Institution
University of Fribourg
Education•Fribourg, Freiburg, Switzerland•
About: University of Fribourg is a education organization based out in Fribourg, Freiburg, Switzerland. It is known for research contribution in the topics: Population & Context (language use). The organization has 6040 authors who have published 14975 publications receiving 542500 citations. The organization is also known as: UNIFR & Universität Freiburg.
Papers published on a yearly basis
Papers
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TL;DR: It is suggested that ABCB21 functions as a facultative importer/exporter controlling auxin concentrations in plant cells, and mediates the 1-N-naphthylphthalamic acid (NPA)-sensitive translocation of auxin in an inward direction when the cytoplasmic IAA concentration is low, whereas this transporter mediates outward transport under high internal IAA.
Abstract: The phytohormone auxin is critical for plant growth and many developmental processes. Members of the P-glycoprotein (PGP/ABCB) subfamily of ATP-binding cassette (ABC) transporters have been shown to function in the polar movement of auxin by transporting auxin over the plasma membrane in both monocots and dicots. Here, we characterize a new Arabidopsis member of the ABCB subfamily, ABCB21/PGP21, a close homolog of ABCB4, for which conflicting transport directionalities have been reported. ABCB21 is strongly expressed in the abaxial side of cotyledons and in junctions of lateral organs in the aerial part, whereas in roots it is specifically expressed in pericycle cells. Membrane fractionation by sucrose density gradient centrifugation followed by Western blot showed that ABCB21 is a plasma membrane-localized ABC transporter. A transport assay with Arabidopsis protoplasts suggested that ABCB21 was involved in IAA transport in an outward direction, while naphthalene acetic acid (NAA) was a less preferable substrate for ABCB21. Further functional analysis of ABCB21 using yeast import and export assays showed that ABCB21 mediates the 1-N-naphthylphthalamic acid (NPA)-sensitive translocation of auxin in an inward direction when the cytoplasmic IAA concentration is low, whereas this transporter mediates outward transport under high internal IAA. An increase in the cytoplasmic IAA concentration by pre-loading of IAA into yeast cells abolished the IAA uptake activity by ABCB21 as well as ABCB4. These findings suggest that ABCB21 functions as a facultative importer/exporter controlling auxin concentrations in plant cells.
125 citations
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TL;DR: It is suggested that, by acting as repressors of gene expression, HP1 proteins may fulfil specific functions in both somatic and germline differentiation processes throughout development.
Abstract: Proteins of the highly conserved heterochromatin protein 1 (HP1) family have been found to function in the dynamic organization of nuclear architecture and in gene regulation throughout the eukaryotic kingdom. In addition to being key players in heterochromatin-mediated gene silencing, HP1 proteins may also contribute to the transcriptional repression of euchromatic genes via the recruitment to specific promoters. To investigate the role played by these different activities in specific developmental pathways, we identified HP1 homologues in the genome of Caenorhabditis elegans and used RNA-mediated interference to study their function. We show that one of the homologues, HPL-2, is required for the formation of a functional germline and for the development of the vulva by acting in an Rb-related pathway. We suggest that, by acting as repressors of gene expression, HP1 proteins may fulfil specific functions in both somatic and germline differentiation processes throughout development.
125 citations
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TL;DR: In this article, the reputation of information providers is determined self-consistently and a ranking method based on the reputation is proposed to rank information providers according to the reputation, which is based on a ranking algorithm.
Abstract: With the explosive growth of accessible information, expecially on the Internet, evaluation-based filtering has become a crucial task. Various systems have been devised aiming to sort through large volumes of information and select what is likely to be more relevant. In this letter we analyse a new ranking method, where the reputation of information providers is determined self-consistently.
125 citations
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TL;DR: It is demonstrated that the microgels used in this study significantly interpenetrate and thus change their size and shape only marginally even for ϕeff ≫ ϕcp, a finding that may require changes in the interpretation of a number of previously published studies on the structural and dynamic properties of dense soft particle systems.
Abstract: Soft particles such as polymeric microgels can form ultra-dense phases, where the average center-to-center distance a
s can be smaller than the initial unperturbed particle diameter σ
0, due to their ability to interpenetrate and compress. However, despite of the effort devoted to microgels at ultrahigh densities, we know surprisingly little about their response to their environment at effective volume fractions ϕ
eff
above close packing (ϕ
cp
), and the existing information is often contradictory. Here we report direct measurements of the size and shape of poly(N-isopropylacrylamide) microgels at concentrations below and above ϕ
cp
using the zero average contrast method in small-angle neutron scattering. We complement these experiments with measurements of the average interparticle distances using small-angle x-ray scattering, and a determination of the glass transition using dynamic light scattering. This allows us to unambiguously decouple interaction effects from density-dependent variations of the particle size and shape at all values of ϕ
eff
. We demonstrate that the microgels used in this study significantly interpenetrate and thus change their size and shape only marginally even for ϕ
eff
≫ ϕ
cp
, a finding that may require changes in the interpretation of a number of previously published studies on the structural and dynamic properties of dense soft particle systems.
125 citations
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University of Jena1, Laval University2, University of Waikato3, University of Fribourg4, Smithsonian Environmental Research Center5, University of the Azores6, University of Catania7, University of Lisbon8, Environment Agency9, Gibraltar Hardware10, University of Plymouth11, University of São Paulo12, University of Roehampton13, University of Bern14, University of Montpellier15, University of Hamburg16, Imperial College London17, University of La Rochelle18, Harvard University19, University of Arizona20, Pontifical Catholic University of Chile21, University of Essex22, University of Münster23, University of Pittsburgh24, Max Planck Society25, University of York26, Instituto Superior Técnico27, Russian Academy of Sciences28, Centre for Environment, Fisheries and Aquaculture Science29, University of Canberra30, Université du Québec à Rimouski31, Peking University32
TL;DR: It is demonstrated that species traits explain striking patterns in the body-size architecture of natural food webs that underpin the stability and functioning of ecosystems, paving the way for community-level management of the most complex natural ecosystems.
Abstract: Predator-prey interactions in natural ecosystems generate complex food webs that have a simple universal body-size architecture where predators are systematically larger than their prey. Food-web theory shows that the highest predator-prey body-mass ratios found in natural food webs may be especially important because they create weak interactions with slow dynamics that stabilize communities against perturbations and maintain ecosystem functioning. Identifying these vital interactions in real communities typically requires arduous identification of interactions in complex food webs. Here, we overcome this obstacle by developing predator-trait models to predict average body-mass ratios based on a database comprising 290 food webs from freshwater, marine and terrestrial ecosystems across all continents. We analysed how species traits constrain body-size architecture by changing the slope of the predator-prey body-mass scaling. Across ecosystems, we found high body-mass ratios for predator groups with specific trait combinations including (1) small vertebrates and (2) large swimming or flying predators. Including the metabolic and movement types of predators increased the accuracy of predicting which species are engaged in high body-mass ratio interactions. We demonstrate that species traits explain striking patterns in the body-size architecture of natural food webs that underpin the stability and functioning of ecosystems, paving the way for community-level management of the most complex natural ecosystems.
125 citations
Authors
Showing all 6204 results
Name | H-index | Papers | Citations |
---|---|---|---|
Jens Nielsen | 149 | 1752 | 104005 |
Sw. Banerjee | 146 | 1906 | 124364 |
Hans Peter Beck | 143 | 1134 | 91858 |
Patrice Nordmann | 127 | 790 | 67031 |
Abraham Z. Snyder | 125 | 329 | 91997 |
Csaba Szabó | 123 | 958 | 61791 |
Robert Edwards | 121 | 775 | 74552 |
Laurent Poirel | 117 | 621 | 53680 |
Thomas Münzel | 116 | 1055 | 57716 |
David G. Amaral | 112 | 302 | 49094 |
F. Blanc | 107 | 1514 | 58418 |
Markus Stoffel | 102 | 620 | 50796 |
Vincenzo Balzani | 101 | 476 | 45722 |
Enrico Bertini | 99 | 865 | 38167 |
Sandeep Kumar | 94 | 1563 | 38652 |