Institut für Biologie

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Should we delay leaf water potential measurements after excision? Dehydration or equilibration?
(2024) Perera‐Castro, Alicia V.; Puértolas, Jaime; Fernández-Marín, Beatriz; González-Rodríguez, Águeda M.; Perera-Castro, Alicia V.; Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna (ULL), 38200, La Laguna, Canary Islands, Spain; Puértolas, Jaime; Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna (ULL), 38200, La Laguna, Canary Islands, Spain; Fernández-Marín, Beatriz; Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna (ULL), 38200, La Laguna, Canary Islands, Spain; González-Rodríguez, Águeda M.; Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna (ULL), 38200, La Laguna, Canary Islands, Spain
Background: Accurate leaf water potential (Ψw) determination is crucial in studying plant responses to water deficit. After excision, water potential decreases, even under low evaporative demand conditions, which has been recently attributed to the equilibration of pre-excision Ψw gradients across the leaf. We assessed the influence of potential re-equilibration on water potential determination by monitoring leaf Ψw and relative water content decline after excision using different storage methods. Results: Even though leaf Ψw declined during storage under low evaporative demand conditions, this was strongly reduced when covering the leaf with a hydrophobic layer (vaseline) and explained by changes in relative water content. However, residual water loss was variable between species, possibly related to morpho-physiological leaf traits. Provided water loss was minimized during storage, pre-excision leaf transpiration rate did not affect to the magnitude of leaf Ψw decline after excision, confirming that transpiration-driven Ψw gradients have no effect on leaf Ψw determination. Conclusions: Disequilibrium in water potentials across a transpiring leaf upon excision is dissipated very quickly, well within the elapsed time between excision and pressurization, therefore, not resulting in overestimation of leaf Ψw measured immediately after excision. When leaf storage is required, the effectiveness of a storage under low evaporative demand varied among species. Covering with a hydrophobic layer is an acceptable alternative.
Inter-laboratory comparison of plant volatile analyses in the light of intra-specific chemodiversity
(2023) Eckert, Silvia; Eilers, Elisabeth J.; Jakobs, Ruth; Anaia, Redouan Adam; Aragam, Kruthika Sen; Bloss, Tanja; Popp, Moritz; Sasidharan, Rohit; Schnitzler, Jörg-Peter; Stein, Florian; Steppuhn, Anke; Unsicker, Sybille B.; van Dam, Nicole M.; Yepes, Sol; Ziaja, Dominik; Müller, Caroline
Introduction: Assessing intraspecific variation in plant volatile organic compounds (VOCs) involves pitfalls that may bias biological interpretation, particularly when several laboratories collaborate on joint projects. Comparative, inter-laboratory ring trials can inform on the reproducibility of such analyses. Objectives: In a ring trial involving five laboratories, we investigated the reproducibility of VOC collections with polydimethylsiloxane (PDMS) and analyses by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). As model plant we used Tanacetum vulgare , which shows a remarkable diversity in terpenoids, forming so-called chemotypes. We performed our ring-trial with two chemotypes to examine the sources of technical variation in plant VOC measurements during pre-analytical, analytical, and post-analytical steps. Methods: Monoclonal root cuttings were generated in one laboratory and distributed to five laboratories, in which plants were grown under laboratory-specific conditions. VOCs were collected on PDMS tubes from all plants before and after a jasmonic acid (JA) treatment. Thereafter, each laboratory (donors) sent a subset of tubes to four of the other laboratories (recipients), which performed TD-GC-MS with their own established procedures. Results: Chemotype-specific differences in VOC profiles were detected but with an overall high variation both across donor and recipient laboratories. JA-induced changes in VOC profiles were not reproducible. Laboratory-specific growth conditions led to phenotypic variation that affected the resulting VOC profiles. Conclusion: Our ring trial shows that despite large efforts to standardise each VOC measurement step, the outcomes differed both qualitatively and quantitatively. Our results reveal sources of variation in plant VOC research and may help to avoid systematic errors in similar experiments.
Development and validation of a novel enzyme-linked immunosorbent assay for the differentiation of tick-borne encephalitis infections caused by different virus subtypes
(2025) Freimane, Zane; Dobler, Gerhard; Chitimia-Dobler, Lidia; Karelis, Guntis; Girl, Philipp; Kuzmane, Sanita; Savicka, Oksana; Erber, Wilhelm; Zavadska, Dace
Objectives: Tick-borne encephalitis (TBE) is an infection caused by the tick-borne encephalitis virus (TBEV) that can lead to symptoms of central nervous system inflammation. There are five subtypes of TBEV, three of which – European, Siberian and Far Eastern – occur in Europe. As it is thought that different subtype infections exhibit varying clinical courses and outcomes, serological differentiation of the virus subtypes is clearly important. However, to date, this has proved difficult to achieve. Methods: An ELISA format was developed based on TBE virus NS1 antigen against the European, Siberian and Far Eastern subtype. The three NS1 antigens were biotechnologically produced in a human cell line and used for ELISA coating. Sera from German (European subtype) and Russian (Siberian and/or Far Eastern subtypes) TBE patients with positive TBEV IgG were used to test the reactivity against these three NS1 antigens. Results: Testing of 23 German and 32 Russian TBEV IgG-positive sera showed that the ELISA was able to differentiate between TBEV European subtype and TBEV Siberian and Far Eastern subtype infections. Conclusions: In geographical areas where two or more TBEV subtype infections can occur, the NS1-IgG ELISA developed here constitutes an important diagnostic tool to differentiate between European subtype infections and Siberian/Far Eastern subtype infections and to use the new assay for epidemiological studies to clarify the importance of particular subtype infections in an area. Consequently, it may help to better describe and anticipate the clinical courses and outcomes of particular TBEV subtype infections.
EvaMol : A python tool for evaluating molecules in hit-to-lead optimization
(2025) Herzog, Anna-Maria; Steuber, Julia; Fritz, Günter
This Python script was developed as a tool in structure-based drug discovery processes, such as fragment-to-lead-optimization, where a large number of variants of an initially identified hit molecule have to be evaluated and ranked in silico. The tool facilitates the identification and selection of follow-up drug candidates with improved predicted pharmacokinetic and binding properties. These candidates can derive from different procedures like similarity search or systematic chemical modifications. The initial hit data are provided either as coordinates of the protein-molecule complex obtained experimentally or by in silico methods such as docking making the script a versatile tool adaptable to variable workflows.
Neuartige Zielproteine für Antibiotika: Respiratorische Flavoproteine aus pathogenen Bakterien
(2025) Vering, Jonatan; Fritz, Günter
Der steigende Anteil antibiotika-resistenter, bakterieller Erreger stellt eine immer größer wer-dende Bedrohung für das Gesundheitssystem von Entwicklungsländern und Industrienationen dar. Mangelnde Disziplin und Fehlverhalten beim Einsatz von Antibiotika sind dabei eine trei-bende Kraft für das vermehrte Auftreten resistenter Stämme. Das Ausmaß des Problems wird durch den Aufruf zur Entwicklung neuartiger Antibiotika durch die Weltgesundheitsorganisa-tion deutlich. Die Entwicklung neuartiger Antibiotika gegen die γ-Proteobakterien Acinetobac-ter baumannii, Klebsiella pneumoniae und Pseudomonas aeruginosa hat laut der WHO höchste Priorität. Flavinkofaktoren sind in allen lebenden Organismen essenziell. Ihre Funktionen sind vielseitig. Am häufigsten sind Flavine allerdings an der Katalyse von Redoxreaktionen beteiligt. Flavine sind somit auch ein wichtiger Bestandteil der Atmungskette von Prokaryoten und Eukaryoten. Die Na+ translozierende NADH:Ubichinon Oxidoreduktase (Na+-NQR) stellt eine Eintrittsstelle für Elektronen in die Atmungskette einer Vielzahl von γ-Proteobakterien dar, darunter klinisch relevante Pathogene. Die Na+-NQR koppelt die Redox-Reaktion an den Aufbau eines Natrium-Gradienten zwischen Cytoplasma und Periplasma. Dieser Gradient wird für die ATP-Gewin-nung, die Osmoregulation und den Metabolitentransport genutzt, und ist somit auch hinsicht-lich der Virulenz eines Erregers bedeutsam. Diese Tatsache macht die Na+-NQR zu einem Ziel-protein für neue Antibiotika. Die Na+-NQR nutzt vier Flavin-Kofaktoren. Zwei Flavinmononuk-leotide sind über eine Phosphodiesterbindung kovalent an das Enzym gebunden. Diese Bin-dung wird durch Enzyme der ApbE Familie katalysiert, die eine Domäne aus konservierten Aminosäureresten für die Insertion des Flavinkofaktors erkennen. Diese Enzymklasse kommt ausschließlich in Prokaryoten vor. Neben der Na+-NQR werden auch weitere Enzyme aus der bakteriellen Atmungskette durch die ApbE Familie kovalent FMNyliert. ApbE stellt somit ein weiteres, vielversprechendes Zielprotein zur Entwicklung neuer Inhibitoren und Antibiotika dar. Erstes Ziel der vorliegenden Arbeit ist die umfassende Charakterisierung des Aktivzentrums der FAD-Domäne der NqrF-Untereinheit der Na+-NQR. Die FAD-Domäne katalysiert die initiale Oxidation von NADH. Aus vorangegangenen strukturbiologischen Untersuchungen der NADH-Bindetasche in der FAD-Domäne aus K. pneumoniae ergaben sich Hinweise für eine weitere NADH (oder NAD+) Bindetasche. Aufgrund dieser Beobachtung wurde die Hypothese aufgestellt, dass diese zweite NAD(H)-Bindetasche von katalytischer Relevanz ist. Durch orts-spezifische Mutagenese, sowie durch kinetische und spektroskopische Analysen wurde ge-zeigt, dass NADH und NAD+ an diese Tasche binden. In der FAD-Domäne der Na+-NQR wird durch diese zweite NADH-Bindetasche eine hohe Affi-nität des Substrats gewährleistet. Dies wurde in vitro unter Verwendung der gereinigten Na+-NQR aus Vibrio cholerae gezeigt, und in vivo in Wachstumsexperimenten mit V. cholerae be-stätigt. Des Weiteren wurde der Mechanismus der Enzyme der ApbE-Familie untersucht. Es war bekannt, dass alle Aminosäurereste der konservierten Tasche des Zielproteins, in der die FMNylierung stattfindet, einen Einfluss auf die FMN-Transferaseaktivität von ApbE bzw. ho-mologen Enzymen haben. Es wurde gezeigt, dass ein Peptid, welches auf der Aminosäurese-quenz der konservierten Flavinylierungstasche basiert, von Enzymen der ApbE-Familie er-kannt und kovalent FMNyliert wird. Dies ermöglicht nun erstmals eine funktionelle Analyse der Enzyme der ApbE-Familie. Die fragment-basierte Identifizierung von neuen Wirkstoffen („fragment-based drug dis-covery“) ist ein kristallographisches Hochdurchsatzverfahren, um kleine Moleküle („frag-ments“) zu identifizieren und weiterzuentwickeln, die an biologische Zielmoleküle wie bei-spielsweise Proteine binden. Hier wurden Enzyme der ApbE-Familie als Zielprotein verwendet, um neuartige Inhibitoren zu entwickeln, die gegen diese essenziellen, bakteriellen Enzyme wirken. Abschließend wurde ein kristallographiebasiertes Fragment Screening durchgeführt. Dazu ist es notwendig, ein Kristallsystem zu etablieren, bei dem das aktive Zentrum gut zugänglich ist. Außerdem müssen die Kristalle eine hohe Toleranz gegenüber DMSO haben, welches das Lö-sungsmittel ist, in dem die Fragmente gelöst werden. Es wurde daher die Hypothese aufgestellt, dass es vorteilhaft ist, mehrere Homologe eines Enzyms zu kristallisieren, um ein Kristallsystem zu identifizieren, welches für den Fragment Screening Ansatz geeignet ist. Nur eines von vier untersuchten Kristallsystemen war für das Fragment Screening geeignet. Dies ermöglichte die Identifizierung von sechs Vorläufermole-külen, die in die Substratbindetasche von ApbE binden. Die gezeigten Daten sind ein wichtiger Baustein für das Verständnis der Mechanismen der Na+-NQR und der ApbE Familie. Die Studien sind grundlegend für das Design von hochaffinen Inhibitoren dieser Enzyme.
TRPL-Recycling in Photorezeptoren von Drosophila : Identifikation beteiligter Gene mittels tsCRISPR Mutagenesescreen
(2025) Zeger, Matthias; Huber, Armin
Die präzise Regulation des intrazellulären Transports von Membranproteinen ist essenziell für die Funktion neuronaler Zellen. Störungen in diesem Prozess, insbesondere im Proteinrecycling über den Retromerkomplex, stehen im Zusammenhang mit neurodegenerativen Erkrankungen wie Alzheimer oder Parkinson. In dieser Arbeit wurde die lichtabhängige Translokation des TRPL (Transient Receptor Potential Like)-Ionenkanals im Drosophila-Komplexauge als Modell genutzt, um molekulare Komponenten des Membranproteintransports zu identifizieren. Bei Dunkelheit ist TRPL in den Rhabdomeren lokalisiert und transloziert nach Belichtung, aus dem Rhabdomer ins Zellinnere. Bei anhaltender Belichtung wandert der Großteil des TRPLs innerhalb von 12 Stunden zu einem Speicherkompartiment, das bislang als das Endoplasmatische Retikulum identifiziert wurde. Bei ausbleibendem Lichtreiz bzw. bei einer erneuten Dunkeladaptation der Photorezeptorzellen von Drosophila wandert TRPL innerhalb von 90–120 min wieder zurück in die rhabdomerische Membran. Ein augenspezifisches CRISPR-Knockout-System für Drosophila wurde etabliert, um gezielt Rab-GTPasen – zentrale Regulatoren des intrazellulären Vesikeltransports – im Zusammenhang mit dem TRPL-Recycling zu untersuchen. Durch die Analyse der TRPL-Lokalisation unter verschiedenen Lichtbedingungen konnten mehrere Rab- Proteine mit potenzieller Funktion im Recyclingprozess identifiziert und immunhistochemisch charakterisiert werden. Besonders starke Effekte auf das TRPLRecycling zeigten die Rab3-, Rab4-, Rab7-, Rab32-, Rab40- und RabX2-Knock-out Mutanten. Rab3, das unter anderem an späten Endosomen lokalisiert ist, wurde erstmals in vivo als Regulator für das Proteinrecycling identifiziert. RabX2 hingegen ist am trans-Golgi lokalisiert; sein Knock-out führte zu einer Akkumulation von TRPL im trans-Golgi während des retrograden Transports zurück in das Rhabdomer. Die Ergebnisse legen nahe, dass TRPL auch über einen zweiten ER-unabhängigen Weg zurück in das Rhabdomer recycelt wird, da ein Knock-Out von Rab3, Rab7, Rab32 oder Rab40 die ER/TRPL-Kolokalisation stark verringert aber der Rücktransport weniger stark beeinflusst wird. Außerdem wurde eine weitere TRPL-Recyclingroute über den trans-Golgi identifiziert welche abhängig von RabX2 ist. VII Im zweiten Teil der Arbeit wurde mittels TurboID-basiertem Biotin-Proximity Labeling nach TRPL-assoziierten Interaktionspartnern gesucht. Eine Auswahl der dabei identifizierten Kandidaten wurde funktionell analysiert, um ihren Einfluss auf die TRPLTranslokation zu bewerten. In dem Screen nach TRPL Interaktionspartnern wurden Signaltransduktionsproteine wie INAD, TRP und NorpA durch TRPL::TbID identifiziert. Darüber hinaus wurden Proteine wie Rab32 und Vps35 detektiert, die mit dem TRPLRecycling in Verbindung stehen, sowie weitere Proteine wie Sec61 und HIP-R, die potenziell mit ER-Stress assoziiert sind. Zu den weiteren identifizierten TRPLInteraktionspartnern gehörten Vap33, PIP82, Orp8, Sec63 und Sec22, die detailliert immunhistochemisch untersucht wurden. Dabei zeigte der Knock-out von Sec22 und Sec63 eine reduzierte Kolokalisation von TRPL mit Calnexin (Cnx), jedoch blieb der Rücktransport weitgehend wildtypisch – ein Phänotyp, der dem von Rab3-, Rab7-, Rab32- und Rab40-Knock-outs ähnelt. Die Orp8 Knock-out-Mutante zeigte nach erneuter Dunkeladaptation weiterhin eine TRPL/Cnx-Kolokalisation, was auf einen Defekt beim ER-Exit hinweist. Die PIP82-Nullmutante verursachte einen Internalisierungsdefekt sowie eine deutliche Abnahme des TRPL-Signals nach Lichtadaptation. Der Vap33 Knock-out führte bereits im Dunkelzustand zu anterograden Transportdefekt, da TRPL teilweise im Zytosol und ER lokalisiert war. Insgesamt konnte in der vorliegenden Arbeit gezeigt werden, dass neben dem ERabhängigen Recyclingweg von TRPL auch ein ER-unabhängiger Transportmechanismus existiert. Beide Routen sind auf die Funktion verschiedener Rab-GTPasen angewiesen. Besonders hervorzuheben ist der Nachweis einer Beteiligung von Rab3 am Proteinrecycling in Drosophila-Photorezeptorzellen – ein bisher nicht beschriebenes Phänomen, das über die bekannte Rolle von Rab3 in der synaptischen Transmission hinausgeht. Darüber hinaus wurde erstmals ein TRPLRecyclingweg über den trans-Golgi-Apparat identifiziert, der auf die Aktivität von RabX2 angewiesen ist. Ergänzend dazu konnten mehrere potenzielle Interaktionspartner von TRPL durch Biotin-Proximity Labelling identifiziert werden, darunter Vap33, PIP82, Orp8, Sec63 und Sec22. Funktionelle Analysen deuten darauf hin, dass diese Proteine einen Einfluss auf die zelluläre Lokalisation und Translokation von TRPL haben und somit eine Rolle in seiner dynamischen Regulation spielen könnten.
Echinococcus multilocularis and other zoonotic helminths in red foxes (Vulpes vulpes) from a southern German hotspot for human alveolar echinococcosis
(2023) Schneider, Carina; Kratzer, Wolfgang; Binzberger, Andreas; Schlingeloff, Patrycja; Baumann, Sven; Romig, Thomas; Schmidberger, Julian
Background: We describe the spatial distribution of Echinococcus multilocularis in its main definitive host, the red fox, and the distribution of human cases of alveolar echinococcosis (AE) within a highly endemic focus in southern Germany (13.7–19.9/100,000 in 1992–2018). Human cases were unequally distributed within the endemicity focus. The purpose of the study was to test whether this is reflected in the small-scale distribution of E. multilocularis in foxes. Methods: Three areas with contrasting numbers of human cases were selected within the counties of Ravensburg and Alb-Donau, Baden-Württemberg, Germany. From 2018 to 2020, a total of 240 fox carcasses were obtained from traditional hunters in these areas. Carcasses were necropsied and examined for the presence of intestinal helminths. The statistical analysis was performed with SAS version 9.4, and the geo-mapping with QGIS version 3.16.0 Hannover. Results: The prevalence of E. multilocularis in foxes was 44/106 (41.5%) in area I (commune Leutkirch and environs), 30/59 (50.8%) in area II (commune Isny and environs), and 31/75 (41.3%) in area III (commune Ehingen and environs). From 1992 to 2018, a total of nine human cases of alveolar echinococcosis were recorded in area I, five cases were recorded in study area III, and no cases were recorded in area II. No statistically significant differences between the areas were observed ( P > 0.05) for intestinal infections with E. multilocularis , and no apparent spatial correlation with the small-scale distribution of human cases was found. Concerning other zoonotic helminths, Toxocara spp. were equally common, with prevalence of 38.7%, 47.4% and 48.0%, respectively, while the frequency of Alaria alata varied among the study areas (0.0–9.4%), probably reflecting the specific habitat requirements for the establishment of its complex life cycle. Conclusions: Echinococcus multilocularis is highly prevalent in foxes in all the studied areas. The varying number of human AE cases within these areas should therefore be caused by factors other than the intensity of parasite transmission in foxes.
Tick hazard in a Central European country: Mapping Europe’s principal tick-borne disease vector across Germany
(2025) Springer, Andrea; Lindau, Alexander; Fachet-Lehmann, Katrin; Kämmer, Daniel; Bulling, Ingrid; Knoll, Steffen; Król, Nina; Fischer, Dominik; Fischer, Luisa; Drehmann, Marco; Chitimia-Dobler, Lidia; Noll, Madeleine; Vineer, Hannah Rose; Kahl, Olaf; Pfeffer, Martin; Strube, Christina; Mackenstedt, Ute
The most common European tick species, Ixodes ricinus, is the principal vector of Borrelia and tick-borne encephalitis virus and several other pathogens of public health relevance in Europe. Comprehensive data on tick abundance and the underlying ecological drivers are crucial for developing awareness and control strategies and to assess future changes in tick-borne disease risk. We aimed to provide a Germany-wide map of I. ricinus abundance to aid in disease transmission risk assessment. During 2018−2020, questing tick density was assessed at 83 sites across the whole country by drag flagging, whereby 49,344 I. ricinus nymphs and adults were collected. Relationships between climate, land cover, and monthly questing I. ricinus nymph density were explored and used to draw an abundance map. Highest tick hazard was observed in areas near the coast with mild winters and moist springs, and in mid-elevation mountain ranges, which represent popular tourist destinations. The ticks’ seasonal activity pattern was predominantly unimodal. The fact that the observed regional differences are contradictory to a previous estimation based on a combination of regional studies illustrates the need for an extensive and coordinated sampling effort to reliably estimate tick abundance at larger spatial scales. Combined with data on tick-borne pathogens, our study enables estimating the density of infected ticks and consequently the risk of acquiring an infectious tick bite. Moreover, the observed relationships with climate and land cover can help to predict future developments of tick hazard under different climate scenarios in Central Europe.
Reactivation of the tRNASer/tRNATyr gene cluster in Arabidopsis thaliana root tips
(2025) Hummel, Guillaume; Kumari, Priyanka; Hua, Chenlei; Wang, Long; Mai, Yan-Xia; Wang, Nan; Shala, Negjmedin; Kaya, Emir Can; Molinier, Jean; Wang, Jia-Wei; Liu, Chang
Plants maintain redundant tRNA genes (tDNAs) in their nuclear genomes, but the significance, regulation, and functional roles of these genes remain poorly understood. A cluster of tandemly repeated tDNAs decoding serine and tyrosine (SYY cluster) is located on Arabidopsis (Arabidopsis thaliana) chromosome 1, intersecting constitutive heterochromatin and remaining transcriptionally silenced in most tissues. The natural conditions inducing their transcription remain unknown. Here, we elucidate the tissue-specific expression pattern of this cluster during seedling establishment. Our findings reveal that SYY cluster tRNAs are primarily produced in the root cap columella and adjacent root cap cells. Transcriptional reactivation of the SYY cluster occurs in these tissues despite high DNA methylation levels. Furthermore, we demonstrate that these cells accumulate high levels of a transgenic glycoprotein rich in serine, tyrosine, and proline, and that CRISPR/Cas9 deletion of the SYY cluster alters the accumulation and stability of the glycoprotein in these specific cells. Our work provides pioneering evidence of a developmental and cell-specific expression program for a plant tDNA. We offer insights into the putative role of specialized tDNAs in enhancing glycoprotein biosynthesis in protective tissues of the meristem.
The RNF/NQR redox pumps: a versatile system for energy transduction in bacteria and archaea
(2025) Buckel, Wolfgang; Ermler, Ulrich; Vonck, Janet; Fritz, Günter; Steuber, Julia
The Na + (or H + )-translocating ferredoxin:NAD + oxidoreductase (also called RNF, rhodobacter nitrogen fixation, complex) catalyzes the oxidation of reduced ferredoxin with NAD + , hereby generating an electrochemical gradient. In the reverse reaction driven by an electrochemical gradient, RNF provides reduced ferredoxin using NADH as electron donor. RNF plays a crucial role in the metabolism of many anaerobes, such as amino acid fermenters, acetogens, or aceticlastic methanogens. The Na + -translocating NADH:quinone oxidoreductase (NQR), which has evolved from an RNF, is found in selected bacterial groups including anaerobic, marine, or pathogenic organisms. Since NQR and RNF are not related to eukaryotic respiratory complex I (NADH:quinone oxidoreductase), members of this oxidoreductase family are promising targets for novel antibiotics. RNF and NQR share a membrane-bound core complex consisting of four subunits, which represent an essential functional module for redox-driven cation transport. Several recent 3D structures of RNF and NQR in different states put forward conformational coupling of electron transfer and Na + translocation reaction steps. Based on this common principle, putative reaction mechanisms of RNF and NQR redox pumps are compared. Key points: • Electrogenic ferredoxin:NAD + oxidoreductases (RNF complexes) are found in bacteria and archaea. • The Na + -translocating NADH:quinone oxidoreductase (NQR) is evolutionary related to RNF. • The mechanism of energy conversion by RNF/NQR complexes is based on conformational coupling of electron transfer and cation transport reactions.
Diversity, ecology and response to climate change of Triassic temnospondyls: an integrative approach on global and regional scales
(2025) Moreno, Raphael; Schoch, Rainer
Temnospondyls are relatives of modern amphibians and represent a significant part of the fossil record of Triassic ecosystems. The Triassic was a period characterised by pronounced climatic and environmental changes. Due to their widespread occurrence temnospondyls offer unique insights into ecologically dynamic environments. In this dissertation, I apply an integrative approach on diverse geographic extents, including studies of global, regional and local measures and different stratigraphic scopes. Through a holistic framework of several methodologies, I aim to study the diversity and ecology of Triassic temnospondyls and their response to the changing Triassic climate. First, I present an extensive review of the global geographic and stratigraphic distribution of Triassic temnospondyls, before engaging in a detailed investigation of temnospondyl diversity within the German Triassic. Herein we identify 20 genera and 29 species of Triassic temnospondyls and advance the taxonomic identification through re-evaluations and identification of a new species occurring in the regional context of the German Triassic. Furthermore, we recognise three pronounced peaks of temnospondyl diversity coinciding with periods of enhanced ecological stability. In the second project, I employ species distribution modelling (SDM) to investigate the palaeogeographic distribution and potential dispersal routes of the temnospondyl fauna of the Central European basin and Central Pangea. I model the group response to changing environmental conditions during the Middle–Late Triassic transition, a period characterised by climatic fluctuations. Notably, this study is the first application of SDM on temnospondyls and highlights the dependency of temnospondyls on suitable abiotic conditions for their biogeographic distribution. Moreover, I quantify the changes in suitable habitat across various time slices from the Middle to Late Triassic period. Crucially, ecological resilience becomes evident as multiple clades persist through (1) phases of habitat reduction and (2) significant environmental and climatic changes. The utilisation of computational simulations on the deep time fossil record enhances our understanding of the interplay between dynamically changing climates and palaeobiological responses. The third project documents the ecological plasticity and adaptability of temnospondyls through new discoveries in depositional environments that have been previously deemed unsuitable for temnospondyl habitation. I assess and identify fragmentary remains of an unexpectedly diverse assemblage of temnospondyls in the sabkha and playa depositional environment of the Grabfeld Formation of southern Germany. The dolomitic banks that yielded some of the temnospondyl remains were deposited during brief marine ingressions from the Tethys Ocean into the Central European basin. The occurrence of sauropterygians and ostracods indicate euryhaline conditions. The identification of Metoposaurus in these layers challenges previous assumptions on the physiological tolerances of the group and further provides the stratigraphically oldest occurrence of this taxon in a global context. Furthermore, the occurrence of Plagiosternum in the same environment supports the general notion for the preferred palaeoenvironmental habitat of Plagiosternum while presenting the stratigraphically youngest occurrence of this taxon. In the last chapter, I investigate the palaeoenvironmental differences in the geographically close and coeval Middle Triassic fossil sites of Kupferzell and Vellberg-Eschenau in Baden-Württemberg, Germany. I investigate the geochemical properties in an attempt to characterise the degree of diagenetic alteration. Subsequent carbon and oxygen isotope analyses of tooth enamel of the temnospondyl Mastodonsaurus giganteus, as well as subsequent analyses of dental and skeletal bioapatite of associated fauna, reveal a substantial variation in the palaeoenvironments of both fossil localities. While both palaeoenvironments are characterised as lacustrine ecosystems, the observed isotopic differences portray Kupferzell as a more stable depositional environment with less episodic fluctuations, while the lacustrine system of Vellberg-Eschenau, especially layer E6, is depicted as more dynamic with greater seasonal and hydrological variabilities. Furthermore, the investigation of intra-tooth sample series fits the interpretation of a seasonally more dynamic setting in Vellberg-Eschenau E6. Overall, this dissertation demonstrates the effectiveness of eclectic approaches to elucidate complex ecological signals in Triassic temnospondyls. Additionally, the integrative framework applied in this dissertation accentuates and refines traditional views of temnospondyl palaeobiology and expands our perspective on the ecology, biogeography and plasticity of these taxa, underscoring their crucial role in Triassic ecosystems. The data presented in this thesis offers a multitude of future research endeavours. By combining the results of this dissertation with other comprehensive data sets the potential for continued advances in broader Triassic vertebrate palaeontology will be greatly enhanced, enabling significant insights into biodiversity patterns, evolutionary processes and ecological responses to environmental fluctuations.
The garden dormouse (Eliomys quercinus): ecology, habitat requirements and threats
(2025) Erhardt, Stefanie; Fietz, Joanna
Global biodiversity is declining rapidly, mainly as a result of anthropogenic pressures. Changes in land, such as deforestation and conversion to agriculture, are the main drivers of biodiversity loss, followed by direct exploitation such as hunting. Climate change and pollution are also contributing factors. The garden dormouse (Eliomys quercinus, Gliridae) is a small mammalian hibernator that has disappeared from more than 50% of its former range in recent decades, mainly in Eastern and Central Europe. The reasons for this decline are not yet fully understood. However, information on its biology, ecology, habitat requirements, and potential threats is needed to implement targeted conservation measures. To address this lack of knowledge, this study focuses on: 1. Filling knowledge gaps in the reproductive biology of the garden dormouse, including its genetic mating system and the timing of reproduction and hibernation (phenology), to better understand its life history strategies. 2. Identifying essential resources for the garden dormouse within the mountain forest, by investigating nesting behavior, home range use, and feeding ecology. 3. Characterizing potential threats for this species within the coniferous mountain forest by investigating the effects of climate change, the loss of essential resources, and habitat fragmentation. Therefore, a capture-mark-recapture study of the garden dormouse was conducted in the Northern Black Forest, one of its last natural distribution areas in Germany. To investigate the reproductive biology and the mating system of the garden dormouse, parentage analyses using five polymorphic microsatellite markers were combined with morphometric and behavioral data. Phenology was analyzed using capture-mark-recapture data in combination with morphometric measurements. To identify key resources during different life history stages, diet composition analysis in fecal samples and home range use and daytime resting sites were investigated by radio telemetry. Potential threats to the species were assessed by analyzing changes in body mass – used as a proxy for fitness – between two time periods (2003-2005 and 2018-2021), and by evaluating the effect of ambient winter temperatures on post-hibernation body mass. Based on the movement patterns of radio-tracked individuals, potential barrier effects of forest paths and trails were investigated. Genetic analyses and indirect indicators revealed that the garden dormouse is promiscuous. Typically for a promiscuous species garden dormice have relatively large testes and minimal sexual dimorphism. Males have extensive home ranges that overlap with those of several females, increasing the probability of mating encounters. This mating system maintains genetic variability, helping to avoid inbreeding and promotes offspring fitness. Garden dormice showed two birth peaks per year between 2003 and 2005, in contrast to only one birth peak in 2018-2021. Late-born juveniles grew faster to build sufficient fat reserves necessary for hibernation survival. The later onset of pre-hibernation fattening observed in adult females compared to adult males suggests that females must compensate for their higher energy demands during reproduction before hibernation starts. The home range provides essential resources for survival and reproduction, including food, resting sites, and mating partners. Garden dormice in the Black Forest showed a median home range size of 3.8 ha, with resting sites used in nest boxes and ground holes. However, ground holes were used more frequently during reproduction and low ambient temperatures, and are therefore an important resource especially during periods of high energy demand. The results of this study show that garden dormice are omnivorous with a preference for arthropods during the critical life history stages of juvenile growth and pre-hibernation fattening. Analyses of the crossing behavior showed that that adult garden dormice avoided crossing 4 m wide forest paths, which poses a significant threat to their survival by limiting their ability to colonize new areas, inhibiting gene flow and mate finding. In addition, this study also found that from 2018 to 2021, garden dormice had a reduced body mass during pre-hibernation fattening and growth compared to 2003 to 2005. As arthropods are the main food resource during this period, the ongoing insect decline may already be negatively affecting the availability of essential food resources, thereby reducing the survival probability of this population. This study found no effect of ambient temperature on post-hibernation body mass or phenology; however, the study sites were located at high altitudes where winters are still cold enough to ensure suitable hibernation conditions for garden dormice. Nonetheless, the ongoing climate change trends are predicted to further elevate winter temperatures even at higher altitudes, which could reduce the survival chances of this population in the future. To support the long-term survival of the garden dormouse, conservation measures should focus on the reduction of habitat fragmentation by rebuilding forest paths or, where this is not possible, creating underpasses with sufficient cover and connection to the surrounding habitat to facilitate dispersal and promiscuous mating. In addition, to support the garden dormouse during critical life history stages and to increase overall forest biodiversity and resilience, it is important to support food resources, especially arthropods, and resting sites by promoting forest structural diversity, increasing the amount of dead wood, and reducing pesticide use in the forest and the surrounding agricultural areas. In addition, natural resting sites such as ground holes should be supported by reducing the use of heavy timber machines and preserving structural habitat features such as rock crevices, underground burrows, tree holes, and cavities in dead wood. Implementing these conservation measures can mitigate the population decline of garden dormice. Reducing barrier effects, maintaining insect diversity and high structural diversity within forests can promote forest ecosystem resilience and support overall biodiversity.
Competitive hierarchies in bryozoan assemblages mitigate network instability by keeping short and long feedback loops weak
(2023) Koch, Franziska; Neutel, Anje-Margriet; Barnes, David K. A.; Tielbӧrger, Katja; Zarfl, Christiane; Allhoff, Korinna T.
Competitive hierarchies in diverse ecological communities have long been thought to lead to instability and prevent coexistence. However, system stability has never been tested, and the relation between hierarchy and instability has never been explained in complex competition networks parameterised with data from direct observation. Here we test model stability of 30 multispecies bryozoan assemblages, using estimates of energy loss from observed interference competition to parameterise both the inter- and intraspecific interactions in the competition networks. We find that all competition networks are unstable. However, instability is mitigated considerably by asymmetries in the energy loss rates brought about by hierarchies of strong and weak competitors. This asymmetric organisation results in asymmetries in the interaction strengths, which reduces instability by keeping the weight of short (positive) and longer (positive and negative) feedback loops low. Our results support the idea that interference competition leads to instability and exclusion but demonstrate that this is not because of, but despite, competitive hierarchy.
Unwanted souvenirs - import routes and pathogen detection of the non-endemic tick Rhipicephalus sanguineus s.l. in Germany
(2025) Fachet-Lehmann, Katrin; Lindau, Alexander; Mackenstedt, Ute
Ticks of the Genus Rhipicephalus occur worldwide. Especially members of Rh. sanguineus s.l. are primarily associated with dogs. As unwanted souvenirs, they are introduced by dogs into non-endemic areas such as Germany, where they can establish and reproduce indoors . A citizen-science study was conducted between 2019 and 2024, asking interested citizens to report tick infestations and send in travel related tick findings which were associated with dogs and were focused on Rhipicephalus species. Tick species were identified using the 16S rRNA gene and tested for pathogens associated with the genus Rhipicephalus . In addition, each tick introduction was considered as a case and categorized and analyzed individually. During the study period, 44 cases were reported. In 17 cases tick specimens were identified as Rh. sanguineus s.s., Rh. rutilus , Rh. linnaei, Rh. turanicus , and Rh. haemaphysaloides which were imported from other European countries and Sri Lanka. Neither Hepatozoon canis , Ehrlichia canis nor Babesia vogeli were detected in any of the 780 received specimens. In contrast, Rickettsia spp. was detected in 50 specimens from six independent cases, with Rickettsia massiliae being identified in 44 specimens. The import of dogs from abroad as well as travel with dogs lacking appropriate tick prophylaxis are responsible for more than 80% of cases. This Project highlights the risk of introductions of non-endemic tick species. Also, professionals such as veterinarians, animal welfare organizations and pest controllers need to be made aware of the possible introduction of Rhipicephalus spp. to ensure early recognition and rapid elimination of the ticks.
Societal changes in Ancient Greece impacted terrestrial and marine environments
(2025) Koutsodendris, Andreas; Maran, Joseph; Kotthoff, Ulrich; Lippold, Jörg; Knipping, Maria; Friedrich, Oliver; Gerdes, Axel; Kaboth-Bahr, Stefanie; Bahr, André; Schulz, Hartmut; Sakellariou, Dimitris; Pross, Jörg
The Aegean hosts some of the earliest cultural centers in European antiquity. To reconstruct the evolution of early anthropogenic impact in this region, we have examined lead (Pb) contents and vegetation dynamics on well-dated environmental archives extending to the early Holocene. We show that the impact of agropastoral societies on terrestrial ecosystems was locally confined during the Bronze and Iron Ages (5200–2750 years ago), although we record an onset of Pb pollution already at 5200 cal. years BP and thus about 1200 years earlier than previous archeological evidence. Our data demonstrate a marked increase in Pb pollution at 2150 cal. years BP that left an imprint across terrestrial and marine settings of the Aegean region. This first manifestation of marine pollution coincides with maximum deforestation and agricultural expansion, signaling pervasive human impact on ecosystems connected to the advanced monetized societies during the Hellenistic and Roman periods in Ancient Greece.
Habitat requirements and home range use of the threatened garden dormouse (Eliomys quercinus) in a coniferous forest
(2025) Erhardt, Stefanie; Pfister, Jan; Beier, Marieke; Vorderbrügge, Rieke; Förschler, Marc I.; Fietz, Joanna
Understanding habitat use and requirements is essential for the conservation of endangered species, such as the garden dormouse (Eliomys quercinus). Therefore, we radio-tracked garden dormice (n = 39) in the Black Forest National Park (Germany) between 2019 and 2021, determined home range size by calculating autocorrelated kernel density estimates, located resting sites during the day, and analyzed their resting behavior. Furthermore, we investigated their crossing behavior across paths varying in width, in the degree of canopy closure, and understory. Median home range size was 3.8 ha (Q25 = 2.3 ha, Q75 = 6.6 ha) in adults and 1.9 ha in juveniles. Adult males increased their home range sizes during reproduction. In September, shortly before hibernation, adults used smaller home ranges, likely to save energy. During the day, garden dormice used nest boxes and natural nests under the ground as resting sites. Ground holes were an important resource as they were most frequently used by reproductive individuals and also at low ambient temperatures (0.1–14.7 °C). In contrast, nest boxes were used only at higher ambient temperatures (> 5.9 °C). Forest trails with tree cover and/or undergrowth were frequently crossed by adults, while 4 m wide forest paths without tree cover or undergrowth were rarely crossed. The results of our study show that the preservation of natural resting sites, the restoration of forest trails, or the installation of crossing structures are important conservation measures for the garden dormouse, facilitating migration and colonization of new habitats and reducing the risk to lose genetic variability.
Phylogenomic approach to integrative taxonomy resolves a century‐old taxonomic puzzle and the evolutionary history of the Acromyrmex octospinosus species complex
(2024) Mera‐Rodríguez, Daniela; Fernández‐Marín, Hermógenes; Rabeling, Christian
Accurately delimiting species boundaries is essential for understanding biodiversity. Here, we assessed the taxonomy of the leaf‐cutting ants in the Acromyrmex octospinosus (Reich) species complex using an integrative approach incorporating morphological, population genetic, phylogenetic and biogeographical data. We sampled populations across the biogeographic distribution of the species complex and reconstructed their evolutionary relationships using ultraconserved elements (UCEs) as molecular markers. We evaluated traditional morphological characters used to distinguish putative taxa and performed species delimitation analyses to investigate divergence between evolutionary lineages. Our results support the hypothesis that the A. octospinosus species complex consists of two species: the widely distributed and polymorphic species A. octospinosus and its inquiline social parasite A. insinuator Schultz et al. We consider A. echinatior (Forel) syn. nov . and A. volcanus Wheeler syn. nov . as well as the subspecies A. octospinosus cubanus Wheeler syn. nov ., A. octospinosus ekchuah Wheeler syn. nov . and A. octospinosus inti Wheeler syn. nov . as junior synonyms of A. octospinosus . We also investigated the biogeographic history of the species complex and the evolutionary origin of the social parasite A. insinuator . We inferred that A. octospinosus originated during the late Miocene approximately 6.9 Ma ago in the Neotropical rainforest. Acromyrmex insinuator shared a common ancestor with A. octospinosus approximately 3.4 Ma ago, with a crown‐group age of approximately 0.9 Ma. Our phylogeny supports the hypothesis that the inquiline social parasite speciated via the intra‐specific route of social parasite evolution in direct sympatry from its host. Our findings reshape our understanding of the A. octospinosus species complex and provide a foundation for future studies of Acromyrmex leaf‐cutting ants.
Ontogenetic variation in the cranium of Mixosaurus cornalianus, with implications for the evolution of ichthyosaurian cranial development
(2023) Miedema, Feiko; Bindellini, Gabriele; Dal Sasso, Cristiano; Scheyer, Torsten M.; Maxwell, Erin E.
Relatively complete ontogenetic series are comparatively rare in the vertebrate fossil record. This can create biases in our understanding of morphology and evolution, since immaturity can represent a source of unrecognized intraspecific variation in both skeletal anatomy and ecology. In the extinct marine reptile clade Ichthyopterygia, ontogenetic series were widely studied only in some Jurassic genera, while the ontogeny of the oldest and most basal members of the clade is very poorly understood. Here, we investigate cranial ontogeny in Mixosaurus cornalianus , from the Middle Triassic Besano Formation of the Swiss and Italian Alps. This small-bodied taxon is represented by a wealth of material from multiple size classes, including fetal material. This allows us to assess ontogenetic changes in cranial morphology, and identify stages in the ontogenetic trajectory where divergence with more derived ichthyosaurs has occurred. Early ontogenetic stages of Mixosaurus show developmental patterns that are reminiscent of the presumed ancestral (early diverging sauropsid) condition. This is prominently visible in the late fetal stage in both the basioccipital, which shows morphology akin to basal tubera, and in the postorbital, which has a triradiate head. The ontogenetic trajectory of at least some of the cranial elements of Mixosaurus is therefore likely still very akin to the ancestral condition, even though the adult cranium diverges from the standard diapsid morphology.
Oncostatin M is a regulator of fibroblast growth factor 23 (FGF23) in UMR106 osteoblast-like cells
(2023) Münz, Sina; Feger, Martina; Föller, Michael
Renal phosphate and vitamin D metabolism is under the control of fibroblast growth factor 23 (FGF23), an endocrine and paracrine factor predominantly produced in bone. FGF23 formation is stimulated by active vitamin D, or parathyroid hormone (PTH), which are further regulators of phosphate homeostasis. In renal, inflammatory, and other diseases, plasma FGF23 reflects disease stage and correlates with outcome. Oncostatin M is part of the interleukin-6 (IL-6) family and regulates remodeling and PTH effects in bone as well as cardiac FGF23 production in heart failure via glycoprotein gp130. Here, we studied whether oncostatin M is a regulator of FGF23 in bone cells. Experiments were performed in UMR106 osteoblast-like cells, Fgf23 mRNA was determined by qRT-PCR, FGF23 protein by Western Blotting and ELISA, and oncostatin M receptor and leukemia inhibitory factor (LIF) receptor gene knockout accomplished by siRNA. As a result, oncostatin M dose-dependently up-regulated Fgf23 expression and protein secretion. The oncostatin M effect on FGF23 was mediated by oncostatin M receptor and gp130 and involved, at least in part, STAT3 and MEK1/2. Taken together, oncostatin M is a regulator of FGF23 through oncostatin M receptor, gp130, as well as STAT3 and MEK1/2 in UMR106 osteoblasts.
Tissue-level integration overrides gradations of differentiating cell identity in beetle extraembryonic tissue
(2024) Mann, Katie E.; Panfilio, Kristen A.; García-Sanz, José A.; Merino, Marisa M.; Chen, Lingyi
During animal embryogenesis, one of the earliest specification events distinguishes extraembryonic (EE) from embryonic tissue fates: the serosa in the case of the insects. While it is well established that the homeodomain transcription factor Zen1 is the critical determinant of the serosa, the subsequent realization of this tissue’s identity has not been investigated. Here, we examine serosal differentiation in the beetle Tribolium castaneum based on the quantification of morphological and morphogenetic features, comparing embryos from a Tc-zen1 RNAi dilution series, where complete knockdown results in amnion-only EE tissue identity. We assess features including cell density, tissue boundary morphology, and nuclear size as dynamic readouts for progressive tissue maturation. While some features exhibit an all-or-nothing outcome, other key features show dose-dependent phenotypic responses with trait-specific thresholds. Collectively, these findings provide nuance beyond the known status of Tc-Zen1 as a selector gene for serosal tissue patterning. Overall, our approach illustrates how the analysis of tissue maturation dynamics from live imaging extends but also challenges interpretations based on gene expression data, refining our understanding of tissue identity and when it is achieved.

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