil parameters and increasing spatial heterogeneity of light and temperature conditions with canopy closure.Mowing alters floristic and functional trajectories along the succession, notably through the decrease of speed in resource-use strategy changes along the succession in mown communities compared to unmown communities. In addition, this recurrent disturbance increases taxonomic and functional diversity within communities, while it decreases taxonomic and functional turnover between communities of the same age. Finally, mowing acts as an additional environmental filter on community assembly along the succession and homogenises vegetation between communities of the same age.The conclusions of this study provide basic knowledge in ecology. It also has implications for the management of road slopes plant communities in the perspective of their revegetation after construction work. Our conclusions suggest, amongst others, that combining mown and unmown vegetation could provide habitats for a higher diversity of associated fauna. In addition, it would allow vegetation to be pleasant to road users, while still ensuring a good visibility for road safety
Succession écologique et influence de la fauche dans des communautés végétales de talus routiers en région méditerranéenne française
The success of revegetation or ecological restauration highly depends on our knowledge of mechanisms underlying changes in composition and structure of the vegetation along the ecological succession. Natural or human-induced disturbances of varying intensity and frequency often occur simultaneously to influence vegetation temporal dynamics. However, the influence of a recurrent disturbance combined with ecological changes along plant succession remains poorly documented.Plant communities growing on road slopes are particularly appropriate to study this issue. Construction work and management history are well documented, so that the age of the vegetation and its disturbance regime by mowing can be precisely informed. Thus, road slopes plant communities represent an in situ quasi-experimental framework particularly adapted to study processes affecting community assembly along the ecological succession under the influence of a recurrent disturbance.The principal objective of this study is to characterise the successional dynamic initiated after road slope construction in the Mediterranean area, and to identify the ecological processes and environmental factors influencing this dynamic. We particularly focused on the influence of recurrent mowing on this dynamic.We studied the floristic composition and the diversity of functional traits (mainly leaf traits and flowering phenology traits) in a 70-year long chronosequence of French Mediterranean (HĂ©rault, France) road slopes, each including both mown and unmown vegetation.The analysis of taxonomical variations between road slopes plant communities reveals a large species turnover along the ecological succession. This floristic turnover relates with functional changes within communities. These functional changes are structured by environmental filters influencing flowering synchrony within communities on one hand, and the diversity of a combination of functional traits between communities of similar age on the other hand. These environmental filters changing along the succession relate with changing soil parameters and increasing spatial heterogeneity of light and temperature conditions with canopy closure.Mowing alters floristic and functional trajectories along the succession, notably through the decrease of speed in resource-use strategy changes along the succession in mown communities compared to unmown communities. In addition, this recurrent disturbance increases taxonomic and functional diversity within communities, while it decreases taxonomic and functional turnover between communities of the same age. Finally, mowing acts as an additional environmental filter on community assembly along the succession and homogenises vegetation between communities of the same age.The conclusions of this study provide basic knowledge in ecology. It also has implications for the management of road slopes plant communities in the perspective of their revegetation after construction work. Our conclusions suggest, amongst others, that combining mown and unmown vegetation could provide habitats for a higher diversity of associated fauna. In addition, it would allow vegetation to be pleasant to road users, while still ensuring a good visibility for road safetyLes mesures de vĂ©gĂ©talisation ou de restauration Ă©cologique nĂ©cessitent de comprendre les mĂ©canismes qui sous-tendent les changements de composition et de structure de la vĂ©gĂ©tation au cours de la succession Ă©cologique. Des perturbations, dâintensitĂ© et frĂ©quence variables, naturelles ou causĂ©es par lâHomme, agissent souvent en interaction sur la dynamique temporelle de la vĂ©gĂ©tation. Cependant, lâinfluence dâune perturbation rĂ©currente combinĂ©e aux changements Ă©cologiques au cours de la succession est restĂ©e peu Ă©tudiĂ©e jusquâĂ prĂ©sent.Les communautĂ©s vĂ©gĂ©tales de talus routiers reprĂ©sentent un modĂšle pertinent pour Ă©tudier cette problĂ©matique. Lâhistorique dâamĂ©nagement et de gestion des talus est particuliĂšrement bien renseignĂ© ; on a donc une connaissance prĂ©cise de lâĂąge des communautĂ©s et de leur rĂ©gime de perturbation par la fauche. Les talus routiers fournissent ainsi un plan quasi-expĂ©rimental in situ permettant lâĂ©tude des processus qui affectent lâassemblage des communautĂ©s au cours de la succession sous lâinfluence dâune perturbation rĂ©currente.Lâobjectif principal de cette Ă©tude est de caractĂ©riser la dynamique successionnelle initiĂ©e par la mise en place dâun talus routier en rĂ©gion mĂ©diterranĂ©enne et de dĂ©terminer les processus Ă©cologiques et les facteurs environnementaux influençant cette dynamique. On sâintĂ©resse en particulier Ă lâinfluence de la fauche rĂ©currente sur cette dynamique.Pour cela, nous avons Ă©tudiĂ© la composition floristique et la diversitĂ© des traits fonctionnels (traits foliaires et de phĂ©nologie de floraison principalement) de la vĂ©gĂ©tation de talus routiers de lâHĂ©rault (France). Chaque talus inclut une partie fauchĂ©e et une partie non fauchĂ©e, lâensemble formant une chronosĂ©quence sur prĂšs de 70 ans.Lâanalyse des variations taxonomiques entre les communautĂ©s vĂ©gĂ©tales de talus routiers montre un large remplacement des espĂšces au cours de la succession. Ce turnover floristique est associĂ© Ă des changements fonctionnels au sein des communautĂ©s. Ces derniers sont structurĂ©s par des filtres environnementaux qui influent (1) sur la synchronie de floraison entre espĂšces au sein des communautĂ©s au cours du temps et (2) sur la diversitĂ© de combinaisons de traits fonctionnels entre communautĂ©s dâĂąge similaire. Ces changements de filtres environnementaux au cours du temps semblent liĂ©s Ă des changements pĂ©dologiques et Ă lâaugmentation de lâhĂ©tĂ©rogĂ©nĂ©itĂ© spatiale des conditions de lumiĂšre et de tempĂ©rature (avec la fermeture progressive de canopĂ©e). La fauche altĂšre les trajectoires floristiques et fonctionnelles, notamment en provoquant un ralentissement du changement de stratĂ©gie dâutilisation des ressources au cours de la succession par rapport Ă la trajectoire naturelle, sans fauche. De plus, cette perturbation rĂ©currente induit une augmentation de la diversitĂ© taxonomique et fonctionnelle au sein des communautĂ©s alors quâelle la rĂ©duit entre communautĂ©s dâĂąge similaire. Finalement, la fauche agit comme un filtre environnemental supplĂ©mentaire sur lâassemblage des communautĂ©s au cours de la succession et induit une homogĂ©nĂ©isation de la vĂ©gĂ©tation entre communautĂ©s dâĂąge similaire.Les conclusions de cette Ă©tude contribuent Ă la connaissance Ă©cologique fondamentale. En termes dâimplications pour la gestion des communautĂ©s vĂ©gĂ©tales de talus routiers, nos conclusions suggĂšrent, entre autres, que lâassociation de vĂ©gĂ©tation fauchĂ©e et non fauchĂ©e au sein des mĂȘmes sites pourrait servir dâhabitat pour une plus grande diversitĂ© de faune associĂ©e. Cette association permettrait de plus dâavoir un rendu paysager agrĂ©able aux usagers de la route, tout en garantissant une bonne visibilitĂ© pour la sĂ©curitĂ© routiĂšre
Flowering overlap in Mediterranean plant communities along an ecological succession with recurrent mowing - Synchrony predominates at earlier stages and under mowing
International audienceIntroduction Flowering phenology is critical for the success of plant reproduction and depends both on abiotic constraints and on biotic interactions with other plants and fauna. Flowering synchrony or asynchrony within communities could thereby reflect local assembly processes associated with reproductive strategy. Changes in flowering phenology along the succession has been little studied. Thus, the interplay of a recurrent disturbance on successional changes in reproductive strategy remains unknown. Road slopes that are yearly mown are a good model to study these effects. Questions How do changing community assembly processes along the succession and due to mowing influence flowering overlap (i.e. synchrony or asynchrony) ? Does flowering overlap depend on pollination strategies and flower colour diversity in communities? Results Decrease of flowering overlap along the succession. Slower successional decrease with mowing. Greater flowering overlap than expected (flowering synchrony) before 30 years without mowing. Longer flowering synchrony with mowing (until 40 years). Higher overlap with lower colour diversity. Lower overlap on North-oriented than on East-oriented slopes. Decrease of overlap with increasing slope angle Lower flowering overlap for strictly entomophilous species than for other species. Significant relationship of flowering overlap with SLA and LDMC at community-level (CWM). Discussion In earliest successional stages, acquisitive plants highly depend on favorable meteorological conditions for vegetative growth and following investment in reproduction, thus resulting in higher flowering synchrony. Assembly appears neutral in regard to flowering phenology in later stages, probably reflecting a lower influence of constraints impeding flowering synchrony for conservative plants. Mowing increases flowering synchrony probably due to a synchronization of vegetative growth and via its influence on resource-use strategy. Flowering synchrony seems related to facilitation for pollinatorsâ attraction with enhanced colour signal (lower flower colour diversity ), for entomophilous species in particular. Conclusion Reproductive timing is an important driver of community assembly and appears tightly related to resource-use strategy. Flower synchrony within communities can reflect both influence of abiotic conditions constraining the optimal period to invest in reproduction in Mediterranean area facilitation processes helping entomophilous species to attract pollinators more efficiently thanks to synchronous homogenously-coloured flowering signal
Two dimensions define the variation of fine root traits across plant communities under the joint influence of ecological succession and annual mowing
International audience1.Quantifying the variation in community-level fine root (40 year old plots) and possessed opposite trait values. Root nitrogen concentration (RNC) did not vary across communities along the succession. The trait values at community-level were not affected by mowing, except for a reduction in root mass density.4.We found covariation of fine root traits across communities along two dimensions: the first dimension (60% of total variation) represented changes in root foraging capacity (related to SRL) and resource conservation (related to RDMC, RCC, mean root diameter) whereas the second dimension (17 to 20% of the variation) represented variations in RNC, potentially related to root respiration and metabolism.5.SRL and SLA (specific leaf area) were correlated regardless of the mowing regime, but there was no analogous relationship between LDMC (leaf dry matter content) and RDMC in mown communities, showing a decoupling in the investment in tissue density above and belowground.6.Synthesis. Our study demonstrates coordinated variations of community-level fine root traits along a succession gradient and provides evidence that fine root traits covaried along two-dimensions, regardless of mowing regime. The relationship between LDMC and RDMC observed in unmown communities was modified by mowing, reflecting an uncoupled response to mowing