310 research outputs found
Genetic Basis of Self-Incompatibility in the Lichen-Forming Fungus Lobaria pulmonaria and Skewed Frequency Distribution of Mating-Type Idiomorphs: Implications for Conservation
No full textFungal populations that reproduce sexually are likely to be genetically more diverse and have a higher adaptive potential than asexually reproducing populations. Mating systems of fungal species can be self-incompatible, requiring the presence of isolates of different mating-type genes for sexual reproduction to occur, or self-compatible, requiring only one. Understanding the distribution of mating-type genes in populations can help to assess the potential of self-incompatible species to reproduce sexually. In the locally threatened epiphytic lichen-forming fungus Lobaria pulmonaria (L.) Hoffm., low frequency of sexual reproduction is likely to limit the potential of populations to adapt to changing environmental conditions. Our study provides direct evidence of self-incompatibility (heterothallism) in L. pulmonaria. It can thus be hypothesized that sexual reproduction in small populations might be limited by an unbalanced distribution of mating-type genes. We therefore assessed neutral genetic diversity (using microsatellites) and mating-type ratio in 27 lichen populations (933 individuals). We found significant differences in the frequency of the two mating types in 13 populations, indicating a lower likelihood of sexual reproduction in these populations. This suggests that conservation translocation activities aiming at maximizing genetic heterogeneity in threatened and declining populations should take into account not only presence of fruiting bodies in transplanted individuals, but also the identity and balanced representation of mating-type genes
FIGURE 3 in Revision of Dimelaena Norman (Caliciaceae, Ascomycota) species containing usnic acid reveals a new species and a new combination from China
No full textFIGURE 3. Morphology and anatomy of Dimelaena altissima (18-58855, KUN). A. Thallus of Dimelaena altissima. B. Straight and plane lobes of radiate-plicate margin. C. Cryptolecanorine apothecia. D. Section of apothecium. E. Buellia-type ascospores, constricted at septum. F. Bacidia-type ascus-apex. Scale bars: 1 mm (A, B); 0.5 mm (C); 25 μm (E); 5 μm (E, F).Published as part of Ai, Min, Zhong, Qiuyi, Scheidegger, Christoph, Wang, Lisong & Wang, Xinyu, 2022, Revision of Dimelaena Norman (Caliciaceae, Ascomycota) species containing usnic acid reveals a new species and a new combination from China, pp. 259-272 in Phytotaxa 574 (4) on page 266, DOI: 10.11646/phytotaxa.574.4.1, http://zenodo.org/record/738905
FIGURE 4 in Revision of Dimelaena Norman (Caliciaceae, Ascomycota) species containing usnic acid reveals a new species and a new combination from China
No full textFIGURE 4. Morphology and anatomy of Dimelaena oreina (18-59460, KUN). A. Thallus of Dimelaena oreina. B. Convex non-linear lobes of radiate-plicate margin. C. Cryptolecanorine apothecia. D. Darkened margin around the areolae. E. Section of apothecium. F. Buellia-type ascospores, constricted at septum. G. Typical Bacidia-type ascus-apex. Scale bars: 1 mm (A, B); 0.5 mm (C, D); 25 μm (E); 5 μm (F, G).Published as part of Ai, Min, Zhong, Qiuyi, Scheidegger, Christoph, Wang, Lisong & Wang, Xinyu, 2022, Revision of Dimelaena Norman (Caliciaceae, Ascomycota) species containing usnic acid reveals a new species and a new combination from China, pp. 259-272 in Phytotaxa 574 (4) on page 267, DOI: 10.11646/phytotaxa.574.4.1, http://zenodo.org/record/738905
The role of the VirB/VirD4/Bep system in "Bartonella henselae"-triggered vascular proliferation
No full textBartonella henselae (Bh) rarely shows any symptoms in its feline reservoir host but is responsible for a number of clinical outcomes during infection of the human incidental host. Bh shares with B. quintana (Bq) and B. bacilliformis (Bb) the remarkable capacity to induce tumour-like vascular proliferations. The study of Bartonella-host cell interactions might not only provide insides into the pathogenesis of Bh but might also serve as a model to investigate general mechanisms involved pathological angiogenesis, which is a hallmark of tumour growth. The Bh VirB/VirD4 type IV secretion system (T4SS) and the thereby translocated Bartonella-effector proteins (Beps) have been shown to be responsible for the subversion of a number of endothelial cell (EC) functions upon infection. This thesis aimed to elucidate the role of the VirB/VirD4/Bep system in Bh-triggered angioproliferation. The first chapter characterizes the Bh VirB T4SS translocated protein BepA as an effector mediating the inhibition of apoptosis in human umbilical vein endothelial cells (HUVECs). Either overexpressed in the effector-less ∆bepA-G mutant or ectopically expressed, BepA was sufficient to promote the anti-apoptotic activity. Delineation of BepA revealed that this activity is confined to the BID (Bep intracellular delivery) domain of BepA. Interestingly, only the homologue BepA2 (corresponding to the BID domain plus C-terminus of BepA) from Bq inhibited apoptosis as well. In contrast to Bh and Bq, B. tribocorum is not associated to vascular proliferation and its BepA-homologue did not show any anti-apoptotic activity. Upon translocation into the host cell BepA was targeted to the membrane. BepA-mediated anti-apoptosis correlated with an increase in cAMP and increased expression of cAMP-responsive genes, pointing to a mechanism involving the regulation of this second messenger. BepA not only inhibited chemically ActD-induced but also CTL-triggered apoptosis. Thus, BepA has the potential to play a role in vasoproliferation in an indirect way by enhancing cell survival. Chapter 2 presents a spheroid-based three-dimensional in vitro sprouting assay established to address the angiogenic potential of Bh. Compared to spheroids from uninfected HUVECs, spheroids from HUVECs pre-infected with Bh wild-type showed an increased sprouting activity, albeit sprout morphology was distinct from the sprouts induced by vascular endothelial growth factor (VEGF). Formation of those sprouts was in part VirB/Bep-dependent. Overexpressed BepA in the ∆bepA-G mutant strongly promoted sprout formation. Delineation of the domain required for this stimulation indicates parallels to the anti-apoptotic activity. BepD showed a moderate sprout-promoting effect. In contrary, BepG, involved in cytoskeletal rearrangement, displayed a potent interference with sprout formation. This novel in vitro model of Bh-triggered sprouting angiogenesis revealed distinct activities of the Beps in modulating sprout formation and contributing to the regulation of the Bh angiogenic activity in the course of the chronic vascular infection. In chapter 3 the effect of exogenous VEGF on Bh-infected ECs is addressed. VEGF is thought to be involved in Bh-induced vascular tumour formation by promoting EC proliferation in a paracrine manner. Assessing the biological activity of VEGF in assays such as proliferation, wound assay and capillary-like sprout formation revealed an intriguing interference of the VirB/VirD4/Bep system with responsiveness of infected ECs to stimulation with VEGF. Analysis of the VEGF receptor 2 pathways showed that Bh inhibited phosphorylation of tyrosine 1175. In Bh-infected ECs stimulated with VEGF, PLCγ1 was less recruited and phosphorylated and consequently downstream calcium flux and ERK1/2 activation were blocked. These data rather challenge the idea of a VEGF-driven paracrine loop in the presence of an active VirB/VirD4/Bep system and emphasize the modulatory role of the VirB T4SS balancing the angiogenic activity of Bh. The last chapter reports the role of the VirB/VirD4/Bep system in the paracrine-loop model of VEGF production. HeLa cells produced VEGF upon exposure to Bh in a VirB/Bep-dependent manner. BepD elicited a strong stimulation of VEGF secretion in HeLa cells when overexpressed in the ∆bepB-G mutant. A shift in colour of the cell culture supernatant, depending on the cell culture media used, was associated to VirB T4SS translocation activity but not particularly to VEGF production. The shift probably is due to acidification of the supernatant. Hence, in addition to the previously reported BadA also the VirB/VirD4/Bep system, especially BepD, independently is able to trigger the production of an essential regulator of angiogenesis
Bioindication: the IAP approach
No full textThe symbiosis between algae and fungi enables lichens to colonise various apparently hostile places, like high mountains and deserts. However, the sensitive balance between the symbiotic partners can be easily disturbed, as lichens are generally sensitive to environmental alteration such as changes in air humidity (forestry, urbanisation) and air pollution
The Red data list of Swiss Macrolichens
No full textA preliminary list of 152 threatened macrolichens in Switzerland (37% ofthe Swiss flora) is presented. 13 taxa (9% ofthe total amount of species comprised in the Red data list) are considered to be extinct, 35 (23%) strongly endangered, 25 (16%) endangered, 45 (30%) vulnerable and 34 (22%) rare. The following species: Cetraria oakesiana, C. sepincola, Lobaria amplissima, L. scrobiculata, Nephroma bellum, Pannaria conoplea, Parmelia arnoldii, P. sinuosa, P. stuppea, Peltigera venosa, Ramalina obtusata, R. roesleri, R. thrausta, Sticta fuliginosa, S. sylvatica et Usnea longissima are comprised in the Red data lists of Austria, Germany and the European Community. They are considered to be threatened in their entire distribution area in Europe. Therefore they and their habitats should be protected in priority. The possibilities of protecting them are briefly discussed
Videogramme / Videograms: Die Bildwelten biologischer Experimentalsysteme als Kunst- und Theorieobjekt / The pictorial worlds of biological experimentation as an object of art and theory
No full textDer Schweizer Künstler und Theoretiker Hannes Rickli (*1959) erforscht seit 1991 audiovisuelles Material aus dem wissenschaftlichen Kontext. Die Videobilder und -töne aus der Verhaltensforschung bei Insekten und Fischen liefern dabei weitreichende Erkenntnisse über naturwissenschaftliche Experimentalsysteme: Dass die Herstellung wissenschaftlicher Tatsachen nicht nach festgelegten Plänen erfolgt, sondern sich im physischen Widerstand zwischen menschlichen, technischen – und tierischen – Akteuren ergibt, wird durch Ricklis künstlerische Reflexionen sichtbar. Dieses umfangreiche Buch reflektiert das aus dem Laborkontext gelöste Videomaterial aus der Perspektive von Wissenschaftssoziologie und -geschichte, Kunst- und Medientheorie, Bild- und Filmwissenschaft und führt die Ergebnisse auch mit Beschreibungen der Laborexperimente sowie Hunderten von Abbildungen vor Augen.
Translation of all texts in English in the Supplement, ISBN 978-3-85881-325-7.+ ID: 579733 + Serientitel: Schriftenreihe des Instituts für Gegenwartskunst ZHd
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