TY - JOUR A1 - Maihoff, Fabienne A1 - Bohlke, Kyte A1 - Brockmann, Axel A1 - Schmitt, Thomas T1 - Increased complexity of worker CHC profiles in Apis dorsata correlates with nesting ecology JF - PLoS ONE N2 - Cuticular hydrocarbons (CHC) are known to serve as discrimination cues and will trigger defence behaviour in a plethora of eusocial insects. However, little is known how about nestmate recognition ability selects for CHC diversification. In this study we investigate differences in CHC composition of four major honey bee species with respect to the differences in their nesting behavior. In contrast to A. mellifera, A. cerana and A. florea, the giant honey bee A. dorsata prefers to build their nests in aggregations with very small spatial distances between nests, which increases the probability of intrusions. Thus, A. dorsata exhibits a particularly challenging nesting behavior which we hypothesize should be accompanied with an improved nestmate recognition system. Comparative analyses of the worker CHC profiles indicate that A. dorsata workers exhibit a unique and more complex CHC profile than the other three honey bee species. This increased complexity is likely based on a developmental process that retains the capability to synthesize methyl-branched hydrocarbons as adults. Furthermore, two sets of behavioral experiments provide evidence that A. dorsata shows an improved nestmate discrimination ability compared to the phylogenetically ancestral A. florea, which is also open-nesting but does not form nest aggregations. The results of our study suggest that ecological traits like nesting in aggregation might be able to drive CHC profile diversification even in closely related insect species. KW - Apis dorsata KW - cuticular hydrocarbons KW - nesting Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-301353 VL - 17 IS - 7 ER - TY - JOUR A1 - Kohl, Patrick L. A1 - Steffan‐Dewenter, Ingolf T1 - Nectar robbing rather than pollinator availability constrains reproduction of a bee‐flowered plant at high elevations JF - Ecosphere N2 - Abiotic factors are generally assumed to determine whether species can exist at the extreme ends of environmental gradients, for example, at high elevations, whereas the role of biotic interactions is less clear. On temperate mountains, insect‐pollinated plant species with bilaterally symmetrical flowers exhibit a parallel elevational decline in species richness and abundance with bees. This suggests that the lack of mutualistic interaction partners sets the elevational range limits of plants via a reduction in reproductive success. We used the bee‐pollinated mountain plant Clinopodium alpinum (Lamiaceae), which blooms along a continuous 1000‐m elevational gradient and has bilaterally symmetrical flowers, as a model to test the predicted parallel elevational decline in flower visitation and seed production. Although the community of flower visitors changed with elevation, the flower visitation rate by the most frequent visitors, bumble bees (33.8% of legitimate visits), and the overall rate of flower visitation by potential pollinators did not vary significantly with elevation. However, we discovered that nectar robbing by bumble bees and nectar theft by ants, two interactions with potentially negative effects on flowers, sharply increased with elevation. Seed set depended on pollinators across elevations and followed a weak hump‐shaped pattern, peaking at mid‐elevations and decreasing by about 20% toward both elevational range edges. Considering the mid‐ and high elevations, elevational variation in seed production could not be explained by legitimate bee visitation rates but was inversely correlated with the frequency of nectar robbing. Our observations challenge the hypothesis that a decrease in the availability of pollinators limits seed production of bee‐flowered plants at high elevations but suggest that an increase in negative interactions (nectar robbing and larceny) constrains reproductive success. KW - altitudinal gradients KW - bee pollination KW - chalcidoid wasps KW - climatic gradients KW - elevational diversity patterns KW - floral larceny KW - fly pollination KW - mountain ecosystems KW - plant–pollinator interactions KW - range limits KW - zygomorphy Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287141 VL - 13 IS - 6 ER - TY - JOUR A1 - Koster, Stefanie A1 - Gurumurthy, Rajendra Kumar A1 - Kumar, Naveen A1 - Prakash, Pon Ganish A1 - Dhanraj, Jayabhuvaneshwari A1 - Bayer, Sofia A1 - Berger, Hilmar A1 - Kurian, Shilpa Mary A1 - Drabkina, Marina A1 - Mollenkopf, Hans-Joachim A1 - Goosmann, Christian A1 - Brinkmann, Volker A1 - Nagel, Zachary A1 - Mangler, Mandy A1 - Meyer, Thomas F. A1 - Chumduri, Cindrilla T1 - Modelling Chlamydia and HPV co-infection in patient-derived ectocervix organoids reveals distinct cellular reprogramming JF - Nature Communications N2 - Coinfections with pathogenic microbes continually confront cervical mucosa, yet their implications in pathogenesis remain unclear. Lack of in-vitro models recapitulating cervical epithelium has been a bottleneck to study coinfections. Using patient-derived ectocervical organoids, we systematically modeled individual and coinfection dynamics of Human papillomavirus (HPV)16 E6E7 and Chlamydia, associated with carcinogenesis. The ectocervical stem cells were genetically manipulated to introduce E6E7 oncogenes to mimic HPV16 integration. Organoids from these stem cells develop the characteristics of precancerous lesions while retaining the self-renewal capacity and organize into mature stratified epithelium similar to healthy organoids. HPV16 E6E7 interferes with Chlamydia development and induces persistence. Unique transcriptional and post-translational responses induced by Chlamydia and HPV lead to distinct reprogramming of host cell processes. Strikingly, Chlamydia impedes HPV-induced mechanisms that maintain cellular and genome integrity, including mismatch repair in the stem cells. Together, our study employing organoids demonstrates the hazard of multiple infections and the unique cellular microenvironment they create, potentially contributing to neoplastic progression. KW - Chlamydia KW - HPV KW - cellular reprogramming Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-301349 VL - 13 IS - 1 ER - TY - JOUR A1 - Kohl, Patrick L. A1 - Rutschmann, Benjamin A1 - Steffan-Dewenter, Ingolf T1 - Population demography of feral honeybee colonies in central European forests JF - Royal Society Open Science N2 - European honeybee populations are considered to consist only of managed colonies, but recent censuses have revealed that wild/feral colonies still occur in various countries. To gauge the ecological and evolutionary relevance of wild-living honeybees, information is needed on their population demography. We monitored feral honeybee colonies in German forests for up to 4 years through regular inspections of woodpecker cavity trees and microsatellite genotyping. Each summer, about 10% of the trees were occupied, corresponding to average densities of 0.23 feral colonies km\(^{−2}\) (an estimated 5% of the regional honeybee populations). Populations decreased moderately until autumn but dropped massively during winter, so that their densities were only about 0.02 colonies km\(^{−2}\) in early spring. During the reproductive (swarming) season, in May and June, populations recovered, with new swarms preferring nest sites that had been occupied in the previous year. The annual survival rate and the estimated lifespan of feral colonies (n = 112) were 10.6% and 0.6 years, respectively. We conclude that managed forests in Germany do not harbour self-sustaining feral honeybee populations, but they are recolonized every year by swarms escaping from apiaries. KW - pollinator decline KW - nest site selection KW - life-history traits KW - wild honeybees KW - beech forests KW - swarming Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-301335 SN - 2054-5703 VL - 9 IS - 8 ER - TY - JOUR A1 - Kaya-Zeeb, Sinan A1 - Engelmayer, Lorenz A1 - Straßburger, Mara A1 - Bayer, Jasmin A1 - Bähre, Heike A1 - Seifert, Roland A1 - Scherf-Clavel, Oliver A1 - Thamm, Markus T1 - Octopamine drives honeybee thermogenesis JF - eLife N2 - In times of environmental change species have two options to survive: they either relocate to a new habitat or they adapt to the altered environment. Adaptation requires physiological plasticity and provides a selection benefit. In this regard, the Western honeybee (Apis mellifera) protrudes with its thermoregulatory capabilities, which enables a nearly worldwide distribution. Especially in the cold, shivering thermogenesis enables foraging as well as proper brood development and thus survival. In this study, we present octopamine signaling as a neurochemical prerequisite for honeybee thermogenesis: we were able to induce hypothermia by depleting octopamine in the flight muscles. Additionally, we could restore the ability to increase body temperature by administering octopamine. Thus, we conclude that octopamine signaling in the flight muscles is necessary for thermogenesis. Moreover, we show that these effects are mediated by β octopamine receptors. The significance of our results is highlighted by the fact the respective receptor genes underlie enormous selective pressure due to adaptation to cold climates. Finally, octopamine signaling in the service of thermogenesis might be a key strategy to survive in a changing environment. KW - honeybee KW - octopamine KW - thermogenesis Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-301327 VL - 11 ER - TY - THES A1 - Rutschmann, Benjamin T1 - Occurrence and population density of wild-living honey bees in Europe and the impact of different habitat types on their foraging and overwintering success T1 - Vorkommen und Populationsdichte von wild lebenden Honigbienen in Europa und die Auswirkungen unterschiedlicher Habitattypen auf ihr Sammelverhalten und den Überwinterungserfolg N2 - The original habitat of native European honey bees (\(Apis\) \(mellifera\)) is forest, but currently there is a lack of data about the occurrence of wild honey bee populations in Europe. Prior to being kept by humans in hives, honey bees nested as wild species in hollow trees in temperate forests. However, in the 20th century, intensification of silviculture and agriculture with accompanying losses of nesting sites and depletion of food resources caused population declines in Europe. When the varroa mite (Varroa destructor), an invasive ectoparasite from Asia, was introduced in the late 1970s, wild honey bees were thought to be eradicated in Europe. Nevertheless, sporadic, mostly anecdotal, reports from ornithologists or forest ecologists indicated that honey bee colonies still occupy European forest areas. In my thesis I hypothesize that near-natural deciduous forests may provide sufficient large networks of nesting sites representing refugia for wild-living honey bees. Using two special search techniques, i.e. the tracking of flight routes of honey bee foragers (the “beelining” method) and the inspection of known cavity trees, I collected for the first time data on the occurrence and density of wild-living honey bees in forest areas in Germany (CHAPTER 3). I found wild-living honey bee colonies in the Hainich national park at low densities in two succeeding years. In another forest region, I checked known habitat trees containing black woodpecker cavities for occupation by wild-living honey bee colonies. It turned out that honey bees regularly use these cavities and occur in similar densities in both studied forest regions, independent of the applied detection method. Extrapolating these densities to all German forest areas, I estimate several thousand wild-living colonies in Germany that potentially interact in different ways with the forest environment. I conclude that honey bees regularly colonize forest areas in Germany and that networks of mapped woodpecker cavities offer unique possibilities to study the ecology of wild-living honey bees over several years. While their population status is ambiguous and the density of colonies low, the fact that honey bees can still be found in forests poses questions about food supply in forest environments. Consequently, I investigated the suitability of woodlands as a honey bee foraging habitat (CHAPTER 4). As their native habitat, forests are assumed to provide important pollen and nectar sources for honey bee colonies. However, resource supply might be spatially and temporally restricted and landscape-scale studies in European forest regions are lacking. Therefore, I set up twelve honey bee colonies in observation hives at locations with varying degree of forest cover. Capitalizing on the unique communication behaviour, the waggle dance, I examined the foraging distances and habitat preferences of honey bees over almost an entire foraging season. Moreover, by connecting this decoded dance information with colony weight recordings, I could draw conclusions about the contribution of the different habitat types to honey yield. Foraging distances generally increased with the amount of forest in the surrounding landscape. Yet, forest cover did not have an effect on colony weight. Compared to expectations based on the proportions of different habitats in the surroundings, colonies foraged more frequently in cropland and grasslands than in deciduous and coniferous forests, especially in late summer when pollen foraging in the forest is most difficult. In contrast, colonies used forests for nectar/honeydew foraging in early summer during times of colony weight gain emphasizing forests as a temporarily significant source of carbohydrates. Importantly, my study shows that the ecological and economic value of managed forest as habitat for honey bees and other wild pollinators can be significantly increased by the continuous provision of floral resources, especially for pollen foraging. The density of these wild-living honey bee colonies and their survival is driven by several factors that vary locally, making it crucial to compare results in different regions. Therefore, I investigated a wild-living honey bee population in Galicia in north-western Spain, where colonies were observed to reside in hollow electric poles (CHAPTER 5). The observed colony density only in these poles was almost twice as high as in German forest areas, suggesting generally more suitable resource conditions for the bees in Galicia. Based on morphometric analyses of their wing venation patterns, I assigned the colonies to the native evolutionary lineage (M-lineage) where the particularly threatened subspecies \(Apis\) \(mellifera\) \(iberiensis\) also belongs to. Averaged over two consecutive years, almost half of the colonies survived winter (23 out of 52). Interestingly, semi-natural areas both increased abundance and subsequent colony survival. Colonies surrounded by more semi-natural habitat (and therefore less intensive cropland) had an elevated overwintering probability, indicating that colonies need a certain amount of semi-natural habitat in the landscape to survive. Due to their ease of access these power poles in Galicia are, ideally suited to assess the population demography of wild-living Galician honey bee colonies through a long-term monitoring. In a nutshell, my thesis indicates that honey bees in Europe always existed in the wild. I performed the first survey of wild-living bee density yet done in Germany and Spain. My thesis identifies the landscape as a major factor that compromises winter survival and reports the first data on overwintering rates of wild-living honey bees in Europe. Besides, I established methods to efficiently detect wild-living honey bees in different habitat. While colonies can be found all over Europe, their survival and viability depend on unpolluted, flower rich habitats. The protection of near-natural habitat and of nesting sites is of paramount importance for the conservation of wild-living honey bees in Europe.   N2 - Das ursprüngliche Habitat der Westlichen Honigbiene (\(Apis\) \(mellifera\)) ist der Wald, doch derzeit fehlt es an Daten über das Vorkommen von wilden Honigbienenpopulationen in Europa. Bevor die Honigbiene von Menschen in künstlichen Behausungen gehalten wurde, nistete sie in den gemäßigten Breiten in hohlen Bäumen als wild lebende Art. Doch die Intensivierung der Forst- und Landwirtschaft, der damit einhergehende Verlust von Nistplätzen und die Verschlechterung der Nahrungsressourcen führten zu einem Rückgang der Honigbienenpopulationen im 20. Jahrhundert. Nachdem die Varroa-Milbe (Varroa destructor), ein invasiver Ektoparasit, in den späten 1970er-Jahren aus Asien eingeschleppt wurde, nahm man an, dass wilde Honigbienen in Europa ausgestorben seien. Nichtsdestotrotz gaben sporadische, hauptsächlich anekdotische Berichte von Ornithologen oder Waldökologen Anlass zur Vermutung, dass Honigbienenvölker immer noch in europäischen Wäldern zu finden seien. In meiner vorliegenden Dissertation stelle ich die Hypothese auf, dass naturnahe Laubwälder ein ausreichend großes Netz von Nistplätzen bieten und als Zufluchtsorte für wild lebende Honigbienen fungieren können. Mit Hilfe zweier spezieller Suchtechniken – dem Nachverfolgen der Flugrouten von Honigbienen-Sammlerinnen (die ‚Bee-Lining‘-Methode) und der Inspektion bekannter Baumhöhlen – habe ich erstmalig Daten über das Vorkommen und die Populationsdichte von wild lebenden Honigbienen in deutschen Waldgebieten gesammelt (CHAPTER 3). In zwei aufeinanderfolgenden Jahren habe ich wild lebende Honigbienenvölker im Hainich Nationalpark entdeckt, wobei die Populationsdichten gering waren. In einem anderen Waldgebiet habe ich kartierte Habitatbäume mit Höhlen des Schwarzspechts auf ihre Besiedlung mit Honigbienenvölker hin überprüft. Es stellte sich heraus, dass Honigbienen diese Schwarzspechthöhlen regelmäßig nutzen und in ähnlich niedrigen Dichten in beiden untersuchten Waldgebieten vorkommen. Mittels Extrapolation schätze ich die Zahl der wild lebenden Bienenvölker in allen deutschen Waldgebieten auf mehrere Tausend, die auf vielfältige Weise mit der Waldumgebung interagieren können. Zusammenfassend zeigte sich, dass Honigbienen regelmäßig deutsche Waldgebiete bewohnen und dass Daten über kartierte Spechthöhlen eine einmalige Möglichkeit bieten, die Ökologie der Honigbienen als Wildtier mittels eines Langzeitmonitorings zu untersuchen. Auch wenn der Populationsstatus noch ungeklärt und die Populationsdichte gering ist, wirft die Existenz wild lebender Honigbienen Fragen bezüglich der Nahrungsversorgung im Wald auf. Folglich habe ich untersucht, ob eine ausreichende Futterversorgung für Honigbienen in Wäldern gegeben ist (CHAPTER 4). Wälder gelten als der ursprüngliche Lebensraum der Westlichen Honigbiene und man nimmt an, dass sie wichtige Pollen- und Nektarquellen für Honigbienenvölker liefern. Das Nahrungsangebot könnte jedoch räumlich und zeitlich begrenzt sein, wobei hierzu bislang Studien in europäischen Waldregionen fehlen. Daher habe ich zwölf Honigbienenvölker in Beobachtungsstöcken, jeweils an Orten mit unterschiedlichem Waldanteil, aufgestellt. Indem ich mir das einzigartige Kommunikationsverhalten – den Schwänzeltanz – zu Nutzen machte, untersuchte ich Sammeldistanzen und Habitatpräferenzen von Honigbienen über fast eine ganze Bienensaison hinweg. Darüber hinaus konnte ich durch die Verknüpfung der entschlüsselten Tanzinformationen mit Gewichtsaufzeichnungen der Bienenvölker Rückschlüsse auf den Beitrag der verschiedenen Habitattypen zum Honigertrag der Völker ziehen. Die Entfernungen bei der Nahrungssuche nahmen grundsätzlich mit dem Waldanteil in der umgebenden Landschaft zu. Obwohl Bienenvölker, die tiefer im Wald stationiert waren, weiter fliegen mussten, war ihre Gewichtszunahme nicht reduziert. Im Vergleich zu den Erwartungen, die sich aus den flächenmäßigen Anteilen der verschiedenen Habitate in der Umgebung ergeben, sammelten die Völker häufiger in Acker- und Grasland als in Laub- und Nadelwald, wobei der Spätsommer die schwierigste Zeit für die Pollenversorgung im Wald war. Auf die Phase im Frühsommer von Mitte Mai bis Mitte Juli bezogen, in der die Völker an Gewicht zunahmen, wurde der Wald zum Sammeln für Nektar/Honigtau beinahe erwartungsgemäß genutzt. Das unterstreicht die Bedeutung des Waldes als wichtige Quelle für Kohlenhydrate während eines kurzen Zeitraums im Jahr. Meine Untersuchungen zeigen, dass der ökologische und ökonomische Wert von Wirtschaftswald als Lebensraum für Honigbienen und andere Bestäuber durch die kontinuierliche Versorgung von Blütenressourcen, insbesondere in Bezug auf Pollen, erheblich gesteigert werden kann. Die Dichte wild lebender Honigbienenvölker und deren Überleben ist durch mehrere Faktoren bestimmt die lokal variieren, weshalb es äußerst wichtig ist, die Ergebnisse hinsichtlich verschiedener Regionen zu vergleichen. Im Zuge dieser Arbeit habe ich daher zusätzlich noch eine wild lebende Honigbienenpopulation in Galicien im Nordwesten Spaniens untersucht, wo die Bienenvölker in hohlen Strommasten nisteten (CHAPTER 5). Die beobachtete Völkerdichte war allein in diesen Strommasten fast doppelt so hoch wie in deutschen Waldgebieten, was auf grundsätzlich geeignetere Bedingungen für Bienen in Galicien schließen lässt. Anhand morphometrischer Analysen der Flügeläderung habe ich die Bienenvölker der einheimischen Evolutionslinie (M-Linie) zugeordnet, zu der auch die besonders bedrohte Unterart \(Apis\) \(mellifera\) \(iberiensis\) gehört. In zwei aufeinander folgenden Jahren überlebte im Durchschnitt fast die Hälfte der Bienenvölker den Winter (23 von 52). Interessanterweise waren in naturnahen Gebieten sowohl die Häufigkeit als auch das Überleben der Bienenvölker höher. Kolonien, die von mehr naturnahen Lebensräumen (und damit weniger intensiv genutzten Ackerflächen) umgeben waren, wiesen eine höhere Überwinterungswahrscheinlichkeit auf, was darauf hindeutet, dass die Kolonien einen gewissen Anteil an naturnahem Lebensraum in der Landschaft zum Überleben benötigen. Diese Strommasten in Galicien sind aufgrund ihrer leichten Zugänglichkeit ideal geeignet, um die Populationsdemografie der dortigen wild lebenden Honigbienen durch ein Langzeit-Monitoring zu untersuchen. Zusammenfassend lässt sich sagen, dass Honigbienen wohl ununterbrochen als wild lebende Spezies in Europa existierten. Im Zuge meiner Doktorarbeit habe ich die erste quantitative Untersuchung wild lebender Honigbienen in Deutschland und Spanien durchgeführt. Meinen Ergebnissen zufolge ist die Landschaft ein entscheidender Faktor, der das Winterüberleben beeinflusst. Zudem beinhaltet meine Arbeit die ersten Daten über Überwinterungsraten von wild lebenden Honigbienen in Europa. Weiters habe ich Methoden entwickelt, um wild lebende Honigbienen in verschiedenen Lebensräumen zuverlässig und schnell zu finden. Alle drei Studien meiner Dissertation betonen, wie wichtig es ist, naturnahe Gebiete für den Schutz von wild lebenden Honigbienen zu erhalten. Zwar sind wild lebende Bienenvölker überall in Europa zu finden, doch ihre Überlebensfähigkeit hängt von blütenreichen, nicht mit Pestiziden belasteten Lebensräumen ab. Der Schutz von Lebensräumen und Nistplätzen ist für die Erhaltung der wild lebenden Honigbienen in Europa von größter Bedeutung. KW - Biene KW - wild-living honey bees KW - honey bee density KW - feral bees KW - forest landscape KW - waggle dance decoding KW - bee-lining Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-286732 ER - TY - THES A1 - Solvie, Daniel Alexander T1 - Molecular Mechanisms of MYC as Stress Resilience Factor T1 - Molekulare Mechanismen von MYC als Stressresistenzfaktor N2 - Cancer is one of the leading causes of death worldwide. The underlying tumorigenesis is driven by the accumulation of alterations in the genome, eventually disabling tumor suppressors and activating proto-oncogenes. The MYC family of proto-oncogenes shows a strong deregulation in the majority of tumor entities. However, the exact mechanisms that contribute to MYC-driven oncogenesis remain largely unknown. Over the past decades, the influence of the MYC protein on transcription became increasingly apparent and was thoroughly investigated. Additionally, in recent years several publications provided evidence for so far unreported functions of MYC that are independent of a mere regulation of target genes. These findings suggest an additional role of MYC in the maintenance of genomic stability and this role is strengthened by key findings presented in this thesis. In the first part, I present data revealing a pathway that allows MYC to couple transcription elongation and DNA double-strand break repair, preventing genomic instability of MYC-driven tumor cells. This pathway is driven by a rapid transfer of the PAF1 complex from MYC onto RNAPII, a process that is mediated by HUWE1. The transfer controls MYC-dependent transcription elongation and, simultaneously, the remodeling of chromatin structure by ubiquitylation of histone H2B. These regions of open chromatin favor not only elongation but also DNA double-strand break repair. In the second part, I analyze the ability of MYC proteins to form multimeric structures in response to perturbation of transcription and replication. The process of multimerization is also referred to as phase transition. The observed multimeric structures are located proximal to stalled replication forks and recruit factors of the DNA-damage response and transcription termination machinery. Further, I identified the HUWE1-dependent ubiquitylation of MYC as an essential step in this phase transition. Cells lacking the ability to form multimers display genomic instability and ultimately undergo apoptosis in response to replication stress. Both mechanisms present MYC as a stress resilience factor under conditions that are characterized by a high level of transcriptional and replicational stress. This increased resilience ensures oncogenic proliferation. Therefore, targeting MYC’s ability to limit genomic instability by uncoupling transcription elongation and DNA repair or disrupting its ability to multimerize presents a therapeutic window in MYC-dependent tumors. N2 - Tumorerkrankungen sind eine der häufigsten Todesursachen weltweit. Für die Entstehung und Entwicklung eines Tumors sind Veränderungen im Genom verantwortlich, wobei Proto-Onkogene aktiviert und Tumorsuppressorgene inaktiviert werden. Die MYC-Familie der Proto-Onkogene ist in der Mehrzahl der menschlichen Tumorerkrankungen stark dereguliert. Der genaue Mechanismus, der in MYC-getriebenen Tumoren eine Rolle spielt, ist aber weiterhin ungeklärt. In den letzten Jahrzehnten wurde die Funktion von MYC als Transkriptionsfaktor in den Vordergrund gestellt. Veröffentlichungen der letzten Jahre deuten zusätzlich auf mehrere, bisher unbekannte Funktionen hin, die unabhängig von einer bloßen Regulation von Zielgenen sind und auf eine zusätzliche Rolle bei der Erhaltung der genomischen Stabilität hinweisen. Diese Rolle wird durch wesentliche Ergebnisse dieser Doktorarbeit gestärkt. In dem ersten Teil der Doktorarbeit präsentiere ich einen Pathway, der es MYC ermöglicht, transkriptionelle Elongation und Doppelstrangbruch-Reparatur zu koppeln, wodurch genomische Instabilität in MYC-gesteuerten Tumorzellen limitiert wird. Dieser Pathway wird durch einen schnellen Transfer des PAF1-Komplexes von MYC auf die RNAPII angetrieben, bei dem HUWE1 eine essenzielle Rolle einnimmt. Der Transfer steuert die MYC-abhängige transkriptionelle Elongation und gleichzeitig die Öffnung der Chromatinstruktur. Dies geschieht durch Ubiquitylierung des Histons H2B zugunsten von sowohl transkriptioneller Elongation als auch der DNA-Doppelstrangbruchreparatur. In dem zweiten Teil der Doktorarbeit analysiere ich die Fähigkeit von MYC-Proteinen, als Reaktion auf eine Störung der Transkription und/oder Replikation multimere Strukturen bilden zu können. Diese Fähigkeit wird auch als Phasentrennung bezeichnet. Die multimere Strukturen befinden sich in der Nähe von blockierten Replikationsgabeln und rekrutieren Faktoren der DNA-Schadensreaktion und der Transkriptionsterminationsmaschinerie. Die HUWE1-abhängige Ubiquitylierung von MYC habe ich als wesentlichen Schritt der Phasentrennung identifiziert. Zellen ohne die Fähigkeit zur Bildung von Multimeren zeigen als Reaktion auf Replikationsstress exzessive genomische Instabilität und letztendlich Apoptose auf. Beide Mechanismen machen MYC zu einem Faktor, der genomische Instabilität als Resultat von unphysiologischem Transkriptions- und Replikationsstress limitiert und damit die onkogene Zellteilung gewährleistet. Eine gezielte Beeinflussung der aufgeführten Mechanismen, durch welche MYC die genomische Instabilität limitiert, kann bei MYC-abhängigen Tumoren von großem therapeutischem Nutzen sein. KW - MYC KW - Krebsforschung KW - DNS-Schädigung KW - DNS-Reparatur KW - Oncogenes Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-305398 ER - TY - JOUR A1 - Buellesbach, Jan A1 - Vetter, Sebastian G. A1 - Schmitt, Thomas T1 - Differences in the reliance on cuticular hydrocarbons as sexual signaling and species discrimination cues in parasitoid wasps JF - Frontiers in Zoology N2 - Background Cuticular hydrocarbons (CHC) have been documented to play crucial roles as species- and sex-specific cues in the chemical communication systems of a wide variety of insects. However, whether they are sufficient by themselves as the sole cue triggering sexual behavior as well as preference of con- over heterospecific mating partners is rarely assessed. We conducted behavioral assays in three representative species of parasitoid wasps (Hymenoptera: Pteromalidae) to determine their reliance on CHC as species-specific sexual signaling cues. Results We found a surprising degree of either unspecific or insufficient sexual signaling when CHC are singled out as recognition cues. Most strikingly, the cosmopolitan species Nasonia vitripennis, expected to experience enhanced selection pressure to discriminate against other co-occurring parasitoids, did not discriminate against CHC of a partially sympatric species from another genus, Trichomalopsis sarcophagae. Focusing on the latter species, in turn, it became apparent that CHC are even insufficient as the sole cue triggering conspecific sexual behavior, hinting at the requirement of additional, synergistic sexual cues particularly important in this species. Finally, in the phylogenetically and chemically most divergent species Muscidifurax uniraptor, we intriguingly found both CHC-based sexual signaling as well as species discrimination behavior intact although this species is naturally parthenogenetic with sexual reproduction only occurring under laboratory conditions. Conclusions Our findings implicate a discrepancy in the reliance on and specificity of CHC as sexual cues in our tested parasitioid wasps. CHC profiles were not sufficient for unambiguous discrimination and preference behavior, as demonstrated by clear cross-attraction between some of our tested wasp genera. Moreover, we could show that only in T. sarcophagae, additional behavioral cues need to be present for triggering natural mating behavior, hinting at an interesting shift in signaling hierarchy in this particular species. This demonstrates the importance of integrating multiple, potentially complementary signaling modalities in future studies for a better understanding of their individual contributions to natural sexual communication behavior. KW - chemical communication KW - assortative mating KW - mate recognition KW - prezygotic reproductive isolation KW - speciation KW - Nasonia KW - Trichomalopsis KW - Muscidifurax KW - Pteromalidae KW - Hymenoptera Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-221702 VL - 15 ER - TY - JOUR A1 - Bartel, Karin A1 - Pein, Helmut A1 - Popper, Bastian A1 - Schmitt, Sabine A1 - Janaki-Raman, Sudha A1 - Schulze, Almut A1 - Lengauer, Florian A1 - Koeberle, Andreas A1 - Werz, Oliver A1 - Zischka, Hans A1 - Müller, Rolf A1 - Vollmar, Angelika M. A1 - Schwarzenberg, Karin von T1 - Connecting lysosomes and mitochondria – a novel role for lipid metabolism in cancer cell death JF - Cell Communication and Signaling N2 - Background The understanding of lysosomes has been expanded in recent research way beyond their view as cellular trash can. Lysosomes are pivotal in regulating metabolism, endocytosis and autophagy and are implicated in cancer. Recently it was discovered that the lysosomal V-ATPase, which is known to induce apoptosis, interferes with lipid metabolism in cancer, yet the interplay between these organelles is poorly understood. Methods LC-MS/MS analysis was performed to investigate lipid distribution in cells. Cell survival and signaling pathways were analyzed by means of cell biological methods (qPCR, Western Blot, flow cytometry, CellTiter-Blue). Mitochondrial structure was analyzed by confocal imaging and electron microscopy, their function was determined by flow cytometry and seahorse measurements. Results Our data reveal that interfering with lysosomal function changes composition and subcellular localization of triacylglycerids accompanied by an upregulation of PGC1α and PPARα expression, master regulators of energy and lipid metabolism. Furthermore, cardiolipin content is reduced driving mitochondria into fission, accompanied by a loss of membrane potential and reduction in oxidative capacity, which leads to a deregulation in cellular ROS and induction of mitochondria-driven apoptosis. Additionally, cells undergo a metabolic shift to glutamine dependency, correlated with the fission phenotype and sensitivity to lysosomal inhibition, most prominent in Ras mutated cells. Conclusion This study sheds mechanistic light on a largely uninvestigated triangle between lysosomes, lipid metabolism and mitochondrial function. Insight into this organelle crosstalk increases our understanding of mitochondria-driven cell death. Our findings furthermore provide a first hint on a connection of Ras pathway mutations and sensitivity towards lysosomal inhibitors. KW - lysosome KW - V-ATPase KW - mitochondria KW - fission KW - apoptosis KW - lipid metabolism KW - cardiolipin Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-221524 VL - 17 ER - TY - JOUR A1 - Jeanclos, Elisabeth A1 - Schlötzer, Jan A1 - Hadamek, Kerstin A1 - Yuan-Chen, Natalia A1 - Alwahsh, Mohammad A1 - Hollmann, Robert A1 - Fratz, Stefanie A1 - Yesilyurt-Gerhards, Dilan A1 - Frankenbach, Tina A1 - Engelmann, Daria A1 - Keller, Angelika A1 - Kaestner, Alexandra A1 - Schmitz, Werner A1 - Neuenschwander, Martin A1 - Hergenröder, Roland A1 - Sotriffer, Christoph A1 - von Kries, Jens Peter A1 - Schindelin, Hermann A1 - Gohla, Antje T1 - Glycolytic flux control by drugging phosphoglycolate phosphatase JF - Nature Communications N2 - Targeting the intrinsic metabolism of immune or tumor cells is a therapeutic strategy in autoimmunity, chronic inflammation or cancer. Metabolite repair enzymes may represent an alternative target class for selective metabolic inhibition, but pharmacological tools to test this concept are needed. Here, we demonstrate that phosphoglycolate phosphatase (PGP), a prototypical metabolite repair enzyme in glycolysis, is a pharmacologically actionable target. Using a combination of small molecule screening, protein crystallography, molecular dynamics simulations and NMR metabolomics, we discover and analyze a compound (CP1) that inhibits PGP with high selectivity and submicromolar potency. CP1 locks the phosphatase in a catalytically inactive conformation, dampens glycolytic flux, and phenocopies effects of cellular PGP-deficiency. This study provides key insights into effective and precise PGP targeting, at the same time validating an allosteric approach to control glycolysis that could advance discoveries of innovative therapeutic candidates. KW - phosphoglycolate phosphatase KW - glycolytic flux control KW - intrinsic metabolism Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300928 VL - 13 IS - 1 ER -