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kerimoglu_204715.pdf (9.239Mb)Kerimoglu, Onur; Straile, Dietmar; Peeters, Frank (2013), Artikel[more][less]
Erschienen in: Oikos ; 122 (2013), 2. - S. 223-234 Zusammenfassung: Environmental change strongly affects primary productivity of ecosystems via modifying bottom–up and top-down regulation of primary producers. Here we present a novel approach to quantify the relative importance of regulating factors in natural systems over various time scales: we calculated daily effect sizes of major factors affecting phytoplankton growth during the spring bloom period during almost three decades of lake oligotrophication using numerical experiments with a data based simulation model. We show that with oligotrophication the regulation of spring phytoplankton shifts from primarily top–down to bottom–up, and that the changes in regulation are non-linearly related to the nutrient (phosphorus) concentrations. Our findings indicate that long-term changes in top–down regulation cannot be understood without considering multiple herbivore taxa, here, microzooplankton (ciliates) and mesozooplankton (daphnids). We further demonstrate that bottom-up and top–down regulation are not independent from each other and that their interaction is time-scale dependent. Dateien zu dieser Publikation: 1
kerimoglu_204715.pdf (9.239Mb) -
Scholz, Diana; Chernyshova, Yana; Leist, Marcel (2013), Artikel[more][less]
Erschienen in: Neurobiology of Aging ; 34 (2013), 1. - S. 184-199 Zusammenfassung: Few studies have compared the processing of endogenous human amyloid precursor protein (APP) in younger and older neurons. Here, we characterized LUHMES cells as a human model to study Alzheimer's disease-related processes during neuronal maturation and aging. Differentiated LUHMES expressed and spontaneously processed APP via the secretase pathways, and they secreted amyloid β (Aβ) peptide. This was inhibited by cholesterol depletion or secretase inhibition, but not by block of tau phosphorylation. In vitro aged cells increased Aβ secretion without upregulation of APP or secretases. We identified the medium constituent glial cell line-derived neurotrophic factor (GDNF) as responsible for this effect. GDNF-triggered Aβ release was associated with rapid upregulation of the GDNF coreceptor “rearranged during transfection” (RET). Other direct (neurturin) or indirect (nerve growth factor) RET activators also increased Aβ, whereas different neurotrophins were ineffective. Downstream of RET, we found activation of protein kinase B (AKT) to be involved. Accordingly, inhibitors of the AKT regulator phosphatidylinositol-3-kinase completely blocked GDNF-triggered AKT phosphorylation and Aβ increase. This suggests that RET signaling affects Aβ release from aging neurons. Dateien zu dieser Publikation: 0
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Stift, Marc; Hunter, Brian D.; Shaw, Ben; Adam, Aileen; Hoebe, Peter N.; Mable, Barbara K. (2013), Artikel[more][less]
Erschienen in: Heredity : an international journal of genetics ; 110 (2013), 1. - S. 19-28 Zusammenfassung: Newly formed selfing lineages may express recessive genetic load and suffer inbreeding depression. This can have a genome-wide genetic basis, or be due to loci linked to genes under balancing selection. Understanding the genetic architecture of inbreeding depression is important in the context of the maintenance of self-incompatibility and understanding the evolutionary dynamics of S-alleles. We addressed this using North-American subspecies of Arabidopsis lyrata. This species is normally self-incompatible and outcrossing, but some populations have undergone a transition to selfing. The goals of this study were to: (1) quantify the strength of inbreeding depression in North-American populations of A. lyrata; and (2) disentangle the relative contribution of S-linked genetic load compared with overall inbreeding depression. We enforced selfing in self-incompatible plants with known S-locus genotype by treatment with CO2, and compared the performance of selfed vs outcrossed progeny. We found significant inbreeding depression for germination rate (δ 0.33), survival rate to 4 weeks (δ 0.45) and early growth (δ 0.07), but not for flowering rate. For two out of four S-alleles in our design, we detected significant S-linked load reflected by an under-representation of S-locus homozygotes in selfed progeny. The presence or absence of S-linked load could not be explained by the dominance level of S-alleles. Instead, the random nature of the mutation process may explain differences in the recessive deleterious load among lineages. Dateien zu dieser Publikation: 0
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Scholz, Diana; Chernyshova, Yana; Leist, Marcel (2013), Artikel[more][less]
Erschienen in: Neurobiology of Aging ; 34 (2013), 1. - S. 184-199 Zusammenfassung: Few studies have compared the processing of endogenous human amyloid precursor protein (APP) in younger and older neurons. Here, we characterized LUHMES cells as a human model to study Alzheimer’s disease-related processes during neuronal maturation and aging. Differentiated LUHMES expressed and spontaneously processed APP via the secretase pathways, and they secreted amyloid (beta) (A(beta) ) peptide. This was inhibited by cholesterol depletion or secretase inhibition, but not by block of tau phosphorylation. In vitro aged cells increased A (beta) secretion without upregulation of APP or secretases. We identified the medium constituent glial cell line-derived neurotrophic factor (GDNF) as responsible for this effect. GDNF-triggered A (beta) release was associated with rapid upregulation of the GDNF coreceptor "rearranged during transfection" (RET). Other direct (neurturin) or indirect (nerve growth factor) RET activators also increased A(beta) , whereas different neurotrophins were ineffective. Downstream of RET, we found activation of protein kinase B (AKT) to be involved. Accordingly, inhibitors of the AKT regulator phosphatidylinositol-3-kinase completely blocked GDNF-triggered AKT phosphorylation and A (beta) increase. This suggests that RET signaling affects A(beta) release from aging neurons. Dateien zu dieser Publikation: 0
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dostal_195006.pdf (742.3Kb)Dostal, Petr; Dawson, Wayne; van Kleunen, Mark; Keser, Lidewij H.; Fischer, Markus (2013), Artikel[more][less]
Erschienen in: Global Ecology and Biogeography ; 22 (2013), 1. - S. 64-72 Zusammenfassung: Aim: Accumulating evidence indicates that species may be pre-adapted for invasion success in new ranges. In the light of increasing global nutrient accumulation, an important candidate pre-adaptation for invasiveness is the ability to grow in nutrient-rich habitats. Therefore we tested whether globally invasive species originating from Central Europe have come from more productive rather than less productive habitats. A further important candidate pre-adaptation for invasiveness is large niche width. Therefore, we also tested whether species able to grow across habitats with a wider range of productivity are more invasive.<br /><br /> Location: Global with respect to invasiveness, and Central European with respect to origin of study species.<br /><br /> Methods: We examined whether average habitat productivity and its width across habitats are significant predictors of the success of Central European species as aliens and as weeds elsewhere in the world based on data in the Global Compendium of Weeds. The two habitat productivity measures were derived from nutrient indicator values (after Ellenberg) of accompanying species present in vegetation records of the comprehensive Czech National Phytosociological Database. In the analyses, we accounted for phylogenetic relatedness among species and for size of the native distribution ranges.<br /><br /> Results: Species from more productive habitats and with a wider native habitatproductivity niche in Central Europe have higher alien success elsewhere in the world.Weediness of species increased with mean habitat productivity. Niche width was also an important determinant of weediness for species with their main occurrence in nutrient-poor habitats, but not for those from nutrient-rich habitats.<br /><br /> Main conclusions: Our results indicate that Central European plant species from productive habitats and those species from nutrient-poor habitat with wide productivity-niche are pre-adapted to become invasive. These results suggest that the world-wide invasion success of many Central European species is likely to have been promoted by the global increase of resource-rich habitats. Dateien zu dieser Publikation: 1
dostal_195006.pdf (742.3Kb) -
song_202365.pdf (7.787Mb)Song, Yao-Bin; Yu, Fei-Hai; Keser, Lidewij H.; Dawson, Wayne; Fischer, Markus; Dong, Ming; van Kleunen, Mark (2013), Artikel[more][less]
Erschienen in: Oecologia ; 171 (2013), 2. - S. 317-327 Zusammenfassung: Many ecosystems are dominated by clonal plants. Among the most distinctive characteristics of clonal plants is their potential for clonal integration (i.e. the translocation of resources between interconnected ramets), suggesting that integration may play a role in their success. However, a general synthesis of effects of clonal integration on plant performance is lacking. We conducted a meta-analysis on the effects of clonal integration on biomass production and asexual reproduction of the whole clone, the recipient part (i.e. the part of a clone that imports resources) and the donor part (i.e. the part of a clone that exports resources). The final dataset contained 389 effect sizes from 84 studies covering 57 taxa. Overall, clonal integration increased performance of recipient parts without decreasing that of donor parts, and thus increased performance of whole clones. Among the studies and taxa considered, the benefits of clonal integration did not differ between two types of experimental approaches, between stoloniferous and rhizomatous growth forms, between directions of resource translocation (from younger to older ramet or vice versa), or among types of translocated resources (water, nutrients and carbohydrates). Clonal taxa with larger benefits of integration on whole-clone performance were not more invasive globally, but taxa in which recipient parts in unfavorable patches benefited more from integration were. Our results demonstrate general performance benefits of clonal integration, at least in the short term, and suggest that clonal integration contributes to the success of clonal plants. Dateien zu dieser Publikation: 1
song_202365.pdf (7.787Mb) -
Manousaki, Tereza; Hull, Pincelli M.; Kusche, Henrik; Machado-Schiaffino, Gonzalo; Franchini, Paolo; Harrod, Chris; Elmer, Kathryn R.; Meyer, Axel (2013), Artikel[more][less]
Erschienen in: Molecular Ecology ; 22 (2013), 3. - S. 650-669 Dateien zu dieser Publikation: 0
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Popp, Oliver; Veith, Sebastian; Fahrer, Jörg; Bohr, Vilhelm; Bürkle, Alexander; Mangerich, Aswin (2013), Artikel[more][less]
Erschienen in: ACS Chemical Biology ; 8 (2013), 1. - S. 179-188 Dateien zu dieser Publikation: 0
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Elmer, Kathryn R.; Lehtonen, Topi K.; Fan, Shaohua; Meyer, Axel (2013), Artikel[more][less]
Erschienen in: Evolution : international journal of organic evolution ; 67 (2013), 1. - S. 281-288 Dateien zu dieser Publikation: 0
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jochimsen_212019.pdf (12.69Mb)Jochimsen, Marc C.; Kümmerlin, Reiner; Straile, Dietmar (2013), Artikel[more][less]
Erschienen in: Ecology Letters ; 16 (2013), 1. - S. 81-89 Zusammenfassung: The link between compensatory dynamics and regime shifts is not well understood. We analyse a regime shift in phytoplankton in a large lake with respect to: (1) environmental forcing and (2) the type of dynamics (compensatory or synchronous) between phytoplankton groups. The regime shift in phytoplankton was related to gradual changes in nutrient levels, but unrelated to an almost concurrent shift in climatic conditions. The relationship between total phytoplankton biomass and phosphorus concentrations was sigmoid. Trajectories of phytoplankton biomass and community dynamics suggest that eutrophication effects can successfully be reversed when management efforts decrease nutrient loading to a level sufficiently low to overcome community resilience. The regime shift was associated with a loss of biomass compensation and compensatory dynamics among the phytoplankton groups. This suggests that the type of interactions is important for a better understanding of the existence and shape of nonlinear responses of phytoplankton biomass to environmental change. Dateien zu dieser Publikation: 1
jochimsen_212019.pdf (12.69Mb)
