Refine
Has Fulltext
- yes (78)
Is part of the Bibliography
- yes (78)
Year of publication
- 2013 (78) (remove)
Document Type
- Journal article (57)
- Doctoral Thesis (21)
Language
- English (78) (remove)
Keywords
- gene expression (6)
- bees (5)
- climate change (4)
- honey bees (4)
- bacterial pathogens (3)
- evolution (3)
- larvae (3)
- Antikörper (2)
- Biene (2)
- Bioinformatik (2)
- DNA-binding proteins (2)
- Drosophila (2)
- Extremereignisse (2)
- Höhengradient (2)
- Klimawandel (2)
- Klimaänderung (2)
- Krebs <Medizin> (2)
- Maus (2)
- Omp85 (2)
- Signaltransduktion (2)
- Taufliege (2)
- Vaccinia-Virus (2)
- Verhalten (2)
- altitudinal gradient (2)
- biomarker (2)
- canola (2)
- chlamydia infection (2)
- differentiation (2)
- foraging (2)
- formicidae (2)
- gene regulation (2)
- gene targeting (2)
- in-vitro (2)
- luciferase (2)
- microarrays (2)
- molecular phylogeny (2)
- oilseed rape (2)
- oncogenes (2)
- oncolytic virus (2)
- pluripotency (2)
- pollen (2)
- polymerase chain reaction (2)
- spillover (2)
- telomeres (2)
- trap nests (2)
- visual system (2)
- 16S ribosomal-RNA (1)
- Acetylated tubulin (1)
- Actin nucleation (1)
- Alpen (1)
- Alps (1)
- Analyse (1)
- B lymphocytes (1)
- BBCH (1)
- BMP (1)
- BMP antagonist (1)
- BMP signaling (1)
- BMP signaling pathway (1)
- BMP-Signaltransduktionsweg (1)
- Bauchfellentzündung (1)
- Bestäubung (1)
- Bestäubungsökologie (1)
- Bevacizumab (1)
- Biodiversität (1)
- Biokompatibilität (1)
- Biologie (1)
- Blattschneiderameisen (1)
- Blut (1)
- Bocas-del-Toro (1)
- Boden (1)
- Boolean function (1)
- Boolean tree (1)
- C-MYC (1)
- CCAP (1)
- Ccl2 (1)
- Chlamydia (1)
- Chromatophor (1)
- Clever Hans Phenomenon (1)
- Cobl domain (1)
- Cristaestruktur (1)
- Cytotoxischer Antikörper (1)
- DM-domain gene (1)
- DNA electrophoresis (1)
- DNA hybridization (1)
- DNA methylation (1)
- DNA replication (1)
- DNA sequences (1)
- DNA transcription (1)
- DNA-binding (1)
- DREAM (1)
- Dimerisierung (1)
- Drosophila melanogaster (1)
- Dufours gland (1)
- EGF receptor (1)
- ENV (1)
- Echinococcus (1)
- Entzündung (1)
- Epidermaler Wachstumsfaktor (1)
- Epidermaler Wachstumsfaktor-Rezeptor (1)
- Epstein-Barr-virus (1)
- Evolution (1)
- Fluoreszenzkorrelationsspektroskopie (1)
- Fluoreszenzlöschung (1)
- Fluorophore (1)
- GP41 cytoplasmic tail (1)
- Gedächtnis (1)
- Gefäßpflanzen (1)
- Gene duplication (1)
- Genome evolution (1)
- Genregulation (1)
- Geruch (1)
- Geschlechtsunterschied (1)
- Glucuronidase <beta-> (1)
- Glykosylierung (1)
- HIV (1)
- Hautkrebs (1)
- Hebbian plasticity (1)
- Hebbsche Lernregel (1)
- Hummel (1)
- Hybrid (1)
- Hypoxia (1)
- Hämodiafiltration (1)
- Hämodialyse (1)
- Höhenstufe (1)
- ITS2 (1)
- Immunsystem (1)
- Immuntherapie (1)
- Import (1)
- In vitro (1)
- Inc (1)
- Inclusion (1)
- Insekten (1)
- Invasion (1)
- Ionenstärke (1)
- Ionic strength (1)
- Kalyx (1)
- Kernhülle (1)
- Knochen-Morphogenese-Proteine (1)
- LS-MIDA (1)
- Landnutzung (1)
- Landscape composition (1)
- Landscape configuration (1)
- Landschaftskomposition (1)
- Landschaftskonfiguration (1)
- Lernen (1)
- Leukämie (1)
- Lumineszenzlöschung (1)
- MAPK signaling cascades (1)
- MET receptor (1)
- Management (1)
- Mathematical modeling (1)
- Mathematische Modellierung (1)
- Meiose (1)
- Meiosis (1)
- Melanom (1)
- Mensch (1)
- Metacestode (1)
- MircoRNA (1)
- Mitochondrien (1)
- Molekularbiologie (1)
- Mutualismus (1)
- Mykose (1)
- NCI-60 (1)
- NF-KAPPA-B (1)
- NFATc1 (1)
- NMR spectroscopy (1)
- Nervendegeneration (1)
- Nervous system (1)
- Nestbau (1)
- Neurobiologie (1)
- Neurodegeneration (1)
- Neuroinflammation (1)
- Neuronale Ceroid Lipofuszinose (1)
- Neuropeptide (1)
- Nisthilfe (1)
- Nuclear envelope (1)
- Onkogen (1)
- Oocytes (1)
- Organisation (1)
- POTRA domain (1)
- Parasitismus (1)
- Parkinsons diesease (1)
- Pflanzen (1)
- Pflanzen-Bestäuber-Interaktionen (1)
- Phylogenetics (1)
- Pilzkörper (1)
- Plant-animal interactions (1)
- Plastizität <Physiologie> (1)
- Pollen (1)
- Pollensammelzeiten (1)
- Pollination (1)
- Polymerase chain reaction (1)
- PorB (1)
- Proteinbindung (1)
- Protoscolex (1)
- Prädation (1)
- RBCL (1)
- RNA secondary structure (1)
- RNA-binding protein (1)
- Reproduktionserfolg (1)
- Rhabdomyosarkom (1)
- SEMA domain (1)
- SMAD signaling (1)
- Scatter factor (1)
- Schwertkärpfling (1)
- Serotonin (1)
- Signal transduction (1)
- Signaling (1)
- Sinne (1)
- Sinnesphysiologie (1)
- Stammzelle (1)
- Stridulation (1)
- Synapse (1)
- Systembiologie (1)
- T cell receptors (1)
- T cells (1)
- T-Lymphozyt (1)
- T-Lymphozyten (1)
- T-RFLP analysis (1)
- T-lymphocytes (1)
- TCR signaling cascade (1)
- TGF-β superfamily (1)
- Tarp (1)
- Theoretical ecology (1)
- Theoretische Ökologie (1)
- Therapie (1)
- Thrombozyt (1)
- Tierökologie (1)
- Toxin (1)
- Trafficking (1)
- Transkriptionsfaktor (1)
- Transport (1)
- Trophic interactions (1)
- Trophische Interaktionen (1)
- Tumor (1)
- Tumor angiogenesis (1)
- Tumorsuppressorgen (1)
- Type III secretion (1)
- Urämie (1)
- Urämietoxine (1)
- VEGFA (1)
- WH2 domain (1)
- Wespen (1)
- Wildbienen (1)
- Xiphophorus (1)
- Zellzyklus (1)
- actin (1)
- adaptive evolution (1)
- adaptive radiation (1)
- advanced (1)
- agrobacterium tumefaciens (1)
- alignment (1)
- alkyloctahydronaphthalene (1)
- alpha (1)
- alpha-tubulin-II (1)
- alpine ecosystems (1)
- alternative splicing (1)
- alternative trapping strategies (1)
- analysis (1)
- animal behavior (1)
- antennal lobe (1)
- antibodies (1)
- antibody engineering (1)
- antimicrobials (1)
- ants (1)
- appeasement substance (1)
- arabidopsis thaliana (1)
- assay systems (1)
- axonal damage (1)
- axonaler Schaden (1)
- bacillus thuringiensis (1)
- bacteria (1)
- bee (1)
- beta-Fassproteine (1)
- beta-TRCP (1)
- beta-barrel-proteins (1)
- beta-glucuronidase (1)
- binary decision diagram (1)
- binding (1)
- biocompatibility (1)
- biodiversity (1)
- biogenesis (1)
- biomarkers (1)
- bispecific antibodies (1)
- bispezifische antikörper (1)
- blocking antibodies (1)
- blood (1)
- bone morphogenetic proteins (1)
- brachtydacyly type A2 (1)
- bursicon (1)
- caco-2 cells (1)
- calyx (1)
- camponotus schmitzi (1)
- cancer (1)
- cancer immunotherapy (1)
- carcinomas (1)
- cell cycle (1)
- cell cycle and cell division (1)
- cell differentation (1)
- cell division (1)
- cell fusion (1)
- cell membranes (1)
- cell staining (1)
- cellcycle (1)
- cells (1)
- cellular proteins (1)
- cephalotes (1)
- chimera formation (1)
- chlamydia (1)
- chlamydia trachomatis (1)
- chlorophyta (1)
- chromosomes (1)
- circular DNA (1)
- citrus (1)
- colon (1)
- colorectal cancer (1)
- communities (1)
- community (1)
- complex (1)
- complexes (1)
- concerted evolution (1)
- confidence interval (1)
- confidence intervals (1)
- corn pollen (1)
- counting (1)
- crematogaster (1)
- cristae (1)
- crystal-structure (1)
- culture (1)
- cultures (1)
- cuticular hydrocarbons (1)
- cytoskeleton (1)
- decision making (1)
- delayed snowmelt (1)
- dendrobates pumilio (1)
- development (1)
- dimerization (1)
- dimorphic expression (1)
- diseases (1)
- distance (1)
- divergent expression regulation (1)
- dominant-negative mutatio (1)
- drosophila melanogaster (1)
- drug selection (1)
- ecdysis (1)
- ecology (1)
- ecosystem function (1)
- ecosystem service (1)
- elevation (1)
- embryonic stem-cells (1)
- environmental filtering (1)
- epiphytic fern (1)
- erythroyte invation (1)
- escherichia coli infections (1)
- evolutionary biology (1)
- extreme events (1)
- eyes (1)
- flowering (1)
- fluorescence (1)
- fluorescence correlation spectroscopy (1)
- fluorescent-probes (1)
- food web (1)
- foraging trip durations (1)
- formin (1)
- fungal infection (1)
- fungal structure (1)
- fungi (1)
- gametocyte (1)
- gametogenesis (1)
- gene encoding noggin (1)
- gene regulatory network evolution (1)
- genetic oscillators (1)
- genetic regulatory network (1)
- genomic organization (1)
- germinal center (1)
- glomeruli (1)
- glycoprotein incorporation (1)
- gonadal development (1)
- gray tree frogs (1)
- green algae (1)
- growth factor beta (1)
- gut bacteria (1)
- h-dimerization (1)
- hemodialysis (1)
- hepatocyte-growth-factor (1)
- heterococcus (1)
- high-risk prostate cancer (1)
- homodimers (1)
- homologous chromosomes (1)
- homologous recombination (1)
- hormone transport (1)
- host cell interface (1)
- human immunodeficiency virus (1)
- hybridomas (1)
- immune serum (1)
- in vivo (1)
- infection (1)
- infectious diseases (1)
- inflammation (1)
- insect (1)
- insect flight (1)
- insects (1)
- interpolation (1)
- interspecific aggression (1)
- intracellular membranes (1)
- intracellular pathogens (1)
- introgressive hybridization (1)
- invasion protein-INLB (1)
- kinase inhibitors (1)
- laboratory techniques and procedures (1)
- lamins (1)
- land use (1)
- language (1)
- latency (1)
- leaf-cutter ants (1)
- leaf-cutting ants (1)
- leaf-litter utilization (1)
- learning (1)
- lexicography (1)
- library screening (1)
- life history traits (1)
- life-cycle (1)
- likelihood approach (1)
- linguistic morphology (1)
- listeria-monocytogenes (1)
- living cells (1)
- locomotion (1)
- macrophages (1)
- malaria (1)
- male mating success (1)
- measles virus (1)
- mechanisms (1)
- medaka fish (1)
- medakafish oryzias latipes (1)
- melanoma (1)
- memory (1)
- metastasis (1)
- miR-205 (1)
- microRNA (1)
- mitochondria (1)
- mitochondrial DNA (1)
- mitochondrion (1)
- mixed models (1)
- molecular mechanism (1)
- molecular mechanisms (1)
- monoclonal antibodies (1)
- monodelphis domestica (1)
- morphogenetic protein receptors (1)
- mosquito (1)
- mouse (1)
- mullerian hormone AMH (1)
- multi-unit recording (1)
- multivariate analyses (1)
- murine gammaherpesvirus 68 (1)
- mushroom bodies (1)
- mushroom body (1)
- mutualistische Netzwerke (1)
- myoinhibitory peptide (1)
- neisseria gonorrhoeae (1)
- nepenthes bicalcarata (1)
- nest building (1)
- nestmate recognition cues (1)
- network analysis (1)
- neurodegeneration (1)
- neuroinflammation (1)
- neuromodulation (1)
- neuronal ceroid lipofuscinosis (1)
- neurons (1)
- nitrogen (1)
- nuclear antigen (1)
- nuclear proe (1)
- nucleator (1)
- numerical cognition (1)
- oophaga pumilio (1)
- operational sex ratio (1)
- oreochromis niloticus (1)
- organisation (1)
- oryzias latipes (1)
- outer-membrane proteins (1)
- parabiotic ants (1)
- parabiotic association (1)
- paracrine release (1)
- parasitism (1)
- parasitophorous vacuole (1)
- parten-offspring conflict (1)
- particles (1)
- pathway (1)
- pheromone (1)
- phosphates (1)
- phosphorylation (1)
- phylogenetic trees (1)
- physiological parameters (1)
- pied flycatchers (1)
- pigment cell (1)
- pili and fimbriae (1)
- plant evolution (1)
- plant genomics (1)
- plasma membrane (1)
- plasmodium falciparum (1)
- platelets (1)
- poeciliidae (1)
- polyergus rufescens (1)
- preexisting bias (1)
- prey (1)
- prognosis (1)
- projection neurons (1)
- prostate cancer (1)
- protein (1)
- protein binding (1)
- protein expression (1)
- protein kinases (1)
- protein-protein recognition (1)
- psbA/rbcL spacer (1)
- psycholinguistics (1)
- pupae (1)
- quality control (1)
- quantity discrimination (1)
- rafflesiana (1)
- rat hepatocytes (1)
- recruitment (1)
- regulatory regions (1)
- rekombinante Antikörper (1)
- reproduction success (1)
- reverse transcriptase-polymerase chain reaction (1)
- risk assessment (1)
- sampling behavior (1)
- selection (1)
- sensory ecology (1)
- sensory systems (1)
- sequence alignment (1)
- sequence databases (1)
- sequence motif analysis (1)
- sequential mate choice (1)
- sexual development (1)
- signal peptide peptidase (1)
- signal tranduction (1)
- signaling pathway (1)
- single-molecule photobleaching (1)
- size determination (1)
- small interferring RNA (1)
- snowmelt (1)
- southern hybridization (1)
- species concept (1)
- spermatocytes (1)
- stable state (1)
- stem cells (1)
- stem-cell (1)
- stepping patterns (1)
- strategies (1)
- stridulation (1)
- structural insights (1)
- synapse (1)
- synapsis (1)
- synaptic signaling (1)
- systematics (1)
- systems biology (1)
- terrestrial habitats (1)
- testes (1)
- therapeutic antibody (1)
- tissue transport (1)
- tool (1)
- transcriptional control (1)
- transcriptome (1)
- transkriptionelle Regulation (1)
- transmission (1)
- transport (1)
- tree selection (1)
- treefrogs hyla-gratiosa (1)
- tropical forest (1)
- type-1 matrix (1)
- tyrosine kinase (1)
- uremic toxin (1)
- usurpation (1)
- vascular plants (1)
- venom (1)
- viral load (1)
- virions (1)
- vision (1)
- volume transmission (1)
- von Willebrand type C domain (1)
- winter (1)
- worker honeybees (1)
- xanthophyceae (1)
- xmrk (1)
- zebrafish (1)
- β-barrel (1)
Institute
- Theodor-Boveri-Institut für Biowissenschaften (78) (remove)
Sonstige beteiligte Institutionen
- DNA Analytics Core Facility, Biocenter, University of Wuerzburg, Wuerzburg, Germany (1)
- EMBL, Structural and Computational Biology Unit, Heidelberg, Germany (1)
- IZKF Laboratory for Microarray Applications, University Hospital of Wuerzburg, Wuerzburg, Germany (1)
- Microarray Core Unit, Interdisciplinary Center for Clinical Science, University of Würzburg, Versbacher Straße, Würzburg 97080, Germany (1)
DNA Methylation Mediated Control of Gene Expression Is Critical for Development of Crown Gall Tumors
(2013)
Crown gall tumors develop after integration of the T-DNA of virulent Agrobacterium tumefaciens strains into the plant genome. Expression of the T-DNA–encoded oncogenes triggers proliferation and differentiation of transformed plant cells. Crown gall development is known to be accompanied by global changes in transcription, metabolite levels, and physiological processes. High levels of abscisic acid (ABA) in crown galls regulate expression of drought stress responsive genes and mediate drought stress acclimation, which is essential for wild-type-like tumor growth. An impact of epigenetic processes such as DNA methylation on crown gall development has been suggested; however, it has not yet been investigated comprehensively. In this study, the methylation pattern of Arabidopsis thaliana crown galls was analyzed on a genome-wide scale as well as at the single gene level. Bisulfite sequencing analysis revealed that the oncogenes Ipt, IaaH, and IaaM were unmethylated in crown galls. Nevertheless, the oncogenes were susceptible to siRNA–mediated methylation, which inhibited their expression and subsequently crown gall growth. Genome arrays, hybridized with methylated DNA obtained by immunoprecipitation, revealed a globally hypermethylated crown gall genome, while promoters were rather hypomethylated. Mutants with reduced non-CG methylation developed larger tumors than the wild-type controls, indicating that hypermethylation inhibits plant tumor growth. The differential methylation pattern of crown galls and the stem tissue from which they originate correlated with transcriptional changes. Genes known to be transcriptionally inhibited by ABA and methylated in crown galls became promoter methylated upon treatment of A. thaliana with ABA. This suggests that the high ABA levels in crown galls may mediate DNA methylation and regulate expression of genes involved in drought stress protection. In summary, our studies provide evidence that epigenetic processes regulate gene expression, physiological processes, and the development of crown gall tumors.
The nuclear lamina is the structural scaffold of the nuclear envelope and is well known for its central role in nuclear organization and maintaining nuclear stability and shape. In the past, a number of severe human disorders have been identified to be associated with mutations in lamins. Extensive research on this topic has provided novel important clues about nuclear lamina function. These studies have contributed to the knowledge that the lamina constitutes a complex multifunctional platform combining both structural and regulatory functions. Here, we report that, in addition to the previously demonstrated significance for somatic cell differentiation and maintenance, the nuclear lamina is also an essential determinant for germ cell development. Both male and female mice lacking the short meiosis-specific A-type lamin C2 have a severely defective meiosis, which at least in the male results in infertility. Detailed analysis revealed that lamin C2 is required for telomere-driven dynamic repositioning of meiotic chromosomes. Loss of lamin C2 affects precise synapsis of the homologs and interferes with meiotic double-strand break repair. Taken together, our data explain how the nuclear lamina contributes to meiotic chromosome behaviour and accurate genome haploidization on a mechanistic level.
The Chaco leaf-cutting ant Atta vollenweideri (Forel) inhabits large and deep subterranean nests composed of a large number of fungus and refuse chambers. The ants dispose of the excavated soil by forming small pellets that are carried to the surface. For ants in general, the organisation of underground soil transport during nest building remains completely unknown. In the laboratory, we investigated how soil pellets are formed and transported, and whether their occurrence influences the spatial organisation of collective digging. Similar to leaf transport, we discovered size matching between soil pellet mass and carrier mass. Workers observed while digging excavated pellets at a rate of 26 per hour. Each excavator deposited its pellets in an individual cluster, independently of the preferred deposition sites of other excavators. Soil pellets were transported sequentially over 2 m, and the transport involved up to 12 workers belonging to three functionally distinct groups: excavators, several short-distance carriers that dropped the collected pellets after a few centimetres, and long-distance, last carriers that reached the final deposition site. When initiating a new excavation, the proportion of long-distance carriers increased from 18% to 45% within the first five hours, and remained unchanged over more than 20 hours. Accumulated, freshly-excavated pellets significantly influenced the workers' decision where to start digging in a choice experiment. Thus, pellets temporarily accumulated as a result of their sequential transport provide cues that spatially organise collective nest excavation.
The ability to perceive the number of objects has been known to exist in vertebrates for a few decades, but recent behavioral investigations have demonstrated that several invertebrate species can also be placed on the continuum of numerical abilities shared with birds, mammals, and reptiles. In this review article, we present the main experimental studies that have examined the ability of insects to use numerical information. These studies have made use of a wide range of methodologies, and for this reason it is striking that a common finding is the inability of the tested animals to discriminate numerical quantities greater than four. Furthermore, the finding that bees can not only transfer learnt numerical discrimination to novel objects, but also to novel numerosities, is strongly suggestive of a true, albeit limited, ability to count. Later in the review, we evaluate the available evidence to narrow down the possible mechanisms that the animals might be using to solve the number-based experimental tasks presented to them. We conclude by suggesting avenues of further research that take into account variables such as the animals’ age and experience, as well as complementary cognitive systems such as attention and the time sense.
Background
The knowledge of metabolic pathways and fluxes is important to understand the adaptation of organisms to their biotic and abiotic environment. The specific distribution of stable isotope labelled precursors into metabolic products can be taken as fingerprints of the metabolic events and dynamics through the metabolic networks. An open-source software is required that easily and rapidly calculates from mass spectra of labelled metabolites, derivatives and their fragments global isotope excess and isotopomer distribution.
Results
The open-source software “Least Square Mass Isotopomer Analyzer” (LS-MIDA) is presented that processes experimental mass spectrometry (MS) data on the basis of metabolite information such as the number of atoms in the compound, mass to charge ratio (m/e or m/z) values of the compounds and fragments under study, and the experimental relative MS intensities reflecting the enrichments of isotopomers in 13C- or 15 N-labelled compounds, in comparison to the natural abundances in the unlabelled molecules. The software uses Brauman’s least square method of linear regression. As a result, global isotope enrichments of the metabolite or fragment under study and the molar abundances of each isotopomer are obtained and displayed.
Conclusions
The new software provides an open-source platform that easily and rapidly converts experimental MS patterns of labelled metabolites into isotopomer enrichments that are the basis for subsequent observation-driven analysis of pathways and fluxes, as well as for model-driven metabolic flux calculations.
Peritonitis is a common disease in man, frequently caused by fungi, such as Candida albicans; however, in seldom cases opportunistic infections with Saccharomyces cerevisiae are described. Resident peritoneal macrophages (prMΦ) are the major group of phagocytic cells in the peritoneum. They express a broad range of surface pattern recognition receptors (PRR) to recognize invaders. Yeast infections are primarily detected by the Dectin-1 receptor, which triggers activation of NFAT and NF-κB pathways.
The transcription of the Nfatc1 gene is directed by the two alternative promoters, inducible P1 and relatively constitutive P2 promoter. While the role of P1-directed NFATc1α-isoforms to promote survival and proliferation of activated lymphocytes is well-established, the relevance of constitutively generated NFATc1β-isoforms, mainly expressed in resting lymphocytes, myeloid and non-lymphoid cells, remains unclear. Moreover, former work at our department indicated different roles for NFATc1α- and NFATc1β-proteins in lymphocytes.
Our data revealed the functional role of NFATc1 in peritoneal resident macrophages. We demonstrated that the expression of NFATc1β is required for a proper immune response of prMΦ during fungal infection-induced acute peritonitis. We identified Ccl2, a major chemokine produced in response to fungal infections by prMΦ, as a novel NFATc1 target gene which is cooperatively regulated through the NFAT- and canonical NF-κB pathways. Consequently, we showed that NFATc1β deficiency in prMΦ results in a decreased infiltration of inflammatory monocytes, leading to a delayed clearance of peritoneal fungal infection.
We could further show that the expression of NFATc1β-isoforms is irrelevant for homeostasis of myeloid and adaptive immune system cells and that NFATc1α- (but not β-) isoforms are required for a normal development of peritoneal B1a cells. In contrast to the situation in myeloid cells, NFATc1β deficiency is compensated by increased expression of NFATc1α-isoforms in lymphoid cells. As a consequence, NFATc1ß is dispensable for activation of the adaptive immune system.
Taken together our results illustrate the redundancy and indispensability of NFATc1-isoforms in the adaptive and innate immune system, indicating a complex regulatory system for Nfatc1 gene expression in different compartments of the immune system and likely beyond that.
In this dissertation, I examine the relationship between specialisation and stability of plant-pollinator networks, with a focus on two issues: Diversity maintenance in animal-pollinated plant communities and robustness of plant-pollinator systems against disturbances such as those caused by anthropogenic climate change. Chapter 1 of this thesis provides a general introduction to the concepts of ecological stability and specialisation with a focus on plant-pollinator systems, and a brief outline of the following chapters. Chapters 2-5 each consist of a research article addressing a specific question. While chapters 2 and 3 deal with different aspects of diversity maintenance in animal-pollinated plant communities, chapters 4 and 5 are concerned with the consequences of climate change in the form of temporary disturbances caused by extreme climatic events (chapter 4) and shifts in phenology of plants and pollinators (chapter 5). From a methodological perspective, the first three articles (chapter 2-4) can be grouped together as they all employ mathematical models of plant-pollinator systems, whereas chapter 5 describes an empirical study of plant-pollinator interactions along an altitudinal gradient in the Alps. The final chapter (6) provides a review of current knowledge on each of the two main themes of this thesis and places the findings of the four research articles in the context of related studies.
The DREAM complex plays an important role in regulation of gene expression during the cell cycle. It was previously shown that the DREAM subunits LIN9 and B-MYB are required for early embryonic development and for the maintenance of the inner cell mass in vitro. In this work the effect of LIN9 or B-MYB depletion on embryonic stem cells (ESC) was examined. It demonstrates that LIN9 and B-MYB knock down changes the cell cycle distribution of ESCs and results in an accumulation of cells in G2 and M and in an increase of polyploid cells. By using genome-wide expression studies it was revealed that the depletion of LIN9 leads to downregulation of mitotic genes and to upregulation of differentiation-specific genes. ChIP-on chip experiments determined that mitotic genes are direct targets of LIN9 while lineage specific markers are regulated indirectly. Importantly, depletion of LIN9 does not alter the expression of the pluripotency markers Sox2 and Oct4 and LIN9 depleted ESCs retain alkaline phosphatase activity. I conclude that LIN9 is essential for proliferation and genome stability of ESCs by activating genes with important functions in mitosis and cytokinesis. The exact molecular mechanisms behind this gene activation are still unclear as no DREAM subunit features a catalytically active domain. It is assumed that DREAM interacts with other proteins or co-factors for transcriptional activation. This study discovered potential binding proteins by combining in vivo isotope labeling of proteins with mass spectrometry
(MS) and further analysed the identified interaction of the tight junction protein ZO-2 with DREAM which is cell cycle dependent and strongest in S-phase. ZO-2 depletion results in reduced cell proliferation and decreased G1 gene expression. As no G2/M genes, typical DREAM targets, are affected upon ZO-2 knock down, it is unlikely that ZO-2 binding is needed for a functional DREAM complex. However, this work demonstrates that with (MS)-based quantitative proteomics, DREAM interacting proteins can be identified which might help to elucidate the mechanisms underlying DREAM mediated gene activation.
Cancer cells frequently escape from immune surveillance by down-regulating two important components of the immune defence: antigen-presenting MHC and costimulatory molecules. Therefore several novel anti-tumour compounds that aim to assist the immune system in recognising and fighting cancer are currently under development. Recombinant bispecific antibodies represent one group of such novel therapeutics. They target two different antigens and recruit cytotoxic effector cells to tumour cells. For cancer immunotherapy, bispecific T cell-engaging antibodies are already well characterised. These antibodies target a tumour-associated antigen and CD3ε, the constant molecule of the T cell receptor complex.
On the one hand, this study presents the development of a bispecific antibody targeting CD3ε and the rhabdomyosarcoma-associated fetal acetylcholine receptor. On the other hand, it describes a novel two-part trispecific antibody format for the treatment of leukaemia and other haematological malignancies in the context of haematopoietic stem cell transplantation (HSCT).
For HSCT, an HLA-identical donor is preferred, but very rarely available. In an HLA-mismatched setting, the HLA disparity could be exploited for targeted cancer treatment. In the present study, a two-part trispecific HLA-A2 × CD45 × CD3 antibody was developed for potential cases in which the patient is HLA-A2-positive, but the donor is not. This holds true for about half the cases in Germany, since HLA-A2 is the most common HLA molecule found here. Combinatorial targeting of HLA-A2 and the leucocyte-common antigen CD45 allows for highly specific dual-antigen restricted tumour targeting.
More precisely, two single-chain antibody constructs were developed: i) a single-chain variable fragment (scFv) specific for HLA-A2, and ii) a scFv against CD45, both linked to the VL and the VH domain of a CD3ε-specific antibody, respectively. It turned out that, after the concomitant binding of these constructs to the same HLA-A2- and CD45-expressing cell, the unpaired variable domains of a CD3ε-specific antibody assembled to a functional scFv. In a therapeutic situation, this assembly should exclusively occur on the recipient’s blood cancer cells, leading to T cell-mediated cancer cell destruction. In this way, a relapse of disease might be prevented, and standard therapy (radiation and chemotherapy) might be omitted.
For both approaches, the antibody constructs were periplasmically expressed in E. coli, purified via His tag, and biochemically characterised. Their binding to the respective targets was proven by flow cytometry. The stimulatory properties of the antibodies were assayed by measuring IL-2 release after incubation with T cells and antigen-expressing target cells. Both the bispecific antibody against rhabdomyosarcoma and the assembled trispecific antibody against blood cancer mediated T-cell activation in a concentration-dependent manner at nanomolar concentrations. For the trispecific antibody, this effect indeed proved to be dual antigen-restricted, as it could be blocked by prior incubation of either HLA-A2- or CD45-specific scFv and did not occur on single-positive (CD45+) or double-negative (HLA-A2- CD45-) target cells. Furthermore, antibodies from both approaches recruited T cells for tumour cell destruction in vitro.
Learning and memory is considered to require synaptic plasticity at presynaptic specializations of neurons. Kenyon cells are the intrinsic neurons of the primary olfactory learning center in the brain of arthropods – the mushroom body neuropils. An olfactory mushroom body memory trace is supposed to be located at the presynapses of Kenyon cells. In the calyx, a sub-compartment of the mushroom bodies, Kenyon cell dendrites receive olfactory input provided via projection neurons. Their output synapses, however, were thought to reside exclusively along their axonal projections outside the calyx, in the mushroom body lobes. By means of high-resolution imaging and with novel transgenic tools, we showed that the calyx of the fruit fly Drosophila melanogaster also comprised Kenyon cell presynapses. At these presynapses, synaptic vesicles were present, which were capable of neurotransmitter release upon stimulation. In addition, the newly identified Kenyon cell presynapses shared similarities with most other presynapses: their active zones, the sites of vesicle fusion, contained the proteins Bruchpilot and Syd-1. These proteins are part of the cytomatrix at the active zone, a scaffold controlling synaptic vesicle endo- and exocytosis. Kenyon cell presynapses were present in γ- and α/β-type KCs but not in α/β-type Kenyon cells.
The newly identified Kenyon cell derived presynapses in the calyx are candidate sites for an olfactory associative memory trace. We hypothesize that, as in mammals, recurrent neuronal activity might operate for memory retrieval in the fly olfactory system.
Moreover, we present evidence for structural synaptic plasticity in the mushroom body calyx. This is the first demonstration of synaptic plasticity in the central nervous system of Drosophila melanogaster. The volume of the mushroom body calyx can change according to changes in the environment. Also size and numbers of microglomeruli - sub-structures of the calyx, at which projection neurons contact Kenyon cells – can change. We investigated the synapses within the microglomeruli in detail by using new transgenic tools for visualizing presynaptic active zones and postsynaptic densities. Here, we could show, by disruption of the projection neuron - Kenyon cell circuit, that synapses of microglomeruli were subject to activity-dependent synaptic plasticity. Projection neurons that could not generate action potentials compensated their functional limitation by increasing the number of active zones per microglomerulus. Moreover, they built more and enlarged microglomeruli. Our data provide clear evidence for an activity-induced, structural synaptic plasticity as well as for the activity-induced reorganization of the olfactory circuitry in the mushroom body calyx.
Bone Morphogenetic Proteins (BMPs) are key regulators for a lot of diverse cellular processes. During embryonic development these proteins act as morphogens and play a crucial role particularly in organogenesis. BMPs have a direct impact on distinct cellular fates by means of concentration-gradients in the developing embryos. Using the diverse signaling input information within the embryo due to the gradient, the cells transduce the varying extracellular information into distinct gene expression profiles and cell fate decisions. Furthermore, BMP proteins bear important functions in adult organisms like tissue homeostasis or regeneration. In contrast to TGF-ß signaling, currently only little is known about how cells decode and quantify incoming BMP signals. There is poor knowledge about the quantitative relationships between signal input, transducing molecules, their states and location, and finally their ability to incorporate graded systemic inputs and produce qualitative responses. A key requirement for efficient pathway modulation is the complete comprehension of this signaling network on a quantitative level as the BMP signaling pathway, just like many other signaling pathways, is a major target for medicative interference. I therefore at first studied the subcellular distribution of Smad1, which is the main signal transducing protein of the BMP signaling pathway, in a quantitative manner and in response to various types and levels of stimuli in murine c2c12 cells. Results indicate that the subcellular localization of Smad1 is not dependent on the initial BMP input. Surprisingly, only the phospho-Smad1 level is proportionally associated to ligand concentration. Furthermore, the activated transducer proteins were entirely located in the nucleus. Besides the subcellular localization of Smad1, I have analyzed the gene expression profile induced by BMP signaling. Therefore, I examined two endogenous immediate early BMP targets as well as the expression of the stably transgenic Gaussia Luciferase. Interestingly, the results of these independent experimental setups and read-outs suggest oscillating target gene expression. The amplitudes of the oscillations showed a precise concentration-dependence for continuous and transient stimulation. Additionally, even short-time stimulation of 15’ activates oscillating gene-expression pulses that are detectable for at least 30h post-stimulation. Only treatment with a BMP type I receptor kinase inhibitor leads to the complete abolishment of the target gene expression. This indicated that target gene expression oscillations depend directly on BMP type I receptor kinase activity.
A large number of metabolic waste products accumulate in the blood of patients with renal failure. Since these solutes have deleterious effects on the biological functions, they are called uremic toxins and have been classified in three groups: 1) small water soluble solutes (MW < 500 Da), 2) small solutes with known protein binding (MW < 500 Da), and 3) middle molecules (500 Da < MW < 60 kDa). Protein bound uremic toxins are poorly removed by conventional hemodialysis treatments because of their high protein binding and high distribution volume. The prototypical protein bound uremic toxins indoxyl sulfate (IS) and p-cresyl sulfate (pCS) are associated with the progression of chronic kidney disease, cardiovascular outcomes, and mortality of patients on maintenance hemodialysis. Furthermore, these two compounds are bound to albumin, the main plasma protein, via electrostatic and/or Van-der-Waals forces. The aim of the present thesis was to develop a dialysis strategy, based on the reversible modification of the ionic strength in the blood stream by increasing the sodium chloride (NaCl) concentration, in order to enhance the removal of protein bound substances, such as IS and pCS, with the ultimate goal to improve clinical patient outcomes. Enhancing the NaCl concentration ([NaCl]) in both human normal and uremic plasma was efficient to reduce the protein bound fraction of both IS and pCS by reducing their binding affinity to albumin. Increasing the ionic strength was feasible during modified pre-dilution hemodiafiltration (HDF) by increasing the [NaCl] in the substitution fluid. The NaCl excess was adequately removed within the hemodialyzer. This method was effective to increase the removal rate of both protein bound uremic toxins. Its ex vivo hemocompatibility, however, was limited by the osmotic shock induced by the high [NaCl] in the substituate. Therefore, modified pre-dilution HDF was further iterated by introducing a second serial cartridge, named the serial dialyzers (SDial) setup. This setting was validated for feasibility, hemocompatibility, and toxin removal efficiency. A better hemocompatibility at similar efficacy was obtained with the SDial setup compared with the modified pre-dilution HDF. Both methods were finally tested in an animal sheep model of dialysis to verify biocompatibility. Low hemolysis and no activation of both the complement and the coagulation systems were observed when increasing the [NaCl] in blood up to 0.45 and 0.60 M with the modified pre-dilution HDF and the SDial setup, respectively. In conclusion, the two dialysis methods developed to transitory enhance the ionic strength in blood demonstrated adequate biocompatibility and improved the removal of protein bound uremic toxins by decreasing their protein bound fraction. The concepts require follow-on clinical trials to assess their in vivo efficacy and their impact on long-term clinical outcomes.
The role of meiotic nuclear envelope components in chromosome dynamics and meiotic progression
(2013)
Meiosis is the specialised cell division which produces haploid germ cells, capable of developing into fertile gametes, from diploid progenitor cells. During meiosis, chromosomes undergo strictly regulated and strongly conserved dynamic processes, at the beginning of which the telomeres are actively tethered and intimately attached to the nuclear envelope (NE). The attached telomeres are then moved within the NE through cytoskeletal forces to cluster within a restricted region, forming the highly conserved bouquet stage. Subsequently, the bouquet is released simultaneously to the completion of the synaptonemal complex assembly tightly linking homologous chromosome pairs together. In combination these processes are essential for the successful completion of meiosis. Because the meiotic NE serves as a platform for telomere attachment and movement it can be assumed to be critically involved in these events crucial for fertility. However, the precise roles of many meiotic NE proteins in the attachment and movement of telomeres still remain elusive. Therefore, it was the aim of this thesis to investigate the functions of two mammalian meiotic NE components in telomere attachment and dynamics. The first part of this thesis is concerned with the meiosis-specific lamin C2. Lamin C2 is the only A-type lamin expressed during meiosis and has in previous studies shown to feature altered meiosis-specific properties, clearly distinguishing it from somatic lamins. Because lamin C2 is enriched at sites of telomere attachment, exhibits a high mobility within the nuclear lamina and influences NE integrity, it has been postulated that it may locally increase NE flexibility to allow efficient meiotic telomere movement. Therefore, possible functions of lamin C2 in the movement of attached telomeres were investigated in this thesis by studying the bouquet formation and release of pubertal mice specifically lacking lamin C2. This revealed that lamin C2 deficient mice show a delayed bouquet release, leading to severe defects in the synaptic pairing of homologous chromosomes, which in turn results in infertility of the males. Therefore, the efficient repositioning of attached meiotic telomeres, facilitated by lamin C2, seems essential for completing meiosis. The second part of this thesis focuses on the protein complex responsible for the attachment of meiotic telomeres to the NE and their coupling to the cytoskeleton. The so-called LINC complex is composed of SUN domain proteins in the inner nuclear membrane interacting with KASH domain proteins of the outer nuclear membrane. In previous studies it had been shown that SUN1, SUN2 and KASH5 localise to the attached meiotic telomeres. Regarding the meiotic role of SUN2, however, contradicting results have recently been discussed, showing the need for further investigations. Using an available SUN1 deficient mouse strain, this thesis was able to show that SUN2 is sufficient for telomere attachment per se although telomere attachment is impaired in SUN1 deficient mice leading to infertility. It is also demonstrated that SUN2 forms a functional LINC complex together with KASH5 to mediate this telomere attachment. This LINC complex in the absence of SUN1 is able to move attached telomeres into a bouquet-like cluster formation. Therefore, this demonstrates that SUN2 is involved in the functional attachment and movement of meiotic telomeres. In summary, this thesis has shown SUN2 and the meiotic nuclear lamina to be directly involved in or essential for the highly conserved attachment and movement of telomeres, making them critical for a successful meiosis. The meiotic NE is therefore in this thesis demonstrated to be a determinant of mammalian fertility.
The Xiphophorus melanoma system is a useful animal model for the study of the genetic basis of tumor formation. The development of hereditary melanomas in interspecific hybrids of Xiphophorus is connected to pigment cell specific overexpression of the mutationally activated receptor tyrosine kinase Xmrk. In purebred fish the oncogenic function of xmrk is suppressed by the molecularly still unidentified locus R. The xmrk oncogene was generated by a gene duplication event from the Xiphophorus egfrb gene and thereby has acquired a new 5’ regulatory sequence, which has probably altered the transcriptional control of the oncogene. So far, the xmrk promoter region was still poorly characterized and the molecular mechanism by which R controls xmrk-induced melanoma formation in Xiphophorus still remained to be elucidated. To test the hypothesis that R controls melanoma development in Xiphophorus on the transcriptional level, the first aim of the thesis was to gain a deeper insight into the transcriptional regulation of the xmrk oncogene. To this end, a quantitative analysis of xmrk transcript levels in different Xiphophorus genotypes carrying either the highly tumorigenic xmrkB or the non-tumorigenic xmrkA allele was performed. I was able to demonstrate that expression of the tumorigenic xmrkB allele is strongly increased in malignant melanomas of R-free backcross hybrids compared to benign lesions, macromelanophore spots, and healthy skin. The expression level of the non-tumorigenic xmrkA allele, in contrast, is not influenced by the presence or absence of R. These findings strongly indicate that differential transcriptional regulation of the xmrk promoter triggers the tumorigenic potential of these xmrk alleles. To functionally characterize the xmrk promoter region, I established a luciferase assay using BAC clones containing the genomic regions where xmrk and egfrb are located for generation of reporter constructs. This approach showed for the first time a melanoma cell specific transcriptional activation of xmrkB by its flanking regions, thereby providing the first functional evidence that the xmrk oncogene is controlled by a pigment cell specific promoter region. Subsequent analysis of different deletion constructs of the xmrkB BAC reporter construct strongly indicated that the regulatory elements responsible for the tumor-inducing overexpression of xmrkB in melanoma cells are located within 67 kb upstream of the xmrk oncogene. Taken together, these data indicate that melanoma formation in Xiphophorus is regulated by a tight transcriptional control of the xmrk oncogene and that the R locus acts through this mechanism. As the identification of the R-encoded gene(s) is necessary to fully understand how melanoma formation in Xiphophorus is regulated, I furthermore searched for alternative R candidate genes in this study. To this end, three genes, which are located in the genomic region where R has been mapped, were evaluated for their potential to be a crucial constituent of the regulator locus R. Among these genes, I identified pdcd4a, the ortholog of the human tumor suppressor gene PDCD4, as promising new candidate, because this gene showed the expression pattern expected from the crucial tumor suppressor gene encoded at the R locus.
Many ant species excavate underground nests. One of the most impressive examples is the Chaco leaf-cutting ant Atta vollenweideri from the Gran Chaco region in South America. The nests excavated by the workers of that species are among the largest insect-built structures on the planet. They are ecavated over years possibly involving millions of working individuals. However, the mechanisms underlying the organisation of collective nest digging in ants remain largely unknown. Considering the sheer dimensions of the nest in comparison to the size and presumably limited perceptual and cognitive abilities of the single worker, the assumption can be made that organising mechanisms are mostly based on responses of individuals to local stimuli within their perceptual range. Among these local stimuli that guide nest digging we can expect environmental variables, stimuli that relate to the requirements of the colony, and stimuli related to the spatial coordination of collective effort. The present thesis investigates the role of local stimuli from these three categories in the organisation of collective digging behaviour in the Chaco leaf-cutting ant. It describes experiments on (1) how workers respond in the context of digging to differences in soil moisture, which comprises an important environmental variable; (2) how available nest space influences nest enlargement; (3) and how the spatial coordination of excavating workers is implemented by responding to stimuli arising from nest mates while engaged in digging behaviour. The experiments on soil water content show that workers prefer to dig in moist materials that allow for fast excavation and transport rates. Accordingly, an unequal distribution of water in the soil around a nest can influence how the nest shape develops. On the other hand, results also indicate that workers strongly avoid excavating in extremely moist materials. Regarding the abundant occurrence of flooding events in the Gran Chaco region, the latter can be interpreted as an adaptation to avoid water inflow into the nest. In the experiments on the effect of nest space, the ants excavated less when presented with larger nests. When a large amount of space was suddenly added to the nest during the digging process, excavation rates decreased according to the new volume. These observations confirm the hypothesis that digging activity is regulated according to space requirements, possibly because crowding conditions inside the nest influence excavation behaviour. However, observations also indicate an intrinsic decrease of digging motivation with time. Moreover, excavation rates correlate with nest size only when comparing nests of similar shape. Distributing a similar nest volume to three smaller chambers, instead of one, resulted in drastically decreased digging rates. A possible explanation for that observation lies in the distribution of workers inside the nest that may vary according to nest geometry: a different distribution of individuals can lead to in different local crowding conditions in similar nest volumes. Furthermore, two different stimuli are described that are used in the spatial coordination of collective digging effort. First, fresh soil pellets deposited close to the digging site on their way from the surface increase the probability that arriving workers join excavation efforts at the same site. The deposition of pellets on the way is a consequence of sequential task partitioning during soil transport. The pellets are carried in transport chains that closely resemble the modalities of leaf transport observed at the surface. Second, workers stridulate while digging. The short-ranged vibrational signals produced thereby also attract nest mates to excavate at the same location. Accordingly, two mutually complementing mechanisms are described that allow to concentrate excavators at one location. In both cases, a local stimulus that is generated by current close-by excavation activity increases the probability of the stimulus receiver to dig close to other excavators. In an environment otherwise poor in digging stimuli, these mechanisms can be especially important to give collective digging efforts a common direction. As a consequence it can be argued that the spatial organisation of collective digging is based on choice copying. Individuals copy nest mate decisions on where to excavate by responding to local stimuli provided by nest mate digging activity. Taken together, responses to local stimuli can determine the direction of nest growth, aid in preventing the inflow of surface water into the nest, guide the adjustment of nest size to colony requirements and spatially coordinate collective digging efforts. Even though it cannot be ruled out that digging responses based e.g. on spatial memory or long-term experience exist, the results presented here clearly demonstrate that responses to local information account for many important aspects of nest development.
The neuronal ceroid lipofuscinoses (NCLs) are fatal neurodegenerative disorders in which the visual system is affected in early stages of disease. A typical accompanying feature is neuroinflammation, the pathogenic impact of which is presently unknown. In this study, the role of inflammatory cells in the pathogenesis was investigated in Palmitoyl-protein thioesterase 1-deficient (Ppt1-/-) and Ceroidlipofuscinosis, neuronal 3-deficient (Cln3-/-) mice, models of the infantile and juvenile forms of NCL, respectively. Focusing predominantly on the visual system, an infiltration of CD8+ cytotoxic Tlymphocytes and an activation of microglia/macrophage-like cells was observed early in disease. To analyze the pathogenic impact of lymphocytes, Ppt1-/- mice were crossbred with mice lacking lymphocytes (Rag1-/-) and axonal transport, perturbation and neuronal survival were scored. Lack of lymphocytes led to a significant amelioration of neuronal disease and reconstitution experiments revealed a crucial role of CD8+ cytotoxic T-lymphocytes. Lack of lymphocytes also caused an improved clinical phenotype and extended longevity. To investigate the impact of microglia/macrophage-like cells, Ppt1-/- and Cln3-/- mice were crossbred with mice lacking sialoadhesin (Sn-/-), a monocyte lineage-restricted cell adhesion molecule important for interactions between macrophage-like cells and lymphocytes. Similar to the lack of lymphocytes, absence of sialoadhesin significantly ameliorated the disease in Ppt1-/- and Cln3-/- mice. Taken together, both T-lymphocytes and microglia/macrophage-like cells were identified as pathogenic mediators in two distinct forms of fatal inherited neurodegenerative storage disorders. These studies expand the concept of secondary inflammation as a common pathomechanistic feature in some neurological diseases and provide novel insights that may be crucial for developing treatment strategies for different forms of NCL.
Bees have had an intimate relationship with humans for millennia, as pollinators of fruit, vegetable and other crops and suppliers of honey, wax and other products. This relationship has led to an extensive understanding of their ecology and behavior. One of the most comprehensively understood species is the Western honeybee, Apis mellifera. Our understanding of sex-specific investment in other bees, however, has remained superficial. Signals and cues employed in bee foraging and mating behavior are reasonably well understood in only a handful of species and functional adaptations are described in some species. I explored the variety of sensory adaptations in three model systems within the bees. Females share a similar ecology and similar functional morphologies are to be expected. Males, engage mainly in mating behavior. A variety of male mating strategies has been described which differ in their spatiotemporal features and in the signals and cues involved, and thus selection pressures. As a consequence, males’ sensory systems are more diverse than those of females. In the first part I studied adaptations of the visual system in honeybees. I compared sex and caste-specific eye morphology among 5 species (Apis andreniformis, A. cerana, A. dorsata, A. florea, A. mellifera). I found a strong correlation between body size and eye size in both female castes. Queens have a relatively reduced visual system which is in line with the reduced role of visual perception in their life history. Workers differed in eye size and functional morphology, which corresponds to known foraging differences among species. In males, the eyes are conspicuously enlarged in all species, but a disproportionate enlargement was found in two species (A. dorsata, A. florea). I further demonstrate a correlation between male visual parameters and mating flight time, and propose that light intensities play an important role in the species-specific timing of mating flights. In the second study I investigated eye morphology differences among two phenotypes of drones in the Western honeybee. Besides normal-sized drones, smaller drones are reared in the colony, and suffer from reduced reproductive success. My results suggest that the smaller phenotype does not differ in spatial resolution of its visual system, but suffers from reduced light and contrast sensitivity which may exacerbate the reduction in reproductive success caused by other factors. In the third study I investigated the morphology of the visual system in bumblebees. I explored the association between male eye size and mating behavior and investigated the diversity of compound eye morphology among workers, queens and males in 11 species. I identified adaptations of workers that correlate with distinct foraging differences among species. Bumblebee queens must, in contrast to honeybees, fulfill similar tasks as workers in the first part of their life, and correspondingly visual parameters are similar among both female castes. Enlarged male eyes are found in several subgenera and have evolved several times independently within the genus, which I demonstrate using phylogenetic informed statistics. Males of these species engage in visually guided mating behavior. I find similarities in the functional eye morphology among large-eyed males in four subgenera, suggesting convergent evolution as adaptation to similar visual tasks. In the remaining species, males do not differ significantly from workers in their eye morphology. In the fourth study I investigated the sexual dimorphism of the visual system in a solitary bee species. Males of Eucera berlandi patrol nesting sites and compete for first access to virgin females. Males have enlarged eyes and better spatial resolution in their frontal eye region. In a behavioral study, I tested the effect of target size and speed on male mate catching success. 3-D reconstructions of the chasing flights revealed that angular target size is an important parameter in male chasing behavior. I discuss similarities to other insects that face similar problems in visual target detection. In the fifth study I examined the olfactory system of E. berlandi. Males have extremely long antennae. To investigate the anatomical grounds of this elongation I studied antennal morphology in detail in the periphery and follow the sexual dimorphism into the brain. Functional adaptations were found in males (e.g. longer antennae, a multiplication of olfactory sensilla and receptor neurons, hypertrophied macroglomeruli, a numerical reduction of glomeruli in males and sexually dimorphic investment in higher order processing regions in the brain), which were similar to those observed in honeybee drones. The similarities and differences are discussed in the context of solitary vs. eusocial lifestyle and the corresponding consequences for selection acting on males.
Background: Measles virus (MV) causes T cell suppression by interference with phosphatidylinositol-3-kinase (PI3K) activation. We previously found that this interference affected the activity of splice regulatory proteins and a T cell inhibitory protein isoform was produced from an alternatively spliced pre-mRNA. Hypothesis: Differentially regulated and alternatively splice variant transcripts accumulating in response to PI3K abrogation in T cells potentially encode proteins involved in T cell silencing. Methods: To test this hypothesis at the cellular level, we performed a Human Exon 1.0 ST Array on RNAs isolated from T cells stimulated only or stimulated after PI3K inhibition. We developed a simple algorithm based on a splicing index to detect genes that undergo alternative splicing (AS) or are differentially regulated (RG) upon T cell suppression. Results: Applying our algorithm to the data, 9% of the genes were assigned as AS, while only 3% were attributed to RG. Though there are overlaps, AS and RG genes differed with regard to functional regulation, and were found to be enriched in different functional groups. AS genes targeted extracellular matrix (ECM)-receptor interaction and focal adhesion pathways, while RG genes were mainly enriched in cytokine-receptor interaction and Jak-STAT. When combined, AS/RG dependent alterations targeted pathways essential for T cell receptor signaling, cytoskeletal dynamics and cell cycle entry. Conclusions: PI3K abrogation interferes with key T cell activation processes through both differential expression and alternative splicing, which together actively contribute to T cell suppression.