Penicillin-binding protein gene alterations in Streptococcus uberis isolates presenting decreased susceptibility to penicillin.

Streptococcus uberis is an environmental pathogen commonly causing bovine mastitis, an infection that is generally treated with penicillin G. No field case of true penicillin-resistant S. uberis (MIC > 16 mg/liter) has been described yet, but isolates presenting decreased susceptibility (MIC of 0.25 to 0.5 mg/liter) to this drug are regularly reported to our laboratory. In this study, we demonstrated that S. uberis can readily develop penicillin resistance in laboratory-evolved mutants. The molecular mechanism of resistance (acquisition of mutations in penicillin-binding protein 1A [PBP1A], PBP2B, and PBP2X) was generally similar to that of all other penicillin-resistant streptococci described so far. In addition, it was also specific to S. uberis in that independent resistant mutants carried a unique set of seven consensus mutations, of which only one (Q(554)E in PBP2X) was commonly found in other streptococci. In parallel, independent isolates from bovine mastitis with different geographical origins (France, Holland, and Switzerland) and presenting a decreased susceptibility to penicillin were characterized. No mosaic PBPs were detected, but they all presented mutations identical to the one found in the laboratory-evolved mutants. This indicates that penicillin resistance development in S. uberis might follow a stringent pathway that would explain, in addition to the ecological niche of this pathogen, why naturally occurring resistances are still rare. In addition, this study shows that there is a reservoir of mutated PBPs in animals, which might be exchanged with other streptococci, such as Streptococcus agalactiae, that could potentially be transmitted to humans.

Risk factors of stroke mortality in the African region: a cohort study

Background: Population-based cohort studies of risk factors of stroke are scarce in developing countries and none has been done in the African region. We conducted a longitudinal study in the Seychelles (Indian Ocean, east of Kenya), a middle-income island state where the majority of the population is of African descent. Such data in Africa are important for international comparison and for advocacy in the region. Methods: Three examination surveys of cardiovascular risk factors were performed in independent samples representative of the general population aged 25-64 in 1989, 1994 and 2004 (n=1081, 1067, and 1255, respectively). Baseline risk factors data were linked with cause-specific mortality from vital statistics up to May 2007 (all deaths are medically certified in the Seychelles and kept in an electronic database). We considered stroke (any type) as a cause of death if the diagnosis was reported in any of the 4 fields in the death certificates for underlying and concomitant causes of death. Results. Among the 2479 persons aged 35-64 at baseline, 280 died including 56 with stroke during follow up (maximum: 18.2 years; mean: 10.2 years). In this age range, age-adjusted mortality rates (/100'000/year) were 969 for all cause and 187 for stroke; age-adjusted prevalence of high blood pressure (≥140/90 mmHg) was 48%. In multivariate Cox survival time regression, stroke mortality was increased by 18% and 35% for a 10-mmHg increase in systolic, respectively diastolic BP (p<0.001). Stroke mortality was also associated with age, smoking ≥5 cigarettes vs. no smoking (HR: 2.4; 95% CI: 1.2-4.8) and diabetes (HR: 1.9; 1.02-3.6) but not with sex, LDL-cholesterol intake, alcohol intake and professional occupation. Conclusion. This first population-based cohort study in the African region demonstrates high mortality rates from stroke in middle-aged adults and confirms associations with high BP and other risk factors. This emphasizes the importance of reducing BP and other modifiable risk factors in high risk individuals and in the general population as a main strategy to reduce the burden of stroke.

Study of the regulation of antifungal activity in plant-associated pseudomas fluorescens

RésuméEn agriculture d'énormes pertes sont causées par des champignons telluriques pathogènes tels que Thielaviopsis, Fusarium, Gaeumannomyces et Rhizoctonia ou encore l'oomycète Pythium. Certaines bactéries dites bénéfiques, comme Pseudomonas fluorescens, ont la capacité de protéger les plantes de ces pathogènes par la colonisation de leur racines, par la production de métabolites secondaires possédants des propriétés antifongiques et par l'induction des mécanismes de défenses de la plante colonisée. P. fluorescens CHAO, une bactérie biocontrôle isolée d'un champ de tabac à Payerne, a la faculté de produire un large spectre de métabolites antifongiques, en particulier le 2,4- diacétylphloroglucinol (DAPG), la pyolutéorine (PLT), le cyanure d'hydrogène (HCN), la pyrrolnitrine (PRN) ainsi que des chélateurs de fer.La plante, par sécrétion racinaire, produit des rhizodéposites, source de carbone et d'azote, qui profitent aux populations bactériennes vivant dans la rhizosphere. De plus, certains stresses biotiques et abiotiques modifient cette sécrétion racinaire, en terme quantitatif et qualitatif. De leur côté, les bactéries bénéfiques, améliorent, de façon direct et/ou indirect, la croissance de la plante hôte. De nombreux facteurs biotiques et abiotiques sont connus pour réguler la production de métabolites secondaires chez les bactéries. Des études récentes ont démontré l'importance de la communication entre la plante et les bactéries bénéfiques afin que s'établisse une interaction profitant à chacun des deux partis. Il est ainsi vraisemblable que les populations bactériennes associées aux racines soient capables d'intégrer ces signaux et d'adapter spécifiquement leur comportement en conséquence.La première partie de ce travail de thèse a été la mise au point d'outils basés sur la cytométrie permettant de mesurer l'activité antifongique de cellules bactériennes individuelles dans un environnent naturel, les racines des plantes. Nous avons démontré, grâce à un double marquage aux protéines autofluorescentes GFP et mCherry, que les niveaux d'expression des gènes impliqués dans la biosynthèse des substances antifongiques DAPG, PLT, PRN et HCN ne sont pas les mêmes dans des milieux de cultures liquides que sur les racines de céréales. Par exemple, l'expression de pltA (impliqué dans la biosynthèse du PLT) est quasiment abolie sur les racines de blé mais atteint un niveau relativement haut in vitro. De plus cette étude a mis en avant l'influence du génotype céréalien sur l'expression du gène phlA qui est impliqué dans la biosynthèse du DAPG.Une seconde étude a révélé la communication existant entre une céréale (orge) infectée par le pathogène tellurique Pythium ultimum et P. fluorescens CHAO. Un système de partage des racines nous a permis de séparer physiquement le pathogène et la bactérie bénéfique sur la plante. Cette méthode a donné la possibilité d'évaluer l'effet systémique, causé par l'attaque du pathogène, de la plante sur la bactérie biocontrôle. En effet, l'infection par le phytopathogène modifie la concentration de certains composés phénoliques dans les exsudats racinaires stimulant ainsi l'expression de phi A chez P.fluorescens CHAO.Une troisième partie de ce travail focalise sur l'effet des amibes qui sont des micro-prédateurs présents dans la rhizosphere. Leur présence diminue l'expression des gènes impliqués dans la biosynthèse du DAPG, PLT, PRN et HCN chez P.fluorescens CHAO, ceci en culture liquide et sur des racines d'orge. De plus, des molécules provenant du surnageant d'amibes, influencent l'expression des gènes requis pour la biosynthèse de ces antifongiques. Ces résultats illustrent que les amibes et les bactéries de la rhizosphere ont développé des stratégies pour se reconnaître et adapter leur comportement.La dernière section de ce travail est consacrée à l'acide indole-acétique (LA.A), une phytohormone connue pour son effet stimulateur sur phlA. Une étude moléculaire détaillée nous a démontré que cet effet de l'IAA est notamment modulé par une pompe à efflux (FusPl) et de son régulateur transcriptionnel (MarRl). De plus, les gènes fusPl et marRl sont régulés par d'autres composés phénoliques tels que le salicylate (un signal végétal) et l'acide fusarique (une phytotoxine du pathogène Fusarium).En résumé, ce travail de thèse illustre la complexité des interactions entre les eucaryotes et procaryotes de la rhizosphère. La reconnaissance mutuelle et l'instauration d'un dialogue moléculaire entre une plante hôte et ses bactéries bénéfiques associées? sont indispensables à la survie des deux protagonistes et semblent être hautement spécifiques.SummaryIn agriculture important crop losses result from the attack of soil-borne phytopathogenic fungi, including Thielaviopsis, Fusarium, Gaeumannomyces and Rhizoctonia, as well as from the oomycete Pythium. Certain beneficial microorganisms of the rhizosphere, in particular Pseudomonas fluorescens, have the ability to protect plants against phytopathogens by the intense colonisation of roots, by the production of antifungal exoproducts, and by induction of plant host defences. P. fluorescens strain CHAO, isolated from a tobacco field near Payerne, produces a large array of antifungal exoproducts, including 2,4-diacetylphloroglucinol (DAPG), pyoluteorin (PLT), hydrogen cyanide (HCN), pyrrolnitrin (PRN) and iron chelators. Plants produce rhizodeposites via root secretion and these represent a relevant source of carbon and nitrogen for rhizosphere microorganisms. Various biotic and abiotic stresses influence the quantity and the quality of released exudates. One the other hand, beneficial bacteria directly or indirectly promote plant growth. Biotic and abiotic factors regulate exoproduct production in biocontrol microorganisms. Recent studies have highlighted the importance of communication in establishing a fine-tuned mutualist interaction between plants and their associated beneficial bacteria. Bacteria may be able to integrate rhizosphere signals and adapt subsequently their behaviour.In a first part of the thesis, we developed a new method to monitor directly antifungal activity of individual bacterial cells in a natural environment, i.e. on roots of crop plants. We were able to demonstrate, via a dual-labelling system involving green and red fluorescent proteins (GFP, mCherry) and FACS-based flow cytometry, that expression levels of biosynthetic genes for the antifungal compounds DAPG, PLT, PRN, and HCN are highly different in liquid culture and on roots of cereals. For instance, expression of pltA (involved in PLT biosynthesis) was nearly abolished on wheat roots whereas it attained a relatively high level under in vitro conditions. In addition, we established the importance of the cereal genotype in the expression of phi A (involved in DAPG biosynthesis) in P. fluorescens CHAO.A second part of this work highlighted the systemic communication that exists between biocontrol pseudomonads and plants following attack by a root pathogen. A split-root system, allowing physical separation between the soil-borne oomycete pathogen Phytium ultimum and P. fluorescens CHAO on barley roots, was set up. Root infection by the pathogen triggered a modification of the concentration of certain phenolic root exudates in the healthy root part, resulting in an induction ofphlA expression in P. fluorescens CHAO.Amoebas are micro-predators of the rhizosphere that feed notably on bacteria. In the third part of the thesis, co-habitation of Acanthamoeba castellanii with P. fluorescens CHAO in culture media and on barley roots was found to significantly reduce bacterial expression of genes involved in the biosynthesis of DAPG, PLT, HCN and PRN. Interestingly, molecular cues present in supernatant of A. castelanii induced the expression of these antifungal genes. These findings illustrate the strategies of mutual recognition developed by amoeba and rhizosphere bacteria triggering responses that allow specific adaptations of their behaviour.The last section of the work focuses on indole-3-acetic acid (IAA), a phytohormone that stimulates the expression of phi A. A detailed molecular study revealed that the IAA-mediated effect on phi A is notably modulated by an efflux pump (FusPl) and its transcriptional regulator (MarRl). Remarkably, transcription of fusPl and marRl was strongly upregulated in presence of other phenolic compounds such as salicylate (a plant signal) and fusaric acid (a phytotoxin of the pathogenic fungus Fusarium).To sum up, this work illustrates the great complexity of interactions between eukaryotes and prokaryotes taking place in the rhizosphere niche. The mutual recognition and the establishment of a molecular cross-talk between the host plant and its associated beneficial bacteria are essential for the survival of the two partners and these interactions appear to be highly specific.

Five (or so) challenges for species distribution modelling

Species distribution modelling is central to both fundamental and applied research in biogeography. Despite widespread use of models, there are still important conceptual ambiguities as well as biotic and algorithmic uncertainties that need to be investigated in order to increase confidence in model results. We identify and discuss five areas of enquiry that are of high importance for species distribution modelling: (1) clarification of the niche concept; (2) improved designs for sampling data for building models; (3) improved parameterization; (4) improved model selection and predictor contribution; and (5) improved model evaluation. The challenges discussed in this essay do not preclude the need for developments of other areas of research in this field. However, they are critical for allowing the science of species distribution modelling to move forward.

Plumage ornaments, bacterial colonisation and signalling in european starling, "Sturnus vulgaris"

Abstract Animal behaviours or structures are used by senders as signals to try to increase their fitness by altering the behaviour of receivers. A large fraction of studies on sexual selection have focussed on male ornaments and have demonstrated that these ornaments signal the quality of their owner and are used by female for mate choice. Although females can also exhibit conspicuous traits, studies on female ornaments are markedly lacking. In chapter 1, we show that female starlings are showier on chest whiteness than males and that females' whiteness may potentially indicate female condition at the start of breeding and provide fitness advantages to breeding birds. Furthermore we point out that feather density and abrasion are important factors shaping the expression of chest whiteness. This suggests that further understanding of the evolution of chest whiteness in Starlings requires to examine the environmental and physiological factors that shape feather condition. Plumage may suffer from damage through abrasion and bacterial activity. In chapter 2, we focus on factors that influence feather-degrading bacterial communities. Within the hypothesis that parental care can be trade-off against the demands of self-maintenance, we show that a brood size manipulation modifies the structure of feather-degrading bacterial communities and the density of free- living bacteria. Thus we have pointed out a potentially poorly known cost of reproduction. In the same context of a trade-off between reproductive activities and individual self-maintenance, chapter 3 shows that at a proximate level in females but not in males, the individual variation in time and/or energy allocated in reproductive activities is associated with prolactin hormone levels. Our study provides evidence for the existence of a sex related difference in the relationship between brood size and prolactin levels. Birds have evolved sanitation behaviours and preen gland secretions to preserve the condition of their plumage. In chapter 4, we describe a method that allows to measure preen gland in situ. Then we use this method to characterize a number of phenotypic and ecological factors that explain variation in preen gland size in free-living individuals. In parent-offspring interactions, parents use offspring signals to provision their brood. In chapter 5, we demonstrate that nestling flanges and body skin reflect in the ultra-violet (UV) wavelengths ant that parents use this UV reflectance in food allocation decisions. Résumé Certains comportements et structures chez les animaux agissent, pour ceux qui les émettent, comme des signaux permettant d'augmenter leur fitness en altérant les comportements de ceux qui les perçoivent. Une grande partie des études sur la sélection sexuelle s'est focalisée sur les ornements mâles. Ces études ont démontré que ces ornements pouvaient signaler la qualité de celui qui les porte et influencer le choix des femelles. Bien que les femelles puissent aussi présenter des traits voyants, les études sur leurs ornements font défaut. Dans le chapitre 1 de ce travail, nous montrons que les étourneaux femelles sont plus voyantes que les mâles sur la base de la blancheur de la poitrine. De plus la blancheur des femelles peut signaler leur condition au début de la saison de reproduction et ainsi être corrélée avec leur fitness. Nous mettons aussi en évidence que la densité et l'abrasion des plumes sont des facteurs importants, contrôlant l'expression de la blancheur de la poitrine. Ceci suggère que des études futures pourraient examiner le rôle des facteurs environnementaux et physiologiques qui influencent la condition des plumes pour mieux comprendre l'évolution de la blancheur chez les étourneaux. Le plumage subit des dommages à travers l'abrasion et probablement aussi par l'activité de dégradation de bactéries. Dans le chapitre 2 de ce travail, nous nous intéressons aux facteurs qui influencent les communautés de bactéries dégradant les plumes. Nous basant sur l'hypothèse selon laquelle il existe un compromis entre les soins parentaux et la maintenance corporelle, nous montrons qu'une manipulation de la taille de nichée modifie la structure des communautés de bactéries dégradant les plumes ainsi que les densités de bactéries libres présentes sur le plumage. Ainsi nous mettons en évidence un coût encore peu connu des activités de reproduction. Dans le même contexte, nous montrons, dans le chapitre 3, que des variations individuelles dans l'énergie et/ou le temps alloué dans les activités de reproduction sont associés, chez les femelles, à un niveau proximal à l'hormone prolactine. Cette relation n'est pas présente chez les mâles. Cette étude montre que la relation entre la taille de nichée et les niveaux de prolactine diffère avec le sexe des individus. Les oiseaux utilisent des comportements de nettoyage associés aux sécrétions de la glande uropygiale afin de préserver la condition de leurs plumes. Dans le chapitre 4 de ce travail, nous décrivons une méthode qui permet de mesurer la taille de la glande in situ. Puis nous caractérisons certains facteurs écologiques et physiologiques qui expliquent les variations de la taille de la glande chez des individus capturés dans leur environnement. Les parents nourrissent leur progéniture en réponse à des signaux émis par ceux-ci. Dans le chapitre 5 de ce travail, nous démontrons que les commissures et la peau sur le corps des oisillons reflètent la lumière dans l'ultraviolet. Nous montrons que les parents utilisent cette réflexion dans l'ultraviolet lors de l'allocation de nourriture pour leurs jeunes.

Do habitat suitability models reliably predict the recovery areas of threatened species?

1. Identifying those areas suitable for recolonization by threatened species is essential to support efficient conservation policies. Habitat suitability models (HSM) predict species' potential distributions, but the quality of their predictions should be carefully assessed when the species-environment equilibrium assumption is violated.2. We studied the Eurasian otter Lutra lutra, whose numbers are recovering in southern Italy. To produce widely applicable results, we chose standard HSM procedures and looked for the models' capacities in predicting the suitability of a recolonization area. We used two fieldwork datasets: presence-only data, used in the Ecological Niche Factor Analyses (ENFA), and presence-absence data, used in a Generalized Linear Model (GLM). In addition to cross-validation, we independently evaluated the models with data from a recolonization event, providing presences on a previously unoccupied river.3. Three of the models successfully predicted the suitability of the recolonization area, but the GLM built with data before the recolonization disagreed with these predictions, missing the recolonized river's suitability and badly describing the otter's niche. Our results highlighted three points of relevance to modelling practices: (1) absences may prevent the models from correctly identifying areas suitable for a species spread; (2) the selection of variables may lead to randomness in the predictions; and (3) the Area Under Curve (AUC), a commonly used validation index, was not well suited to the evaluation of model quality, whereas the Boyce Index (CBI), based on presence data only, better highlighted the models' fit to the recolonization observations.4. For species with unstable spatial distributions, presence-only models may work better than presence-absence methods in making reliable predictions of suitable areas for expansion. An iterative modelling process, using new occurrences from each step of the species spread, may also help in progressively reducing errors.5. Synthesis and applications. Conservation plans depend on reliable models of the species' suitable habitats. In non-equilibrium situations, such as the case for threatened or invasive species, models could be affected negatively by the inclusion of absence data when predicting the areas of potential expansion. Presence-only methods will here provide a better basis for productive conservation management practices.

Progenitor cell therapy for heart disease.

Many cell types are currently being studied as potential sources of cardiomyocytes for cell transplantation therapy to repair and regenerate damaged myocardium. The question remains as to which progenitor cell represents the best candidate. Bone marrow-derived cells and endothelial progenitor cells have been tested in clinical studies. These cells are safe, but their cardiogenic potential is controversial. The functional benefits observed are probably due to enhanced angiogenesis, reduced ventricular remodeling, or to cytokine-mediated effects that promote the survival of endogenous cells. Human embryonic stem cells represent an unlimited source of cardiomyocytes due to their great differentiation potential, but each step of differentiation must be tightly controlled due to the high risk of teratoma formation. These cells, however, confront ethical barriers and there is a risk of graft rejection. These last two problems can be avoided by using induced pluripotent stem cells (iPS), which can be autologously derived, but the high risk of teratoma formation remains. Cardiac progenitor cells have the advantage of being cardiac committed, but important questions remain unanswered, such as what is the best marker to identify and isolate these cells? To date the different markers used to identify adult cardiac progenitor cells also recognize progenitor cells that are outside the heart. Thus, it cannot be determined whether the cardiac progenitor cells identified in the adult heart represent resident cells present since fetal life or extracardiac cells that colonized the heart after cardiac injury. Developmental studies have identified markers of multipotent progenitors, but it is unknown whether these markers are specific for adult progenitors when expressed in the adult myocardium. Cardiac regeneration is dependent on the stability of the cells transplanted into the host myocardium and on the electromechanical coupling with the endogenous cells. Finally, the promotion of endogenous regenerative processes by mobilizing endogenous progenitors represents a complementary approach to cell transplantation therapy.

Parvalbumin interneurons mediate neuronal circuitry-neurogenesis coupling in the adult hippocampus.

Using immunohistology, electron microscopy, electrophysiology and optogenetics, we found that proliferating adult mouse hippocampal neural precursors received immature GABAergic synaptic inputs from parvalbumin-expressing interneurons. Recently shown to suppress adult quiescent neural stem cell activation, parvalbumin interneuron activation promoted newborn neuronal progeny survival and development. Our results suggest a niche mechanism involving parvalbumin interneurons that couples local circuit activity to the diametric regulation of two critical early phases of adult hippocampal neurogenesis.

The squeeze cell hypothesis for the activation of jasmonate synthesis in response to wounding

Jasmonates are lipid mediators that control defence gene expression in response to wounding and other environmental stresses. These small molecules can accumulate at distances up to several cm from sites of damage and this is likely to involve cell-to-cell jasmonate transport. Also, and independently of jasmonate synthesis, transport and perception, different long-distance wound signals that stimulate distal jasmonate synthesis are propagated at apparent speeds of several cmmin(-1) to tissues distal to wounds in a mechanism that involves clade 3 GLUTAMATE RECEPTOR-LIKE (GLR) genes. A search for jasmonate synthesis enzymes that might decode these signals revealed LOX6, a lipoxygenase that is necessary for much of the rapid accumulation of jasmonic acid at sites distal to wounds. Intriguingly, the LOX6 promoter is expressed in a distinct niche of cells that are adjacent to mature xylem vessels, a location that would make these contact cells sensitive to the release of xylem water column tension upon wounding. We propose a model in which rapid axial changes in xylem hydrostatic pressure caused by wounding travel through the vasculature and lead to slower, radially dispersed pressure changes that act in a clade 3 GLR-dependent mechanism to promote distal jasmonate synthesis.

Regulation of the integration of newly generated neurons in the adult hippocampus

Hippocampal adult neurogenesis results in the continuous formation of new neurons in the adult hippocampus, which participate to learning and memory. Manipulations increasing adult neurogenesis have a huge clinical potential in pathologies involving memory loss. Intringuingly, most of the newborn neurons die during their maturation. Thus, increasing newborn neuron survival during their maturation may be a powerful way to increase overall adult neurogenesis. The factors governing this neuronal death are yet poorly known. In my PhD project, we made the hypothesis that synaptogenesis and synaptic activity play a role in the survival of newborn hippocampal neurons. We studied three factors potentially involved in the regulation of the synaptic integration of adult-born neurons. First, we used propofol anesthesia to provoke a global increase in GABAergic activity of the network, and we evaluated the outcome on newborn neuron synaptic integration, morphological development and survival. Propofol anesthesia impaired the dendritic maturation and survival of adult-born neurons in an age-dependent manner. Next, we examined the development of astrocytic ensheathment on the synapses formed by newborn neurons, as we hypothesized that astrocytes are involved in their synaptic integration. Astrocytic processes ensheathed the synapses of newborn neurons very early in their development, and the processes modulated synaptic transmission on these cells. Finally, we studied the cell-autonomous effects of the overexpression of synaptic adhesion molecules on the development, synaptic integration and survival of newborn neurons, and we found that manipulating of a single adhesion molecule was sufficient to modify synaptogenesis and/or synapse function, and to modify newborn neuron survival. Together, these results suggest that the activity of the neuronal network, the modulation of glutamate transport by astrocytes, and the synapse formation and activity of the neuron itself may regulate the survival of newborn neurons. Thus, the survival of newborn neurons may depend on their ability to communicate with the network. This knowledge is crucial for finding ways to increase neurogenesis in patients. More generally, understanding how the neurogenic niche works and which factors are important for the generation, maturation and survival of neurons is fundamental to be able to maybe, one day, replace neurons in any region of the brain.

Adaptive diversity in heterogeneous environments for populations regulated by a mixture of soft and hard selection

The stable co-existence of two haploid genotypes or two species is studied in a spatially heterogeneous environment submitted to a mixture of soft selection (within-patch regulation) and hard selection (outside-patch regulation) and where two kinds of resource are available. This is analysed both at an ecological time-scale (short term) and at an evolutionary time-scale (long term). At an ecological scale, we show that co-existence is very unlikely if the two competitors are symmetrical specialists exploiting different resources. In this case, the most favourable conditions are met when the two resources are equally available, a situation that should favour generalists at an evolutionary scale. Alternatively, low within-patch density dependence (soft selection) enhances the co-existence between two slightly different specialists of the most available resource. This results from the opposing forces that are acting in hard and soft regulation modes. In the case of unbalanced accessibility to the two resources, hard selection favours the most specialized genotype, whereas soft selection strongly favours the less specialized one. Our results suggest that competition for different resources may be difficult to demonstrate in the wild even when it is a key factor in the maintenance of adaptive diversity. At an evolutionary scale, a monomorphic invasive evolutionarily stable strategy (ESS) always exists. When a linear trade-off exists between survival in one habitat versus that in another, this ESS lies between an absolute adjustment of survival to niche size (for mainly soft-regulated populations) and absolute survival (specialization) in a single niche (for mainly hard-regulated populations). This suggests that environments in agreement with the assumptions of such models should lead to an absence of adaptive variation in the long term.

Role of glast-positive glial cells during photoreceptor development

Purpose: Taking advantage of two transgenic lines, glast.DsRed and crx.gfp, that express fluorescent proteins in glial and photoreceptor cells respectively, we investigate the role of glast-positive glial cells (GPCs) in the survival/differentiation/proliferation of age-matched photoreceptor cells. Methods: Primary retinal cells were isolated from newborn transgenic mouse retina (glast.dsRed::crx.gfp) at postnatal day (P0/P1) and propagated in defined medium containing epidermal growth factor (EGF) and fibroblast growth factor 2 (bFGF). By flow-sorting another population of pure GPCs was isolated. Both populations were expanded and analyzed for the presence of specific retinal cell markers. Notably, the primary cell culture collected from the transgenic line glast.dsRed::crx.gfp showed a conspicuous presence of immature photoreceptors growing on top of GPCs. In order to reveal the role of such cells in the survival/differentiation/proliferation of photoreceptors we set up in vitro cultures of retina-derived cells that allowed long-term time-lapse recordings charting every cell division, death and differentiation event. To assess the regenerative potential of GPCs we challenged them with compounds mimicking retinal degeneration (NMU, NMDA, Zaprinast). Mass spectrometry (MS), immunostainings and other molecular approaches were performed to reveal adhesion molecules involved in the relationship between glial cells and photoreceptors. Results: Both primary cell lines were highly homogenous, with an elongated morphology and the majority expressed Müller glia markers (MG) such as glast, blbp, glt-1, vimentin, glutamine synthetase (GS), GFAP, cd44, mash1 and markers of reactive Müller glia such as nestin, pax6. Conversely, none of them were found positive for retinal neuron markers like tuj1, otx2, recoverin. Primary cultures of GPCs show the incapability of glial cells to give rise to photoreceptors in both wild type or degenerative environment. Furthermore, primary cultures of pure GPCs challenged with different compounds did not highlight the production of new glial cell-derived photoreceptors. Adhesion molecules involved in the contact between photoreceptors and glial cells are still under investigation. Conclusions: Primary glia cells do not give rise to photoreceptor cells in wt and degenerative conditions at least in vitro. The roles of glial cells seem to be more linked to the maintenance/proliferation of photoreceptor cells.

Predicting potential distribution of the jaguar (Panthera onca) in Mexico: identification of priority areas for conservation

Aim The jaguar, Panthera onca, is a species of global conservation concern. In Mexico, the northernmost part of its distribution range, its conservation status, is particularly critical, while its potential and actual distribution is poorly known. We propose an ensemble model (EM) of the potential distribution for the jaguar in Mexico and identify the priority areas for conservation.Location Mexico.Methods We generated our EM based on three presence-only methods (Ecological Niche Factor Analysis, Mahalanobis distance, Maxent) and considering environmental, biological and anthropogenic factors. We used this model to evaluate the efficacy of the existing Mexican protected areas (PAs), to evaluate the adequacy of the jaguar conservation units (JCUs) and to propose new areas that should be considered for conservation and management of the species in Mexico.Results Our results outline that 16% of Mexico (c. 312,000 km2) can be considered as suitable for the presence of the jaguar. Furthermore, 13% of the suitable areas are included in existing PAs and 14% are included in JCUs (Sanderson et al., 2002).Main conclusions Clearly much more should be carried out to establish a proactive conservation strategy. Based on our results, we propose here new jaguar conservation and management areas that are important for a nationwide conservation blueprint.

Smed454 dataset: unravelling the transcriptome of Schmidtea mediterranea

Background: Freshwater planarians are an attractive model for regeneration and stem cell research and have become a promising tool in the field of regenerative medicine. With the availability of a sequenced planarian genome, the recent application of modern genetic and high-throughput tools has resulted in revitalized interest in these animals, long known for their amazing regenerative capabilities, which enable them to regrow even a new head after decapitation. However, a detailed description of the planarian transcriptome is essential for future investigation into regenerative processes using planarians as a model system. Results: In order to complement and improve existing gene annotations, we used a 454 pyrosequencing approach to analyze the transcriptome of the planarian species Schmidtea mediterranea Altogether, 598,435 454-sequencing reads, with an average length of 327 bp, were assembled together with the ~10,000 sequences of the S. mediterranea UniGene set using different similarity cutoffs. The assembly was then mapped onto the current genome data. Remarkably, our Smed454 dataset contains more than 3 million novel transcribed nucleotides sequenced for the first time. A descriptive analysis of planarian splice sites was conducted on those Smed454 contigs that mapped univocally to the current genome assembly. Sequence analysis allowed us to identify genes encoding putative proteins with defined structural properties, such as transmembrane domains. Moreover, we annotated the Smed454 dataset using Gene Ontology, and identified putative homologues of several gene families that may play a key role during regeneration, such as neurotransmitter and hormone receptors, homeobox-containing genes, and genes related to eye function. Conclusions: We report the first planarian transcript dataset, Smed454, as an open resource tool that can be accessed via a web interface. Smed454 contains significant novel sequence information about most expressed genes of S. mediterranea. Analysis of the annotated data promises to contribute to identification of gene families poorly characterized at a functional level. The Smed454 transcriptome data will assist in the molecular characterization of S. mediterranea as a model organism, which will be useful to a broad scientific community.

Smed454 dataset: unravelling the transcriptome of Schmidtea mediterranea

Background Freshwater planarians are an attractive model for regeneration and stem cell research and have become a promising tool in the field of regenerative medicine. With the availability of a sequenced planarian genome, the recent application of modern genetic and high-throughput tools has resulted in revitalized interest in these animals, long known for their amazing regenerative capabilities, which enable them to regrow even a new head after decapitation. However, a detailed description of the planarian transcriptome is essential for future investigation into regenerative processes using planarians as a model system. Results In order to complement and improve existing gene annotations, we used a 454 pyrosequencing approach to analyze the transcriptome of the planarian species Schmidtea mediterranea Altogether, 598,435 454-sequencing reads, with an average length of 327 bp, were assembled together with the ~10,000 sequences of the S. mediterranea UniGene set using different similarity cutoffs. The assembly was then mapped onto the current genome data. Remarkably, our Smed454 dataset contains more than 3 million novel transcribed nucleotides sequenced for the first time. A descriptive analysis of planarian splice sites was conducted on those Smed454 contigs that mapped univocally to the current genome assembly. Sequence analysis allowed us to identify genes encoding putative proteins with defined structural properties, such as transmembrane domains. Moreover, we annotated the Smed454 dataset using Gene Ontology, and identified putative homologues of several gene families that may play a key role during regeneration, such as neurotransmitter and hormone receptors, homeobox-containing genes, and genes related to eye function. Conclusions We report the first planarian transcript dataset, Smed454, as an open resource tool that can be accessed via a web interface. Smed454 contains significant novel sequence information about most expressed genes of S. mediterranea. Analysis of the annotated data promises to contribute to identification of gene families poorly characterized at a functional level. The Smed454 transcriptome data will assist in the molecular characterization of S. mediterranea as a model organism, which will be useful to a broad scientific community.