Dissertations / Theses on the topic 'Physiology of landscape'

Natural nesting habitat for Common Nighthawks (Chordeiles minor ) in the Northern Prairie region of North America is in decline due to row-crop conversion. Other nesting habitats used by nighthawks in this region includes flat, gravel rooftops, but such rooftop habitat is scheduled to be replaced by other materials within the next 20 years. These changes present substantial challenges to population persistence for nighthawks in this region.

This study used point counts and land cover analysis at 396 points in two study areas in southeastern South Dakota, northeastern Nebraska and northwestern Iowa to document that nighthawk presence is positively associated with flat, gravel rooftops and heterogeneous land cover and negatively associated with row crops in agriculturally dominated landscapes.

In addition to land cover change challenges, continuing trends toward increasing summer temperatures, decreasing cloud cover and increasing humidity might make rooftops unsuitable for nest habitat. Mean daily minimum, average and maximum operative temperatures (T_e) recorded at rooftop nest sites in 2016-2017 were 26.3, 31.7, and 36.3 °C, respectively, with a 71.1 °C overall maximum T_e. I monitored 50 rooftop nests during 2015-2017 in southeastern South Dakota. Like many nightjars, 7- to 14-day old nighthawk chicks are extremely heat tolerant. Evaporative water loss rates rapidly increased at temperatures above 44.1 °C in humid conditions (i.e. up to 16 °C dew point), and chicks had similar evaporative water loss rates at 51°C (2.44 g H₂0 h^-1) to adult nightjars. However, baseline corticosterone levels increased in chicks acutely exposed to high ambient temperatures, suggesting that these temperatures were stressful. In addition, low hatching (0.252) and fledging (0.262) success rates, similar to those for other declining nighthawk populations, and a negative association between ambient temperature and hatching success, suggest that future microclimate trends may make rooftops an unsuitable nesting habitat.

This study recommends conservation of grasslands and heterogeneous landscapes of row crops and grazed pastures to promote nighthawk occurrence in the region where row crops dominate. In addition, provision of urban ecoroofs, with gravel patches, as alternative nesting habitats in agriculturally dominated landscapes will also be important for maintaining populations of this declining aerial insectivore species.

Urbanization greatly alters plant and pollinator communities and can affect pollinator movement and subsequent gene flow. Plants persisting in urban areas must adjust to local environmental conditions often different from those in which they naturally evolved, and cultivation techniques for landscaping species have developed traits suitable for existence in urban habitats. Cultivated varieties and native conspecifics often exist in geographic proximity, and if pollinator movement is not blocked by urban structural components, functional differences may negatively impact spatially proximate native populations. I used spatial analysis of successful pollination of Cornus florida to estimate how pollinator movement is affected by urban features. My results suggest that buildings and canopy are the most important components which influence reproductive success in urban habitats. Additionally, I compared functional responses of both adult and offspring C. florida cultivars and native plants to differential light environments in the urban and natural understory habitats, and we found differences in physiology and morphology that could lead to negative fitness consequences for native populations should gene escape from urban cultivar to native populations occur via pollinator movement.

Our understanding of the natural world is constantly evolving and strengthening as more observations are made and experiments are performed. For example, we understand that tree stems grow toward the light (positive phototropism; Darwin 1880, Loehle 1986, Christie et al. 2013) and against gravity (negative gravitropism; Knight 1806, Hashiguchi et al. 2013). We also know that plants respond to mechanical stimulus and perturbation (thigmotropism; Braam 2005). Genes and their resulting proteins have been described to uncover some of the mechanisms for these environmental responses, but relatively speaking, we have just scratched the surface (Wyatt et al. 2013). While the discovery of the molecular mechanisms responsible for these behaviors is certainly dependent on the ever-improving lab technology available, every molecular discovery is dependent on a macroscopic observation. In this manuscript I present the two novel macroscopic observations I made on members of Araucaria in the urban forest. The first describes a hemisphere-dependent lean in A. columnaris, and the second provides genetic and morphological evidence that hybrids exist between A. columnaris and A. heterophylla. Araucaria columnaris (J.R. Forst.) Hooker, or the Cook Pine is a conifer with a narrow native range that has been cultivated worldwide and grows unlike any other tree known. The initial observation we made was that trees in California and Hawaii lean south, and trees in California lean to a greater extent than trees in Hawaii. Measuring 250 trees in 16 regions worldwide, however, produced statistically significant evidence for a hemisphere dependent directional leaning pattern. Trees in the northern hemisphere lean south, and trees in the southern hemisphere lean north. Additionally, the lean becomes more pronounced at greater distances from the equator. We also gathered morphological and genetic evidence in the California urban forest that A. columnaris and A. heterophylla (Salisb.) Franco are hybridizing. Many individuals have intermediate characteristics of both species, which originally led me to believe that hybrids exist in cultivation. After analyzing several individuals with microsatellite genetic markers, I have enough evidence to conclude that hybrids between A. columnaris and A. heterophylla exist. This is an important observation mainly for municipalities and arborists interested in properly identifying trees in the urban forest. Knowing the proper identity of trees is imperative to informing decisions about their protection or removal. As we continue to ask questions about the inner workings of nature we will continue to gain a better appreciation for what we still do not know. The evidence provided in this manuscript better informs our future questions about a leaning pattern in A. columnaris and about the history of the cultivation of Araucaria.

La recherche en paysage habite le dehors mentalement. Le paysage, celui qui nous émeut ou nous dégoûte, sensoriel, est envisagé ici comme une fiction concrète du corps en voyage. Éprouvée, par les voies multiples qui escortent le paysage à chaque traversée, j’interroge la validité de cet objet d’étude. Et si le paysage échappait aussitôt à chaque essai de capture ? Et comment ses multiples formes se resserrent-elles autour de soi pour nicher une complétude de l’être ? C’est ici que peut se formuler une conception du paysage comme celle d’un tissu, non plus seulement déployé sur le fond géographique mais emprisonnant dans sa fibre les corps et âme de chaque être. Le dehors, comme habitat de chaque créature, n’est plus purement un environnement, il devient un paysage. Proposer des exercices d’accès au dehors, pour pouvoir adresser le paysage de manière collective, est l’objectif de ce travail de thèse. C’est dans le contexte où habiter n’est plus proclamé par un paysage d’accueil que mon travail cherche à remettre le corps en exercice, puis en capacité d’évaluer un paysage. Un paysage se dé- clare à la fois par des représentations et des façons. Les unes traitent des expressions, les autres des matières. Entre la locution et la substance, qu’est-ce qui fait motif ? Le corps est-il susceptible de s’avancer vers le paysage et celui-ci a-t-il des ressources pour le recevoir ? Dans une première partie, plutôt que le texte déployé et discuté par des voix dissidentes, je mets en jeu des mots clefs proposés par l’enseignement pour l’élaboration d’un discours. A l’angle de la recherche et de la pratique, je construis ma thèse depuis ma place de paysagiste praticienne et enseignante du projet de paysage à L’ENSP de Versailles. Je m’appuie sur une critique de « Mouvance, 50 mots pour le paysage » proposée en 1999 par six chercheurs en paysage qui ont construit une première proposition théorique. Après un exposé, ils sont mis en débat avec un lexique construit lors des quatre années de la préparation de cette thèse. J’éprouve enfin, avec mes étudiants, la vitalité de ces mots dans des lieux de paysage ou des situations de pratiques professionnelles afin de construire sur une base vivifiée, le corpus même de ce qui peut s’exprimer en paysage. Ces termes sont la base abstraite de travaux pédagogiques conduits sur le terrain présenté dans une seconde partie. Le Parc des Lilas, à Vitry-sur-Seine est le cadre d’étude des exercices donnés dans des ateliers de projets de paysage sur lesquels travaillent mes étudiants. Ce parc, amorcé en 1980, est en cours d’agencement. Sans effet de signature, il ne trouve pas son nom, est qualifié d’inattendu, d’alias, de tempo. Des qualités lui confèrent sa substance : il devient un produit allochtone en son propre lieu. Sa chronique permet de mettre au jour une façon mobile d’accréditer le paysage d’un lieu. Le parc des Lilas sert d’appui à l’épreuve de définition des termes du lexique et se mesure à la pensée du Parc, en tant qu’objet de paysage produit. La proposition, développée en troisième partie, place le corps dans un acte de perception pour expertiser le paysage. Le protocole de recherche, immédiat, se définit à partir des produits successifs du geste, du discours oral, puis de la production écrite. La production est celle de la recherche en marche, arrêtée, glosée ; elle même projetant plus loin l’énoncé. Je présente ici une notice pour l’usage du commentaire composé de paysage (CCP), un avatar vers le projet en pédagogie appliquée. Proposition d’innovation pédagogique où protocoles et préalables participent à la remise de l’énoncé. Niveaux de langue et niveaux d’abstraction ne sont plus des obstacles à un entendement du paysage. Le CCP tient le cadre d’un don du paysage à une population entière. Réel et imaginaire revigorés sont redistribués par le jeu de leur apparition. Corps et paysage s’alimentent en une « physiologie du paysage » qui s’enseigne par fréquentation
The research in landscape mentally inhabits the outside. The landscape, the one which moves us or disgusts us, sensory, is here envisaged as a realistic fction of the traveling body. Experienced with the multiple paths which go alongside the landscape with each crossing, I question the validity of this research topic. What if the landscape escaped straight away at each attempt to capture it? How do its multiple shapes gather around themselves to nest the wholeness of one being? Here, we can try to phrase a conception of the landscape as a fabric, not only spread at a geographical level but also imprisoning in its fbers the body and the soul of each being. The outside, as the habitat of each creature, is no longer just an environment, but becomes a landscape. Suggesting exercises to access the outside to address the landscape collectively is the aim of this Ph.D. research. It is in this context where living is no longer claimed by a welcoming landscape that my work attempts to put the body back in movement and then to render it able to assess a landscape. A landscape is expressed both through representations and ways. The former are about expressions and the latter are about materials. Between the locution and the substance, what is the pattern? Is the body susceptible to move towards the landscape and does the landscape have the resources to receive it? In the frst part, rather than a text displayed and discussed by dissident voices, I involve the keywords offered by education to develop a discourse. At a crossroad between research and practice, I build my thesis from my position as a practicing landscaper and as a landscape project teacher at the ENSP in Versailles. My work relies on a criticism of Mouvance, 50 mots pour le paysage, written in 1999 by six landscape researchers, who built a frst theoretical approach. After a presentation, their views are debated with a lexicon elaborated during the four years spent working on this thesis. At last, I test with my students the vitality of these words in different landscape places or professional practice situations, in order to build on a freshened basis the very corpus of what can be expressed in the landscape. These words are the abstract basis of feldwork teaching sessions detailed in the second part. The Parc des Lilas, in Vitry-sur-Seine is the study framework of exercises done with my students in a landscape project. This park, started in 1980, is still under arrangement. Without a signature, it has no name and is defned as unexpected, an alias, a tempo. Its qualitiesualities give it its substance: it has become allochtonous, an alien product in its own place. Its chronicles enables one to unearth a changing way to ascertain the landscape of a place. The Parc des Lilas is used as a basis for the lexicon’s defnition and evaluation of the Parc’s conception as a produced landscape. In the third part, the proposition is to place the body in a landscape in order to assess it. The research protocol is immediate and is defned from successive products of movements, of speech and then of written production. The production is that of a research in action, stopped and commented, the research itself going further than its formulation. I offer here a guide for the commentaire composé de paysage (CCP), the composed commentary of the landscape, an avatar towards educational applied project, a proposition of educational innovation, where protocols and prerequisites are part of the formulation. Linguistic and abstraction levels are no longer obstacles to understanding the landscape. The CCP is the frame of a landscape offered to everyone. The real and the imaginary are redistributed as they appear. Body and landscape feed into a «landscape physiology», which is taught through attendance

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A presente dissertação se propôs à investigar as implicações da morfotectônica na organização da paisagem na bacia hidrográfica do Rio Preto (RJ/MG), cuja localização corrobora para a análise de feições morfotectônicas entre duas unidades geomorfológicas do sudeste brasileiro, o Alinhamento de Cristas do Paraíba do Sul e o Planalto do Itatiaia. Diante dos objetivos traçados foram selecionadas técnicas morfométricas de aplicação sobre o relevo e a drenagem, representações cartográficas e incursões a campo, que conjuntamente à Fisiologia da Paisagem, em seus três níveis de abordagem, ampararam o entendimento sobre a o quadro morfoestrutural e morfotectônico presente no recorte espacial selecionado. As feições registradas em campo e os resultados coletados em laboratório apontam conjuntamente para a atividade neotectônica concomitante à dinâmica superficial da paisagem comum em regiões tropicais, que muitas vezes mascara feições de uma tectônica passiva sobre a paisagem. Resultados concretos alcançados revelam a neotectônica atualmente no Sudeste brasileiro, corroborando para feições paisagísticas morfotectônicas.
This dissertation proposes to investigate the implications of dynamic neotectonic in the organization of the landscape in Rio Preto basin (RJ/MG), whose location supports for analyzing morphotectonic features between two geomorphological units of southeastern Brazil, the Alinhamento de Cristas do Paraíba do Sul and the Planalto do Itatiaia. Before the objectives were selected for morphometric techniques application on the topography and drainage, cartographic representations and raids the countryside, which jointly to the physiology of the landscape, in its three levels of approach, bolstered the understanding about the dynamics showed this in the space selected clipping. The features recorded in the field and the results collected in laboratory point together to neotectonic activity concomitant to the superficial common landscape dynamics in tropical regions, which often masks a passive tectonic features on the landscape, but in many of the results it was possible to show that the study area is located in a dynamic tectonic framework.

Elite athletes of today use specialized, scientific training methods and the increasing role of science in sports is undeniable. Scientific methods and equipment has even found its way into the practice of everyday exercisers, a testament to the impact of sport science. From the experiential, personal training regimes of the first half of the 20th century to the scientific training theories of the 1970s, the ideas about training and the athletic body shifted. The rationalization process started in endurance sports in the 1940s. It was part of a struggle between two models of training; natural training and rational training. Physiologists wanted to rid training of individual and local variations and create a universal model of rational, scientific training. The rationalization of training and training landscapes is here understood as an aspect of sportification, a theory commonly used to describe similar developments in sports where increasing regimentation, specialization and rationalization are among the main criteria. This dissertation adds the concept of technologies of sportification to explain the role that micro-technologies and practices (such as training logs, training camps and scientific tests) have in the scientization of training. This thesis thus sets out to analyze the role that science has played in training during the 20th century. It is a history about the rationalization of training, but also about larger issues regarding the role of personal, experiential knowledge and scientific knowledge. The main conclusions are that the process of scientization never managed to rid training of components from natural, experiential training, and that the effort by Swedish physiologists to introduce rational training was part of the larger rationalization movement at the time. In the end, training knowledge was a co-production between practitioners and theoreticians, skiers and scientists.

QC 20161114

Rationell träning: vetenskapliggörandet äv träning för längdskidåkning

A presente pesquisa estudou a dinâmica dos processos de arenização atuantes no areal do Cerro da Esquina, no município de São Francisco de Assis - RS pela perspectiva da fisiologia da paisagem proposta por Ab’Saber em 1969. O recorte temporal do estudo foi de um ano, de junho de 2016 a março de 2017. Nesse período foram realizados quatro trabalhos de campo, no final de cada estação do ano, nos quais foram efetuados levantamentos aerofotogramétricos com um veículo aéreo não tripulado. A partir dos produtos cartográficos obtidos, foram identificadas as principais micro-feições de relevo e realizada a compartimentação do areal em cinco setores de acordo com a sua drenagem. Tais compartimentos foram analisados e caracterizados de acordo com os processos atuantes. A partir da análise minuciosa de cada setor, foi elaborado um mapa síntese da fisiologia da paisagem do areal. Durante o período estudado, observou-se que os processos de erosão, transporte e deposição de origem hídrica foram os predominantes na maior parte do areal. Em relação à área ocupada pelo areal, observou-se que esta não sofreu alteração significativa, ou seja, areal manteve-se estável. Não foram observados avanços significativos da mancha de areia em direção ao campo, nem o contrário – avanço do campo sobre o areal. Considera-se, por fim, que o monitoramento com a utilização de VANT apoiado por outras técnicas de levantamento topográfico é muito eficiente em pesquisas como a que foi realizada, pois permite o levantamento de um grande volume de informações com qualidade cartográfica, com menores custos e com resolução temporal variável de acordo com os objetivos da pesquisa.
The present research has studied the dynamics of sand forming process in sandspot of Cerro da Esquina, in São Francisco de Assis – RS under the perspective of the physiology studies of landscapes proposed by Ab’Saber in 1969. The time frame for the study was one year – from June, 2016 to March, 2017 –, in which were performed four aerophotogrammetric surveys through unmanned aerial vehicle, one survey at the end of each season of the year. Based on the cartographic data obtained, it was possible to identify the main micro features of relief and the area was compartmentalized in five sections, according to its drainage process. The compartments were analyzed and described according to the processes active in them. A sintesys map of the physiology of the areal landscape was created based on a detailed analysis of each section. During the time frame of the study, the data showed that the processes prevailing in the major part of the area were erosion, transportation and deposition with hydric origins. In what regards the total area occupied by the areal, it didn’t suffer any significant changes, what means it kept stable. There were not found significative advances in sandspots towards the surrounding meadow, nor the opposite – from the meadow towards the areal. Lastly, there are strong indications that monitoring an area with unmanned aerial vehicle and the support of other techniques of topographic survey is highly efficient in researches like the present study, once it enables a large data collection with cartographic quality, with lesser costs and the adequate variable temporal resolution according to the objectives of the research.

La vigne est une culture fruitière largement cultivée, qui abrite naturellement un microbiome complexe, i.e. colonisée par des microorganismes neutres, phytopathogènes ou bénéfiques. Parmi les phytopathogènes, ceux associés aux maladies du bois (MDB) induisent des maladies très destructrices, et les traitements disponibles pour les contrôler ont actuellement une efficacité partielle. Les microorganismes bénéfiques (BCA) peuvent jouer un rôle spécifique dans la protection des plantes contre les phytopathogènes et le défi actuel est de comprendre comment ces microorganismes interagissent avec les plantes et leur potentiel biotechnologique pour le développement de stratégies innovantes. Dans ce contexte, l'objectif de cette étude était d'abord de caractériser les communautés microbiennes associées à la vigne tout au long de son cycle végétatif et, d'autre part, de mieux comprendre les interactions entre la vigne- BCA – MDB. Pour cela, deux potentiels BCA isolés de la vigne ont été testés contre des espèces de Botryosphaeriaceae et leur potentiel de colonisation, l'induction de mécanismes de défense dans la vigne, en présence ou non de D. seriata (F98.1), ont été caractériser ainsi que l’analyse de leur génome.Les résultats ont montré que le microbiome de la vigne était très dynamique au cours de son cycle végétatif. Comme prévu, la biodiversité microbienne était plus élevée dans les sols, et les communautés variaient entre le sol et les feuilles. Une proportion de communautés microbiennes était similaire dans les sols et les feuilles, ce qui suggère l'existence d'un microbiome commun. Plusieurs isolats ont été obtenus à partir de vignes qui appartenaient principalement aux genres Bacillus, Streptomyces et Aureobasidium. Certains d'entre eux ont considérablement diminué la croissance du mycélium de plusieurs espèces de Botryosphaeriaceae, telles que Streptomyces sp. Fito_S127B et A. pullulans Fito_F278 qui ont été sélectionnés comme BCA. Ces souches ont montré qu'elles produisaient une gamme élevée d'enzymes extracellulaires importantes pour le biocontrôle et ont pu coloniser avec succès la vigne : Fito_S127B était une épiphyte du système racinaire de la vigne, tandis que Fito_F278 pouvait coloniser l’ensemble de la plante, des racines aux feuilles. L'inoculation artificielle des tiges avec D. seriata F98.1 a montré que la longueur des nécroses causées par l'agent pathogène a été significativement réduite par Fito_S127B, contrairement à Fito_F278 qui était moins efficace. De plus, ces BCAs sont capables d’activer certaines réponses de défense de la vigne, permettant une réponse plus rapide et plus forte de la plante contre le pathogène. L'analyse du génome a également montré que ces souches sont une source des composés bioactifs, importants pour le contrôle biologique.Dans l'ensemble, cette étude a apporté de nouvelles connaissances sur la structure des communautés microbiennes de la vigne et leurs interactions. De plus, elle a confirmé que la vigne est une source naturelle de microorganismes prometteurs pour une gestion biologique des MDB et qu'ils peuvent promouvoir les réponses de défense des plantes. Ainsi, ces résultats fournissent non seulement une meilleure compréhension des interactions entre la vigne et les BCAs-MDB, mais aussi une forte contribution à la future stratégie de gestion des MDB.Mots-clés : microbiome de la vigne, MDB, D. seriata, microorganismes bénéfiques, Fito_S127B, Fito_F278, colonisation de la vigne, mécanismes de défense, protection
Vitis vinifera L. is a widely cultivated fruit crop, that naturally harbours a complex microbial ecosystem or plant microbiome, such as neutral, phytopathogenic or beneficial microorganisms. Among phytopathogens, those implied in Grapevine trunk diseases (GTDs) are responsible for the most destructive diseases worldwide, and currently no highly effective treatments are available. Beneficial microorganisms (BCAs) may play specific roles on plant protection against phytopathogens though, the present challenge is to understand how such microorganisms interact with plant and their biotechnological potential for development of innovation strategies. In this context, the aim of this study was firstly to unveil the microbial communities associated with grapevine along its growth cycle and, secondly, to better understand the grapevine – BCAs – GTDs interactions. For this, two potential BCAs isolated from grapevine were tested against Botryosphaeriaceae species and then deep characterized, namely for their colonisation potential, induction of defence mechanisms in grapevine, in the presence or not of D. seriata (F98.1) and their genome analysis. Results showed that grapevine microbiome was very dynamic along the growth cycle. As expected, the microbial biodiversity was higher in soils, and these microbial communities differed significantly from those of leaves. A proportion of microbial communities was shared within soils and leaves, suggesting the existence of a core microbiome. Several isolates were then obtained from grapevine which mostly belonged to Bacillus, Streptomyces and Aureobasidium genera. Some of them significantly decreased in vitro the mycelium growth of several Botryosphaeriaceae species, such as Streptomyces sp. Fito_S127B and A. pullulans Fito_F278 which were highly effective and thus selected as potential BCAs. These strains showed to produce a high range of extracellular enzymes with biocontrol value, and were able to successfully colonize grapevine: Fito_S127B was an epiphyte from rhizosphere, while Fito_F278 colonised grapevine from roots to leaves. The artificial inoculation of green stems with D. seriata F98.1 on cutting plants showed that the necrotic lesions length caused by the pathogen was significantly reduced by Fito_S127B, in contrast to Fito_F278 which was less effective. Furthermore, these BCAs activated some specific defence responses of grapevine, allowing a more rapid and solid response of plant against the pathogen. The genome analysis also showed that these BCAs strains are an important source of bioactive compounds of biocontrol value. Overall, this study brought new insights on the structure of microbial communities of grapevine and their interactions. Moreover, highlighted that grapevine is a natural source of microorganisms with a promising biocontrol against GTDs, and that they can promote plant defense responses. Thus, these findings provide not only a better understand of the grapevine- BCAs- GTDs interactions but also a strong contribution to future GTDs management strategy. Key-words: Grapevine microbiome, GTDs, D. seriata, beneficial microorganisms, Fito_S127B, Fito_F278, grapevine colonisation, plant defence mechanisms, grapevine protection

Mon travail de thèse se consacre à l'étude des interactions entre les prédateurs marins et leur environnement marin physique à la meso-echelle (10-100 km, semaines-mois). Comme les réseaux trophiques marins sont des systèmes complexes j'ai travaillé à partir de différents types de données : données satellitaires et in situ pour les propriétés physiques de l'océan, des échantillons biologiques, des données de biologging des animaux et de la modélisation
Marine top predators play a fundamental role in maintaining the structure and functioning of healthy marine ecosystems. In the last decades the development of bio-Iogging (i. E. Deployment of autonomous recording tags on free-living animals) has radically changed the study of top predators and their interactions with their environment. Combinations of sensors measuring position (Argos and GPS), environmental properties (water temperature, light) and proxies for foraging behavior (accelerometers) have enabled relating migrations of large fish, marine mammals, sea turtles and seabirds to basin scale patterns of ocean currents, temperature, and productivity. However, what influences marine predators' movement at smaller spatial and temporal scales, such as the ones they experience during their foraging trips, is still largely unknown. This project analyses the interaction between marine top predators (elephant seals and macaroni penguins) and sub-mesoscale (few days-months, 10-100 km) ocean dynamics. This is achieved by combining in-situ observations, bio-logging data, remote-sensing, ecological modelling and a Lagrangian approach (i. E. Based on the tracking of water parcels). The study is conducted in the sub-Antarctic region around the Kerguelen Plateau (Indian Sector of the Southern Ocean)

Les récepteurs couplés aux protéines G (GPCRs en anglais) représentent la famille de récepteurs intégrales de membrane plus vaste dans la majorité des cellules eucaryotes. Ils jouent un rôle clé dans la transduction de signal, ainsi que la compréhension de leur mécanisme de signalisation représente une des questions principales dans la biologie d'aujourd'hui. Dans la caractérisation du paysage énergétique de ces récepteurs à l'échelle atomique, les structures cristallographiques publiées pendant la décennie dernière par cristallographie aux rayons X représentent la percée scientifique majeure et donnent une contribution fondamentale dans la biologie structurelle de GPCRS. Ces structures représentent un point de départ précieux dans la compréhension du mécanisme de transduction de signal, en plaçant des structures dans l'ensemble conformationnel de ces récepteurs le long du processus d'activation. Pour compléter ce cadre de structures statiques qui correspondent aux états à basse l'énergie et fortement peuplés, une caractérisation de l'ensemble conformationnel et des barrières cinétiques qui sont associées est un point nécessaire et fondamentale. À ce but nous proposons une approche innovant avec la finalité d'observer le paysage conformationnel dynamique des GPCR et étudier la modulation de ces récepteurs par des ligands et des lipides, qui sont connus pour jouer un rôle clé dans la structure et les fonctions des protéines de membrane (e.g.). Un des outilles le plus approprié pour explorer les barrières cinétiques de GPCR c'est la résonance magnétique nucléaire (RMN) en solution. Pour tirer profit au mieux de cette technique, nous avons utilisé des sondes marqués 13CH3 immergées dans un environnement perdeuteré, qui constitue le marquage isotopique le plus approprié en RMN pour examiner les paysages conformationnels des protéines de grosses dimensionnes ou des complexes de protéines. Nous avons choisi Escherichia coli comme système d'expression pour sa capacité de pousser dans des conditions très hostiles comme des solutions 100%-D2O. Pour surmonter les difficultés habituellement rencontrées lors de l'expression des GPCRs, nous avons appliqué un protocole innovant qui cible l'expression de GPCRs directement aux corps d'inclusion. Ceci permet la production des bonnes quantités de protéines (jusqu’à 6 mg/litres de culture de pur 13CH3-u-2H-GPCRs). Une fois purifié, le récepteur est foldé en amphipols et transféré ensuite à une double couche lipidique appelée nanometric lipid bilayer ou nanodisc (NLB). De façon très important, les mesures pharmacologiques quantitatives indiquent que les récepteurs incorporés dans des NLBs après ce protocole sont stables et entièrement actifs dans les conditions des expériences de NMR.Les investigations par RMN conduites sur le GPCR en NLB ont donné lieu à une résolution jamais obtenue dans le domaine, grâce à la biochimie finement accordée et à la perdeuteration du récepteur. Selon les données obtenues, notre récepteur modèle, le récepteur 2 pour le leukotriene B4 (BLT2), est capable d'explorer plusieurs conformations différentes, même dans l'état pas lié aux ligands, y compris l'état actif. Ce paysage conformationnel est également modulé par des ligands et des lipides. Dans le cas spécifiques, nous avons observé que un incrément dans le contenu de stérol dans la membrane modifie la distribution des différents états conformationnels du récepteur, en favorisant l'état actif, qui indique une régulation allosteric positif du stérol sur l'activation de ce récepteur, comme confirmé aussi par les mesures de liaison du GTP à la protéine G. Cette propriété du stérol est probablement importante pour le contrôle de mécanisme de signalisation de GPCRs
G protein-coupled receptors (GPCRs) are the largest family of integral membrane protein receptors present in most eukaryotic cells. They play a key role in signal transduction and understanding their signalling mechanism represents one of the main issues in biology today. In the characterization of the energy landscape of these receptors, at the atomic scale, X-ray crystal atomic structures published during the last decade represent the major breakthrough and contribution in the structural biology of GPCRs. They represent a precious starting point in the understanding of the mechanism of signal transduction by placing structures in the conformational ensemble of these receptors along the activation pathway. To complete these static snapshots that correspond to low energy and highly populated states, a characterization of the whole conformational ensemble and associated kinetic barriers is fundamental to complete the picture. To this aim we proposed an innovative approach to observe GPCRs dynamic conformational landscape and how it is modulated by ligands and lipids, that are known to play a key role in membrane protein structures and functions (e.g.). One of the most appropriate tool to explore GPCR kinetic barriers is solution state NMR. To do so, we used 13CH3 probes immersed in a perdeuterated environment, the most appropriate isotope-labelling scheme to investigate conformational landscapes of large proteins or protein complexes with this spectroscopy. We chose Escherichia coli as expression system for its ability to grow in very hostile conditions like 100%-D2O solutions. In order to overcome the usual expression issues concerning GPCRs, we applied an innovative protocol which targets the expression directly to inclusion bodies. This allows the production of high amounts of proteins (up to 6 mg/litre of culture of pure 13CH3-u-2H-GPCRs). Once purified, receptors are folded in amphipols and then transferred to nanometric lipid bilayers or nanodiscs. Importantly quantitative pharmacological measurements indicate that receptors embedded in NLBs following this protocol are stable and fully active in the conditions of the NMR experiments. NMR investigation of a GPCR in a NLB gave rise to a resolution never achieved in the field thanks to a fine tuned biochemistry and a perdeuteration of the receptor. According to our data, the prototypical receptor, the leukotriene B4 receptor (BLT2), is able to explore multiple different conformations, even in the unliganded state, including the active state. This conformational landscape is further modulated by ligands and lipids. In particular, we observed that an increment in the sterol content of the membrane modifies the distribution of the different conformational states of the receptor in favour of the active one, indicating a positive allosteric regulation of the sterol on the activation of this receptor, as confirmed by GTP-to-G protein binding measurements. This property of the sterol is likely important for the control of the signalling properties of GPCRs

The aim of this research is to assess various options for the management of topsoil stockpiles on disturbed lands and to evaluate the viability and germinability over time of the seedbanks in these stockpiles for use in rehabilitation. To predict their success, experimental trials were designed and conducted.

Although a common plant response to environmental gradients, leaf trait plasticity is often uncharted in agroforestry systems. The objective of this study was to examine the effect of a i) local-scale gradient (light, nutrients) induced by shade tree diversity and ii) large-scale gradient (climato-edaphic) induced by altitude on coffee plant response on multiple agroforestry research farms in Costa Rica. Results show large variability of coffee traits: leaf photosynthetic rates, specific leaf area (SLA) and number of fruiting nodes deviate along both gradients. Mean SLA increased with increasing shade tree diversity. However, with increasing altitude, full sun coffee photosynthesized at higher rates than shaded coffee. Concurrently, other coffee leaf physiological and morphological traits differentiated between full sun and shaded coffee with increasing altitude. Results suggest soil moisture and light availability dominate environmental correlates to intraspecific coffee trait plasticity, providing insight to sources of coffee performance variability in monoculture and agroforestry systems.