DEPARTMENT of BIOLOGY at the UNIVERSITY of FRIBOURG
The Department of Biology is now composed of four functional groups - Biochemistry, Ecology and Evolution, Plant Biology and Zoology, each with several distinct research groups which you are invited to visit at the above links. Teaching at both the Bachelor and Master levels reflects the interests of the research groups and the respective programmes can be consulted using the appropriate links in the left column (in French and German for the Bachelor and in English for the Master).
Coming events & news
- The next Biology seminar will held on 9th July
At 11.00h in lecture theatre 0.110 at Plant Biology, Ricardo Neves (Pharmazentrum, University of Basle) will give a talk entitled "Phyla Cycliophora and Loricifera: weird animals need advanced microscopy techniques
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Publication "hot spot"
Salicylic acid (SA) is central for the defense of plants to pathogens and abiotic stress. SA is synthesized in chloroplasts from chorismic acid by an isochorismate synthase (ICS1); SA biosynthesis is negatively regulated by auto-inhibitory feedback at ICS1. Genetic studies indicated that the MATE (Multidrug And Toxin Extrusion) transporter EDS5, is necessary for SA accumulation after biotic and abiotic stress but so far it is not understood how EDS5 controls the biosynthesis of SA. Here we show that EDS5 co-localizes with a marker of the chloroplast envelope and that EDS5 functions as a MATE-like transporter in the export of SA from the chloroplast to the cytoplasm where it controls the innate immune response. The location at the chloroplast envelope supports a model of the effect of EDS5 on SA biosynthesis: in the eds5 mutant, stress-induced SA is trapped in the chloroplast and inhibits its own accumulation by auto-inhibitory feedback. |
N Panchaud, MP Péli-Gulli & C De Virgilio (2013). Amino Acid Deprivation Inhibits TORC1 Through a GTPase-Activating Protein Complex for the Rag Family GTPase Gtr1. Science Signaling 6 (227): ra42. The Rag family of guanosine triphosphatases (GTPases) regulates eukaryotic cell growth in response to amino acids by activating the target of rapamycin complex 1 (TORC1). In humans, this pathway is often deregulated in cancer. In yeast, amino acids promote binding of GTP (guanosine 5′-triphosphate) to the Rag family GTPase Gtr1, which, in combination with a GDP (guanosine diphosphate)-bound Gtr2, forms the active, TORC1-stimulating GTPase heterodimer. We identified Iml1, which functioned in a complex with Npr2 and Npr3, as a GAP (GTPase-activating protein) for Gtr1. Upon amino acid deprivation, Iml1 transiently interacted with Gtr1 at the vacuolar membrane to stimulate its intrinsic GTPase activity and consequently decrease the activity of TORC1. Our results delineate a potentially conserved mechanism by which the Iml1, Npr2, and Npr3 orthologous proteins in humans may suppress tumor formation. |
Ypc1p and Ydc1p are alkaline ceramide hydrolases, which reside in the ER. Ypc1p can catalyze the reverse reaction, i.e. the condensation of free fatty acids with phytosphingosine or dihydrosphingosine and overexpression of YPC1 or YDC1 can provide enough ceramide synthesis as to rescue the viability of cells lacking the normal acyl-CoA-dependent ceramide synthases. To better understand the coexistence of acyl-CoA dependent ceramide synthases and ceramidases in the ER we investigated the membrane topology of Ypc1p by probing cysteine accessibility of natural and substituted cysteines with membrane non-permeating mass-tagged probes. The N- and C-terminal ends of Ypc1p are oriented towards the lumen and cytosol, respectively. Two of the 5 natural cysteines, Cys27 and Cys219, are essential for enzymatic activity and form a disulfide bridge. The data allow inferring that all amino acids of Ypc1p that are conserved in the pfam PF05875 ceramidase motif and the CREST superfamily are located in or near the ER lumen. Microsomal assays using a lysine-specific reagent show that the reverse ceramidase activity can only be blocked when the reagent has access to Ypc1p from the lumenal side. Overall the data suggest that the active site of Ypc1p resides at the lumenal side of the ER membrane. |
Egger B, Van Giesen L, Moraru M & Sprecher SG (2013). In vitro imaging of primary neural cell culture from Drosophila. Nature Protocols 8: 958-965. Cell culture systems are widely used for molecular, genetic and biochemical studies. Primary cell cultures of animal tissues offer the advantage that specific cell types can be studied in vitro outside of their normal environment. We provide a detailed protocol for generating primary neural cell cultures derived from larval brains of Drosophila melanogaster. The developing larval brain contains stem cells such as neural precursors and intermediate neural progenitors, as well as fully differentiated and functional neurons and glia cells. We describe how to analyze these cell types in vitro by immunofluorescent staining and scanning confocal microscopy. Cell type-specific fluorescent reporter lines and genetically encoded calcium sensors allow the monitoring of developmental, cellular processes and neuronal activity in living cells in vitro. The protocol provides a basis for functional studies of wild-type or genetically manipulated primary neural cells in culture, both in fixed and living samples. The entire procedure takes ∼3 weeks. . |
S Bontron, M Jaquenoud, S Vaga, N Talarek, B Bodenmiller, R Aebersold &C De Virgilio (2013). Yeast endosulfines control entry into quiescence and chronological life span by inhibiting protein phosphatase 2A. Cell Reports 3: 16-22 (doi:10.1016/j.celrep.2012.11.025) The TORC1 and PKA protein kinases are central elements of signaling networks that regulate eukaryotic cell proliferation in response to growth factors and/or nutrients. In yeast, attenuation of signaling by these kinases following nitrogen and/or carbon limitation activates the protein kinase Rim15, which orchestrates the initiation of a reversible cellular quiescence program to ensure normal chronological life span. The molecular elements linking Rim15 to distal readouts including the expression of Msn2/4- and Gis1-dependent genes involve the endosulfines Igo1/2. We show that Rim15, analogous to the greatwall kinase in Xenopus, phosphorylates endosulfines to directly inhibit the Cdc55-protein phosphatase 2A (PP2ACdc55). Inhibition of PP2ACdc55 preserves Gis1 in a phosphorylated state and consequently promotes its recruitment to and activation of transcription from promoters of specific nutrient-regulated genes. These results close a gap in our perception of and delineate a role for PP2ACdc55 in TORC1-/PKA-mediated regulation of quiescence and chronological life span.
This publication is also the subject of a newsfeed from the University
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Alien insects are increasingly being dispersed around the world through international trade, causing a multitude of negative environmental impacts and billions of dollars in economic losses annually. Border controls form the last line of defense against invasions, whereby inspectors aim to intercept and stop consignments that are contaminated with harmful alien insects. In Europe, member states depend on one another to prevent insect introductions by operating a first point of entry rule - controlling goods only when they initially enter the continent. However, ensuring consistency between border control points is difficult because there exists no optimal inspection strategy. For the first time, we developed a method to quantify the volume of agricultural trade that should be inspected for quarantine insects at border control points in Europe, based on global agricultural trade of over 100 million distinct origin-commodity-species-destination pathways. This metric was then used to evaluate the performance of existing border controls, as measured by border interception results in Europe between 2003 and 2007. Alarmingly, we found significant gaps between the trade pathways that should be inspected and actual number of interceptions. Moreover, many of the most likely introduction pathways yielded none or very few insect interceptions, because regular interceptions are only made on only a narrow range of pathways. European countries with gaps in border controls have been invaded by higher numbers of quarantine alien insect species, indicating the importance of proper inspections to prevent insect invasions. Equipped with an optimal inspection strategy based on the underlying risks of trade, authorities globally will be able to implement more effective and consistent border controls.
This publication is also the subject of a newsfeed from the University
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