174 research outputs found

    Petrogenesis of Tertiary Alkaline Magmas in the Siebengebirge, Germany

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    Basanites from the Tertiary Siebengebirge area of Germany (part of the Central European Volcanic Province; CEVP) have high Mg# (>0·60), moderate to high Cr (>300 ppm) and Ni (>200 ppm) contents and strong light rare earth element enrichment, but systematic depletion in Rb and K relative to trace elements of similar compatibility in anhydrous mantle. Rare earth element melting models can explain the petrogenesis of these basanites in terms of partial melting of a spinel peridotite source containing residual amphibole. It is inferred that amphibole, indicated by the relative K and Rb depletion and the melting model, was precipitated in the spinel peridotite lithospheric mantle beneath the Siebengebirge, by metasomatic fluids or melts from a rising mantle diapir or plume. Alkali basalts and more differentiated rocks have lower Mg# and lower abundances of Ni and Cr, and have undergone fractionation of mainly olivine, clinopyroxene, Fe-Ti oxides, amphibole and plagioclase. Most of the basanites and alkali basalts approach the Sr-Nd-Pb isotope compositions inferred for the European Asthenospheric Reservoir component. Trace element constraints (i.e. low Nb/U and Ce/Pb ratios) and the Sr-Nd-Pb isotope composition of the differentiated rocks indicate that assimilation of lower crustal material has modified the composition of the primary mantle-derived magmas. High 207Pb/204Pb ratios in the differentiated lavas point to assimilation of ancient lower crustal components having high U/Pb and Th/Pb ratios. Relatively shallow melting of inferred amphibole-bearing spinel peridotite sources may suggest an origin from the metasomatized part of the thermal boundary layer. Application of new thermobarometric equations for the basaltic magmas indicates relatively normal mantle potential temperatures (1300-1400°C); thus the inferred mantle ‘baby plume' or ‘hot finger' is not thermally anomalou

    Linkage scan of nicotine dependence in the University of California, San Francisco (UCSF) Family Alcoholism Study

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    Nicotine dependence has been shown to represent a heritable condition, and several research groups have performed linkage analysis to identify genomic regions influencing this disorder though only a limited number of the findings have been replicated

    Parasitic Nematodes Modulate PIN-Mediated Auxin Transport to Facilitate Infection

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    Plant-parasitic nematodes are destructive plant pathogens that cause significant yield losses. They induce highly specialized feeding sites (NFS) in infected plant roots from which they withdraw nutrients. In order to establish these NFS, it is thought that the nematodes manipulate the molecular and physiological pathways of their hosts. Evidence is accumulating that the plant signalling molecule auxin is involved in the initiation and development of the feeding sites of sedentary plant-parasitic nematodes. Intercellular transport of auxin is essential for various aspects of plant growth and development. Here, we analysed the spatial and temporal expression of PIN auxin transporters during the early events of NFS establishment using promoter-GUS/GFP fusion lines. Additionally, single and double pin mutants were used in infection studies to analyse the role of the different PIN proteins during cyst nematode infection. Based on our results, we postulate a model in which PIN1-mediated auxin transport is needed to deliver auxin to the initial syncytial cell, whereas PIN3 and PIN4 distribute the accumulated auxin laterally and are involved in the radial expansion of the NFS. Our data demonstrate that cyst nematodes are able to hijack the auxin distribution network in order to facilitate the infection process

    Linkage scan of alcohol dependence in the UCSF Family Alcoholism Study

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    Ample data suggest alcohol dependence represents a heritable condition, and several research groups have performed linkage analysis to identify genomic regions influencing this disorder. In the present study, a genome-wide linkage scan for alcohol dependence was conducted in a community sample of 565 probands and 1080 first-degree relatives recruited through the UCSF Family Alcoholism Study. The Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) was used to derive DSM-IV alcohol dependence diagnoses. Although no loci achieved genome-wide significance (i.e., LOD score > 3.0), several linkage peaks of interest (i.e., LOD score > 1.0) were identified. When the strict DSM-IV alcohol dependence diagnosis requiring the temporal clustering of symptoms served as the phenotype, linkage peaks were identified on chromosomes 1p36.31–p36.22, 2q37.3, 8q24.3, and 18p11.21–p11.2. When the temporal clustering of symptoms was not required, linkage peaks were again identified on chromosomes 1p36.31–p36.22 and 8q24.3 as well as novel loci on chromosomes 1p22.3, 2p24.3–p24.1, 9p24.1–p23, and 22q12.3–q13.1. Follow-up analyses were conducted by performing linkage analysis for the 12 alcohol dependence symptoms assessed by the SSAGA across the support intervals for the observed linkage peaks. These analyses demonstrated that different collections of symptoms often assessing distinct aspects of alcohol dependence (e.g., uncontrollable drinking and withdrawal vs. tolerance and drinking despite health problems) contributed to each linkage peak and often yielded LOD scores exceeding that reported for the alcohol dependence diagnosis. Such findings provide insight into how specific genomic regions may influence distinct aspects of alcohol dependence

    Construction of a consistent YAC contig for human chromosome region 3p14.1

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    Chromosomal deletions and translocations of human chromosome region 3p14 are observed in various human malignancies and suggest the existence of a tumor suppressor gene locus within this region. Tumors most frequently affected by these aberrations are small-cell lung cancer and renal-cell carcinoma. In continuation of our previously published YAC contig of chromosome region 3p14.2-p14.3, we report here on the construction of a YAC contig of at least 11 Mb that consisted of 171 YACs and covers the entire subregion 3p14.1. This contig includes the t(3;8) breakpoint of a hereditary renal-cell carcinoma localized in 3p14.2 and extends into human chromosome region 3p12-p13. It defines the order of 34 DNA probes in relation to reference markers D3S6 and D3S30 as well as the human protein tyrosine phosphatase-gamma gene. For 31 DNA probes we identified nonchimeric YACs by fluorescence in situ hybridization. The minimal tiling pathway consists of 16 yeast artificial chromosomes. As a prerequisite for identification of a putative tumor suppressor gene within this region, this contig renders human chromosome region 3p14.1 accessible to gene isolation

    Arabidopsis CULLIN3 Genes Regulate Primary Root Growth and Patterning by Ethylene-Dependent and -Independent Mechanisms

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    CULLIN3 (CUL3) together with BTB-domain proteins form a class of Cullin-RING ubiquitin ligases (called CRL3s) that control the rapid and selective degradation of important regulatory proteins in all eukaryotes. Here, we report that in the model plant Arabidopsis thaliana, CUL3 regulates plant growth and development, not only during embryogenesis but also at post-embryonic stages. First, we show that CUL3 modulates the emission of ethylene, a gaseous plant hormone that is an important growth regulator. A CUL3 hypomorphic mutant accumulates ACS5, the rate-limiting enzyme in ethylene biosynthesis and as a consequence exhibits a constitutive ethylene response. Second, we provide evidence that CUL3 regulates primary root growth by a novel ethylene-dependant pathway. In particular, we show that CUL3 knockdown inhibits primary root growth by reducing root meristem size and cell number. This phenotype is suppressed by ethylene-insensitive or resistant mutations. Finally, we identify a function of CUL3 in distal root patterning, by a mechanism that is independent of ethylene. Thus, our work highlights that CUL3 is essential for the normal division and organisation of the root stem cell niche and columella root cap cells

    Over-expression of the IGI1 leading to altered shoot-branching development related to MAX pathway in Arabidopsis

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    Shoot branching and growth are controlled by phytohormones such as auxin and other components in Arabidopsis. We identified a mutant (igi1) showing decreased height and bunchy branching patterns. The phenotypes reverted to the wild type in response to RNA interference with the IGI1 gene. Histochemical analysis by GUS assay revealed tissue-specific gene expression in the anther and showed that the expression levels of the IGI1 gene in apical parts, including flowers, were higher than in other parts of the plants. The auxin biosynthesis component gene, CYP79B2, was up-regulated in igi1 mutants and the IGI1 gene was down-regulated by IAA treatment. These results indicated that there is an interplay regulation between IGI1 and phytohormone auxin. Moreover, the expression of the auxin-related shoot branching regulation genes, MAX3 and MAX4, was down-regulated in igi1 mutants. Taken together, these results indicate that the overexpression of the IGI1 influenced MAX pathway in the shoot branching regulation
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