Die essentielle Rolle des Transkriptionsfaktors SPL7 bei der Aufrechterhaltung der Kupfer-Homöostase in Arabidopsis thaliana

Das Spurenelement Kupfer ist für höhere Pflanzen lebensnotwendig und wird als Kofaktor in Proteinen hauptsächlich wegen seines geringen Redoxpotentials eingesetzt, zum Beispiel im Plastocyanin, einem wichtigen Elektronentransporter der Photosynthesekomplexe. Ohne Kupfer als Kofaktor des Plastocyanins könnten keine Elektronen vom Cytochrom-b6/f-komplex auf das Photosystem I übertragen werden, wodurch die Photosynthese in höheren Pflanzen nicht möglich wäre. So wichtig Kupfer auch ist, so toxisch ist es auch in ungebundener Form. Deswegen ist es für Pflanzen unerlässlich, dass sie eine gut funktionierende Kupfer-Homöostase besitzen, damit sie ihre Metalloproteine ausreichend versorgen können, aber dennoch keine toxischen Mengen aufnehmen. Um eine bessere Kenntnis über die molekulargenetischen Mechanismen zu erlangen, die der Kupfer-Homöostase in höheren Pflanzen zugrunde liegen, wurde die Funktion von SPL7 (SQUAMOSA PROMOTOR BINDING PROTEIN LIKE7) in Arabidopsis thaliana studiert. SPL7 ist das Homolog des SBP-Box Transkriptionsfaktor CRR1 (COPPER RESPONSE REGULATOR1) aus Chlamydomonas, das für das transkriptionelle Umschalten bei Kupfermangel verantwortlich ist. Für die Analyse wurden Funktionsverlustmutanten von SPL7 unter unterschiedlichen Bedingungen kultiviert und ihr Phänotyp analysiert. Dabei zeigte sich, dass unter Kupfermangelkonzentrationen, bei denen der Wildtyp keine Mangelerscheinungen hatte, die Mutanten ein stark verlangsamtes Wachstum und einen deutlich späteren Übergang in die reproduktive Phase aufwiesen. Darüber hinaus zeigten sie große Defizite in der Samenproduktion, so dass sich unter Kurztagbedingungen gar keine Samen entwickelten oder aber die Pflanzen starben, bevor sie in die reproduktive Phase übergehen konnten. Auch das Wurzelsystem war wesentlich schlechter ausgebildet und wuchs deutlich langsamer. Die phänotypische Analyse der spl7-Mutanten zeigte außerdem, dass die Pflanzen eine gestörte Lignifizierung aufwiesen. So waren beispielsweise die Leitbündel in allen Geweben, wenn überhaupt, nur sehr gering lignifiziert. Auch die Defiziete in der Samenproduktion ließen sich auf eine gestörte Lignifizierung zurückführen, da auch das Endothecium der Antheren kaum lignifiziert war, wodurch eine Selbstung sehr erschwert wurde. Zusammen mit den anderen phänotypischen Merkmalen der spl7-Mutanten, deutete dies auf eine Mangelversorgung der gesamten Pflanze mit Nährstoffen hin. Interessanter Weise verschwanden sämtliche phänotypische Unterschiede zwischen Wildtypen und spl7-Mutanten, sobald die Kupferkonzentration im Substrat erhöht wurde. Unter diesen Bedingungen hatten die spl7-Mutanten einen wildtypischen Phänotyp. Eine differentielle Transkriptom-Analyse der spl7-Mutante und des Wildtyps unter optimalen und pessimalen Kupferbedingungen gab Hinweise darauf, dass SPL7 eine regulierende Funktion in der Kupfer-Homöostase von A. thaliana haben könnte. Durch unterschiedliche Genexpression in den Wurzeln (Kupfer-aufnehmendes Gewebe) und den überirdischen Teilen der Pflanze (Kupfer verbrauchendes Gewebe) kann man folgern, dass SPL7 nicht nur für die erhöhte Aufnahme von Kupfer über die Wurzeln, sondern auch für das Remobilisieren desselben aus anderen Geweben verantwortlich sein könnte. Schließlich ist der Transport von Kupfer vermutlich auch, wenn auch nur indirekt, von SPL7 abhängig, da die Lignifizierung der Leitbündel gestört ist. Diese Beobachtungen werden von den kürzlich veröffentlichten Forschungsergebnissen von Yamasaki und Mitarbeitern (2009) bestätigt. Diese Doktorarbeit bestätigt nicht nur, dass SPL7 für die allgemeine Kupfer-Homöostase wichtig ist, sondern offenbart darüber hinaus differenzierte Regulationsmechanismen, die über die Verteilung zwischen den Geweben einer Pflanze die optimale Kupferversorgung der einzelnen Zelle gewährleisten. Durch Übertragung dieser Erkenntnisse wäre es möglich, landwirtschaftliche Nutzpflanzen für Böden mit geringem Kupfergehalt zu optimieren, so dass die derzeitigen durch Kupfermangel bedingten Ertragseinbußen verringert würden

Wetting of Carbon Cathodes by Molten Electrolyte and Aluminium

The extent to which the carbon cathode is wetted by molten electrolyte or molten aluminium metal is important for understanding the cathode wear during aluminium electrolysis. The present paper reports on a laboratory study of the wettability of four different carbon materials using the immersion–emersion technique. The effect of polarization of the carbon cathode on the wettability was also included in the study. The measurements demonstrated that the carbon material is poorly wetted by the molten electrolyte or the metal. After polarization of the carbon in the cathodic direction, the cathode became quickly wetted by the molten electrolyte. The presence of aluminium during the experiments resulted in enhanced wettability by the molten electrolyte. The carbon materials were analyzed by microscopy after the experiments and formation of Al4C3 was observed on the surfaces of the materials. The role of sodium in relation to enhanced wettability by molten electrolyte is discussed.acceptedVersio

Transcriptome sequencing identifies SPL7-regulated copper acquisition genes FRO4/FRO5 and the copper dependence of iron homeostasis in Arabidopsis

24 Pags., 9 Figs., 2 Tabls., with Supplemental Data (15 Figs., 3 Tabls., 1 Method, 1 Data Set).The transition metal copper (Cu) is essential for all living organisms but is toxic when present in excess. To identify Cu deficiency responses comprehensively, we conducted genome-wide sequencing-based transcript profiling of Arabidopsis thaliana wild-type plants and of a mutant defective in the gene encoding SQUAMOSA PROMOTER BINDING PROTEIN-LIKE7 (SPL7), which acts as a transcriptional regulator of Cu deficiency responses. In response to Cu deficiency, FERRIC REDUCTASE OXIDASE5 (FRO5) and FRO4 transcript levels increased strongly, in an SPL7-dependent manner. Biochemical assays and confocal imaging of a Cu-specific fluorophore showed that high-affinity root Cu uptake requires prior FRO5/FRO4-dependent Cu(II)-specific reduction to Cu(I) and SPL7 function. Plant iron (Fe) deficiency markers were activated in Cu-deficient media, in which reduced growth of the spl7 mutant was partially rescued by Fe supplementation. Cultivation in Cu-deficient media caused a defect in root-to-shoot Fe translocation, which was exacerbated in spl7 and associated with a lack of ferroxidase activity. This is consistent with a possible role for a multicopper oxidase in Arabidopsis Fe homeostasis, as previously described in yeast, humans, and green algae. These insights into root Cu uptake and the interaction between Cu and Fe homeostasis will advance plant nutrition, crop breeding, and biogeochemical research.We acknowledge postdoctoral fellowships to M.B. from the Alexander von Humboldt Foundation and the Spanish Ministry of Science and Innovation; a Deutsche Forschungsgemeinshaft Heisenberg fellowship and funding from the FRONTIERS program at the University of Heidelberg, Germany, and the European Union InP Public Health Impact of Long-Term, Low-Level Mixed Element Exposure in Susceptible Population Strata (FOOD-CT-2006-016253) to U.K.; a grant from the National Science Foundation (IOS-0919739) to E.L.C.; a postdoctoral fellowship from the Spanish Foundation of Science and Technology (MEC-FECYT) to D.C.; National Institutes of Health Grant GM42143 to S.S.M.; and support from the University of California, Los Angeles–Department of Energy Institute for Genomics and Proteomics under Contract DE-FC02-02ER63421 to M.P.Peer reviewe

The microRNA regulated SBP-box genes SPL9 and SPL15 control shoot maturation in Arabidopsis

Throughout development the Arabidopsis shoot apical meristem successively undergoes several major phase transitions such as the juvenile-to-adult and floral transitions until, finally, it will produce flowers instead of leaves and shoots. Members of the Arabidopsis SBP-box gene family of transcription factors have been implicated in promoting the floral transition in dependence of miR156 and, accordingly, transgenics constitutively over-expressing this microRNA are delayed in flowering. To elaborate their roles in Arabidopsis shoot development, we analysed two of the 11 miR156 regulated Arabidopsis SBP-box genes, i.e. the likely paralogous genes SPL9 and SPL15. Single and double mutant phenotype analysis showed these genes to act redundantly in controlling the juvenile-to-adult phase transition. In addition, their loss-of-function results in a shortened plastochron during vegetative growth, altered inflorescence architecture and enhanced branching. In these aspects, the double mutant partly phenocopies constitutive MIR156b over-expressing transgenic plants and thus a major contribution to the phenotype of these transgenics as a result of the repression of SPL9 and SPL15 is strongly suggested

Detection of cannabinoid receptor type 2 in native cells and zebrafish with a highly potent, cell-permeable fluorescent probe.

Despite its essential role in the (patho)physiology of several diseases, CB2R tissue expression profiles and signaling mechanisms are not yet fully understood. We report the development of a highly potent, fluorescent CB2R agonist probe employing structure-based reverse design. It commences with a highly potent, preclinically validated ligand, which is conjugated to a silicon-rhodamine fluorophore, enabling cell permeability. The probe is the first to preserve interspecies affinity and selectivity for both mouse and human CB2R. Extensive cross-validation (FACS, TR-FRET and confocal microscopy) set the stage for CB2R detection in endogenously expressing living cells along with zebrafish larvae. Together, these findings will benefit clinical translatability of CB2R based drugs

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Role of Pitting in the Formation of Potholes in Carbon Cathodes - A Review

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Automatic Demand Response referred to electricity spot price. Demo description

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Assessment of the Thermodynamic Stability of Thermal Insulating Materials in Aluminium Electrolysis Cells

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