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11.
Perrine Pelosse Christopher M. Kribs-Zaleta Marine Ginoux Jorge E. Rabinovich Sébastien Gourbière Frédéric Menu 《PloS one》2013,8(8)
Insects are known to display strategies that spread the risk of encountering unfavorable conditions, thereby decreasing the extinction probability of genetic lineages in unpredictable environments. To what extent these strategies influence the epidemiology and evolution of vector-borne diseases in stochastic environments is largely unknown. In triatomines, the vectors of the parasite Trypanosoma cruzi, the etiological agent of Chagas’ disease, juvenile development time varies between individuals and such variation most likely decreases the extinction risk of vector populations in stochastic environments. We developed a simplified multi-stage vector-borne SI epidemiological model to investigate how vector risk-spreading strategies and environmental stochasticity influence the prevalence and evolution of a parasite. This model is based on available knowledge on triatomine biodemography, but its conceptual outcomes apply, to a certain extent, to other vector-borne diseases. Model comparisons between deterministic and stochastic settings led to the conclusion that environmental stochasticity, vector risk-spreading strategies (in particular an increase in the length and variability of development time) and their interaction have drastic consequences on vector population dynamics, disease prevalence, and the relative short-term evolution of parasite virulence. Our work shows that stochastic environments and associated risk-spreading strategies can increase the prevalence of vector-borne diseases and favor the invasion of more virulent parasite strains on relatively short evolutionary timescales. This study raises new questions and challenges in a context of increasingly unpredictable environmental variations as a result of global climate change and human interventions such as habitat destruction or vector control. 相似文献
12.
Simona Nardozza Helen L. Boldingh M. Peggy Kashuba Regina Feil Dan Jones Amali H. Thrimawithana Hilary S. Ireland Marine Philippe Mark W. Wohlers Tony K. McGhie Mirco Montefiori John E. Lunn Andrew C. Allan Annette C. Richardson 《Plant, cell & environment》2020,43(4):819-835
Kiwifruit (Actinidia spp.) is a recently domesticated fruit crop with several novel-coloured cultivars being developed. Achieving uniform fruit flesh pigmentation in red genotypes is challenging. To investigate the cause of colour variation between fruits, we focused on a red-fleshed Actinidia chinensis var. chinensis genotype. It was hypothesized that carbohydrate supply could be responsible for this variation. Early in fruit development, we imposed high or low (carbon starvation) carbohydrate supplies treatments; carbohydrate import or redistribution was controlled by applying a girdle at the shoot base. Carbon starvation affected fruit development as well as anthocyanin and carbohydrate metabolite concentrations, including the signalling molecule trehalose 6-phosphate. RNA-Seq analysis showed down-regulation of both gene-encoding enzymes in the anthocyanin and carbohydrate biosynthetic pathways. The catalytic trehalose 6-phosphate synthase gene TPS1.1a was down-regulated, whereas putative regulatory TPS7 and TPS11 were strongly up-regulated. Unexpectedly, under carbon starvation MYB10, the anthocyanin pathway regulatory activator was slightly up-regulated, whereas MYB27 was also up-regulated and acts as a repressor. To link these two metabolic pathways, we propose a model where trehalose 6-phosphate and the active repressor MYB27 are involved in sensing the carbon starvation status. This signals the plant to save resources and reduce the production of anthocyanin in fruits. 相似文献
13.
14.
Marine Pouget Sami Youssef Jérémy Migliore Marianick Juin Frédéric Médail Alex Baumel 《Annals of botany》2013,112(7):1409-1420
Background and Aims
Understanding the factors that shape variation in genetic diversity across the geographic ranges of species is an important challenge in the effort to conserve evolutionary processes sustaining biodiversity. The historical influences leading to a central–marginal organization of genetic diversity have been explored for species whose range is known to have expanded from refugia after glacial events. However, this question has rarely been addressed for Mediterranean endemic plants of azonal habitats such as rocky slopes or screes. In this context, this comprehensive study examined molecular and field data from Arenaria provincialis (Caryophyllaceae), a narrow endemic plant of south-eastern France.Methods
Across the whole geographic range, an investigation was made of whether high levels of abundance and genetic diversity (estimated from amplified fragment length polymorphism markers) are centrally distributed, to evaluate the relevance of the central–marginal hypothesis. Phylogeographic patterns inferred from chloroplast DNA (cpDNA) were used, applying Bayesian methods to test the influence of past biogeographic events. Multivariate analysis combining phylogeographic and ecological data was used to reveal the historical and ecological distinctiveness of populations.Key Results
Despite the narrow distribution of A. provincialis, a high level of nucleotide variation is found within cpDNA loci, supporting its persistence throughout the Pleistocene period. The area characterized by the highest genetic diversity is centrally located. Structured phylogeography and Bayesian factor analysis supported the hypothesis that the central area of the distribution was the source of both westward and eastward migrations, probably during arid periods of the Pleistocene, and more recently was a crossroads of backward migrations. By contrast, the two areas located today at the range limits are younger, have reduced genetic diversity and are marginal in the ecological gradients.Conclusions
This study highlights a case of strong population distinctiveness within a narrow range. Phylogeography sheds light on the historical role of the areas centrally situated in the distribution. The current range size and abundance patterns are not sufficient to predict the organization of genetic diversity. 相似文献15.
Valeri B. Arakelyan Poghos O. Vardevanyan Zaven E. Navoyan Marine A. Parsadanyan Gohar G. Hovhannesyan Armen T. Karapetian 《Journal of biomolecular structure & dynamics》2013,31(2):330-335
In the present work, the adsorption kinetics of extended ligands on DNA duplexes at small fillings when molecules of DNA duplexes are on the underlayer within diffusion layer has been investigated. Both diffusion of ligands in solution (diffusion stage) and adsorption of ligands (kinetic stage) are taken into consideration at adsorption of ligands on DNA duplexes. Nonlinear system of differential equations describing adsorption of ligands where not only diffusion stage but also kinetic stage is taken into account, is obtained, moreover the equations allow localizing duplexes in arbitrary place within diffusion layer. Numeric solution of the equations makes possible to investigate the filling kinetics of DNA duplexes by ligands depending on parameters controlling adsorption process. It has been shown that depending on relation between adsorption parameters different kinetic regimes of adsorption – kinetic, complex, and diffusion regimes may be realized. 相似文献
16.
Poghos O. Vardevanyan Ara P. Antonyan Marine A. Parsadanyan Mariam A. Shahinyan Lilit A. Hambrdzumyan Mikayel V. Minasyants 《Journal of biomolecular structure & dynamics》2013,31(1)
The interaction of methylene blue (MB) with DNA has been investigated by UV absorption spectra, Fluorescence spectra and UV-melting method. Analysis of the results of the melting experiments shows that melting temperature (T m) of the complexes increases with the [total ligand]: DNA ratio (r) at two concentrations of Na+ (2?mM Na+ and 20?mM Na+) providing support for conclusion that MB is a stabilizer of DNA helix structure. By contrast, the shapes of dependences of width of transition (ΔT) on r at low and high [Na+] are different which points to the existence of different types of binding modes of MB with DNA. UV-spectroscopy experiments and fluorescence spectra indicated that the binding modes of MB with DNA depended on r. At high r (r?>?0.25), remarkable hypochromic effect with no shift of λ max in the absorption spectra of MB was observed. The fluorescence of MB was quenched which indicated that MB was bound to phosphate groups of DNA by electrostatic interaction. At low r ratios (r?<?0.2), the absorption spectra of MB upon increasing the concentration of DNA showed gradually decrease in the peak intensities with a red shift. This phenomenon is usually associated with molecular intercalation into the base stack of the ds-DNA. Using the Scatchard’s model, the complex formation constants for MB with DNA were determined: the binding constant K?≈?6.5?×?105 and binding site size n?≈?4. Obtained data are not typical for intercalation model of ligands to DNA. Moreover, comparison between these data and our early experimental results of interaction of ethidium bromide with DNA made it possible to suggest that this binding type of MB is, more probably, semi-intercalation mode (Vardevanyan et al., 2003). This conclusion is in accordance with the analysis of the model structures of MB–DNA complexes which clearly shows the importance of solvent contributions in suggested structural form (Tong et al., 2010). 相似文献
17.
Pierre Le Maréchal Paulette Decottignies Christophe H. Marchand Jeril Degrouard Danièle Jaillard Thierry Dulermo Marine Froissard Aleksey Smirnov Violaine Chapuis Marie-Joelle Virolle 《Applied and environmental microbiology》2013,79(19):5907-5917
Streptomyces lividans TK24 is a strain that naturally produces antibiotics at low levels, but dramatic overproduction of antibiotics occurs upon interruption of the ppk gene. However, the role of the Ppk enzyme in relation to the regulation of antibiotic biosynthesis remains poorly understood. In order to gain a better understanding of the phenotype of the ppk mutant, the proteomes of the wild-type (wt) and ppk mutant strains, grown for 96 h on R2YE medium limited in phosphate, were analyzed. Intracellular proteins were separated on two-dimensional (2D) gels, spots were quantified, and those showing a 3-fold variation or more were identified by mass spectrometry. The expression of 12 proteins increased and that of 29 decreased in the ppk mutant strain. Our results suggested that storage lipid degradation rather than hexose catabolism was taking place in the mutant. In order to validate this hypothesis, the triacylglycerol contents of the wt and ppk mutant strains of S. lividans as well as that of Streptomyces coelicolor M145, a strain that produces antibiotics at high levels and is closely related to S. lividans, were assessed using electron microscopy and thin-layer chromatography. These studies highlighted the large difference in triacylglycerol contents of the three strains and confirmed the hypothetical link between storage lipid metabolism and antibiotic biosynthesis in Streptomyces. 相似文献
18.
Ileana Pătru-Stupariu Per Angelstam Marine Elbakidze Alina Huzui Kjell Andersson 《Biodiversity and Conservation》2013,22(9):2023-2039
Naturally dynamic forests have a high proportion of biotopes with old large trees, diverse vertical and horizontal structure at multiple scales, and much dead wood. As such, they provide habitat to species and ecosystem processes that forests managed for wood production cannot provide to the same degree. Whether termed old-growth, ancient, virgin, intact, primeval or continuity forests, a major challenge and need is to map such potential high conservation value forest for subsequent inclusion in functional habitat networks for biodiversity conservation in forest landscapes. Given that the delivery time of natural forest properties is much longer than of industry wood, we explore the usefulness of using historical maps to identify forests that have been continuously present for 220 years (potential old-growth) versus 140 years (potential aging forest) in a case study in the Romanian Carpathian Mountains (see Online Resource 1). While the total forest cover increased by 35 % over the past two centuries, the area of potential aging and potential old-growth forest declined by 56 and 34 %, respectively. Spatial modelling of edge effects and patch size for virtual species with different requirements indicated an even greater decrease in the area of functional habitat networks of old-growth and ageing forest. Our analyses show that compared to simple mapping of potential high conservation forests, the area of functional habitat patches is severely overestimated, and caution is needed when estimating the area of potential high conservation value forests that form functional habitat networks, i.e. a green infrastructure. In addition, the landscape and regional scale connectivity of patches needs to be considered. We argue that the use of historical maps combined with assessment of spatial patterns is an effective tool for identifying and analyzing potential high conservation value forests in a landscape context. 相似文献
19.
Rahel Struchen Marine Pascal Michel Pascal Martin C. Fischer Thomas Higham Selina Brace Simon Y. W. Ho Jean‐Pierre Quéré Paul O'Higgins Laurent Excoffier Gerald Heckel A. Rus Hoelzel Jeremy B. Searle 《Molecular ecology》2013,22(20):5205-5220
Oceanic islands have been a test ground for evolutionary theory, but here, we focus on the possibilities for evolutionary study created by offshore islands. These can be colonized through various means and by a wide range of species, including those with low dispersal capabilities. We use morphology, modern and ancient sequences of cytochrome b (cytb) and microsatellite genotypes to examine colonization history and evolutionary change associated with occupation of the Orkney archipelago by the common vole (Microtus arvalis), a species found in continental Europe but not in Britain. Among possible colonization scenarios, our results are most consistent with human introduction at least 5100 bp (confirmed by radiocarbon dating). We used approximate Bayesian computation of population history to infer the coast of Belgium as the possible source and estimated the evolutionary timescale using a Bayesian coalescent approach. We showed substantial morphological divergence of the island populations, including a size increase presumably driven by selection and reduced microsatellite variation likely reflecting founder events and genetic drift. More surprisingly, our results suggest that a recent and widespread cytb replacement event in the continental source area purged cytb variation there, whereas the ancestral diversity is largely retained in the colonized islands as a genetic ‘ark’. The replacement event in the continental M. arvalis was probably triggered by anthropogenic causes (land‐use change). Our studies illustrate that small offshore islands can act as field laboratories for studying various evolutionary processes over relatively short timescales, informing about the mainland source area as well as the island. 相似文献
20.
Aline Bertin Marine Chanson Jo?l Delaveau Frédéric Mercerand Erich M?stl Ludovic Calandreau Cécile Arnould Christine Leterrier Anne Collin 《PloS one》2013,8(2)