miR-199a-5p Is Upregulated during Fibrogenic Response to Tissue Injury and Mediates TGFbeta-Induced Lung Fibroblast Activation by Targeting Caveolin-1

As miRNAs are associated with normal cellular processes, deregulation of miRNAs is thought to play a causative role in many complex diseases. Nevertheless, the precise contribution of miRNAs in fibrotic lung diseases, especially the idiopathic form (IPF), remains poorly understood. Given the poor response rate of IPF patients to current therapy, new insights into the pathogenic mechanisms controlling lung fibroblasts activation, the key cell type driving the fibrogenic process, are essential to develop new therapeutic strategies for this devastating disease. To identify miRNAs with potential roles in lung fibrogenesis, we performed a genome-wide assessment of miRNA expression in lungs from two different mouse strains known for their distinct susceptibility to develop lung fibrosis after bleomycin exposure. This led to the identification of miR-199a-5p as the best miRNA candidate associated with bleomycin response. Importantly, miR-199a-5p pulmonary expression was also significantly increased in IPF patients (94 IPF versus 83 controls). In particular, levels of miR-199a-5p were selectively increased in myofibroblasts from injured mouse lungs and fibroblastic foci, a histologic feature associated with IPF. Therefore, miR-199a-5p profibrotic effects were further investigated in cultured lung fibroblasts: miR-199a-5p expression was induced upon TGFβ exposure, and ectopic expression of miR-199a-5p was sufficient to promote the pathogenic activation of pulmonary fibroblasts including proliferation, migration, invasion, and differentiation into myofibroblasts. In addition, we demonstrated that miR-199a-5p is a key effector of TGFβ signaling in lung fibroblasts by regulating CAV1, a critical mediator of pulmonary fibrosis. Remarkably, aberrant expression of miR-199a-5p was also found in unilateral ureteral obstruction mouse model of kidney fibrosis, as well as in both bile duct ligation and CCl4-induced mouse models of liver fibrosis, suggesting that dysregulation of miR-199a-5p represents a general mechanism contributing to the fibrotic process. MiR-199a-5p thus behaves as a major regulator of tissue fibrosis with therapeutic potency to treat fibroproliferative diseases. © 2013 Lino Cardenas et al

Do Stacked Species Distribution Models Reflect Altitudinal Diversity Patterns?

The objective of this study was to evaluate the performance of stacked species distribution models in predicting the alpha and gamma species diversity patterns of two important plant clades along elevation in the Andes. We modelled the distribution of the species in the Anthurium genus (53 species) and the Bromeliaceae family (89 species) using six modelling techniques. We combined all of the predictions for the same species in ensemble models based on two different criteria: the average of the rescaled predictions by all techniques and the average of the best techniques. The rescaled predictions were then reclassified into binary predictions (presence/absence). By stacking either the original predictions or binary predictions for both ensemble procedures, we obtained four different species richness models per taxa. The gamma and alpha diversity per elevation band (500 m) was also computed. To evaluate the prediction abilities for the four predictions of species richness and gamma diversity, the models were compared with the real data along an elevation gradient that was independently compiled by specialists. Finally, we also tested whether our richness models performed better than a null model of altitudinal changes of diversity based on the literature. Stacking of the ensemble prediction of the individual species models generated richness models that proved to be well correlated with the observed alpha diversity richness patterns along elevation and with the gamma diversity derived from the literature. Overall, these models tend to overpredict species richness. The use of the ensemble predictions from the species models built with different techniques seems very promising for modelling of species assemblages. Stacking of the binary models reduced the over-prediction, although more research is needed. The randomisation test proved to be a promising method for testing the performance of the stacked models, but other implementations may still be developed

Structures spatiales et traits biologiques du voisinage de la plante au paysage: Le cas des digues restaurées des canaux de dérivation du Rhône

The spatial patterning of organisms and their resultant consequences are central questions within the science of both pure and applied ecology. Spatial heterogeneity is indeed of primary interest within the field of ecological restoration for both the conception and evaluation of projects. The work that has been developed during this PhD project encompasses a study of spatial patterning set against a background of ecological restoration. The study was carried out with a model study system, within an anthropogenic system: the banks of channels deriving the river Rhône. I have analysed the links between plant spatial patterns and their biological traits in this model system with an underlying aim of understanding their role in both community structuring and functioning within a hierarchical system. This approach is based upon the analysis of spatial patterns from the plant neighbourhood through to the landscape scale: i.e. from centimetric scales to kilometric scales. In doing so, this needed to combine concepts and methodological techniques derived from remote sensing, spatial statistics and functional ecology. The results provided an explanation of the development of spatial pattern of vegetation, at various scales, in interpreting the role of biological traits related to endogenous processes (dispersion and biotic interactions) and/or plant responses to exogenous factors (environmental conditions that have been imposed by restoration work and disturbance). The results also highlighted: (1) the role of three spatial strategies in shaping the pattern of herbaceous communities; (2) some variable relationships between the fine-scale spatial aggregation of tillers of competitive graminoïds and local species coexistence; and, (3) strong correlations between the functional structure and diversity of local communities and the reflectance properties of vegetation derived from high resolution remotely-sensed imagery. Taken together, these results allowed me to establish continuity between local functional assemblages and the spatial heterogeneity of complex ecosystem properties at the landscape level. A synthesis of the results from this study led to the development of a conceptual model that integrates the role of spatial vegetation pattern, plant traits and their interrelationships in the functioning of plant communities at a range of spatial scales from the landscape to the plant neighbourhood. The results from this work also offer practical management perspectives for the evaluation of restoration projects.La structuration et les effets de l'hétérogénéité spatiale des organismes font l'objet d'un questionnement transversal à l'écologie. Leur prise en compte correspond aussi à une préoccupation grandissante pour la conception et l'évaluation des projets de restauration écologique. Le travail qui a été développé au cours de cette thèse s'inscrit dans ce contexte. Avec comme modèle d'étude un système fortement anthropisé – les digues restaurées des canaux de dérivation du Rhône – j'ai analysé les liens unissant la structure spatiale des plantes à leurs traits biologiques, en vue de comprendre leurs rôles dans la structure et le fonctionnement des communautés végétales intégrées au coeur d'un système hiérarchisé. Cette démarche repose sur l'analyse des structures spatiales qui s'étendent du voisinage de la plante au paysage, c'est-à-dire des dimensions géographiques allant du centimètre jusqu'au kilomètre. Dans cette perspective il a été nécessaire de croiser des approches issues des statistiques spatiales, de l'écologie fonctionnelle et de la télédétection. Les résultats obtenus permettent d'expliquer la genèse de structures spatiales végétales, à diverses échelles, à partir de traits biologiques qui interviennent dans la manifestation de processus endogènes (dispersion et interactions biotiques) et/ou dans la réponse des plantes à des facteurs exogènes (conditions environnementales imposées par des travaux de restauration et perturbations). Ils mettent également en lumière 1) le rôle de trois stratégies spatiales dans la structuration des communautés herbacées; 2) des relations variables entre l'agrégation fine de graminées monopolistes et la coexistence des espèces au niveau du voisinage de la plante ; et 3) des relations fortes entre la structure/diversité fonctionnelle des communautés et les propriétés de réflectance de la végétation dérivées d'images aériennes à haute définition. Ceci permet d'établir une continuité entre des assemblages fonctionnels locaux et l'hétérogénéité spatiale de propriétés écosystémiques complexes au niveau du paysage. Une synthèse de cette étude conduit à proposer un modèle conceptuel qui intègre le rôle des structures spatiales végétales, des traits des plantes et de leurs interactions, dans le fonctionnement des communautés végétales en lien avec leurs niveaux adjacents (n+1 : le paysage ; n-1 : le voisinage de la plante). Enfin, les résultats qui ressortent de ce travail ouvrent des perspectives d'application pour l'évaluation et la gestion des projets de restauration

A general modelling framework for resource-ratio and CSR theories of plant community dynamics.

1. Grime’s CSR and Tilman’s resource-ratio theories are two major contributions to our understanding of plant community dynamics. They have both been corroborated empirically, whilst providing several contradictory predictions. Notably, contrary to Tilman, Grime predicts that competition for soil resources is unimportant on poor soils. 2. We show that Grime’s CSR theory can be modelled with the same type of differential equations for resource and plant biomass dynamics used by Tilman in his resource-ratio theory. 3. Using this unified modelling framework, we demonstrate that both models predict intense competition for soil resources on poor soils, as long as biomass loss per unit mass is modelled as a size-independent process. When considering biomass loss per unit mass as a size-dependent process mimicking farming activities, both models predict a unimodal relationship between soil fertility and the intensity of soil resource competition, and a decreasing relationship between disturbance rate and resource competition. 4. Synthesis. Our modelling analysis reveals that the resource-ratio and CSR theories make different predictions regarding competition on poor soils, not because of their differing schemes of plant strategies, but because of the different disturbance types that they are considering. Tilman’s predictions apply to little disturbed natural habitats, whilst Grime’s predictions apply to disturbed ones

Macroecology of seed banks: The role of biogeography, environmental stochasticity and sampling

The study of seed banks has been mainly conducted at local scales, thereby hampering our general understanding of the assembly processes of these biodiversity reservoirs. Here, we aim to document worldwide macroecological patterns of seed bank diversity and of their similarity with aboveground vegetation. Our second aim is to investigate the likely drivers of these macroecological patterns and to lay the foundation of a metacommunity theory of seed banks

Inter-and intraspecific variability of plant individual growth and its role on species ranking in grasslands

International audienceAims Individual growth constitutes a major component of individual fitness. However, measuring growth rates of herbaceous plants non-destructively at the individual level is notoriously difficult. This study, based on an accurate non-destructive method of aboveground biomass estimation, aims to assess individual relative growth rates (RGRs) of some species, identify its environmental drivers and test its consequences on community patterning. We specifically address three questions: (i) to what extent environmental conditions explain differences in individual plant growth between sites, (ii) what is the magnitude of intraspecific variability of plant individual growth within and between sites and (iii) do species-averaged (dis-)advantage of individual growth compared with the whole vegetation within a site correlate with species ranking at the community level?Methods We monitored the growth of individuals of four common perennial species in 18 permanent grasslands chosen along a large pedoclimatic gradient located in the Massif Central, France. We measured soil properties, levels of resources and meteorological parameters to characterize environmental conditions at the site level. This design enables us to assess the influence of environmental conditions on individual growth and the relative extent of inter-individual variability of growth explained within and between sites. We determined the ranking of each of the four species in each site with botanical surveys to assess the relationship between species-averaged growth (dis-) advantage relative to the whole community and species rank in the community.Important Findings We found that environmental conditions explain a significant proportion of individual growth variability, and that this proportion is strongly variable between species. Light availability was the main driver of plant growth, followed by rainfall amount and potential evapotranspiration, while soil properties had only a slight effect. We further highlighted a moderate to high within-site interindividual variability of growth. We finally showed that there was no correlation between species ranking and species-averaged individual growth

Structures spatiales et traits biologiques du voisinage de la plante au paysage (le cas des digues restaurées des canaux de dérivation du Rhône)

The spatial patterning of organisms and the resultant consequences are central questions within the science ofboth pure and applied ecology. Spatial heterogeneity is indeed of primary interest within the field of ecological restoration for both the conception and evaluation of projects. The work that has been developed during this PhD project encompasses a study of spatial patterning set against a background of ecological restoration. The study was carried out with a model study system, within an anthropogenic system: the banks of channels deriving the river Rhône. The links between plant spatial patterns and their biological traits have been analysed in this model system with an underlying aim of understanding their role in both community structuring and functioning within a hierarchical system. This approach is based upon the analysis of spatial patterns &om the plant neighbourhood through to the landscape scale. ln doing so, this needed to combine concepts and methodological techniques derived &om remote sensing, spatial statistics and functional ecology. The results provided an explanation of the development of spatial pattern of vegetation, at various scales, in interpreting the role ofbiological traits related to endogenous processes and/or plant responses to exogenous factors. A synthesis of the results from this study led to the development of a conceptual model that integrates the role of spatial vegetation pattern, plant traits and their interrelationships in the functioning of plant communities. The results from this work also offer practical management perspectives for the evaluation of restoration projects.La structuration et les effets de l'hétérogénéité spatiale des organismes font l'objet d'un questionnement transversal à l'écologie. Leur prise en compte correspond aussi à une préoccupation grandissante pour la conception et l'évaluation des projets de restauration écologique. Le travail qui a été développé au cours de cette thèse s'inscrit dans ce contexte. Avec comme modèle d'étude un système fortement anthropisé -les digues restaurées des canaux de dérivation du Rhône -les liens unissant la structure spatiale des plantes à leurs traits biologiques ont été analysés, en vue de comprendre leurs rôles dans la structure et le fonctionnement des communautés végétales intégrées au cœur d'un système hiérarchisé. Cette démarche repose sur l'analyse des structures spatiales qui s'étendent du voisinage de la plante au paysage. Dans cette perspective il a été nécessaire de croiser des approche! issues des statistiques spatiales, de l'écologie fonctionnelle et de la télédétection. Les résultats obtenus permettent d'expliquer la genèse de structures spatiales végétales, à diverses échelles, à partir de traits biologiques qui interviennent dans la manifestation de processus endogènes et/ou dans la réponse des plantes à des facteurs exogènes. Une synthèse de cette étude conduit à proposer un modèle conceptuel qui intègre le rôle des structures spatiales végétales, des traits des plantes et de leurs interactions, dans le fonctionnement des communautés végétales. Enfm, les résultats qui ressortent de ce travail ouvrent des perspectives d'application pour l'évaluation et la gestion des projets de restauration.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Spatial Heterogeneity of Vegetation Structure, Plant N Pools and Soil N Content in Relation to Grassland Management

International audienceSpatial heterogeneity in plant and soil properties plays a key role for biogeochemical cycling, nutrient losses and ecosystem function. Different management practices are expected to inducevaryinglevelsofspatialheterogeneityinagroecosystems,buttheeffectsofcontrastingbiomass removal regimes and herbivore species on grassland variability and spatial pattern have faced little attention. Wecarriedoutaspatially-explicitsamplingcampaignandgeostatisticalanalysestoquantify the spatial heterogeneity of the biomass and N in plants and soil for three management treatments (mowing, cattle grazing and sheep grazing) within a long-term grassland experiment. All plant and soil properties showed within-site variation, irrespective of management treatment. Within-site variationinplantvariablescouldberankedasgrazing>mowing. Cattlegrazingincreasedvariability in vegetation structure, soil mineral N and soil C:N compared with sheep grazing. In addition, the cattle-grazed field had a higher degree of spatial structure and a more coarse-grained pattern of spatial heterogeneity in plant properties than the sheep-grazed field. However, both grazing treatments showed spatial asynchrony in above- and below-ground responses to grazing. These results demonstrate the importance of herbivore species identity as a driver of grassland spatial heterogeneity, with implications for spatial uncoupling of nutrient cycles at the field scale

A model reduction method for the post-buckling analysis of cellular microstructures

International audienc