TY - THES A1 - Ankenbrand, Markus Johannes T1 - Squeezing more information out of biological data - development and application of bioinformatic tools for ecology, evolution and genomics T1 - Mehr aus biologischen Daten herausholen - Entwicklung und Anwendung bioinformatischer Programme für Ökologie, Evolution und Genomik N2 - New experimental methods have drastically accelerated the pace and quantity at which biological data is generated. High-throughput DNA sequencing is one of the pivotal new technologies. It offers a number of novel applications in various fields of biology, including ecology, evolution, and genomics. However, together with those opportunities many new challenges arise. Specialized algorithms and software are required to cope with the amount of data, often requiring substantial training in bioinformatic methods. Another way to make those data accessible to non-bioinformaticians is the development of programs with intuitive user interfaces. In my thesis I developed analyses and programs to tackle current problems with high-throughput data in biology. In the field of ecology this covers the establishment of the bioinformatic workflow for pollen DNA meta-barcoding. Furthermore, I developed an application that facilitates the analysis of ecological communities in the context of their traits. Information from multiple public databases have been aggregated and can now be mapped automatically to existing community tables for interactive inspection. In evolution the new data are used to reconstruct phylogenetic trees from multiple genes. I developed the tool bcgTree to automate this process for bacteria. Many plant genomes have been sequenced in current years. Sequencing reads of those projects also contain data from the chloroplasts. The tool chloroExtractor supports the targeted extraction and analysis of the chloroplast genome. To compare the structure of multiple genomes specialized software is required for calculation and visualization of the relationships. I developed AliTV to address this. In contrast to existing programs for this task it allows interactive adjustments of produced graphics. Thus, facilitating the discovery of biologically relevant information. Another application I developed helps to analyze transcriptomes even if no reference genome is present. This is achieved by aggregating the different pieces of information, like functional annotation and expression level, for each transcript in a web platform. Scientists can then search, filter, subset, and visualize the transcriptome. Together the methods and tools expedite insights into biological systems that were not possible before. N2 - Neue experimentelle Methoden haben die Geschwindigkeit und Masse, in der biologische Daten generiert werden, in den letzten Jahren enorm gesteigert. Eine zentrale neue Technologie ist die Hochdurchsatzsequenzierung von DNA. Diese Technik eröffnet eine ganze Reihe Anwendungsmöglichkeiten in vielen Bereichen der Biologie, einschließlich der Ökologie, Evolution und Genomik. Neben den neuen Möglichkeiten treten jedoch auch neue Herausforderungen auf. So bedarf es spezialisierter Algorithmen und Computerprogramme, um mit der Masse an Daten umgehen zu können. Diese erfordern in der Regel ein fundiertes Training in bioinformatischen Methoden. Ein Weg, die Daten auch Wissenschaftlern ohne diesen Hintergrund zugänglich zu machen ist die Entwicklung von Programmen, die sich intuitiv bedienen lassen. In meiner Doktorarbeit habe ich Analysen und Programme entwickelt, um einige aktuelle Probleme mit Hochdurchsatzdaten in der Biologie zu lösen. Im Bereich der Ökologie umfasst das die Etablierung der bioinformatischen Methode, um Pollen DNA Metabarcoding durchzuführen. Darüberhinaus habe ich eine Anwendung entwickelt, die es ermöglicht Artgemeinschaften im Kontext ihrer Eigenschaften zu erforschen. Dazu wurden Informationen aus diversen öffentlichen Datenbanken zusammen getragen. Diese können nun automatisch auf bestehende Projekte übertragen und interaktiv analysiert werden. Im Bereich der Evolution ermöglichen die neuen Daten phylogenetische Berechnungen mit multiplen Genen durchzuführen. Um dies für Bakterien zu automatisieren habe ich das Programm bcgTree entwickelt. In den letzten Jahren wurden viele pflanzliche Genome sequenziert. Die Sequenzdaten des pflanzlichen Genoms enthalten auch die des Chloroplasten. Das Programm chloroExtractor unterstützt die gezielte Analyse des Chloroplasten Genoms. Um jedoch die Struktur mehrerer Genome miteinander vergleichen zu können, wird spezielle Software benötigt, die den Vergleich berechnen und visuell darstellen kann. Daher habe ich das Programm AliTV entwickelt. Im Gegensatz zu bestehenden Programmen erlaubt AliTV interaktive Anpassungen der erzeugten Grafik. Das erleichtert es die relevanten Informationen zu finden. Ein weiteres von mir entwickeltes Programm hilft dabei Transkriptom Daten zu analysieren, auch wenn kein Referenzgenom vorliegt. Dazu werden Informationen zu jedem Transkript, z.B. Funktion und Expressionslevel, in einer Webanwendung aggregiert. Forscher können diese durchsuchen, filtern und graphisch darstellen. Zusammen eröffnen die entwickelten Methoden und Programme die Möglichkeit, Erkenntnisse über biologische Systeme zu erlangen, die bislang nicht möglich waren. KW - bioinformatics KW - research software KW - ecology KW - evolution KW - genomics Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-156344 ER - TY - JOUR A1 - Baalbergen, Els A1 - Helwerda, Renate A1 - Schelfhorst, Rense A1 - Castillo Cajas, Ruth F. A1 - van Moorsel, Coline H. M. A1 - Kundrata, Robin A1 - Welter-Schultes, Francisco W. A1 - Giokas, Sinos A1 - Schilthuizen, Menno T1 - Predator-Prey Interactions between Shell-Boring Beetle Larvae and Rock-Dwelling Land Snails JF - PLOS ONE N2 - Drilus beetle larvae (Coleoptera: Elateridae) are specialized predators of land snails. Here, we describe various aspects of the predator-prey interactions between multiple Drilus species attacking multiple Albinaria (Gastropoda: Clausiliidae) species in Greece. We observe that Drilus species may be facultative or obligate Albinaria-specialists. We map geographically varying predation rates in Crete, where on average 24% of empty shells carry fatal Drilus bore holes. We also provide first-hand observations and video-footage of prey entry and exit strategies of the Drilus larvae, and evaluate the potential mutual evolutionary impacts. We find limited evidence for an effect of shell features and snail behavioral traits on inter-and intraspecifically differing predation rates. We also find that Drilus predators adjust their predation behavior based on specific shell traits of the prey. In conclusion, we suggest that, with these baseline data, this interesting predator-prey system will be available for further, detailed more evolutionary ecology studies. KW - clausiliidae KW - evolution KW - pulmonata KW - albinaria KW - behavior KW - species gastropoda Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-115963 SN - 1932-6203 VL - 9 IS - 6 ER - TY - JOUR A1 - Biscotti, Maria Assunta A1 - Adolfi, Mateus Contar A1 - Barucca, Marco A1 - Forconi, Mariko A1 - Pallavicini, Alberto A1 - Gerdol, Marco A1 - Canapa, Adriana A1 - Schartl, Manfred T1 - A comparative view on sex differentiation and gametogenesis genes in lungfish and coelacanths JF - Genome Biology and Evolution N2 - Gonadal sex differentiation and reproduction are the keys to the perpetuation of favorable gene combinations and positively selected traits. In vertebrates, several gonad development features that differentiate tetrapods and fishes are likely to be, at least in part, related to the water-to-land transition. The collection of information from basal sarcopterygians, coelacanths, and lungfishes, is crucial to improve our understanding of the molecular evolution of pathways involved in reproductive functions, since these organisms are generally regarded as “living fossils” and as the direct ancestors of tetrapods. Here, we report for the first time the characterization of >50 genes related to sex differentiation and gametogenesis in Latimeria menadoensis and Protopterus annectens. Although the expression profiles of most genes is consistent with the intermediate position of basal sarcopterygians between actinopterygian fish and tetrapods, their phylogenetic placement and presence/absence patterns often reveal a closer affinity to the tetrapod orthologs. On the other hand, particular genes, for example, the male gonad factor gsdf (Gonadal Soma-Derived Factor), provide examples of ancestral traits shared with actinopterygians, which disappeared in the tetrapod lineage. KW - sex differentiation KW - Latimeria menadoensis KW - Protopterus annectens KW - evolution KW - testis KW - gametogenesis KW - ovary Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-176774 VL - 10 IS - 6 ER - TY - JOUR A1 - Biscotti, Maria Assunta A1 - Carducci, Federica A1 - Barucca, Marco A1 - Gerdol, Marco A1 - Pallavicini, Alberto A1 - Schartl, Manfred A1 - Canapa, Adriana A1 - Contar Adolfi, Mateus T1 - The transcriptome of the newt Cynops orientalis provides new insights into evolution and function of sexual gene networks in sarcopterygians JF - Scientific Reports N2 - Amphibians evolved in the Devonian period about 400 Mya and represent a transition step in tetrapod evolution. Among amphibians, high-throughput sequencing data are very limited for Caudata, due to their largest genome sizes among terrestrial vertebrates. In this paper we present the transcriptome from the fire bellied newt Cynops orientalis. Data here presented display a high level of completeness, comparable to the fully sequenced genomes available from other amphibians. Moreover, this work focused on genes involved in gametogenesis and sexual development. Surprisingly, the gsdf gene was identified for the first time in a tetrapod species, so far known only from bony fish and basal sarcopterygians. Our analysis failed to isolate fgf24 and foxl3, supporting the possible loss of both genes in the common ancestor of Rhipidistians. In Cynops, the expression analysis of genes described to be sex-related in vertebrates singled out an expected functional role for some genes, while others displayed an unforeseen behavior, confirming the high variability of the sex-related pathway in vertebrates. KW - developmental biology KW - evolution Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-227326 VL - 10 ER - TY - JOUR A1 - Bodem, Jochen A1 - Rethwilm, Axel T1 - Evolution of Foamy Viruses: The Most Ancient of All Retroviruses JF - Viruses N2 - Recent evidence indicates that foamy viruses (FVs) are the oldest retroviruses (RVs) that we know and coevolved with their hosts for several hundred million years. This coevolution may have contributed to the non-pathogenicity of FVs, an important factor in development of foamy viral vectors in gene therapy. However, various questions on the molecular evolution of FVs remain still unanswered. The analysis of the spectrum of animal species infected by exogenous FVs or harboring endogenous FV elements in their genome is pivotal. Furthermore, animal studies might reveal important issues, such as the identification of the FV in vivo target cells, which than require a detailed characterization, to resolve the molecular basis of the accuracy with which FVs copy their genome. The issues of the extent of FV viremia and of the nature of the virion genome (RNA vs. DNA) also need to be experimentally addressed. KW - foamy viruses KW - retroviruses KW - hepadnaviruses KW - evolution KW - genetic conservation KW - recombination Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-97312 ER - TY - JOUR A1 - Borges, Alyssa R. A1 - Link, Fabian A1 - Engstler, Markus A1 - Jones, Nicola G. T1 - The Glycosylphosphatidylinositol Anchor: A Linchpin for Cell Surface Versatility of Trypanosomatids JF - Frontiers in Cell and Developmental Biology N2 - The use of glycosylphosphatidylinositol (GPI) to anchor proteins to the cell surface is widespread among eukaryotes. The GPI-anchor is covalently attached to the C-terminus of a protein and mediates the protein’s attachment to the outer leaflet of the lipid bilayer. GPI-anchored proteins have a wide range of functions, including acting as receptors, transporters, and adhesion molecules. In unicellular eukaryotic parasites, abundantly expressed GPI-anchored proteins are major virulence factors, which support infection and survival within distinct host environments. While, for example, the variant surface glycoprotein (VSG) is the major component of the cell surface of the bloodstream form of African trypanosomes, procyclin is the most abundant protein of the procyclic form which is found in the invertebrate host, the tsetse fly vector. Trypanosoma cruzi, on the other hand, expresses a variety of GPI-anchored molecules on their cell surface, such as mucins, that interact with their hosts. The latter is also true for Leishmania, which use GPI anchors to display, amongst others, lipophosphoglycans on their surface. Clearly, GPI-anchoring is a common feature in trypanosomatids and the fact that it has been maintained throughout eukaryote evolution indicates its adaptive value. Here, we explore and discuss GPI anchors as universal evolutionary building blocks that support the great variety of surface molecules of trypanosomatids. KW - cell surface proteome KW - evolution KW - GPI-anchor KW - Kinetoplastea Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-249253 SN - 2296-634X VL - 9 ER - TY - INPR A1 - Dandekar, Thomas T1 - Biological heuristics applied to cosmology suggests a condensation nucleus as start of our universe and inflation cosmology replaced by a period of rapid Weiss domain-like crystal growth N2 - Cosmology often uses intricate formulas and mathematics to derive new theories and concepts. We do something different in this paper: We look at biological processes and derive from these heuristics so that the revised cosmology agrees with astronomical observations but does also agree with standard biological observations. We show that we then have to replace any type of singularity at the start of the universe by a condensation nucleus and that the very early period of the universe usually assumed to be inflation has to be replaced by a period of rapid crystal growth as in Weiss magnetization domains. Impressively, these minor modifications agree well with astronomical observations including removing the strong inflation perturbations which were never observed in the recent BICEP2 experiments. Furthermore, looking at biological principles suggests that such a new theory with a condensation nucleus at start and a first rapid phase of magnetization-like growth of the ordered, physical laws obeying lattice we live in is in fact the only convincing theory of the early phases of our universe that also is compatible with current observations. We show in detail in the following that such a process of crystal creation, breaking of new crystal seeds and ultimate evaporation of the present crystal readily leads over several generations to an evolution and selection of better, more stable and more self-organizing crystals. Moreover, this explains the “fine-tuning” question why our universe is fine-tuned to favor life: Our Universe is so self-organizing to have enough offspring and the detailed physics involved is at the same time highly favorable for all self-organizing processes including life. This biological theory contrasts with current standard inflation cosmologies. The latter do not perform well in explaining any phenomena of sophisticated structure creation or self-organization. As proteins can only thermodynamically fold by increasing the entropy in the solution around them we suggest for cosmology a condensation nucleus for a universe can form only in a “chaotic ocean” of string-soup or quantum foam if the entropy outside of the nucleus rapidly increases. We derive an interaction potential for 1 to n-dimensional strings or quantum-foams and show that they allow only 1D, 2D, 4D or octonion interactions. The latter is the richest structure and agrees to the E8 symmetry fundamental to particle physics and also compatible with the ten dimensional string theory E8 which is part of the M-theory. Interestingly, any other interactions of other dimensionality can be ruled out using Hurwitz compositional theorem. Crystallization explains also extremely well why we have only one macroscopic reality and where the worldlines of alternative trajectories exist: They are in other planes of the crystal and for energy reasons they crystallize mostly at the same time, yielding a beautiful and stable crystal. This explains decoherence and allows to determine the size of Planck´s quantum h (very small as separation of crystal layers by energy is extremely strong). Ultimate dissolution of real crystals suggests an explanation for dark energy agreeing with estimates for the “big rip”. The halo distribution of dark matter favoring galaxy formation is readily explained by a crystal seed starting with unit cells made of normal and dark matter. That we have only matter and not antimatter can be explained as there may be right handed mattercrystals and left-handed antimatter crystals. Similarly, real crystals are never perfect and we argue that exactly such irregularities allow formation of galaxies, clusters and superclusters. Finally, heuristics from genetics suggest to look for a systems perspective to derive correct vacuum and Higgs Boson energies. KW - heuristics KW - inflation KW - cosmology KW - crystallization KW - crystal growth KW - E8 symmetry KW - Hurwitz theorem KW - evolution KW - Lee Smolin Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-183945 ER - TY - INPR A1 - Dandekar, Thomas T1 - Some general system properties of a living observer and the environment he explores N2 - In a nice assay published in Nature in 1993 the physicist Richard God III started from a human observer and made a number of witty conclusions about our future prospects giving estimates for the existence of the Berlin Wall, the human race and all the rest of the universe. In the same spirit, we derive implications for "the meaning of life, the universe and all the rest" from few principles. Adams´ absurd answer "42" tells the lesson "garbage in / garbage out" - or suggests that the question is non calculable. We show that experience of "meaning" and to decide fundamental questions which can not be decided by formal systems imply central properties of life: Ever higher levels of internal representation of the world and an escalating tendency to become more complex. An observer, "collecting observations" and three measures for complexity are examined. A theory on living systems is derived focussing on their internal representation of information. Living systems are more complex than Kolmogorov complexity ("life is NOT simple") and overcome decision limits (Gödel theorem) for formal systems as illustrated for cell cycle. Only a world with very fine tuned environments allows life. Such a world is itself rather complex and hence excessive large in its space of different states – a living observer has thus a high probability to reside in a complex and fine tuned universe. N2 - Dieser Aufsatz ist ein Preprint und Discussion Paper und versucht - ähnlich wie ein hervorragendes Beispiel eines Physikers, Richard God III (1993 in Nature veröffentlicht) mit einfachen Grundannahmen sehr generelle Prinzipien für uns abzuleiten. In meinem Aufsatz sind das insbesondere Prinzipien für Beobachten, für die Existenz eines Beobachters und sogar für die Existenz unserer komplexen Welt, die Fortentwicklung von Leben, die Entstehung von Bedeutung und das menschliche Entscheiden von Grundlagenfragen. Aufs erste kann so ein weitgehendes Anliegen nicht wirklich vollständig und akkurat gelingen, der Aufsatz möchte deshalb auch nur eine amüsante Spekulation sein, exakte (und bescheidenere) Teilaussagen werden aber später dann auch nach peer Review veröffentlicht werden. KW - Komplex KW - Entscheidung KW - Natürliche Auslese KW - Evolution KW - Bedeutung KW - Komplexität KW - Gödel KW - Entscheidungen KW - complexity KW - decision KW - evolution KW - selection KW - meaning Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-33537 ER - TY - THES A1 - del Olmo Toledo, Valentina T1 - Evolution of DNA binding preferences in a family of eukaryotic transcription regulators T1 - Evolutionäre Entwicklung der Bindeaffinität an bestimmte DNA Sequenzen in einer Familie von eukaryotischen Transkriptionsfaktoren N2 - Regulation of gene expression by the control of transcription is essential for any cell to adapt to the environment and survive. Transcription regulators, i.e. sequence-specific DNA binding proteins that regulate gene expression, are central elements within the gene networks of most organisms. Transcription regulators are grouped into distinct families based on structural features that determine, to a large extent, the DNA sequence(s) that they can recognise and bind. Less is known, however, about how the DNA binding preferences can diversify within transcription regulator families during evolutionary timescales, and how such diversification can affect the biology of the organism. In this dissertation I study the SREBP (sterol regulatory element binding protein) family of transcriptional regulators in yeasts, and in Candida albicans in particular, as an experimental system to address these questions. The SREBPs are conserved from fungi to humans and represent a subgroup of basic helix-loop-helix DNA binding proteins. Early chromatin immunoprecipitation experiments with SREBPs from humans and yeasts showed that these proteins bound in vivo to the canonical DNA sequence, termed E-box, most basic helix-loop-helix proteins bind to. By contrast, most recent analysis carried out with less-studied fungal SREBPs revealed a non-canonical DNA motif to be the most overrepresented sequence in the bound regions. This study aims to establish the intrinsic DNA binding preferences of key branches of this family and to determine how the divergence in DNA binding affinities originated. To this end, I combined phylogenetic and ancestral reconstruction with extensive biochemical characterisation of key SREBP proteins. The results indicated that while the most-studied SREBPs (in mammals) indeed show preference for the E-box, a second branch of the family preferentially binds the non-E-box, and a third one is able to bind both sequences with similar affinity. The preference for one or the other DNA sequence is an intrinsic property of each protein because their purified DNA binding domain was sufficient to recapitulate their in vivo binding preference. The ancestor that gave rise to these two different types of SREBPs (the branch that binds E-box and the one that binds non-E-box DNA) appears to be a protein with a broader DNA binding capability that had a slight preference for the non-canonical motif. Thus, the results imply these two branches originated by either enhancing the original ancestral preference for non-E-box or tilting it towards the E-box DNA and flipping the preference for this sequence. The main function associated with members of the SREBP family in most eukaryotes is the control of lipid biosynthesis. I have further studied the function of these proteins in the lineage that encompasses the human associated yeast C. albicans. Strikingly, the three SREBPs present in the fungus’ genome contribute to the colonisation of the mammalian gut by regulating cellular processes unrelated to lipid metabolism. Here I describe that two of the three C. albicans SREBPs form a regulatory cascade that regulates morphology and cell wall modifications under anaerobic conditions, whereas the third SREBP has been shown to be involved in the regulation of glycolysis genes. Therefore, I posit that the described diversification in DNA binding specificity in these proteins and the concomitant expansion of targets of regulation were key in enabling this fungal lineage to associate with animals. N2 - Für jede Zelle ist es essenziell die Transkription über die Genexpression zu regulieren, um sich an unterschiedliche Lebensbedingungen anzupassen. Regulatoren der Transkription, zum Beispiel sequenzspezifische DNA-binde Proteine, sind ein zentrales Element des Genregulationsnetzwerks in den meisten Organismen. Auf Grund ihres Aufbaus sowie der daraus resultierenden spezifischen Eigenschaften DNA zu binden, werden diese Regulatoren in unterschiedliche Familien unterteilt. Bisher ist wenig darüber bekannt, wie unterschiedlich die DNA Sequenzen sein können, welche von einer Familie von Transkriptionsregulatoren gebunden werden, wie sich diese Diversität der Bindung in der Evolution über die Zeit verändert hat und ob diese unterschiedlichen Bindeaffinitäten die Biologie eines Organismus beeinflussen. In dieser Dissertation befasse ich mich mit der Transkriptionsregulator Familie der SREBPs (sterol regulatory element binding protein) in Hefen, als Modelorganismus diente dabei Candida albicans. Die Familie der SREBPs ist vom Pilz zu den Menschen genetisch weitestgehend konserviert und repräsentiert eine Unterfamilie der Helix-loop-helix DNA-binde Proteine. Erste Chromatin-Immunpräzipitation Experimente der SREBPs in Menschen und Hefen zeigen in vivo eine Bindung an eine kanonische DNA Sequenz genannt E-box, welche von den meisten der Helix-loop-helix Proteine gebunden wird. Im Gegensatz zeigen neuere Analysen, welche mit weniger bekannten SREBPs aus Pilzen durchgeführt wurden, dass hauptsächlich nicht-kanonische DNA Sequenzen gebunden werden. Diese Arbeit versucht die Präferenzen, mit welchen einige der wichtigsten Mitglieder der Familie der SREBPs an bestimmte DNA Sequenzen binden aufzudecken und heraus zu finden wie es innerhalb dieser Gruppe zu unterschiedlichen Bindungsaffinitäten kam. Dafür wurden phylogenetische Rekonstruktionsanalysen und aufwändige biochemische Charakterisierungen einiger der Proteine der SREBP Familie durchgeführt. Die Ergebnisse zeigen, dass die meisten der bisher charakterisierten SREBPs (in Säugetieren) es vorziehen an die E-box Sequenz zu binden, ein anderer Zweig des SREBP Familienstammbaums bevorzugt hingegen die non-E-box Sequenz, ein dritter Zweig des Stammbaums ist in der Lage beide Sequenzen mit gleicher Affinität zu binden. Das Bevorzugen einer der beiden DNA Sequenzen ist eine natürliche Eigenschaft des jeweiligen Proteins, da in Experimenten die isolierte DNA-binde Domäne der Proteine ausreichend war, um die in vivo Bindepräferenzen zu replizieren. Der Ursprung dieser beiden Gruppen (der E-box bindenden Gruppe und der Gruppe die non-E-box Sequenzen bindet) liegt wahrscheinlich in einem Protein, welches beide Sequenzen binden konnte, mit einem Vorzug für die nicht-kanonische Sequenz. Dies impliziert, dass die Gruppen entstanden sind indem sich entweder eine Präferenz des Vorgängerproteins für die nicht-kanonische Sequenz durchgesetzt hat oder, dass sich eine Präferenz für die E-box bindende Sequenz durchgesetzt hat und somit die Affinität dahingehend verschoben wurde. Die Hauptfunktion der meisten Proteine der SREBP Familie in Eukaryoten ist die Kontrolle der Lipid Biosynthese. In meiner Arbeit habe ich mich auf die Erforschung der SREBPs in einer Gruppe von Organismen zugewandt, die auch den mit dem Menschen assoziierten Hefepilz Candida albicans umfasst. Erstaunlicherweise beeinflussen die drei SREBPs die im Candida albicans Genom zu finden sind, die Kolonisierung des Säugetierdarms, jedoch nicht durch die Kontrolle der Lipid Biosynthese. Im Folgenden werde ich beschreiben wie zwei der drei SREBPs aus Candida albicans eine regulatorische Kaskade bilden, welche Einfluss auf die Regulierung der Morphologie und der Zellwandzusammensetzung des Pilzes unter anaeroben Bedingungen hat, wohingegen das dritte Protein der SREBP Familie für die Regulierung der Glykolyse von Bedeutung ist. Ich habe festgestellt, dass die beschriebene Vielfalt mit der diese Proteine an bestimmte DNA Sequenzen binden und die damit einhergehende Expansion der regulierbaren Ziele ein wesentlicher Grund dafür ist, dass Organismen dieses Stammbaums erfolgreich Säugetiere kolonisieren können. KW - Candida albicans KW - SREBP KW - evolution Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187890 ER - TY - THES A1 - Dornhaus, Anna T1 - The role of communication in the foraging process of social bees T1 - Die Rolle der Kommunikation beim Fouragieren von sozialen Bienen N2 - In the various groups of social bees, different systems of communication about food sources occur. These communication systems are different solutions to a common problem of social insects: efficiently allocating the necessary number of workers first to the task of foraging and second to the most profitable food sources. The solution chosen by each species depends on the particular ecological circumstances as well as the evolutionary history of that species. For example, the outstanding difference between the bumble bee and the honey bee system is that honey bees can communicate the location of profitable food sources to nestmates, which bumble bees cannot. To identify possible selection pressures that could explain this difference, I have quantified the benefits of communicating location in honey bees. I show that these strongly depend on the habitat, and that communicating location might not benefit bees in temperate habitats. This could be due to the differing spatial distributions of resources in different habitats, in particular between temperate and tropical regions. These distributions may be the reason why the mostly temperate-living bumble bees have never evolved a communication system that allows them to transfer information on location of food sources, whereas most tropical social bees (all honey bees and many stingless bees) are able to recruit nestmates to specific points in their foraging range. Nevertheless, I show that in bumble bees the allocation of workers to foraging is also regulated by communication. Successful foragers distribute in the nest a pheromone which alerts other bees to the presence of food. This pheromone stems from a tergite gland, the function of which had not been identified previously. Usage of a pheromone in the nest to alert other individuals to forage has not been described in other social insects, and might constitute a new mode of communicating about food sources. The signal might be modulated depending on the quality of the food source. Bees in the nest sample the nectar that has been brought into the nest. Their decision whether to go out and forage depends not only on the pheromone signal, but also on the quality of the nectar they have sampled. In this way, foraging activity of a bumble bee colony is adjusted to foraging conditions, which means most bees are allocated to foraging only if high-quality food sources are available. In addition, foraging activity is adjusted to the amount of food already stored. In a colony with full honeypots, no new bees are allocated to foraging. These results help us understand how the allocation of workers to the task of food collection is regulated according to external and internal nest conditions in bumble bees. N2 - Innerhalb der sozialen Bienen tritt eine Vielzahl verschiedender Systeme zur Kommunikation über Futterquellen auf. Diese Kommunikationssysteme sind verschiedene Lösungen eines Problems, mit dem alle sozialen Insekten konfrontiert sind: wie lässt sich regulieren, daß die benötigte Anzahl an Arbeiterinnen der Aufgabe des Futtersammelns, und dazu möglichst den besten vorhandenen Futterquellen, zugeteilt wird? Die von einer Art gewählte Lösung hängt von den speziellen ökologischen Rahmenbedingungen, aber auch von der evolutionären Vorgeschichte dieser Art ab. Ein herausragender Unterschied zwischen Honigbienen und Hummeln beispielsweise ist, daß Honigbienen den Ort einer profitablen Futterquelle ihren Nestgenossinnen mitteilen können, was Hummeln nicht tun. Um Selektionsdrücke zu identifizieren, die diesen Unterschied bewirken könnten, habe ich den Nutzen einer solchen Kommunikation quantifiziert. Es zeigt sich, daß dieser Nutzen stark vom Habitat der Bienen abhängt, und daß Kommunikation über den Ort von Futterquellen in temperaten Habitaten unter Umständen keine Vorteile für Bienen bedeutet. Das könnte daran liegen, daß sich die räumliche Verteilung der Ressourcen zwischen Habitaten, und besonders zwischen temperaten Gebieten und den Tropen, unterscheidet. Dieser Umstand könnte der Grund dafür sein, daß die hauptsächlich in temperaten Regionen lebenden Hummeln nie eine Methode zur Kommunikation von Information über den Ort von Futterquellen evolviert haben, während die meisten tropischen sozialen Bienenarten (alle Honigbienen und viele stachellose Bienen) Nestgenossinnen zu bestimmten Orten rekrutieren können. Jedoch stellte sich in meinen Experimenten heraus, daß auch bei Hummeln die Zuordnung von Arbeiterinnen zur Aufgabe des Futtersammelns über Kommunikation reguliert wird. Erfolgreiche Sammlerinnen produzieren ein Pheromon, welches andere Hummeln auf die Präsenz einer Futterquelle aufmerksam macht. Dieses Pheromon stammt aus einer Tergaldrüse am Abdomen, deren Funktion bisher nicht bekannt war. Die Benutzung eines Pheromons zur Kommunikation über Futterquellen im Nest ist von anderen sozialen Insekten bisher nicht bekannt. Das Pheromonsignal wird vermutlich abhängig von der Qualität der Futterquelle moduliert. Hummeln im Nest kosten außerdem den neu eingetragenen Nektar. Ihre Entscheidung auszufliegen und zu sammeln ist sowohl vom Pheromonsignal als auch von der Qualität des von ihnen gekosteten Nektars abhängig. Die Sammelaktivität der Hummelkolonie wird damit an die Sammelbedingungen angepasst – nur wenn profitable Futterquellen vorhanden sind, werden viele Sammlerinnen aktiviert. Zusätzlich hängt die Sammelaktivität von der Vorratssituation im Stock ab. Sind die Honigtöpfe gefüllt, werden keine neuen Arbeiterinnen zum Sammeln aktiviert. Diese Ergebnisse helfen uns zu verstehen, wie bei Hummeln die Anzahl der aktiven Sammlerinnen je nach den Bedingungen innerhalb und außerhalb der Kolonie reguliert wird. KW - Hummel KW - Bienen KW - Kommunikation KW - Nahrungserwerb KW - Evolution KW - Pheromon KW - Schwänzeltanz KW - Evolution KW - Rekrutierung KW - Hummeln KW - Bombus KW - Futtersammeln KW - foraging KW - recruitment KW - evolution KW - bumble bees KW - Bombus KW - waggle dance Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-3468 ER -