Characterization of choline uptake in Trypanosoma brucei procyclic and bloodstream forms

Choline is an essential nutrient for eukaryotic cells, where it is used as precursor for the synthesis of choline-containing phospholipids, such as phosphatidylcholine (PC). According to published data, Trypanosoma brucei parasites are unable to take up choline from the environment but instead use lyso-phosphatidylcholine as precursor for choline lipid synthesis. We now show that T. brucei procyclic forms in culture readily incorporate [3H]-labeled choline into PC, indicating that trypanosomes express a transporter for choline at the plasma membrane. Characterization of the transport system in T. brucei procyclic and bloodstream forms shows that uptake of choline is independent of sodium and potassium ions and occurs with a Km in the low micromolar range. In addition, we demonstrate that choline uptake can be blocked by the known choline transport inhibitor, hemicholinium-3, and by synthetic choline analogs that have been established as anti-malarials. Together, our results show that T. brucei parasites express an uptake system for choline and that exogenous choline is used for PC synthesis.

A versatile proline/alanine transporter in the unicellular pathogen Leishmania donovani regulates amino acid homoeostasis and osmotic stress responses

Unlike all other organisms, parasitic protozoa of the family Trypanosomatidae maintain a large cellular pool of proline that, together with the alanine pool, serve as alternative carbon sources as well as reservoirs of organic osmolytes. These reflect adaptation to their insect vectors whose haemolymphs are exceptionally rich in the two amino acids. In the present study we identify and characterize a new neutral amino acid transporter, LdAAP24, that translocates proline and alanine across the Leishmania donovani plasma membrane. This transporter fulfils multiple functions: it is the sole supplier for the intracellular pool of proline and contributes to the alanine pool; it is essential for cell volume regulation after osmotic stress; and it regulates the transport and homoeostasis of glutamate and arginine, none of which are its substrates. Notably, we provide evidence that proline and alanine exhibit different roles in the parasitic response to hypotonic shock; alanine affects swelling, whereas proline influences the rate of volume recovery. On the basis of our data we suggest that LdAAP24 plays a key role in parasite adaptation to its varying environments in host and vector, a phenomenon essential for successful parasitism.

Altered expression of the PTR/NRT1 homologue OsPTR9 affects nitrogen utilization efficiency, growth and grain yield in rice

The plant PTR/NRT1 (peptide transporter/nitrate transporter 1) gene family comprises di/tripeptide and low-affinity nitrate transporters; some members also recognize other substrates such as carboxylates, phytohormones (auxin and abscisic acid), or defence compounds (glucosinolates). Little is known about the members of this gene family in rice (Oryza sativa L.). Here, we report the influence of altered OsPTR9 expression on nitrogen utilization efficiency, growth, and grain yield. OsPTR9 expression is regulated by exogenous nitrogen and by the day-night cycle. Elevated expression of OsPTR9 in transgenic rice plants resulted in enhanced ammonium uptake, promotion of lateral root formation and increased grain yield. On the other hand, down-regulation of OsPTR9 in a T-DNA insertion line (osptr9) and in OsPTR9-RNAi rice plants had the opposite effect. These results suggest that OsPTR9 might hold potential for improving nitrogen utilization efficiency and grain yield in rice breeding.

Traffic Routes and Signals for the Tonoplast

Tonoplast, the membrane delimiting plant vacuoles, regulates ion, water and nutrient movement between the cytosol and the vacuolar lumen through the activity of its membrane proteins. Correct traffic of proteins from the endoplasmic reticulum (ER) to the tonoplast requires (i) approval by the ER quality control, (ii) motifs for exit from the ER and (iii) motifs that promote sorting to the tonoplast. Recent evidence suggests that this traffic follows different pathways that are protein-specific and could also reflect vacuole specialization for lytic or storage function. The routes can be distinguished based on their sensitivity to drugs such as brefeldin A and C834 as well as using mutant plants that are defective in adaptor proteins of vesicle coats, or dominant-negative mutants of Rab GTPases.

The European Modern Pollen Database (EMPD) project

Modern pollen samples provide an invaluable research tool for helping to interpret the quaternary fossil pollen record, allowing investigation of the relationship between pollen as the proxy and the environmental parameters such as vegetation, land-use, and climate that the pollen proxy represents. The European Modern Pollen Database (EMPD) is a new initiative within the European Pollen Database (EPD) to establish a publicly accessible repository of modern (surface sample) pollen data. This new database will complement the EPD, which at present holds only fossil sedimentary pollen data. The EMPD is freely available online to the scientific community and currently has information on almost 5,000 pollen samples from throughout the Euro-Siberian and Mediterranean regions, contributed by over 40 individuals and research groups. Here we describe how the EMPD was constructed, the various tables and their fields, problems and errors, quality controls, and continuing efforts to improve the available data.

Erratum to: The European Modern Pollen Database (EMPD) project

Unfortunately, the list of authors contains a number of duplications, omissions and other errors in the original publication of the article. The correct list appears in this erratum.

Ungarische Sexarbeiterinnen in Zürich zwischen Marginalisierung und Selbstbestimmung

Seit 2008 arbeiten vermehrt Roma-Frauen (Romnija) aus dem Nordosten Ungarns in westeuropäischen Städten auf dem Straßenstrich. Sie haben in den Jahren davor mit ihren Körpern Prostitutionsorte in Ungarn konstituiert bis schließlich die Prostitutionsverordnung von staatlicher Seite neu interpretiert wurde. Heute verändern sie Räume in Städten wie Amsterdam und Zürich. Mit ihrer Entscheidung, Sex an legalen Orten in Europa anzubieten, versuchen sie ihre Familien finanziell zu unterstützen. So wurden sie von einer durch ein patriarchalisches System geprägten Romni zur transnationa-len Mutter, Arbeitsmigrantin, Ausländerin und Sexarbeiterin. Diese neue Wirklichkeit führte nicht nur zu räumlichen Veränderungen an den verschiedensten Orten in Europa, sondern auch zu einem Wandel mit ethnischen, sozialen und geschlechterspezifischen Dimensionen.

Sprache als Mittel der „Grenzüberschreitung“ – von Hürden und vom „Brücken bauen“ in multikulturellen Regionen der Slowakei und Serbiens

Dieser Beitrag befasst sich mit Sprache als Mittel der „Grenzüberschreitung“ in multikulturellen Regionen der Slowakei und Serbiens. Es wird aufgezeigt, welche Rolle Sprache in den inter-ethnischen Beziehungen in Ostmitteleuropa spielt, welche Hürden existieren und aufgebaut werden, gleichzeitig aber auch, wie diese abgebaut werden können, oder versucht wird, diese abzubauen. Es geht dabei erstens um die Problematik des Sprachunterrichts in geteilten, multikulturellen Gesellschaften sowie den Herausforderungen für Minderheiten in diesem Zusammenhang. In einem zweiten Schritt werden Initiativen der Zivilgesellschaft diskutiert und dabei Möglichkeiten aufgezeigt, wie Grenzen mithilfe von Sprache gerade in einem politisch heiklen Umfeld überwunden werden können.