Refine
Year of publication
Document Type
- Article (22)
- Preprint (2)
- Contribution to a Periodical (1)
Has Fulltext
- yes (25)
Is part of the Bibliography
- no (25)
Keywords
- Sprachkritik (3)
- Malpighiales (2)
- Medien (2)
- Sprachphilosophie (2)
- phylogenomics (2)
- Affective disorders (1)
- Anglizismus (1)
- Brain tumors (1)
- COVID-19 (1)
- Caenorhabditis elegans (1)
Institute
CXCL12-CXCR4 signaling controls multiple physiological processes and its dysregulation is associated with cancers and inflammatory diseases. To discover as-yet-unknown endogenous ligands of CXCR4, we screened a blood-derived peptide library for inhibitors of CXCR4-tropic HIV-1 strains. This approach identified a 16 amino acid fragment of serum albumin as an effective and highly specific CXCR4 antagonist. The endogenous peptide, termed EPI-X4, is evolutionarily conserved and generated from the highly abundant albumin precursor by pH-regulated proteases. EPI-X4 forms an unusual lasso-like structure and antagonizes CXCL12-induced tumor cell migration, mobilizes stem cells, and suppresses inflammatory responses in mice. Furthermore, the peptide is abundant in the urine of patients with inflammatory kidney diseases and may serve as a biomarker. Our results identify EPI-X4 as a key regulator of CXCR4 signaling and introduce proteolysis of an abundant precursor protein as an alternative concept for chemokine receptor regulation.
Premise: Both universal and family-specific targeted sequencing probe kits are becoming widely used for reconstruction of phylogenetic relationships in angiosperms. Within the pantropical Ochnaceae, we show that with careful data filtering, universal kits are equally as capable in resolving intergeneric relationships as custom probe kits. Furthermore, we show the strength in combining data from both kits to mitigate bias and provide a more robust result to resolve evolutionary relationships.
Methods: We sampled 23 Ochnaceae genera and used targeted sequencing with two probe kits, the universal Angiosperms353 kit and a family-specific kit. We used maximum likelihood inference with a concatenated matrix of loci and multispecies-coalescence approaches to infer relationships in the family. We explored phylogenetic informativeness and the impact of missing data on resolution and tree support.
Results: For the Angiosperms353 data set, the concatenation approach provided results more congruent with those of the Ochnaceae-specific data set. Filtering missing data was most impactful on the Angiosperms353 data set, with a relaxed threshold being the optimum scenario. The Ochnaceae-specific data set resolved consistent topologies using both inference methods, and no major improvements were obtained after data filtering. Merging of data obtained with the two kits resulted in a well-supported phylogenetic tree.
Conclusions: The Angiosperms353 data set improved upon data filtering, and missing data played an important role in phylogenetic reconstruction. The Angiosperms353 data set resolved the phylogenetic backbone of Ochnaceae as equally well as the family specific data set. All analyses indicated that both Sauvagesia L. and Campylospermum Tiegh. as currently circumscribed are polyphyletic and require revised delimitation.
Background: Leaf venation traits are important for many research fields such as systematics and evolutionary biology, plant physiology, climate change, and paleoecology. In spite of an increasing demand for vein trait data, studies are often still data-limited because the development of methods that allow rapid generation of large sets of vein data has lagged behind. Recently, non-destructive X-ray technology has proven useful as an alternative to traditional slow and destructive chemical-based methods. Non-destructive techniques more readily allow the use of herbarium specimens, which provide an invaluable but underexploited resource of vein data and related environmental information. The utility of 2D X-ray technology and microfocus X-ray computed tomography, however, has been compromised by insufficient image resolution. Here, we advanced X-ray technology by increasing image resolution and throughput without the application of contrast agents.
Results: For 2D contact microradiography, we developed a method which allowed us to achieve image resolutions of up to 7 µm, i.e. a 3.6-fold increase compared to the industrial standard (25 µm resolution). Vein tracing was further optimized with our image processing standards that were specifically adjusted for different types of leaf structure and the needs of higher imaging throughput. Based on a test dataset, in 91% of the samples the 7 µm approach led to a significant improvement in estimations of minor vein density compared to the industrial standard. Using microfocus X-ray computed tomography, very high-resolution images were obtained from a virtual 3D–2D transformation process, which was superior to that of 3D images.
Conclusions: Our 2D X-ray method with a significantly improved resolution advances rapid non-destructive bulk scanning at a quality that in many cases is sufficient to determine key venation traits. Together with our high-resolution microfocus X-ray computed tomography method, both non-destructive approaches will help in vein trait data mining from museum collections, which provide an underexploited resource of historical and recent data on environmental and evolutionary change. In spite of the significant increase in effective image resolution, a combination of high-throughput and full visibility of the vein network (including the smallest veins and their connectivity) remains challenging, however.
Plastid DNA sequence data have been traditionally widely used in plant phylogenetics because of the high copy number of plastids, their uniparental inheritance, and the blend of coding and non-coding regions with divergent substitution rates that allow the reconstruction of phylogenetic relationships at different taxonomic ranks. In the present study, we evaluate the utility of the plastome for the reconstruction of phylogenetic relationships in the pantropical plant family Ochnaceae (Malpighiales). We used the off-target sequence read fraction of a targeted sequencing study (targeting nuclear loci only) to recover more than 100 kb of the plastid genome from the majority of the more than 200 species of Ochnaceae and all but two genera using de novo and reference-based assembly strategies. Most of the recalcitrant nodes in the family’s backbone were resolved by our plastome-based phylogenetic inference, corroborating the most recent classification system of Ochnaceae and findings from a phylogenomic study based on nuclear loci. Nonetheless, the phylogenetic relationships within the major clades of tribe Ochnineae, which comprise about two thirds of the family’s species diversity, received mostly low support. Generally, the phylogenetic resolution was lowest at the infrageneric level. Overall there was little phylogenetic conflict compared to a recent analysis of nuclear loci. Effects of taxon sampling were invoked as the most likely reason for some of the few well-supported discords. Our study demonstrates the utility of the off-target fraction of a target enrichment study for assembling near-complete plastid genomes for a large proportion of samples.
Ochnaceae is a pantropical family with multiple transoceanic disjunctions at deep and shallow levels. Earlier attempts to unravel the processes that led to such biogeographic patterns suffered from insufficient phylogenetic resolution and unclear delimitation of some of the genera. In the present study, we estimated divergence time and ancestral ranges based on a phylogenomic framework with a well-resolved phylogenetic backbone to tackle issues of the timing and direction of dispersal that may explain the modern global distribution of Ochnaceae. The nuclear data provided the more robust framework for divergence time estimation compared to the plastome-scale data, although differences in the inferred clade ages were mostly small. While Ochnaceae most likely originated in West Gondwana during the Late Cretaceous, all crown-group disjunctions are inferred as dispersal-based, most of them as transoceanic long-distance dispersal (LDD) during the Cenozoic. All LDDs occurred in an eastward direction except for the SE Asian clade of Sauvagesieae, which was founded by trans-Pacific dispersal from South America. The most species-rich clade by far, Ochninae, originated from either a widespread neotropical-African ancestor or a solely neotropical ancestor which then dispersed to Africa. The ancestors of this clade then diversified in Africa, followed by subsequent dispersal to the Malagasy region and tropical Asia on multiple instances in three genera during the Miocene-Pliocene. In particular, Ochna might have used the South Arabian land corridor to reach South Asia. Thus, the pantropical distribution of Ochnaceae is the result of LDD either transoceanic or via land bridges/corridors, whereas vicariance might have played a role only along the stem of the family.
Nicht zuletzt durch die Entwicklung und Verbreitung der sogenannten Neuen Medien ist das Thema 'Medialität' im gesamten Bereich der Geistes- und Kulturwissenschaften virulent geworden. Im Rahmen der aktuellen Diskurse um den Begriff des Mediums ist zu beobachten, daß dieser Ausdruck häufig unterschiedslos auf so verschiedene Referenzobjekte wie Internet, Fernsehen, Printmedien, Computer, Schrift, Bilder, Schallwellen u. v. a. bezogen wird. Das Medium orale Sprache gerät dabei sonderbarerweise häufig aus dem Blickfeld. - Warum ist dies so?
Woher kommt das neuerwachte Interesse an Sprachrichtigkeit? Woher kommt die ausgeprägte sprachliche Unsicherheit, die auch bei vielen hochgebildeten Menschen den Wunsch entstehen lässt, von Sprachpflegern über ihr Ureigenstes, nämlich ihre Muttersprache, belehrt zu werden? Obwohl Antworten auf diese Fragen letztlich spekulativ bleiben, wage ich doch die These, dass eine Ursache hierfür die Rechtschreibreform ist, die von einem Großteil der Bevölkerung nach wie vor nicht angenommen wird, die insgesamt weder zur Vereinfachung noch zu einer höheren Einheitlichkeit geführt hat; die aber andererseits ein öffentliches Nachdenken und Diskutieren über Sprachrichtigkeit in Gang setzte. – Jedenfalls ist die Verunsicherung ein Faktum, das von Linguisten nicht ignoriert werden sollte.
Ausgangspunkt: Die Kritik am "Zwei-Welten-Modell": Die grundlegende linguistische Unterscheidung zwischen "Sprache" und "Sprechen" ist im Rahmen der neueren Debatten um Sprachmedialität wieder verstärkt thematisiert und kritisiert worden. Lässt sich dieses schulbildende, in der Linguistik geradezu eherne Begriffspaar überhaupt noch sinnvollerweise aufrechterhalten? Oder muss es mindestens umdefiniert, vielleicht sogar gänzlich verworfen werden? Hat sich insbesondere die auf Chomsky zurückgehende Unterscheidung von Sprachkompetenz und -performanz nicht von selbst ad absurdum geführt, nachdem der linguistische Kognitivismus chomskyscher Provenienz Sprache als lebendiges Phänomen, als Medium menschlicher Kommunikation, vollständig aus dem Blick verloren hat? Führt nicht schon die scheinbar harmlose linguistische Differenzierung zwischen einer Sprachregel und ihrer Anwendung zu einer irreführenden und unangemessenen Verdinglichung von Sprache? ...
Ziel des vorliegenden Aufsatzes ist es, zu einer neuerlichen Diskussion der Begriffe 'Medium' und 'Kommunikation' in der Linguistik beizutragen. Dabei versuche ich insbesondere, den philosophisch-kulturwissenschaftlichen Diskurs, in welchem die Themen 'Medialität' und 'Perfonnanz' seit längerer Zeit intensiv diskutiert werden, zu dem in der Angewandten Linguistik geläufigen Modell der Kommunikationsformen in Beziehung zu setzen und Möglichkeiten einer Verbindung dieser beiden Diskurse zumindest anzudeuten. Der Aufsatz gliedert sich in vier Abschnitte: Zunächst werden einige geläufige Mediendefinitionen vorgestellt. Im zweiten Kapitel stelle ich dann die Frage 'Ist Kommunikation ein Transportvorgang?', um auf dieser Grundlage im dritten Kapitel eine alternative Medienkonzeption vorzustellen. Im letzten Kapitel wird dieser Medienbegriff dann sowohl vom Begriff des Zeichensystems, als auch von dem der Kommunikationsform abgegrenzt.