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Sökning: L773:0028 0836 OR L773:1476 4687 > (2010-2019)

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21.
  • Aplin, Lucy M., et al. (författare)
  • Experimentally induced innovations lead to persistent culture via conformity in wild birds
  • 2015
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 518:7540, s. 538-541
  • Tidskriftsartikel (refereegranskat)abstract
    • In human societies, cultural norms arise when behaviours are transmitted through social networks via high-fidelity social learning'. However, a paucity of experimental studies has meant that there is no comparable understanding of the process by which socially transmitted behaviours might spread and persist in animal populations'''. Here we show experimental evidence of the establishment of foraging traditions in a wild bird population. We introduced alternative novel foraging techniques into replicated wild sub-populations of great tits (Parus major) and used automated tracking to map the diffusion, establishment and long-term persistence of the seeded innovations. Furthermore, we used social network analysis to examine the social factors that influenced diffusion dynamics. From only two trained birds in each sub-population, the information spread rapidly through social network ties, to reach an average of 75% of individuals, with a total of 414 knowledgeable individuals performing 57,909 solutions over all replicates. The sub-populations were heavily biased towards using the technique that was originally introduced, resulting in established local traditions that were stable over two generations, despite a high population turnover. Finally, we demonstrate a strong effect of social conformity, with individuals disproportionately adopting the most frequent local variant when first acquiring an innovation, and continuing to favour social information over personal information. Cultural conformity is thought to be a key factor in the evolution of complex culture in humans''. In providing the first experimental demonstration of conformity in a wild non-primate, and of cultural norms in foraging techniques in any wild animal, our results suggest a much broader taxonomic occurrence of such an apparently complex cultural behaviour.
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22.
  • Arnegard, Matthew E., et al. (författare)
  • Genetics of ecological divergence during speciation
  • 2014
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 511:7509, s. 307-311
  • Tidskriftsartikel (refereegranskat)abstract
    • Ecological differences often evolve early in speciation as divergent natural selection drives adaptation to distinct ecological niches, leading ultimately to reproductive isolation. Although this process is a major generator of biodiversity, its genetic basis is still poorly understood. Here we investigate the genetic architecture of niche differentiation in a sympatric species pair of threespine stickleback fish by mapping the environment-dependent effects of phenotypic traits on hybrid feeding and performance under semi-natural conditions. We show that multiple, unlinked loci act largely additively to determine position along the major niche axis separating these recently diverged species. We also find that functional mismatch between phenotypic traits reduces the growth of some stickleback hybrids beyond that expected from an intermediate phenotype, suggesting a role for epistasis between the underlying genes. This functional mismatch might lead to hybrid incompatibilities that are analogous to those underlying intrinsic reproductive isolation but depend on the ecological context.
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23.
  • Arner, Peter, et al. (författare)
  • Dynamics of human adipose lipid turnover in health and metabolic disease
  • 2011
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 478:7367, s. 110-113
  • Tidskriftsartikel (refereegranskat)abstract
    • Adipose tissue mass is determined by the storage and removal of triglycerides in adipocytes(1). Little is known, however, about adipose lipid turnover in humans in health and pathology. To study this in vivo, here we determined lipid age by measuring (14)C derived from above ground nuclear bomb tests in adipocyte lipids. We report that during the average ten-year lifespan of human adipocytes, triglycerides are renewed six times. Lipid age is independent of adipocyte size, is very stable across a wide range of adult ages and does not differ between genders. Adipocyte lipid turnover, however, is strongly related to conditions with disturbed lipid metabolism. In obesity, triglyceride removal rate (lipolysis followed by oxidation) is decreased and the amount of triglycerides stored each year is increased. In contrast, both lipid removal and storage rates are decreased in non-obese patients diagnosed with the most common hereditary form of dyslipidaemia, familial combined hyperlipidaemia. Lipid removal rate is positively correlated with the capacity of adipocytes to break down triglycerides, as assessed through lipolysis, and is inversely related to insulin resistance. Our data support a mechanism in which adipocyte lipid storage and removal have different roles in health and pathology. High storage but low triglyceride removal promotes fat tissue accumulation and obesity. Reduction of both triglyceride storage and removal decreases lipid shunting through adipose tissue and thus promotes dyslipidaemia. We identify adipocyte lipid turnover as a novel target for prevention and treatment of metabolic disease.
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24.
  • Askarieh, Glareh, et al. (författare)
  • Self-assembly of spider silk proteins is controlled by a pH-sensitive relay
  • 2010
  • Ingår i: Nature. - Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 465, s. 236-U125
  • Tidskriftsartikel (refereegranskat)abstract
    • Nature's high-performance polymer, spider silk, consists of specific proteins, spidroins, with repetitive segments flanked by conserved non-repetitive domains(1,2). Spidroins are stored as a highly concentrated fluid dope. On silk formation, intermolecular interactions between repeat regions are established that provide strength and elasticity(3,4). How spiders manage to avoid premature spidroin aggregation before self-assembly is not yet established. A pH drop to 6.3 along the spider's spinning apparatus, altered salt composition and shear forces are believed to trigger the conversion to solid silk, but no molecular details are known. Miniature spidroins consisting of a few repetitive spidroin segments capped by the carboxy-terminal domain form metre-long silk-like fibres irrespective of pH(5). We discovered that incorporation of the amino-terminal domain of major ampullate spidroin 1 from the dragline of the nursery web spider Euprosthenops australis (NT) into mini-spidroins enables immediate, charge-dependent self-assembly at pH values around 6.3, but delays aggregation above pH7. The X-ray structure of NT, determined to 1.7 angstrom resolution, shows a homodimer of dipolar, antiparallel five-helix bundle subunits that lack homologues. The overall dimeric structure and observed charge distribution of NT is expected to be conserved through spider evolution and in all types of spidroins. Our results indicate a relay-like mechanism through which the N-terminal domain regulates spidroin assembly by inhibiting precocious aggregation during storage, and accelerating and directing self-assembly as the pH is lowered along the spider's silk extrusion duct.
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25.
  • Axelsson, Erik, et al. (författare)
  • The genomic signature of dog domestication reveals adaptation to a starch-rich diet
  • 2013
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 495:7441, s. 360-364
  • Tidskriftsartikel (refereegranskat)abstract
    • The domestication of dogs. was an important episode in the development of human civilization. The precise timing and location of this event is debated(1-5) and little is known about the genetic changes that accompanied the transformation of ancient wolves into domestic dogs. Here we conduct whole-genome resequencimg of dogs and wolves to identify 3.8 million genetic variants used to identify 36 genomic regions that probably represent targets for selection during dog domestication. Nineteen of these regions contain genes important in brain function, eight of which belong to nervous system development pathways and potentially underlie behavioural changes central to dog domestication(6). Ten genes with key roles in starch digestion and fat metabolism also show signals of selection. We identify candidate mutations in key genes and provide functional support for an increased starch digestion in dogs relative to wolves. Our results indicate that novel adaptations allowing the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in the early domestication of dogs.
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26.
  • Bader, Erik, et al. (författare)
  • Identification of proliferative and mature beta-cells in the islets of Langerhans
  • 2016
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 535:7612, s. 430-
  • Tidskriftsartikel (refereegranskat)abstract
    • Insulin-dependent diabetes is a complex multifactorial disorder characterized by loss or dysfunction of beta-cells. Pancreatic beta-cells differ in size, glucose responsiveness, insulin secretion and precursor cell potential(1-5); understanding the mechanisms that underlie this functional heterogeneity might make it possible to develop new regenerative approaches. Here we show that Fltp (also known as Flattop and Cfap126), a Wnt/planar cell polarity (PCP) effector and reporter gene(6), acts as a marker gene that subdivides endocrine cells into two subpopulations and distinguishes proliferation-competent from mature beta-cells with distinct molecular, physiological and ultrastructural features. Genetic lineage tracing revealed that endocrine subpopulations from Fltp-negative and -positive lineages react differently to physiological and pathological changes. The expression of Fltp increases when endocrine cells cluster together to form polarized and mature 3D islet mini-organs(7-9). We show that 3D architecture and Wnt/PCP ligands are sufficient to trigger beta-cell maturation. By contrast, the Wnt/PCP effector Fltp is not necessary for beta-cell development, proliferation or maturation. We conclude that 3D architecture and Wnt/PCP signalling underlie functional beta-cell heterogeneity and induce beta-cell maturation. The identification of Fltp as a marker for endocrine subpopulations sheds light on the molecular underpinnings of islet cell heterogeneity and plasticity and might enable targeting of endocrine subpopulations for the regeneration of functional beta-cell mass in diabetic patients.
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27.
  • Bahram, Mohammad (författare)
  • Structure and function of the global topsoil microbiome
  • 2018
  • Ingår i: Nature. - Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 560, s. 233-
  • Tidskriftsartikel (refereegranskat)abstract
    • Soils harbour some of the most diverse microbiomes on Earth and are essential for both nutrient cycling and carbon storage. To understand soil functioning, it is necessary to model the global distribution patterns and functional gene repertoires of soil microorganisms, as well as the biotic and environmental associations between the diversity and structure of both bacterial and fungal soil communities(1-4). Here we show, by leveraging metagenomics and metabarcoding of global topsoil samples (189 sites, 7,560 subsamples), that bacterial, but not fungal, genetic diversity is highest in temperate habitats and that microbial gene composition varies more strongly with environmental variables than with geographic distance. We demonstrate that fungi and bacteria show global niche differentiation that is associated with contrasting diversity responses to precipitation and soil pH. Furthermore, we provide evidence for strong bacterial-fungal antagonism, inferred from antibiotic-resistance genes, in topsoil and ocean habitats, indicating the substantial role of biotic interactions in shaping microbial communities. Our results suggest that both competition and environmental filtering affect the abundance, composition and encoded gene functions of bacterial and fungal communities, indicating that the relative contributions of these microorganisms to global nutrient cycling varies spatially.
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28.
  • Bakkeren, Erik, et al. (författare)
  • Salmonella persisters promote the spread of antibiotic resistance plasmids in the gut
  • 2019
  • Ingår i: Nature. - NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 573:7773, s. 276-280
  • Tidskriftsartikel (refereegranskat)abstract
    • The emergence of antibiotic-resistant bacteria through mutations or the acquisition of genetic material such as resistance plasmids represents a major public health issue(1,2). Persisters are subpopulations of bacteria that survive antibiotics by reversibly adapting their physiology(3-10), and can promote the emergence of antibiotic-resistant mutants(11). We investigated whether persisters can also promote the spread of resistance plasmids. In contrast to mutations, the transfer of resistance plasmids requires the co-occurrence of both a donor and a recipient bacterial strain. For our experiments, we chose the facultative intracellular entero-pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) and Escherichia coli, a common member of the microbiota(12). S. Typhimurium forms persisters that survive antibiotic therapy in several host tissues. Here we show that tissue-associated S. Typhimurium persisters represent long-lived reservoirs of plasmid donors or recipients. The formation of reservoirs of S. Typhimurium persisters requires Salmonella pathogenicity island (SPI)-1 and/or SPI-2 in gut-associated tissues, or SPI-2 at systemic sites. The re-seeding of these persister bacteria into the gut lumen enables the co-occurrence of donors with gut-resident recipients, and thereby favours plasmid transfer between various strains of Enterobacteriaceae. We observe up to 99% transconjugants within two to three days of re-seeding. Mathematical modelling shows that rare re-seeding events may suffice for a high frequency of conjugation. Vaccination reduces the formation of reservoirs of persisters after oral infection with S. Typhimurium, as well as subsequent plasmid transfer. We conclude that-even without selection for plasmid-encoded resistance genes-small reservoirs of pathogen persisters can foster the spread of promiscuous resistance plasmids in the gut.
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29.
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30.
  • Berggren, Gustav, et al. (författare)
  • Biomimetic assembly and activation of [FeFe]-hydrogenases
  • 2013
  • Ingår i: Nature. - Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.. - 0028-0836 .- 1476-4687. ; 499:7456, s. 66-69
  • Tidskriftsartikel (refereegranskat)
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