132 research outputs found

    Assembling the Tree of Life in Europe (AToLE)

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    A network of scientists under the umbrella of 'Assembling the Tree of Life in Europe (AToLE)' seeks funding under the FP7-Theme: Cooperation - Environment (including Climate Change and Biodiversity Conservation) programme of the European Commission.
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    Higher order mode damper for low energy RHIC electron cooler SRF booster cavity

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    To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under commissioning at BNL. The Linac of LEReC is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with rms dp/p less than 5e-4. A 704 MHz superconducting radio frequency (SRF) booster cavity in this Linac provides up to 2.2 MeV accelerating voltage. With such a low energy and very demanding energy spread requirement, control of Higher Order Modes (HOMs) in the cavities becomes critical and needs to be carefully evaluated to ensure minimum impact on the beam. In this paper, we report the multiphysics design of the HOM damper for this cavity to meet the energy spread requirement, as well as experimental results of the cavity with and without the HOM damper.Comment: 9 pages, 7 figure

    The genomic basis of the plant island syndrome in Darwin’s giant daisies

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    The repeated, rapid and often pronounced patterns of evolutionary divergence observed in insular plants, or the ‘plant island syndrome’, include changes in leaf phenotypes, growth, as well as the acquisition of a perennial lifestyle. Here, we sequence and describe the genome of the critically endangered, Galápagos-endemic species Scalesia atractyloides Arnot., obtaining a chromosome-resolved, 3.2-Gbp assembly containing 43,093 candidate gene models. Using a combination of fossil transposable elements, k-mer spectra analyses and orthologue assignment, we identify the two ancestral genomes, and date their divergence and the polyploidization event, concluding that the ancestor of all extant Scalesia species was an allotetraploid. There are a comparable number of genes and transposable elements across the two subgenomes, and while their synteny has been mostly conserved, we find multiple inversions that may have facilitated adaptation. We identify clear signatures of selection across genes associated with vascular development, growth, adaptation to salinity and flowering time, thus finding compelling evidence for a genomic basis of the island syndrome in one of Darwin’s giant daisies

    Transcription factor MITF and remodeller BRG1 define chromatin organisation at regulatory elements in melanoma cells

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    Microphthalmia-associated transcription factor (MITF) is the master regulator of the melanocyte lineage. To understand how MITF regulates transcription, we used tandem affinity purification and mass spectrometry to define a comprehensive MITF interactome identifying novel cofactors involved in transcription, DNA replication and repair, and chromatin organisation. We show that MITF interacts with a PBAF chromatin remodelling complex comprising BRG1 and CHD7. BRG1 is essential for melanoma cell proliferation in vitro and for normal melanocyte development in vivo. MITF and SOX10 actively recruit BRG1 to a set of MITF-associated regulatory elements (MAREs) at active enhancers. Combinations of MITF, SOX10, TFAP2A, and YY1 bind between two BRG1-occupied nucleosomes thus defining both a signature of transcription factors essential for the melanocyte lineage and a specific chromatin organisation of the regulatory elements they occupy. BRG1 also regulates the dynamics of MITF genomic occupancy. MITF-BRG1 interplay thus plays an essential role in transcription regulation in melanoma

    DNA Damage in Plant Herbarium Tissue

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    Dried plant herbarium specimens are potentially a valuable source of DNA. Efforts to obtain genetic information from this source are often hindered by an inability to obtain amplifiable DNA as herbarium DNA is typically highly degraded. DNA post-mortem damage may not only reduce the number of amplifiable template molecules, but may also lead to the generation of erroneous sequence information. A qualitative and quantitative assessment of DNA post-mortem damage is essential to determine the accuracy of molecular data from herbarium specimens. In this study we present an assessment of DNA damage as miscoding lesions in herbarium specimens using 454-sequencing of amplicons derived from plastid, mitochondrial, and nuclear DNA. In addition, we assess DNA degradation as a result of strand breaks and other types of polymerase non-bypassable damage by quantitative real-time PCR. Comparing four pairs of fresh and herbarium specimens of the same individuals we quantitatively assess post-mortem DNA damage, directly after specimen preparation, as well as after long-term herbarium storage. After specimen preparation we estimate the proportion of gene copy numbers of plastid, mitochondrial, and nuclear DNA to be 2.4–3.8% of fresh control DNA and 1.0–1.3% after long-term herbarium storage, indicating that nearly all DNA damage occurs on specimen preparation. In addition, there is no evidence of preferential degradation of organelle versus nuclear genomes. Increased levels of C→T/G→A transitions were observed in old herbarium plastid DNA, representing 21.8% of observed miscoding lesions. We interpret this type of post-mortem DNA damage-derived modification to have arisen from the hydrolytic deamination of cytosine during long-term herbarium storage. Our results suggest that reliable sequence data can be obtained from herbarium specimens

    A Set of 100 Chloroplast DNA Primer Pairs to Study Population Genetics and Phylogeny in Monocotyledons

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    Chloroplast DNA sequences are of great interest for population genetics and phylogenetic studies. However, only a small set of markers are commonly used. Most of them have been designed for amplification in a large range of Angiosperms and are located in the Large Single Copy (LSC). Here we developed a new set of 100 primer pairs optimized for amplification in Monocotyledons. Primer pairs amplify coding (exon) and non-coding regions (intron and intergenic spacer). They span the different chloroplast regions: 72 are located in the LSC, 13 in the Small Single Copy (SSC) and 15 in the Inverted Repeat region (IR). Amplification and sequencing were tested in 13 species of Monocotyledons: Dioscorea abyssinica, D. praehensilis, D. rotundata, D. dumetorum, D. bulbifera, Trichopus sempervirens (Dioscoreaceae), Phoenix canariensis, P. dactylifera, Astrocaryum scopatum, A. murumuru, Ceroxylon echinulatum (Arecaceae), Digitaria excilis and Pennisetum glaucum (Poaceae). The diversity found in Dioscorea, Digitaria and Pennisetum mainly corresponded to Single Nucleotide Polymorphism (SNP) while the diversity found in Arecaceae also comprises Variable Number Tandem Repeat (VNTR). We observed that the most variable loci (rps15-ycf1, rpl32-ccsA, ndhF-rpl32, ndhG-ndhI and ccsA) are located in the SSC. Through the analysis of the genetic structure of a wild-cultivated species complex in Dioscorea, we demonstrated that this new set of primers is of great interest for population genetics and we anticipate that it will also be useful for phylogeny and bar-coding studies
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