Institut für Biologie

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Ontogenetic variation in the skull of Stenopterygius quadriscissus with an emphasis on prenatal development
(2022) Miedema, Feiko; Maxwell, Erin E.; Miedema, Feiko; Department of Paleontology, Hohenheim University, Stuttgart, Germany; Maxwell, Erin E.; Staatliches Museum Für Naturkunde Stuttgart, Stuttgart, Germany
The availability of a large sample size from a range of ontogenetic stages makes Stenopterygius quadriscissus a good model to study ontogenetic variation in a fossil sauropsid. We qualitatively examined pre- and postnatal ontogenetic changes in the cranium of S. quadriscissus . The prenatal ossification sequence is similar to other diapsids, exhibiting delayed chondrocranial ossification compared to the dermatocranium. In the dermatocranium, the circumorbital area is more ossified earlier in development relative to other elements, especially those of the skull roof where ossification is comparatively weaker across prenatal stages. Perinatally all cranial elements are ossified, and many scarf and step joints are already closed. We propose four prenatal and three postnatal stages in S. quadriscissus on the basis of relative ossification, size and qualitative cranial characters pertaining to the jugal, parietal, frontal, pterygoid and surangular. These will provide a basis for determining ontogenetic stages in other ichthyosaurs. Moreover, our postnatal observations aid in refining ontogenetic characters for phylogenetic studies. Lastly, we observed that the antimeric sutures of the midline of the skull roof are open perinatally and that fusion of the midline only appears in the adult stage. We hypothesize that the loose connection of the midline functions as a fontanelle, limiting potential damage during birth.
Modelling net CO₂ assimilation of two Sphagnum species from temperature and water content response
(2025) Perera‐Castro, Alicia V.; Nadal, Miquel; Perera‐Castro, Alicia V.; Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna, La Laguna, Canary Islands, Spain; Nadal, Miquel; AgroParisTech, INRAE, UMR Silva, Université de Lorraine, Nancy, France
Photosynthesis and respiration respond differently to the combined effects of temperature and water status. Quantifying their responses is crucial to predict the carbon balance of Sphagnum peatlands in different scenarios of climate change. A first approach was done for two Sphagnum species inhabiting a boreal peatland in Finland. Gas exchange at different temperatures and moss hydration were measured to model net assimilation using simultaneous measurements of photosynthesis and dark respiration. In addition, measurements of moss surface temperature at different water content were performed in the field, covering natural conditions of sun exposure and air temperature. We also accounted for the interaction effect between moss canopy temperature and air temperature, radiation, and water content. Our model accurately predicted net assimilation and was used to estimate net primary productivity based on meteorological inputs and moss water content. The two Sphagnum species presented optimum temperatures for net CO2 assimilation around 25°C, with minimum changes at other temperatures. In contrast, dark respiration increased exponentially with temperature, which makes losses of carbon during the night and the duration of dark conditions key determinants in the carbon balance of Sphagnum. The modeled net primary productivity revealed an enhancement of CO2 fixation under warming conditions (averaged +10°C), concomitant to the expected transformation of peatlands from sink to source of CO2. Our model highlighted the importance of respiration restriction in ensuring positive assimilation in Sphagnum. Therefore, day and night temperature oscillation and short night photoperiods are more important than the optimum temperature of photosynthesis for carbon balance.
Metabolic rewiring compensates for the loss of amino acid biosynthesis in Bacillus subtilis
(2024) Yousef Mardoukhi, Mohammad Saba; Commichau, Fabian M.
Amino acids are considered as some of the earliest organic molecules to form on Earth. Serving as the building blocks of proteins, they are intricately connected to nearly every life process. Therefore, amino acid metabolism needs to be precisely regulated in any living organism. Amino acid metabolism includes the biochemical pathways responsible for the synthesis, degradation, and utilization of amino acids. Most of the bacteria, particularly the Gram-positive model bacterium Bacillus subtilis, have the capability to synthesize all proteinogenic amino acids or, if available, import them from the environment. Throughout evolution, different metabolic pathways have emerged to maintain metabolites level inside the cells. Some biosynthetic pathways are unknown as they are not primary routes or are typically inactive under normal conditions. However, they may become active under specific circumstances. Two very important pathways, previously not known to be substituted by alternative routes, involve de novo biosynthesis of glutamate, which is an essential amino group donor in every cell. Many bacteria can synthesize glutamate using a NADPH + H+-dependent glutamate dehydrogenase (GDH). Alternatively, glutamate can be produced by the combined action of the ATP-dependent glutamine synthetase (GS) and the NADPH + H+-dependent glutamate synthase (GOGAT). B. subtilis only employs the GS-GOGAT pathway for de novo synthesis of glutamate. In the context of this work, it was shown that a B. subtilis deficient for the GS-GOGAT pathway may employ the aspartase AnsB and aspartate transaminase AspB for the synthesis of glutamate in biologically significant amounts. Genetic analyses revealed that the aspartase AnsB converts ammonium and the tricarboxylic acid cycle intermediate fumarate to aspartate. Subsequently, the aspartate transaminase AspB transfers the amino group from aspartate to α-ketoglutarate, resulting in the production of L-glutamate and oxaloacetate. This observation challenges the well-established point of view of whether the GS-GOGAT-dependent pathway is indeed the only route for de novo synthesis of glutamate in nature. It was also set out to explore which amino acids could serve as the sole sources of carbon and nitrogen in the background of a B. subtilis strain that is a genetically stable glutamate auxotroph. The aim was to understand the conversion of the amino acids into glutamate and further to α-ketoglutarate, a reaction that is facilitated by the enzymatic activity of the GDHs RocG/GudB. It turned out that some of the amino acids are toxic for B. subtilis. However, B. subtilis can quickly develop resistance by the acquisition of mutations that result in reduced and enhanced amino acid uptake and export, respectively. Moreover, the toxicity of some amino acids may be reduced by increased degradation of glutamate. Furthermore, with focus on the toxicity of asparagine, it could be demonstrated that AimA, which has been characterized as a general amino acid importer, serves as a low affinity asparagine transporter in B. subtilis. Finally, AzlCD, which was previously described as an exporter for histidine and branched-chain amino acids, also exports asparagine. Thus, B. subtilis can adapt to amino acid toxicity in various ways.
Genome-wide development of simple sequence repeat (SSR) markers at 2-Mb intervals in lotus (Nelumbo Adans.)
(2025) Liu, Fengluan; Xi, Lin; Fu, Naifeng; Liu, Fengluan; Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, No. 3888 Chenhua Road, Songjiang District, 201602, Shanghai, China; Xi, Lin; Department of Plant Systems Biology, University of Hohenheim, 70599, Stuttgart, Germany; Fu, Naifeng; Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, No. 3888 Chenhua Road, Songjiang District, 201602, Shanghai, China
Background: Despite the rapid advancement of high-throughput sequencing, simple sequence repeats (SSRs) remain indispensable molecular markers for various applied and research tasks owing to their cost-effectiveness and ease of use. However, existing SSR markers cannot meet the growing demand for research on lotus ( Nelumbo Adans.) given their scarcity and weak connections to the lotus genome. Methods: Using whole-genome resequencing, active SSR loci were identified throughout the genomes of eight typical Asian lotus. After that, high polymorphism SSR molecular markers were mined from each 2n + 0.5 Mb site on each chromosome (e.g., Chr.1-2.5, 4.5, 6.5 Mb) through four steps: online primer design, primer pair evaluation, agarose gel electrophoresis testing using six Asian lotus, one American lotus, and two their hybrids, and DNA sequence alignment. Finally, the polymerase chain reaction (PCR) efficiency of several SSR markers was validated in 20 Asian temperate lotus, eight Asian tropical lotus, and one American lotus. Results: A total of 463 SSR markers were developed based on each 2n + 0.5 Mb site of the eight lotus chromosomes (totaling 821.29 Mb). These markers were evenly distributed throughout the lotus genome at a density of 1 SSR per 1.76 Mb. The chromosomal locations of the SSR markers were determined precisely, and the specificity of the primer pairs for each site was verified by sequencing the PCR products. We further provided a set of genome-wide SSR loci, covering 129 per Mb, identified from eight representative Asian lotus, allowing other researchers to independently discover specific SSR markers for particular experiments. Conclusion: These SSR markers, which have a density of 1 SSR marker per 1.76 Mb in this study, will act as a bridge connecting lotus phenotypes with the genome. This work reveals a novel and convenient strategy for developing highly polymorphic SSR markers at any location throughout the lotus genome, and it sheds light on the development of SSR molecular markers in other plant species.
Analyse altersabhängiger Änderungen der DNA-Methylierung
(2024) Holländer, Olivia; Fricke, Florian
This study investigated age-dependent DNA methylation patterns to estimate chronological age. DNA methylation is a covalent bond of a methyl group at the 5'-carbon atom of a cytosine, which in mammals occurs almost exclusively in sequences of cytosine-phosphate-guanine, so-called CpG sites. For criminal proceedings, it is highly relevant whether a person has reached a legally relevant age limit of 14, 18 or 21 years. Estimating the age is also relevant for unaccompanied refugee minors who are entitled to special protection by law. There is often a lack of valid documents that can confirm that they are minors. Furthermore, estimating the age of unknown perpetrators of biological crime scene evidence can support police investigations in order to narrow down the circle of possible trace donors. In 2016, the German Ethics Commission expressed that they do not consider the medical methods currently used to estimate age to be suitable, as they violate the fundamental rights to physical integrity, human dignity and the general right to privacy. As buccal mucosal swabs or saliva samples represent a practicable, cost-effective and, above all, non-invasive alternative, an estimation model based on buccal mucosa was sought. The first research hypothesis covered age estimation of adolescents and young individuals. First, 88 age-dependent CpG sites of the eight markers PDE4C, ELOVL2, ITGA2B, ASPA, EDARADD, SST, KLF14 and SLC12A5 were analysed by bisulphite conversion and subsequent pyrosequencing. For this purpose, 141 buccal mucosal swabs from individuals between 21 and 69 years of age were analysed. In 54 of the 88 CpG sites analysed (in six markers PDE4C, ELOVL2, EDARADD, SST, KLF14 and SLC12A5), age-dependent methylation patterns were identified. This study showed that a reliable estimation of age is possible using as little as three CpG sites (PDE4C, EDARADD and KLF14) and that this model can also be successfully transferred to another sequencing method, namely minisequencing. In the second step, research focused on estimating the age of adolescent individuals. For this purpose, buccal swabs from 230 individuals between 1 and 88 years of age were used. Eight CpG sites of already established markers (PDE4C, EDARADD, SST, KLF14, ELOVL2, FHL2, C1orf132 and TRIM59) were analysed using mini sequencing. After analysing the correlation of the methylation status of the individual CpG sites with the chronological age of the test subjects, a logarithmic rather than linear relationship from birth to adulthood was observed, particularly for the markers ELOVL2 and TRIM59. To deal with this phenomenon, 20 years was defined as the ‘cut-off’ value, at which the chronological age is transformed in order to adjust the chronological age to the epigenetic age. A MAD of 4.680 years was thus achieved in the training set and a MAD of 4.695 years in the independent validation set. The estimates were most accurate in the lower age segment from 0 to 19 years (MAD of only 2.64 years), thus achieving the goal of a model that is suitable for age estimation for adolescents and young adults. To answer the second research hypothesis, the contribution of hydroxymethylation to the improvement of age estimation models was analysed. The term DNA methylation usually refers to 5-methylcytosine (5mC), but bisulphite conversion cannot distinguish between 5- hydroxymethylcytosine (5hmC) and 5mC. By subjecting a portion of the sample to an oxidation step prior to bisulphite conversion, in which 5hmC is oxidised and later treated like an unmethylated cytosine, 5mC and 5hmC can be analysed separately. Methylation values of 40 CpG sites in eight markers (EDARADD, PDE4C, SST, KLF14, SLC12A5, TOX2, LRRN2 and STK12A) were analysed by pyrosequencing in 108 individuals. Estimation models including 5hmC markers or take ydroxymethylation into account reveal similar accuracy as those that only take 5mC markers (so-called ‘true 5mC methylation’) into account and models based on the gold standard (undifferentiated 5mC+5hmC values). In any case, this makes 5hmC another promising marker for forensic age estimation. However, no significant improvement in estimation accuracy was achieved, which is why the second research hypothesis could not be confirmed. The 5hmC methylation values of individual CpG sites showed weak to moderate correlations with chronological age. The literature indicates that 5hmC shows better genome- wide correlation with age than 5mC and that it also regulates different genes. This suggests that the best 5hmC markers for age estimation may not yet have been found. Methods that can analyse longer sections of the genome are better suited for a future search for the best markers.
Hitze als Schlüssel zur Aufklärung der Lysogenie beim SPß-Phagen
(2025) Kohm, Katharina; Kohm, Katharina; Institut Biologie, Universität Hohenheim, Garbenstraße 30, D-70599, Stuttgart, Deutschland
Reduced body mass in a highly insectivorous mammal, the garden dormouse — ecological consequences of insect decline?
(2025) Erhardt, Stefanie; Förschler, Marc I.; Fietz, Joanna; Erhardt, Stefanie; Department of Zoology, Institute of Biology, University of Hohenheim, Stuttgart, Germany; Förschler, Marc I.; Department for Ecological Monitoring, Research and Species Protection, Black Forest National Park, Seebach, Germany; Fietz, Joanna; Department of Zoology, Institute of Biology, University of Hohenheim, Stuttgart, Germany
Biodiversity is decreasing worldwide, and early indicators are needed to identify endangered populations before they start to decline in abundance. In mammals, body mass (BM) is regarded as an indicator of fitness, and its loss is used as an early warning signal preceding population decline. The garden dormouse ( Eliomys quercinus , Gliridae, BM: 60–110 g) is a small mammalian hibernator that has disappeared from over 50% of its former range in the last decades. The aim of this study was to investigate whether garden dormice from a presumably thriving and stable population already show early warning signals, which may precede a population decline. We therefore conducted capture‐mark‐recapture studies during 2003–2005 (Period 1) and 2018–2021 (Period 2) in the Northern Black Forest, one of its last natural distribution areas in Germany. We collected fecal samples, measured BM, and tibia length as a proxy for size and age. Results revealed that in Period 2 adult dormice had a significantly lower (12%) pre‐hibernation BM, corrected for body size, and juveniles showed a significantly lower BM gain after weaning than nearly two decades ago. Fecal samples collected in Period 2 showed that arthropods represented the main food residues in fecal samples during juvenile growth and pre‐hibernation fattening. Ambient temperature during hibernation showed no correlation with BM at emergence. We could not detect a phenological time shift in reproduction; however, we found only one birth peak in Period 2, compared with two birth peaks in Period 1. Observed changes in BM and reproduction pattern represent early warning signals, as they point to an insufficient availability of high‐quality food, which prevents dormice from meeting their nutritional requirements, with potentially serious consequences for their reproductive success and survival. As arthropods are the dominant food resource, their decline may at least partly explain this phenomenon.
Analyse viraler Promotoren von Phycodnaviren und deren Interaktion mit Transkriptionsfaktoren
(2025) Wahl, Benjamin; Pfitzner, Artur
Acanthocystis turfacea Chlorella Virus 1 (ATCV-1) ist ein dsDNA-Virus aus der Gattung Chloroviren, welches Chlorella heliozoae infiziert. Das Virus besitzt 860 offene Leserahmen (open reading frames, ORF), die für die Gene codieren, die für einen korrekten Virusreplikationszyklus benötigt werden. Diese Gene werden in sehr frühe/frühe/späte Gene eingeteilt. Diese Einteilung basiert auf den Zeitpunkten der Expression der Gene. Für die Expression dieser Gene nutzt ATCV-1 virale Promotoren, die eine Mischung aus eukaryotischen und prokaryotischen Bestandteilen darstellen. Die erfolgreiche Initialisierung des Replikationszyklus mit Hilfe von sehr frühen und frühen Genen ist essenziell für eine vollständige Virusreplikation. In früheren Arbeiten konnten Gene in Paramecium busaria Chlorella Virus 1 (PBCV-1) identifiziert werden, die als sehr frühe Gene klassifiziert wurden. Das Ziel dieser Arbeit beinhaltet die Untersuchung sehr früher/ früher Gene und deren Promotoren. Im zweiten Teil der Arbeit sollte die Interaktion von Proteinen, deren Promotor ein Hex-Motiv (XXXCGTGG) enthalten, mit verschiedenen Faktoren untersucht werden. Basierend auf Sequenzvergleich-Analysen zwischen den sehr frühen Genen aus PBCV-1 und den Genen aus ATCV-1 wurden 20 Gene identifiziert. Die Promotoren dieser Gene wurden auf ihre Motive analysiert. Mit Hilfe einer RT-qPCR konnte gezeigt werden, dass diese Gene in der sehr frühen Phase der Virusreplikation (5 min p.i.) alle aktiv waren. Die Analyse in Pflanzen konnte zeigen, dass das Hex-Motiv in Verbindung mit mindestens einer TATA-Box ideal für die Expression der frühen Promotoren ist. Weitere Analysen konnten zeigen, dass für eine generelle Expression in Pflanzen mindestens zwei TATA-Box-Motiv in Verbindung mit anderen Motiven existieren müssen. In HEK293-Zellen konnte für die Promotoren mit dem Hex-Motiv ebenfalls eine Aktivität demonstriert werden. In der Arbeit konnte gezeigt werden, dass das Arg7-ASL-System zur Untersuchung der Aktivität von viralen Promotoren genutzt werden konnte. Alle frühen Promotoren zeigten eine Aktivität in Chlamydomonas reinhardtii, inklusive Promotoren anderer Viren. Promotoren mit dem Hex-Motiv zeigten, im Vergleich zu Promotoren ohne dieses Motiv, eine Interaktion mit einer Vielzahl von unterschiedlichen Transkriptionsfaktoren, die zu den bZIP-Transkriptionsfaktoren gezählt werden. Mit Hilfe zweier Proteine, Z174L und Z765R, deren Promotoren das Hex-Motiv besitzen, konnten mehrere mögliche Interaktionspartner mit Hilfe von „proximity based labeling“, darunter Proteine wie z.B. Actin, Thioredoxin und ein Histon-Acetlytransferase-Protein, identifiziert werden. Diese Proteine können mit der Transkription in Verbindung gebracht werden, was die vermutete Funktion von Z765R als Transkriptionsfaktor stützt. Z174L ist vermutlich ein Transkriptionsfaktor bzw. eine Endonuklease. Auch hierfür konnten Proteine, die diese Hypothese unterstützen, mit Hilfe der Massenspektrometrie identifiziert werden. In dem dritten Teil der Arbeit konnte mit Hilfe von Yeast-1-Hybrid-Analysen und dem Promotor von Z063L ein neues Protein, Activating protein 63 (Ap63), in Chlamydomonas reinhardtii identifiziert werden. Dieses Protein besitzt Motive, die mit DNA-Bindung in Verbindung gebracht werden. Kombiniert mit Analysen der Sequenz, handelt es sich bei dem hier entdeckten Protein vermutlich um einen Transkriptionsfaktor. Das Gesamtbild dieser Studie zeigt auf, wie abhängig das Virus von seinem Wirt für eine erfolgreiche Replikation ist und wie breit das Spektrum der Virus-Wirt-Interaktion ist. Die sehr frühe Genexpression (5 min p.i.) spielt eine essenzielle Rolle für die Replikation. Hierfür macht sich das Virus Proteine (vor allem Transkriptionsfaktoren) des Wirts zunutze, um die gesamte Genexpression der Wirtszelle auf die Virusreplikation umzuprogrammieren.
The paradox of the bryozoans
unravelling the relation between structure and stability in benthic competition networks
(2025) Koch, Franziska; Allhoff, Korinna T.
Classical ecological models struggle to explain the persistence of diverse communities, where many species compete for the same resources. For example, traditional stability theory based on large, random matrices predicts that diverse communities should generally be unstable. Furthermore, according to the principle of competitive exclusion, two species competing for one resource should not be able to coexist. Parametrising network models with empirical data has revealed that real networks tend to contain specific non-random patterns of weak and strong links, which enable their stability. However, such patterns have been studied in food webs as well as mutualistic networks, while potential stabilising patterns of interaction strengths in competitive systems remain largely unexplored. Instead, simplified competition networks are often used, in which interactions are binary, so that potential stabilising effects due to specific patterns in weak and strong links cannot be considered. In such studies, intransitive competition, where competitive links are arranged as in a rock-papers-scissors game, is considered the only mechanism that can avoid competitive exclusion. In this thesis, I studied the role of interaction strengths in the stability of competition networks. To achieve this, I used data on encrusting bryozoan assemblages in order to parametrise weighted interaction networks. Bryozoans are small aquatic animals that grow in colonies on the sea bed. Individual colonies compete for space by overgrowing each other. My approach allowed me to obtain Jacobian matrices from species abundances and recorded overgrowths. I could thus connect this abstract mathematical modelling approach with empirical data. Based on the Jacobian matrices, I assessed network stability, as well as the strengths of amplifying and dampening feedback loops in the systems, which allowed me to draw connections between structure and stability. In Chapter 1, I analysed a data set of 30 polar bryozoan assemblages. These assemblages were quite hierarchical, meaning that species could be sorted from strongest to weakest competitors. I showed that as a result of this hierarchy, the Jacobian matrices contained asymmetric patterns of interaction strengths and that these patterns had a stabilising effect. While all empirical networks were unstable, destroying asymmetry by randomising the matrix elements increased the level of instability. This is because the asymmetric patterns keep feedback loops of all lengths weak. This applies to short, positive 2-link loops which can destabilise the system by amplifying perturbations, as well as to longer, negative loops which can cause unstable oscillations. Positive 2-link loops that are formed between each pair of competing species played a key role, and I found that the strongest 2-link loop in a matrix could be used as a predictor of network instability. I could thus identify hierarchy to have a stabilising effect in weighted competition networks, which contrasts with the common idea that intransitive competition stabilised complex systems. In Chapter 2, I additionally looked at the role of distributions of interaction strengths. I showed that the interaction strengths in my empirical data sets were very skewed, with few strong and many weak links. Similar patterns have also been found in the link strengths of both food webs and mutualistic networks, pointing towards a general pattern. I tested whether this skewed distribution of link strengths influenced the stabilising effect of asymmetry by building theoretical community matrices with asymmetric patterns and various distributions of link strengths. My results indicated that the full stabilising effect of asymmetry could only be reproduced when a skewed distribution of interaction strengths was used. This has important implications for many theoretical studies, where normal and uniform distributions of link strengths are often used, meaning that some stabilising patterns might be overlooked. Finally, in Chapter 3, I contrasted networks from polar regions to additional data sets collected at temperate and tropical locations. By comparing several network indices, I identified latitudinal differences in the strength of asymmetric patterns, which were generally stronger in polar networks. Due to the stabilising effect of asymmetry, this also leads to differences in network stability, with tropical networks having stronger positive 2-link feedback loops and thus being more unstable. Across all data sets, I found that again, the strongest 2-link loop closely predicted stability, emphasising the generality of this stability predictor. However, the strength of asymmetry varied significantly within some regions, which could potentially be linked to assemblage age and disturbance history. To summarise, my work extends our understanding of stabilising patterns in interaction strengths to competitive systems. A key result is that positive, amplifying 2-link feedback loops determine the stability of competition networks, and that asymmetric arrangement of link strengths reduce their amplifying effect. I identified the maximum 2-link loop weight as a predictor of network stability, which is in line with previous results on food webs, where the maximum 3-link loop determines stability. Finally, I was able to show that some insights derived from random matrix models and models of intransitive competition, which are both commonly used in theoretical ecology, might not be transferable to real systems. This highlights a further need to combine mathematical modelling approaches with empirical research.
Unbiased anchors for reliable genome-wide synteny detection
(2025) Käther, Karl K.; Remmel, Andreas; Lemke, Steffen; Stadler, Peter F.; Käther, Karl K.; Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, Leipzig University, Härtelstrasse 16-18, D-04017, Leipzig, Germany; Remmel, Andreas; Zoology Department, University of Hohenheim, 10587, Stuttgart, Germany; Lemke, Steffen; Zoology Department, University of Hohenheim, 10587, Stuttgart, Germany; Stadler, Peter F.; Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, Leipzig University, Härtelstrasse 16-18, D-04017, Leipzig, Germany
Orthology inference lies at the foundation of comparative genomics research. The correct identification of loci which descended from a common ancestral sequence is not only complicated by sequence divergence but also duplication and other genome rearrangements. The conservation of gene order, i.e. synteny, is used in conjunction with sequence similarity as an additional factor for orthology determination. Current approaches, however, rely on genome annotations and are therefore limited. Here we present an annotation-free approach and compare it to synteny analysis with annotations. We find that our approach works better in closely related genomes whereas there is a better performance with annotations for more distantly related genomes. Overall, the presented algorithm offers a useful alternative to annotation-based methods and can outperform them in many cases.
Protein interactions between the bacteriophage T4 tail tip and the inner membrane of Escherichia coli
(2025) Wenzel, Sabrina; Kuhn, Andreas
The infection process of bacteriophage T4 represents a fascinating series of orchestrated events, involving highly coordinated conformational changes and molecular interactions. While the initial stages, such as adsorption, host receptor recognition, and tail sheath contraction, are well-characterized (Islam et al., 2019; Leiman et al., 2004), the molecular mechanism underlying the translocation of the T4 genome across the inner host membrane remains poorly understood. The transport of the T4 DNA across bacterial membranes is particularly challenging due to its hydrophilic, polyanionic nature and the need to traverse the hydrophobic barriers of bacterial membranes. This step is critical for infection success, as it must occur without disrupting the host cell’s membrane potential or metabolic energy supply, which are essential for phage propagation. The central spike complex, comprising gp5Cβ and gp5.4, is the first component to enter the periplasm upon contraction of the T4 phage tail. This study aimed to investigate the interactions between the T4 phage tail tip proteins gp27, gp5, and gp5.4 and periplasm and inner membrane components of Escherichia coli. The first part of this study examined the behavior of the T4 central spike complex, specifically the gp5Cβ-gp5.4 component, after penetrating the outer membrane of E. coli. The spike complex, composed of three gp5Cβ and one gp5.4 subunit, punctures the outer membrane during tail contraction and enters the periplasm. To explore potential interactions with periplasmic components, in vitro binding assays using purified gp5Cβ-gp5.4 complexes and E. coli spheroplasts were performed. Results indicated that the spike complex lacked significant affinity for membrane bilayers, consistent with its structural properties, which lack hydrophobic or amphipathic regions. Cross-linking experiments with spheroplasts revealed a transient interaction between the spike complex and the periplasmic chaperone PpiD. This interaction was confirmed using proteoliposomes reconstituted with purified PpiD, which showed enhanced binding of the spike complex compared to control liposomes. PpiD is a periplasmic chaperone anchored to the inner membrane and is known for its role in stabilizing unfolded proteins. It is hypothesized that PpiD transiently interacts with the spike complex, stabilizing it or facilitating its positioning near the inner membrane for subsequent stages of infection. The biological relevance of PpiD was assessed using an efficiency of plating (EOP) assay, which revealed a reduction in infection efficiency in PpiD deletion mutants, with plaque formation decreasing to approximately 80% of wild type levels. This suggests that while PpiD is not essential for infection, it provides a supportive role, potentially complemented by other periplasmic chaperones. The second part of the study focused on the tail tip protein gp27 and its interactions with the inner membrane. Gp27, which forms a trimeric structure associated with gp5, is proposed to play a crucial role in forming a channel for DNA translocation. To investigate its potential binding to inner membrane proteins, T4 phage particles carrying His-tagged gp27 were constructed, and cross-linking experiments were performed in vivo. These studies identified several host proteins that interact with gp27, including DamX and PpiD. DamX, a cell division protein involved in peptidoglycan remodeling and septal ring stabilization, was identified as a key binding partner of gp27. Cross-linking and affinity purification confirmed this interaction, and subsequent infection assays demonstrated a significant reduction in T4 infection efficiency to 60% in DamX deletion mutants. These findings underscore the critical role of DamX in facilitating phage DNA translocation across the inner membrane. The study suggests that DamX may provide a structural or functional scaffold, stabilizing the phage-host interface during infection. PpiD, which was also identified in the first part of the study, was co-purified with gp27, highlighting its involvement in multiple stages of the infection process. Its role in stabilizing the phage at the inner membrane or facilitating structural rearrangements required for DNA translocation warrants further investigation. In addition to identifying these interactions, the study explored the functional implications of DamX and PpiD during infection. Complementary experiments demonstrated that both proteins are not only important for initial binding but may also be involved in facilitating the structural transitions required for successful DNA translocation.
Soil drought sets site specific limits to stem radial growth and sap flow of Douglas-fir across Germany
(2024) Niessner, Armin; Ehekircher, Stefan; Zimmermann, Reiner; Horna, Viviana; Reichle, Daniel; Land, Alexander; Spangenberg, Göran; Hein, Sebastian; Niessner, Armin; Department of Silviculture, University of Applied Forest Sciences, Rottenburg am Neckar, Germany; Ehekircher, Stefan; Department of Silviculture, University of Applied Forest Sciences, Rottenburg am Neckar, Germany; Zimmermann, Reiner; Ecological Botanical Gardens ÖBG, University of Bayreuth, Bayreuth, Germany; Horna, Viviana; Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Jena, Germany; Reichle, Daniel; Institute of Biology, University of Hohenheim, Stuttgart, Germany; Land, Alexander; Department of Silviculture, University of Applied Forest Sciences, Rottenburg am Neckar, Germany; Spangenberg, Göran; Department of Silviculture, University of Applied Forest Sciences, Rottenburg am Neckar, Germany; Hein, Sebastian; Department of Silviculture, University of Applied Forest Sciences, Rottenburg am Neckar, Germany
Introduction: Soil drought during summer in Central Europe has become more frequent and severe over the last decades. European forests are suffering increasing damage, particularly Norway spruce. Douglas-fir ( Pseudotsuga menziesii (Mirbel) Franco), a non-native tree species, is considered as a promising alternative to build drought-resilient forests. The main goal of this study was to investigate the intraannual radial stem growth and sap flow performance of Douglas-fir along a precipitation gradient across Germany under severe drought. Material and methods: Sap flow and stem radial changes of up to ten trees each at four sites with different precipitation regimes were measured in combination with volumetric soil water content during the growing season of 2022. Measurements of stem radial changes were used to calculate the trees’ stem water deficit, a proxy for tree water status and drought stress. Results: The severe summer drought of 2022 led to an early growth cessation and a significant reduction in daily sap flow at all four sites monitored. We could identify a site-specific threshold in soil water availability ranging between 21.7 and 29.6% of relative extractable water (REW) under which stem water reserves cannot be replenished and thereby inhibiting radial growth. We could also demonstrate that at this threshold, sap flow is heavily reduced to between 43.5 and 53.3%, and for a REW below 50%, sap flow linearly decreases by 1.1–2.0% per 1% reduction in REW. This reduction tends to follow the humidity gradient, being more pronounced at the most oceanic characterized site and suggesting an adaptation to site conditions. Even though Douglas-fir is considered to be more drought stress resistant than Norway spruce, growth and sap flow are greatly reduced by severe summer drought, which became more frequent in recent years and their frequency and intensity is likely to increase. Conclusions: Our results suggest that timber production of Douglas-fir in Central Europe will decline considerably under projected climate change, and thus pointing to site specific growth constraints for a so far promising non-native tree species in Europe.
Conformational dynamics of proteins in bacterial pathogens and the innate immune response
(2024) Hau, Jann-Louis; Fritz, Günter
Global health is facing two major threads, the rapid rise of multi-drug resistant bacterial pathogens and the increase autoimmune diseases. Therefore, studying the components of host-pathogen interactions is crucially important for the development of novel drugs and diagnostic tools to fight these threats. Both, virulence factors of pathogenic bacteria and the components of the host’s innate immune response are build up by multimeric protein complexes. In order to understand how these systems respond to different conditions and environments and to uncover the underlying molecular mechanisms, the conformational dynamics of these proteins must be resolved. This study focuses on the two important examples of a host-defence protein, S100A8/A9, and a bacterial virulence factor, the Na+-translocating NADH:ubiquinone oxidoreductase (NQR). The heterodimeric protein complex S100A8/A9 is secreted in very high amounts by immune cells at sites of infection and tissue damage. S100A8/A9 is a key element of the innate immune system. It strongly activates inflammatory response and exhibits antimicrobial properties by binding of essential transition metal nutrients. Therefore it is defined as a danger-associated molecular pattern (DAMP). Its role as a DAMP during inflammation and absence in healthy tissue defines S100A8/A9 is used as an excellent biomarker for a variety of inflammatory diseases in human and veterinary medicine. Only the human S100A8/A9 is thoroughly characterised so far. Imaging of S100A8/A9 by a tracer molecule would allow for sensitive and accurate imaging of pathogenic or sterile inflammation. Here, a new protocol for fast and and efficient isolation of human and porcine S100A8/A9 is established, which is also applicable to S100A8/A9 of other species. The characterisation of porcine S100A8/A9 revealed similar properties with respect to structure and metal binding to human S100A8/A9, while the antimicrobial properties of the porcine protein are less pronounced than in the human orthologue. The structures of human S100A9 in complex with different tracer molecules were determined by X-ray crystallography, revealing that the molecular benzimidazole core of the tracer binds into a dynamically adapting pocket of S100A9. Applying a newly established tryptophan fluorescence-based assay, it was shown that the affinity of the tracer is not affected by different imaging tags attached to the benzimidazole core. Since the bezimidazole core exhibits non-favourable pharmacokinetic properties, novel lead compounds for the targeting of S100A8/A9 in inflammation have to be established. New lead structures, which could serve as novel molecular cores, were identified by fragment-based crystallographic screening. As exemplified by the benzimidazole imaging tracers, S100A8/A9 ligands have to fulfil the requirements of the dynamic binding pocket. The identified molecules represent an excellent starting point for the development of a novel class of imaging probes for the sensitive detection of inflammation. The NQR is part of the respiratory chain of the human pathogen Vibrio cholerae. It couples the oxidation of NADH and the reduction of ubiquinone to the translocation of Na+ from the cytoplasm to the periplasm. The resulting Na+ electrochemical gradient, the sodium motive force, is vital for V. cholerae and drives several processes critical for pathogenesis, like e.g. movement of the flagellum and efflux of antibiotics. NQR-activity is linked to the expression of pathogenic factors including the cholera toxin and is therefore classified as a virulence factor itself. Since the NQR has no homologs in humans and is widespread among Gram-negative pathogenic bacteria, it is a promising target for the development of novel classes of antibiotics. However, the mechanism of electron transfer and the coupled sodium translocation as well as the quinone binding site had been elusive. Based on first structural information on the NQR, which exhibited unusual large distances between redox cofactors, drastic conformational changes had been proposed (Steuber et al., 2014). In this study, the structure of the NQR with substrates or inhibitors bound was determined by single particle cryo electron microscopy. The structures reveal that the coupling of electron transfer to conformational changes in the NQR subunits NqrC and NqrF are governed by the redox state of the intramembrane [2Fe-2S] cluster between NqrD/E, defining the NQR as a conformationally coupled redox pump. Furthermore, the binding site of ubiquinone and the NQR inhibitor HQNO was located in NqrB. Sodium ions were identified bound in NqrB, which could represent exit sites of the sodium translocation path. These findings were confirmed for the NQR of Prevotella byrantii by homology modelling. Taken together, the molecular mechanism described for the V. cholerae NQR applies also to NQRs from other organisms and homologous complexes. The described NQR mechanism and substrate binding sites lay the foundation for the structure-based design of NQR-inhibitors which could serve as new antibacterial drugs. In summary, the findings presented in this study promote the development of novel diagnostic tools and new antibiotics to combat the emerging threats of autoimmune diseases and multidrug resistant bacterial pathogens.
Integrative description of Temnothorax siculus sp. n.: a new ant species from Sicily, Italy (Hymenoptera, Formicidae)
(2025) Schifani, Enrico; Alicata, Antonio; Prebus, Matthew M.; Csősz, Sándor; Schifani, Enrico; Department of Chemistry, Environmental Sustainability, and Life Sciences, University of Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy; Alicata, Antonio; Department of Biological, Geological and Environmental Sciences, University of Catania, Via Androne 81, 95124 Catania, Italy;; Prebus, Matthew M.; Social Insect Research Group, School of Life Sciences, Arizona State University, 550 E Orange St., Tempe, AZ 85281, USA;; Csősz, Sándor; HUN-REN-ELTE-MTM Integrative Ecology Research Group, Pázmány Péter ave 1/C, 1117 Budapest, Hungary; Fernández, Fernando; Guerrero, Roberto José
The mostly Holarctic genus Temnothorax (Hymenoptera, Formicidae) is the most diverse ant genus in temperate regions. The Mediterranean, a biodiversity hotspot of rare ant species, hosts over 150 Temnothorax taxa, including several short-range endemics. Over the last few years, phylogenomic reconstructions and integrative taxonomy have significantly improved the understanding of global Temnothorax diversity, but much taxonomic work is still needed in the Mediterranean region. Here, we present the integrative description of a new species of the genus, discovered in the central Mediterranean island of Sicily: Temnothorax siculus sp. n. is defined and compared to congeneric species integrating morphometrics and phylogenomics. It is a ground-nesting, lowland species, of which workers were regularly observed foraging on bushes and small trees. In the global phylogeny, covering all the main lineages of the region, it belongs to the Palearctic clade and is related to the tuberum and unifasciatus complexes. Morphological separation from other Sicilian Temnothorax species can generally be achieved on qualitative characters, but we also provide morphometric discriminant functions to separate it from T. apenninicus and especially T. unifasciatus . Temnothorax siculus has been rarely collected but appears to be widespread in Sicily, and may occur in neighboring regions.
Morphological and molecular identification of sarcocystis arctica in captive cheetahs (Acinonyx jubatus) in China helps clarify phylogenetic relationships with Sarcocystis caninum and Sarcocystis felis
(2025) Liao, Zhe; Zhu, Niuping; Yang, Yurong; Deng, Shuangsheng; Jäkel, Thomas; Hu, Junjie; Liao, Zhe; Yunnan Key Laboratory for Plateau Mountain Ecology, Restoration of Degraded Environments, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650091, China;; Zhu, Niuping; College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, China; (N.Z.); (Y.Y.); Yang, Yurong; College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, China; (N.Z.); (Y.Y.); Deng, Shuangsheng; Joint Laboratory of Virology & Immunity, School of Biological Sciences, Yunnan University, Kunming 650091, China;; Jäkel, Thomas; Institute of Biology, Department of Parasitology, University of Hohenheim, 70599 Stuttgart, Germany; Hu, Junjie; Yunnan Key Laboratory for Plateau Mountain Ecology, Restoration of Degraded Environments, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650091, China;; Salvarani, Felipe M.; Domingues, Sheyla Farhayldes Souza; Da Silveira, Júlia Angélica Gonçalves
To date, only one case is known where protozoan parasites of the genus Sarcocystis were found to infect cheetahs ( Acinonyx jubatus ); the cysts in the musculature were morphologically identified as S. felis . Here, we characterized sarcocysts by morphological and molecular methods that were observed in cheetahs who died in zoos in China. Only one type of sarcocyst was present in two of six cheetahs. By light microscopy, the sarcocyst wall was striated, 1.4–2.1 μm thick. Ultrastructurally, the wall had irregular-shaped, small villar protrusions, resembling wall type 9c, similar to those of S. arctica , S. caninum , and S. felis . The samples shared their highest molecular identity values with those of S. arctica and S. caninum : 99.9–100% and 99.8–100% (18S rRNA), 99.5% and 99.3–99.5% (28S rRNA), 95.9–97.5% and 96.3–97.3% (ITS-1), and 99.6% and 99.2–99.7% ( cox 1), respectively. Compared with ITS-1 of S. felis , identities ranged between 87.5% and 88.9%. Phylogenetic reconstruction revealed that the newly sequenced Sarcocystis clustered with S. arctica and S. caninum , whereas S. felis (ITS-1) and S. canis (ITS-1, 18S rRNA, cox 1) were sister species. Thus, we addressed the Sarcocystis species from the cheetahs as S. arctica , which is the first record of a Sarcocystis species believed to be specific for canids as intermediate hosts to infect a feline host.
Exploring ND-011992, a quinazoline-type inhibitor targeting quinone reductases and quinol oxidases
(2023) Kägi, Jan; Sloan, Willough; Schimpf, Johannes; Nasiri, Hamid R.; Lashley, Dana; Friedrich, Thorsten; Kägi, Jan; Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; Sloan, Willough; Department of Chemistry, William & Mary, Williamsburg, USA; Schimpf, Johannes; Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; Nasiri, Hamid R.; Department of Cellular Microbiology, University Hohenheim, Stuttgart, Germany; Lashley, Dana; Department of Chemistry, William & Mary, Williamsburg, USA; Friedrich, Thorsten; Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
Bacterial energy metabolism has become a promising target for next-generation tuberculosis chemotherapy. One strategy to hamper ATP production is to inhibit the respiratory oxidases. The respiratory chain of Mycobacterium tuberculosis comprises a cytochrome bcc:aa3 and a cytochrome bd ubiquinol oxidase that require a combined approach to block their activity. A quinazoline-type compound called ND-011992 has previously been reported to ineffectively inhibit bd oxidases, but to act bactericidal in combination with inhibitors of cytochrome bcc:aa3 oxidase. Due to the structural similarity of ND-011992 to quinazoline-type inhibitors of respiratory complex I, we suspected that this compound is also capable of blocking other respiratory chain complexes. Here, we synthesized ND-011992 and a bromine derivative to study their effect on the respiratory chain complexes of Escherichia coli. And indeed, ND-011992 was found to inhibit respiratory complex I and bo3 oxidase in addition to bd-I and bd-II oxidases. The IC50 values are all in the low micromolar range, with inhibition of complex I providing the lowest value with an IC50 of 0.12 µM. Thus, ND-011992 acts on both, quinone reductases and quinol oxidases and could be very well suited to regulate the activity of the entire respiratory chain.
Disc mower versus bar mower: Evaluation of the direct effects of two common mowing techniques on the grassland arthropod fauna
(2025) von Berg, Lea; Frank, Jonas; Betz, Oliver; Steidle, Johannes L. M.; Böttinger, Stefan; Sann, Manuela; von Berg, Lea; Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology, University of Tübingen, Tübingen, Germany; Frank, Jonas; Fundamentals of Agricultural Engineering, Institute for Agricultural Engineering, University of Hohenheim, Stuttgart, Germany; Betz, Oliver; Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology, University of Tübingen, Tübingen, Germany; Steidle, Johannes L. M.; Chemical Ecology, Institute for Biology, University of Hohenheim, Stuttgart, Germany; Böttinger, Stefan; Fundamentals of Agricultural Engineering, Institute for Agricultural Engineering, University of Hohenheim, Stuttgart, Germany; Sann, Manuela; Chemical Ecology, Institute for Biology, University of Hohenheim, Stuttgart, Germany
1. In Central Europe, species‐rich grasslands are threatened by intensive agriculture with frequent mowing, contributing to the reduction of arthropods such as insects and spiders. However, comprehensive and standardised studies on the direct effects of the two most agriculturally relevant mowing techniques, e.g., double‐blade bar mower versus disc mower, are lacking. 2. In a 2‐year experiment, we have investigated the direct effect of mowing on eight abundant arthropod groups in grassland, covering two seasonal mowing events in both years, using a randomised block design. We compared (a) an unmown control, (b) a double‐blade bar mower and (c) a disc mower. 3. For most of the taxonomic groups studied, a significantly lower number of individuals was found in the experimental plots immediately after mowing, regardless of the mowing technique, compared to an unmown control. This was not the case for Orthoptera and Coleoptera, which did not show a significant reduction in the number of individuals for both mowing techniques (Orthoptera) or only for the double‐blade bar mower (Coleoptera). 4. Between both mowing techniques, no significant differences were found for all taxonomic groups investigated. 5. Synthesis and applications: Our findings suggest that mowing in general has a negative impact on abundant arthropod groups in grassland, regardless of the method used. Tractor‐driven double‐blade bar mowers do not seem to be a truly insect‐friendly alternative to a conventional disc mower. Other factors such as cutting height and mowing regimes should be seriously considered to protect spiders and insects from the negative effects of mowing. In addition, we strongly recommend the maintenance of unmown refugia. Insects and spiders that are spared by mowing can take refuge in these unmown areas to avoid subsequent harvesting and thermally unfavourable conditions that arise on mown areas. Further, unmown refugia are basic habitat structures for a subsequent recolonisation of mown areas once the flora has recovered.
Identification of novel genes including NAV2 associated with isolated tall stature
(2023) Weiss, Birgit; Ott, Tim; Vick, Philipp; Lui, Julian C.; Roeth, Ralph; Vogel, Sebastian; Waldmüller, Stephan; Hoffmann, Sandra; Baron, Jeffrey; Wit, Jan M.; Rappold, Gudrun A.
Very tall people attract much attention and represent a clinically and genetically heterogenous group of individuals. Identifying the genetic etiology can provide important insights into the molecular mechanisms regulating linear growth. We studied a three-generation pedigree with five isolated (non-syndromic) tall members and one individual with normal stature by whole exome sequencing; the tallest man had a height of 211 cm. Six heterozygous gene variants predicted as damaging were shared among the four genetically related tall individuals and not present in a family member with normal height. To gain insight into the putative role of these candidate genes in bone growth, we assessed the transcriptome of murine growth plate by microarray and RNA Seq. Two (Ift140, Nav2) of the six genes were well-expressed in the growth plate. Nav2 (p-value 1.91E-62) as well as Ift140 (p-value of 2.98E-06) showed significant downregulation of gene expression between the proliferative and hypertrophic zone, suggesting that these genes may be involved in the regulation of chondrocyte proliferation and/or hypertrophic differentiation. IFT140, NAV2 and SCAF11 have also significantly associated with height in GWAS studies. Pathway and network analysis indicated functional connections between IFT140, NAV2 and SCAF11 and previously associated (tall) stature genes. Knockout of the all-trans retinoic acid responsive gene, neuron navigator 2 NAV2, in Xenopus supports its functional role as a growth promotor. Collectively, our data expand the spectrum of genes with a putative role in tall stature phenotypes and, among other genes, highlight NAV2 as an interesting gene to this phenotype.
Association between vitamin D status and eryptosis - results from the German National Cohort Study
(2023) Ewendt, Franz; Schmitt, Marvin; Kluttig, Alexander; Kühn, Julia; Hirche, Frank; Kraus, Frank B.; Ludwig-Kraus, Beatrice; Mikolajczyk, Rafael; Wätjen, Wim; Bürkner, Paul-Christian; Föller, Michael; Stangl, Gabriele I.; Ewendt, Franz; Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany; Schmitt, Marvin; Cluster of Excellence SimTech, University of Stuttgart, Stuttgart, Germany; Kluttig, Alexander; Institute of Medical Epidemiology, Biostatistics, and Informatics, Medical Faculty of the Martin Luther University Halle-Wittenberg, Halle (Saale), Germany; Kühn, Julia; Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany; Hirche, Frank; Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany; Kraus, Frank B.; Central Laboratory, Department of Laboratory Medicine, University Hospital Halle, Halle (Saale), Germany; Ludwig-Kraus, Beatrice; Central Laboratory, Department of Laboratory Medicine, University Hospital Halle, Halle (Saale), Germany; Mikolajczyk, Rafael; Institute of Medical Epidemiology, Biostatistics, and Informatics, Medical Faculty of the Martin Luther University Halle-Wittenberg, Halle (Saale), Germany; Wätjen, Wim; Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany; Bürkner, Paul-Christian; Cluster of Excellence SimTech, University of Stuttgart, Stuttgart, Germany; Föller, Michael; Department of Physiology, University of Hohenheim, Stuttgart, Germany; Stangl, Gabriele I.; Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
Vitamin D, besides its classical effect on mineral homeostasis and bone remodeling, can also modulate apoptosis. A special form of apoptosis termed eryptosis appears in erythrocytes. Eryptosis is characterized by cell shrinkage, membrane blebbing, and cell membrane phospholipid disorganization and associated with diseases such as sepsis, malaria or iron deficiency, and impaired microcirculation. To our knowledge, this is the first study that linked vitamin D with eryptosis in humans. This exploratory cross-sectional trial investigated the association between the vitamin D status assessed by the concentration of plasma 25-hydroxyvitamin D (25(OH)D) and eryptosis. Plasma 25(OH)D was analyzed by LC–MS/MS, and eryptosis was estimated from annexin V-FITC-binding erythrocytes by FACS analysis in 2074 blood samples from participants of the German National Cohort Study. We observed a weak but clear correlation between low vitamin D status and increased eryptosis ( r = − 0.15; 95% CI [− 0.19, − 0.10]). There were no differences in plasma concentrations of 25(OH)D and eryptosis between male and female subjects. This finding raises questions of the importance of vitamin D status for eryptosis in terms of increased risk for anemia or cardiovascular events.
Kinetics and dynamics of plant toxins in sequestering insects
(2024) Betz, Anja; Petschenka, Georg
Many plants produce a variety of chemical compounds to protect themselves from herbivorous insects. However, numerous insects have developed adaptations to tolerate and even utilize these toxins. These adaptations can include behavioral changes (feeding on or avoiding toxic plant parts), detoxification (metabolizing or excreting the toxins), barriers (preventing uptake or protecting target sites), or sequestration (storing secondary plant compounds in the body for self-defense). A widely distributed group of phytochemicals are the cardiac glycosides, which have been extensively studied in chemical ecology. These toxic steroids act in a highly specific manner by inhibiting the Na+/K+-ATPase, an essential transmembrane cation carrier that is ubiquitously expressed in animal cells. A cardiac glycoside-resistant Na+/K+-ATPase was first described in the monarch butterfly (Danaus plexippus, Lepidoptera: Danaini), which sequesters cardiac glycosides from its food plants. This led to the hypothesis that the evolution of a resistant Na+/K+-ATPase is linked to the sequestration of cardiac glycosides. It is now known that species from at least six insect orders possess Na+/K+-ATPases with reduced affinity for cardiac glycosides. This resistance is mediated by a few amino acid substitutions in the binding site, a mechanism referred to as "target site insensitivity." Interestingly, the ability to tolerate dietary cardiac glycosides does not necessarily require a resistant Na+/K+-ATPase. For example, the non-sequestering common crow (Euploea core, Lepidoptera: Danaini) can develop on cardiac glycoside-containing plants without expressing a resistant Na+/K+-ATPase. Although plant toxin sequestration has been documented in more than 275 insect species, the underlying kinetics and dynamics of toxin transport - such as the duration and mode of transport, target sites, barriers, and potential modified binding sites - remain largely unknown. Like the Danaini, milkweed bugs (Heteroptera: Lygaeinae) also have the ability to sequester cardiac glycosides. Remarkably, one species within this family, Spilostethus saxatilis, is able to sequester not only cardiac glycosides but also colchicine alkaloids from autumn crocus (Colchicum autumnale, Liliales: Colchicaceae). Colchicine binds to unpolymerized betatubulin at the interface with alpha-tubulin, thereby inhibiting microtubule formation. However, it is not known how colchicine resistance is achieved in S. saxatilis and whether there is also target site insensitivity. In my dissertation, I investigated the mechanisms behind the sequestration of cardiac glycosides in D. plexippus and colchicine in S. saxatilis within a phylogenetic framework. In D. plexippus, I was able to show that sequestration begins at the behavioral level, because unlike related species, caterpillars can increase their toxicity in the adult stage by drinking plant latex containing cardiac glycosides. I also found that a large portion of cardiac glycosides is lost during metamorphosis, suggesting that excessive toxin intake during the larval stage may be important. Furthermore, I could show that the uptake of the toxin by the intestinal epithelium is a very rapid process although probably not specific to D. plexippus, as uptake in nonsequestering lepidopterans does also occur. Regarding the sequestration of colchicine in S. saxatilis, I identified an amino acid substitution in the colchicine binding site of tubulin. Subsequently, an in vitro colchicine binding assays with crude tubulin extract of bug tissue and an in vivo feeding experiment with genetically modified Drosophila with one matching substitution in the colchicine binding site were conducted. Together both experiments suggest that this modification may play a crucial role in the sequestration of colchicine, indicating a novel natural target site resistance. My dissertation provides new insights into how insects adapt to toxic food plants and how they sequester their toxic metabolites. This contributes not only to a better understanding of how insects cope with natural plant toxins, but also to a better understanding of the physiological complexity of these adaptations.

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