Biology subjects

Kurtz, J.

Publications and source records attributed to Kurtz, J..

18 recordsLinked to original sources

bioRxiv2026

An HSP90-released reduced-eye phenotype alters light-dependent behaviour in Tribolium castaneum

Heat Shock Protein 90 (HSP90) functions as an evolutionary capacitor, allowing populations to store cryptic genetic variation that can be released under stress. While former studies have described the release of morphological variation, its behavioural consequences remain unexplored. In the red flour beetle, Tribolium castaneum, HSP90 inhibition released a phenotype with much smaller, less defined eyes that confers fitness benefits in continuous light and was subsequently assimilated. We hypothesized that altered eye morphology affects light perception and thereby changes light-dependent behaviours. To test whether phenotypes released via evolutionary capacitance can beneficially alter behaviour, we examined locomotor activity rhythm entrainment to light-dark cycles as well as individual and group light choice behaviour. Males of the reduced-eye phenotype exhibited a diminished startle response to sudden light exposure in locomotor activity assays. We also found reduced negative phototaxis in groups of beetles with reduced eyes. This modified behaviour, indicating reduced light sensitivity, may stem from impaired light perception caused by altered eye morphology. Lower light sensitivity could be beneficial under stressful environmental conditions by promoting the exploration of alternative niches. Therefore, this study provides the first evidence for potentially beneficial behavioural changes in a HSP90-released phenotype, reinforcing HSP90s role as an evolutionary capacitor.

evolutionary biology↗

bioRxiv2025

Single-cell multiomic human brain atlas reveals regulatory drivers of cortical regionality

Distinct regional functionality of the human cortex is orchestrated by diverse cellular and molecular processes, yet the underlying regulatory mechanisms remain poorly understood. We performed multiomic single-cell and spatial characterization of nine regions of the human cortex to define the gene regulatory networks and transcription factors that govern cell-type and region specificity. With the combined data of over three million cells, two striking patterns of cortical neuron specialization were uncovered: a rostral-caudal gradient of calcium regulatory machinery, and subunit switching of multiple signaling receptor families across the transmodal-sensory axis. Gene regulatory network analysis revealed putative transcriptional regulators of cortical neuron specialization with cell-type- and region-specific gene regulation patterns. While regionalization was observed in gene expression, chromatin accessibility, and spatial distributions, these modalities exhibited distinct cortical patterns. Our findings illuminate critical neuronal pathways that vary throughout the cortex and the gene regulatory networks that establish cortical regionalization in the human brain.

neuroscience↗

bioRxiv2025

MBD2/3 lost its methyl-CpG binding ability in multiple families of Holometabola

DNA methylation is sparse in insects, compared to vertebrates. This reduction is even more pronounced in Holometabola, where the loss of DNA methyltransferases DNMT1 and DNMT3 has occurred several times. In some Holometabola, DNA methylation is lost entirely. Methyl-CpG-binding domain (MBD) proteins bind methylated CpGs and are therefore important readers of these epigenetic marks. We hypothesize that the evolutionary reduction of genome-wide methylation may be paralleled by changes to MBD proteins. Among insects, only a single MBD family member, MBD2/3, is known. Two isoforms of MBD2/3 have been identified in Bombyx mori, MBD2/3-L and MBD2/3-S. The long isoform MBD2/3-L contains a complete MBD domain spanning the first two exons, whereas the short isoform MBD2/3-S lacks the second exon and therefore half of its MBD domain. It has been reported that only the MBD2/3-L isoform is able to bind methyl-CpGs. In this study, we analyzed transcriptomic and genomic sequence data across holometabolous orders to identify MBD2/3 genes and their isoforms. Our findings reveal that MBD2/3 is highly conserved in sequence and gene structure. While both isoforms are present in most hemimetabolous orders, the long isoform MBD2/3-L, capable of binding methylated CpG, has been lost in multiple holometabolous orders. The results suggest that MBD2/3 has lost its ability to bind methyl-CpG in several insect orders, with several independent losses in Holometabola. This occurred through different changes to the MBD domain, from sequence divergence within the domain to the absence of half of the MBD domain. These losses may be linked to the reduced levels of CpG DNA methylation.

bioinformatics↗

bioRxiv2025

Experimental Removal of Niche Construction Alters the Pace and Mechanisms of Resistance Evolution

Niche construction, a central eco-evolutionary process in which organisms modify their environment, is hypothesised to enhance evolutionary adaptability through feedback between genetic inheritance and the lasting effects of environmental change--known as ecological inheritance. However, while theoretically intriguing, direct empirical support for the effect of niche construction on adaptation is lacking. Red flour beetles modify their environment by releasing quinone-rich stink gland secretions, a form of external immunity. Here, we test in an evolution experiment how experimental removal of niche construction--using RNAi of a key gene needed to produce stink gland secretions--affects the beetles adaptation to the bacterial entomopathogen Bacillus thuringiensis. In each generation, beetles inhabited conditioned flour either with regular or drastically reduced stink gland secretion content. Compared to the non-exposed control, all bacteria-exposed regimes rapidly evolved bacterial resistance within only six generations. However, beetles evolving with intact niche construction acquired resistance as soon as after three generations, indicating that adaptation was initially facilitated by niche construction. RNAseq of evolved beetles showed that gene expression differed strongly between the selection regimes, revealing that the mechanisms underlying resistance were dependent on niche construction. Thus, our findings provide urgently needed empirical evidence on the role of niche construction for resistance evolution and its potential genetic basis.

evolutionary biology↗

bioRxiv2025

Host-parasite interactions of an avian blood parasite elucidated by single-cell transcriptomics

Parasites and hosts perform fine-tuned cellular and molecular interactions, known from few well-explored model systems. Recent methodological advances now allow such deep insights into non-model parasites, their hosts, and their intense reciprocal manipulation. We applied single cell RNA-sequencing to blood samples of a long-lived bird host, infected at high and low intensity with malaria-related parasites. We identify diverse parasitic traits for immune evasion and potential manipulation of the avian host immune response. The transcriptomic response of immune cells was decoupled from the infection load, consistent with evidently low pathogenicity. Changes of immune cell populations showed low activation of adaptive immunity, such as clonal expansion of lymphoid cells. This absence of antagonism indicates immunosuppression by the parasite, which may mitigate virulence and thereby facilitate host-parasite coadaptation. The identified cell-type specific markers provide an important reference and will help to understand the evolutionary forces that shape host immunity in birds. Our study illuminates in rare molecular detail a benign host-parasite interaction and bridges a large coevolutionary knowledge gap of the gradient from parasitism to commensalism and mutualism.

ecology↗

bioRxiv2025

Environmental dynamics influence scale cortisol levels in Mexican cavefish

Cortisol is a key hormone involved in stress responses, and its regulation reflects how organisms cope with environmental stressors. While acute stress responses are well studied, much less is known about how cumulative, long-term stress shapes the responses of populations adapted to different habitats. Here, we investigated scale cortisol - a biomarker of long-term stress exposure in fish - in wild and laboratory reared populations of Astyanax mexicanus, a species with surface and cave-dwelling ecotypes adapted to contrasting environments. We measured scale cortisol levels in six populations (four cave and two surface) over two consecutive years, alongside abiotic parameters in the respective habitats. Some cave populations exhibited lower scale cortisol levels than surface fish under both wild and laboratory conditions, suggesting a genetically based enhancement of stress-coping ability or altered cortisol-mediated metabolic and osmoregulatory processes. Moreover, populations experiencing more environmental variability - such as the lake surface habitat and hydrologically dynamic cave systems - showed higher scale cortisol levels and increased inter-individual variation. These results suggest that evolutionary adaptations to different habitats shape long-term stress physiology in A. mexicanus, and they highlight scale cortisol as a valuable tool for assessing how organisms physiologically cope with diverse and extreme environments.

ecology↗

bioRxiv2025

Three species, three labs, three experiments: testing the reproducibility of ecological studies on insect behaviour in a multi-laboratory setting

The reproducibility of studies involving insect species is an underexplored area in the broader discussion about poor reproducibility in science. Our study addresses this gap by conducting a systematic multi-laboratory investigation into the reproducibility of ecological studies on insect behaviour. We implemented a 3x3 experimental design, incorporating three study sites, and three independent experiments on three insect species from different orders: the turnip sawfly (Athalia rosae, Hymenoptera), the meadow grasshopper (Pseudochorthippus parallelus, Orthoptera) and the red flour beetle (Tribolium castaneum, Coleoptera). Using random-effect meta-analysis, we compared the consistency and accuracy of treatment effects on insect behavioural traits across replicate experiments. We successfully reproduced the overall statistical treatment effect in 83% of the replicate experiments, but overall effect size replication was achieved in only 66% of the replicates. Thus, though demonstrating sufficient reproducibility in some measures, this study also provides first experimental evidence for cases of poor reproducibility in insect experiments. Our findings further show that reasons causing poor reproducibility established in rodent research also hold for other study organisms and research questions. We believe that a rethinking of current best practices is required to face reproducibility issues in insect studies, but also across disciplines. Specifically, we advocate for adopting open research practices and the implementation of methodological strategies that reduce bias and problems arising from over-standardization. With respect to the latter, the introduction of systematic variation through multi-laboratory or heterogenized designs may contribute to improved reproducibility in studies involving any living organisms.

animal behavior and cognition↗

bioRxiv2025

Multiomics reveal associations between CpG methylation, histone modifications and transcription in a species that has lost DNMT3, the Colorado potato beetle

Insects display exceptional phenotypic plasticity, which can be mediated by epigenetic modifications, including CpG methylation and histone modifications. In vertebrates, both are interlinked and CpG methylation is associated with gene repression. However, little is known about these regulatory systems in invertebrates, where CpG methylation is mainly restricted to gene bodies of transcriptionally active genes. A widely conserved mechanism involves the co-transcriptional deposition of H3K36 trimethylation and the targeted methylation of unmethylated CpGs by the de novo DNA methyltransferase DNMT3. However, DNMT3 has been lost multiple times in invertebrate lineages raising the question of how the links between CpG methylation, histone modifications and gene expression are affected by its loss. Here, we report the epigenetic landscape of Leptinotarsa decemlineata, a beetle species that has lost DNMT3 but retained CpG methylation. We combine RNA-seq, enzymatic methyl-seq and CUT&Tag to study CpG methylation and patterns of H3K36me3 and H3K27ac histone modifications on a genome-wide scale. Despite the loss of DNMT3, H3K36me3 mirrors CpG methylation patterns. Together, they give rise to signature profiles for expressed and non-expressed genes. H3K27ac patterns, which show no association with CpG methylation, have a prominent peak at the transcription start site that is predictive of expressed genes. Our study provides new insights into the evolutionary flexibility of epigenetic modification systems that urge caution when generalizing across species. Research highlightsDespite lacking DNMT3, EM-seq revealed CpG methylation in the Colorado potato beetle. CUT&Tag showed an association of H3K36me3 and H3K27ac with transcription, while only H3K36me3 aligns with CpG methylation, demonstrating epigenetic flexibility.

evolutionary biology↗

bioRxiv2024

Experimental evolution of a pathogen confronted with innate immune memory increases variation in virulence

Understanding the drivers and mechanisms of virulence evolution is still a major goal of evolutionary biologists and epidemiologists. Theory predicts that the way virulence evolves depends on the balance between the benefits and costs it provides to pathogen fitness. Additionally, host responses to infections, such as resistance or tolerance, play a critical role in shaping virulence evolution. But, while the evolution of pathogens has been traditionally studied under the selection pressure of host adaptive immunity, less is known about their evolution when confronted to simpler and less effective forms of immunity such as immune priming. In this study, we used a well-established insect model for immune priming - red flour beetles and their bacterial pathogen Bacillus thuringiensis tenebrionis - to test whether this form of innate immune memory favors the evolution of higher virulence. Through controlled experimental evolution of the pathogen in primed versus non-primed hosts, we found no change in average virulence after eight selection cycles in primed host. However, we found a significant increase in the variation of virulence (i.e., host-killing ability) among independent pathogen lines evolved in primed host, and bacteria were unable to evolve resistance against host priming. Whole genome sequencing revealed increased activity in the bacterial mobilome (prophages and plasmids). Expression of the Cry toxin - a well-known virulence factor - was linked to evolved differences in copy number variation of the cry-carrying plasmid, though this did not correlate directly with virulence. These findings highlight that innate immune memory can drive variability in pathogen traits, which may favor adaptation to variable environments. This underscores the need to consider pathogen evolution in response to innate immune memory when applying these mechanisms in medicine, aquaculture, pest control, and insect mass production.

evolutionary biology↗

bioRxiv2024

Immune priming in the insect gut: a dynamic response revealed by ultrastructural and transcriptomic changes

Research on forms of memory in innate immune systems has recently gained momentum with the study of trained immunity in vertebrates and immune priming in invertebrates. Immune priming provides protection against previously encountered pathogens. However, causes and mechanisms of immune priming are still not well understood in most organisms. In this work, we combine RNA sequencing with transmission electron microscopy to investigate the dynamic processes during priming in the gut of a well-established model for oral immune priming, consisting of the host Tribolium castaneum and its entomopathogen Bacillus thuringiensis tenebrionis (Btt). We show that priming with specific, pathogen-derived virulence-relevant factors causes damage in the gut of T. castaneum larvae, which leads to an early physiological stress response as well as the upregulation of a specific set of immune genes. This response diminishes over time yet enables the gut to upregulate genes known to interfere with Btt virulence when T. castaneum larvae are later exposed to infectious Btt spores. The identification of these processes increases our understanding of immune priming as a dynamic process where cellular responses in concert with specific gene regulation prepare the gut tissue and thereby enable more efficient protection against infection. Such work can further help us understand the origin and mechanism of innate immune memory. Author summaryInvertebrate animals do not possess a classical adaptive immune system. And yet, many of these animals show forms of immune memory, collectively called immune priming. In this work, we investigate the causes of oral immune priming in the red flour beetle Tribolium castaneum in response to its bacterial entomopathogen Bacillus thuringiensis tenebrionis. Primary exposure to Btt spent culture media supernatants enables the larvae of T. castaneum to better withstand a subsequent infection with infectious Btt spores. We show that exposing T. castaneum larvae to those supernatants leads to damage in the gut resulting in a strong stress and immune response early after priming and a targeted up-regulation of beneficial genes upon the secondary re-encounter with Btt. These results suggest fundamental stress responses can be involved in innate immune memory phenomena, which has implications in translational research across species.

evolutionary biology↗

bioRxiv2024

Deciphering a beetle clock: individual and sex-dependent variation in daily activity patterns

Circadian clocks are inherent to most organisms, including cryptozoic animals that seldom encounter direct light, and regulate their daily activity cycles. A conserved suite of clock genes underpins these rhythms. In this study, we explore the circadian behaviors of the red flour beetle Tribolium castaneum, a significant pest impacting stored grain globally. We report on how daily light and temperature cues synchronize distinct activity patterns in these beetles, characterized by reduced morning activity and increased evening activity, anticipating the respective environmental transitions. Although less robust, rhythmicity in locomotor activity is maintained in constant dark and constant light conditions. Notably, we observed more robust rhythmic behaviors in males than females with individual variations exceeding those previously reported for other insect species. RNA interference targeting the Clock gene disrupted locomotor activity rhythms. Our findings demonstrate the existence of a circadian clock and of clock-controlled behaviors in T. castaneum. Furthermore, they highlight substantial individual differences in circadian activity, laying the groundwork for future research on the relevance of individual variation in circadian rhythms in an ecological and evolutionary context.

animal behavior and cognition↗

bioRxiv2024

Tapeworm infection affects sleep behavior in three-spined stickleback

Sleep is a highly complex and conserved biological process that affects several body functions and behaviors. Recent evidence suggests that there is a reciprocal interaction between sleep and immunity. For instance, fragmented sleep can increase the probability of parasitic infections and reduce the ability of infected hosts to fight infections. It is also known, particularly in humans and other mammals, that viral and bacterial infections alter the sleep patterns of infected individuals. However, the effects of macro-parasitic infections on sleep remain largely unknown. In this study, we investigated whether macro-parasite infections could alter the sleep of their hosts. We experimentally infected three-spined sticklebacks (Gasterosteus aculeatus) with the tapeworm Schistocephalus solidus and used a hidden Markov model to characterize sleep-associated behaviors in the sticklebacks. At an early time-point, 1-4 days after parasite exposure, infected fish showed no difference in sleep compared with non-exposed fish, whereas fish that were exposed but could fend off the infection slept less during the daytime. At a later time-point, 29-32 days after exposure, infected fish slept more than uninfected fish, while exposed-but-not-infected fish slept less than non-exposed fish. Using RNA-seq of brain tissue, we identified several immune- and sleep-associated genes that potentially underlie the observed behavioral changes. These results provide the first insight into the complex association between macro-parasite infection, immunity, and sleep in fish and may thus contribute to a better understanding of the reciprocal interaction between sleep and immunity.

animal behavior and cognition↗

bioRxiv2021

Immune stimulation alters chemical profiles of Tribolium castaneum

Group-living individuals experience immerse risk of disease transmission and parasite infection. Especially in social, but also in some non-social insects, disease control with immunomodulation takes place not only via individual immune defenses, but also via infochemicals such as contact cues and (defensive) volatiles to mount a group level immunity. However, little is known about whether an activation of the immune system leads to changes in chemical phenotypes, which may mediate these responses. We here asked whether individual immune experience resulting from wounding or injection of heat-killed Bacillus thuringiensis leads to changes in the chemical profiles of female and male adult red flour beetles (Tribolium castaneum), which are non-social but gregarious. We analyzed insect extracts using GC-FID to study the chemical composition of (1) cuticular hydrocarbons (CHCs) as candidates for the transfer of immunity-related information between individuals via contact, and (2) stink gland secretions, with target analysis of benzoquinones as main active compounds regulating external immunity. Despite a pronounced sexual dimorphism in CHC profiles, wounding stimulation led to similar profile changes in males and females with increases in the proportion of methyl-branched alkanes compared to naive beetles. While changes in the overall secretion profiles were less pronounced, absolute amounts of benzoquinones were transiently elevated in wounded compared to naive females. We suggest that the changes in different infochemicals may mediate immune status signaling in the context of both internal and external immune responses in groups of this non-social insect, thus showing parallels to social immunity.

evolutionary biology↗

bioRxiv2021

Serial passage of the human probiotic E. coli Nissle 1917 in an insect host leads to changed bacterial phenotypes

Probiotics are living microorganisms that are increasingly and successfully used for the therapy of various diseases. The most common use of probiotics is the therapeutic and preventive application for gastrointestinal disorders. The probiotic Escherichia coli strain Nissle 1917 (EcN) has been proven to effectively prevent and alleviate intestinal diseases, including various types of inflammatory bowel disease. Despite the widespread medical application of EcN, the underlying mechanisms of its protective effect remain elusive. The present work aimed to establish an insect model system to enable further research on the modes of action of EcN and the dynamics of adaptation to a novel host organism. Using a long-term serial passage approach, we orally introduced EcN to the host, the red flour beetle Tribolium castaneum. After multiple cycles of intestinal colonization in beetle larvae, several attributes of the passaged replicate lines were assessed. We observed phenotypic changes in growth and motility but no genetic changes in the lines after passaging through the host and its flour environment. One of the EcN lines exposed to the host displayed peculiar morphological and physiological characteristics showing that serial passage of EcN can generate differential phenotypes.

microbiology↗

bioRxiv2019

An HSP90-regulated reduced-eye phenotype in Tribolium shows fitness benefits and thus provides evidence for evolutionary capacitance

Evolution relies on genetic variation as the raw material for adaptation. The release of cryptic genetic variation (CGV), which can be regulated by the evolutionary capacitor heat shock protein 90 (HSP90), may thus be important for rapid adaptation. However, the fitness benefits of HSP90-regulated phenotypes are still under debate. Here, we show in the important model insect Tribolium castaneum that HSP90 impairment by two independent methods, RNA interference and chemical inhibition, revealed the same reduced-eye phenotype, which was stably inherited without further HSP90 inhibition. The penetrance and fitness of this trait increased under ambient light stress. This is the first demonstration that a phenotype released through HSP90 inhibition can be adaptive.

evolutionary biology↗

bioRxiv2018

Dnmt1 has an essential function despite the absence of CpG DNA methylation in the red flour beetle Tribolium castaneum

Epigenetic mechanisms, such as CpG DNA methylation enable phenotypic plasticity and rapid adaptation to changing environments. CpG DNA methylation is established by DNA methyltransferases (DNMTs), which are well conserved across vertebrates and invertebrates. There are insects with functional DNA methylation despite lacking a complete set of Dnmts. But at least one of the enzymes, DNMT1, appears to be required to maintain an active DNA methylation system. The red flour beetle, Tribolium castaneum, lacks Dnmt3 but possesses Dnmt1 and it has been controversial whether it has a functional DNA methylation system.\n\nUsing whole genome bisulfite sequencing, we did not find any defined patterns of CpG DNA methylation in embryos. Nevertheless, we found Dnmt1 expressed throughout the entire life cycle of the beetle, with mRNA transcripts significantly more abundant in eggs and ovaries. A maternal knockdown of Dnmt1 caused a developmental arrest in offspring embryos.\n\nWe show that Dnmt1 plays an essential role in T. castaneum embryos and that its downregulation leads to an early developmental arrest. This function appears to be unrelated to DNA methylation, since we did not find any evidence for this modification. This strongly suggests an alternative role of this protein.

evolutionary biology↗

bioRxiv2018

Transgenerational developmental effects of immune priming in the red flour beetle Tribolium castaneum

Immune priming, the increased chance to survive a secondary encounter with a pathogen, has been described for many invertebrate species, which lack the classical adaptive immune system of vertebrates. Priming can be specific even for closely related bacterial strains, last up to the entire lifespan of an individual, and in some species, it can also be transferred to the offspring and is then called transgenerational immune priming (TGIP). In the red flour beetle Tribolium castaneum, a pest of stored grains, TGIP has even been shown to be transferred paternally after injection of adult beetles with heat-killed Bacillus thuringiensis.\n\nHere we studied whether TGIP in T. castaneum is also transferred to the second filial generation, whether it can also occur after oral and injection priming of larvae and whether it has effects on offspring development. We found that paternal priming with B. thuringiensis does not only protect the first but also the second offspring generation. Also, fitness costs of the immune priming became apparent, when the first filial generation produced fewer offspring. Furthermore, we used two different routes of exposure to prime larvae, either by injecting them with heat-killed bacteria or orally feeding them B. thuringiensis spore culture supernatant. Neither of the parental larval priming methods led to any direct benefits regarding offspring resistance. However, the injections slowed down development of the injected individuals, while oral priming with both a pathogenic and a non-pathogenic strain of B. thuringiensis delayed offspring development.\n\nThe long-lasting transgenerational nature of immune priming and its impact on offspring development indicate that potentially underlying epigenetic modifications might be stable over several generations. Therefore, this form of phenotypic plasticity might impact pest control and should be considered when using products of bacterial origin against insects.

evolutionary biology↗

bioRxiv2018

Paternal knockdown of Dnmt2 increases offspring susceptibility to bacterial infection

Intergenerational effects from fathers to offspring are increasingly reported from diverse organisms, but the underlying mechanisms remain speculative. Paternal trans-generational immune priming (TGIP) was demonstrated in the red flour beetle Tribolium castaneum: non-infectious bacterial exposure of fathers protects their offspring against an infectious challenge for at least two generations. Epigenetic processes, such as cytosine methylation of nucleic acids, have been proposed to enable transfer of information from fathers to offspring. Here we studied a potential role in TGIP of the Dnmt2 gene (renamed as Trdmt1 in humans), which encodes a highly conserved enzyme that methylates different RNAs, including specific cytosines of a set of tRNAs. Dnmt2 has previously been reported to be involved in intergenerational epigenetic inheritance in mice and protection against viruses in fruit flies. We first studied gene expression and found that Dnmt2 is expressed in various life history stages and tissues of T. castaneum, with high expression in the reproductive organs. RNAi-mediated knockdown of Dnmt2 in fathers was systemic, slowed down offspring larval development and increased mortality of the adult offspring upon bacterial infection. However, these effects were independent of bacterial exposure of the fathers. In conclusion, our results point towards a role of Dnmt2 for paternal effects, while elucidation of the mechanisms behind paternal TGIP needs further studies.

evolutionary biology↗