Winter 1011
From EESwiki
EES and Forschergruppe Seminars take place on Mondays at 17:00h in the Biozentrum, first floor, right lecture hall.
25/10/10. Prof Laura Rose "Molecular evolution of disease resistance genes in wild tomatoes"
LMU Munich and Heinrich-Heine-Universität, Düsseldorf
Website: http://evol.bio.lmu.de/_rose/labmembers.html
Abstract: I will describe our investigations of the evolutionary history of five genes in a defense signaling pathway in wild tomatoes. Pathway theory predicts that genes that function downstream in the pathway, which serve as convergence points for upstream signals, should show greater evolutionary constraint. We find that two of the upstream genes evolve under strong evolutionary constraint, while the other genes, which operate further downstream in the pathway, show evidence of balancing selection. This counterintuitive observation may be likely in pathways involved in pathogen defense. Pathogens may specifically target downstream positions in resistance pathways to manipulate or nullify host resistance. However, plants also express pathogen specific receptors that function upstream in resistance pathways and activate the resistance responses upon pathogen detection. Therefore, it is likely that genes throughout defense pathways serve as targets for coevolution between hosts and pathogens.
Contact person: John Parsch <parsch"at"bio.lmu.de>
15/11/10. Prof William Martin "Endosymbiosis, anaerobes, and the origin of eukaryotes"
Institut fur Botanik III, Heinrich-Heine-Universität, Düsseldorf, Germany
Website: http://www.molevol.de/lab/martin.html
Abstract: All complex life is composed of eukaryotic (nucleated) cells. The eukaryotic cell arose from prokaryotes just once in four billion years, and otherwise prokaryotes show no tendency to evolve greater complexity. Why not? Prokaryotic genome size is constrained by bioenergetics. The endosymbiosis that gave rise to mitochondria restructured the distribution of DNA in relation to bioenergetic membranes, permitting a remarkable 200,000-fold expansion in the number of genes expressed. This vast leap in genomic capacity was strictly dependent on mitochondrial power, and prerequisite to eukaryote complexity: the key innovation en route to multicellular life. Without mitochondria, prokaryotes-even giant polyploids-cannot pay the energetic price of complexity; the lack of true intermediates in the prokaryote-to-eukaryote transition has a bioenergetic cause.
Contact person: Winfried Hense <hense"at"bio.lmu.de>
16/11/10 (15:30). Prof Eörs Szathmáry "Evolution and the Origin of Life"
The Parmenides Foundation Pullach/München Collegium Budapest(Institute for Advanced Study)
Website: http://www.colbud.hu/fellows/szathmary.shtml
Abstract:Life is a symbiosis between templates, metabolism and membranes. The question is how such systems could have self-assembled in early chemical and biological evolution. Synthesis of organics can be achieved by various means, but we should also enquire about the origin of chemical supersystems, out of which some will show characteristics of life. The main problem of the origin of life is the notorious presence of side reactions. In contemporary living systems enzymes are sufficient to ensure that required reactions win over side reactions, but of course one cannot start with enzymes in the earliest times. Spontaneous degradation of molecules, high mutation rates, nucleotide elongation competing with replication, and tar formation are all plagues to our understanding how life could have originated. The RNA world idea at least helps us separate the very problem of the origin of life from that of the genetic code. Snags are that we do not know where RNA came from and we still do not have a functioning replicase ribozyme. Even if the replication problem is solved, we still need to solve the earliest appearances of intragenomic conflict. I shall analyze various models and offer a few conclusions regarding the first major transitions in the history of life.
Contact person: Forschergruppe, John Parsch <parsch"at"bio.lmu.de>
22/11/10. Dr Joanna Rutkowska "Offspring sex adjustment in birds: current evidence and future directions"
Institute of Environmental Sciences, Jagiellonian University, Krakow, Poland
Website: http://www.eko.uj.edu.pl/rutkowska/pro_e.htm
Abstract: Female birds have been repeatedly reported to overcome the rigid process of chromosomal sex determination, adjusting primary sex ratio of their offspring to environmental, social and physiological cues. Firstly, I review some of the most famous examples of such manipulation. Secondly, I present series of experiments on zebra finches (Taeniopygia guttata) that looked at the physiological mechanism of offspring sex ratio manipulation. I demonstrate that the mechanism might be very precise and thus allow for fast reaction to changing environmental/social conditions, yet it is not free from constrains. Finally, I suggest potential proximate mechanisms of offspring sex manipulation at the cellular level.
Contact person: Justyna Wolinska <wolinska"at"bio.lmu.de>
29/11/10. Prof Hans Stenoien "Phylogeography of peat mosses (Sphagnum): globetrotters or unmoving sphinxes from the past?"
Norwegian University of Science and Technology, Trondheim, Norway
Website: http://www.ntnu.edu/employees//hans.stenoien
Abstract: Genetic and morphological similarity between populations separated by large distances may be caused by frequent long-distance dispersal or retained ancestral polymorphism. The frequent lack of differentiation between disjunct conspecific moss populations on different continents has traditionally been explained by the latter model, and has been cited as evidence that many or most moss species are extremely ancient and slowly diverging. Peat mosses (genus Sphagnum) constitute a major part of northern hemisphere wetland and mire biodiversity. Recent studies show that despite the ancient divergence between Sphagnum and other mosses, and despite their widespread occurrence, high diversity and ecological importance, extant Sphagnum species are surprisingly young. On the other hand, highly disjunct populations often show high genetic similarity, even in species seemingly lacking means for long-distance dispersal. Here I will present results from recent studies on Sphagnum phylogeography.
Contact person: Forschergruppe: John Parsch <parsch"at"bio.lmu.de>
06/12/10. Dr Francis Jiggins "The evolution of the Drosophila immune system"
Department of Genetics, University of Cambridge, UK
Website: http://www.gen.cam.ac.uk/research/Jiggins/
Abstract: Hosts and pathogens are engaged in a never-ending battle of adaptation and counter-adaptation. In Drosophila, viruses are the most important group of pathogens known in the wild, and we have found that genes involved in the antiviral immune system evolve exceptionally fast and experience frequent selective sweeps. In natural populations resistance to viruses is controlled by major-effect polymorphisms, and in several cases the resistant allele has arisen recently and is sweeping through the population under directional selection. Our results suggest that resistance to viruses often evolves through major changes to the proteins involved in antiviral immunity, and studying these genes is providing new insights into the mechanisms by which insects can evolve resistance to viruses.
Contact person: Aurelien Tellier <tellier"at"bio.lmu.de>
13/12/10. Prof Andreas Wagner "The origins of evolutionary innovations"
Department of Biochemistry, University of Zurich, Switzerland
Website: http://www.bioc.uzh.ch/wagner/
Abstract: Life can be viewed as a four billion year long history of innovations. These range from dramatic macroscopic innovations like the evolution of wings or eyes, to a myriad molecular changes that form the basis of macroscopic innovations. We know many examples of innovations -- qualitatively new phenotypes that can provide a critical advantage in the right environment -- but have no systematic understanding of the principles that allow organisms to innovate. Most phenotypic innovations result from changes in three classes of systems: metabolic networks, regulatory circuits, and protein or RNA molecules. I will discuss evidence that these classes of systems share two important features that are essential for their ability to innovate.
Contact person: Pavlos Pavlidis <pavlidis"at"bio.lmu.de>
10/01/11. Prof Asger Hobolth "Estimating Ancestral Population Parameters"
Department of Mathematical Sciences, Aarhus University, Denmark
Website: http://www.daimi.au.dk/~asger/index.html
Abstract: For closely related species, the evolutionary history of an individual gene need not reflect the history of species divergences. Partly because of gene tree discordance, phylogenies of species reconstructed from different parts of a genome may suggest different relationships among the various species. We are developing theory that takes gene tree discordance into account, and we use the phenomenon to estimate population genetic parameters for closely related species. I will broadly discuss the methodology that we use for analysing various types of population genetic data sets.
Contact person: Forschergruppe: John Parsch <parsch"at"bio.lmu.de>
17/01/11. Dr Floyd Reed "Underdominance Predictions and Population Transformations"
Max-Planck Institute for Evolutionary Biology, Ploen, Germany
Website: http://www.evolbio.mpg.de/~reed/
Abstract: Interest has been rapidly increasing in recent years in using genetic systems to manage wild insect populations. This ranges from population suppression using sterile insect technique to genetically transforming a population with desirable alleles using "selfish" genetic systems. However, many of these population transformation approaches are not predicted to be spatially contained or reversible (able to be completely removed from the wild). Underdominace is an "old" idea that we are revisiting as a method to transform populations with desirable alleles in a safe and reversible fashion. Underdominant constructs, under certain conditions, are not predicted to spread far from population to population by migration, and conditions exist where these genetic modifications can be completely removed from the wild by natural selection.
Contact person: Forschergruppe: John Parsch <parsch"at"bio.lmu.de>
24/01/11. Prof Henrik Kaessmann "Comparative RNA sequencing reveals the evolution of gene expression in mammalian organs"
Center for Integrative Genomics, University of Lausanne, Switzerland
Website: http://www.unil.ch/cig/page7858_en.html
Abstract: Evolutionary changes in gene regulation have long been thought to underlie most phenotypic differences between species. However, evolutionary analyses of gene expression variation were long hampered by the limitations of microarrays for between-species comparisons. The recent development of RNA sequencing now affords essentially unbiased transcriptome comparisons at unprecedented resolution. We have generated detailed qualitative and quantitative transcriptome data using next generation sequencing technologies for a unique collection of germline and somatic tissues from representatives of all major mammalian lineages: placental mammals (humans, apes, monkeys, rodents), marsupials (gray short-tailed opossum), and the egg–laying monotremes (platypus). Our comparative and evolutionary analyses of these unprecedented data provide detailed insights into patterns of gene expression change in mammals and the underlying evolutionary forces. The data also allow us to explore, for the first time, the relevance of observed gene expression changes for the evolution of mammalian phenotypes.
Contact person: Forschergruppe: John Parsch <parsch"at"bio.lmu.de>
31/01/11. Prof Janis Antonovics "Evolution of host-pathogen genetic systems: from plants to humans"
Department of Biology, University of Virginia, USA
Website: http://people.virginia.edu/~ja8n/labhome/homepage.htm
Abstract: Genetic variation in host resistance to pathogens is sometimes essentially absent, whereas at other times it exhibits complex, Rococco-like, genetics. We don't know why. I will present our recent studies addressing this question, namely, (a) evolution of genetic specificity in the flax-rust gene-for-gene system, (b) co-evolution between resistance pathways that are independent at the molecular level, and (c) a comparative study of human genetic variation in resistance to different infectious diseases.
Contact person: Laura Rose <rose"at"bio.lmu.de>
07/02/11. Dr Lluis Quintana-Murci "From evolutionary genetics to human immunology: of natural selection and infectious disease"
Human Evolutionary Genetics, Department Genomes and Genetics, Institut Pasteur, Paris, France
Website: http://www.pasteur.fr/ip/easysite/go/03b-00003g-0v8
Abstract: The past few years have seen an increase in studies that aim to characterize how natural selection has targeted regions of the human genome. The (re)emergence of the field of evolutionary genetics has been bolstered by the advent of massive genome-wide surveys of genetic variation based on genotyping and resequencing data in human populations. Because infection has always been a major cause of human mortality, natural selection is expected to act strongly on host defence genes. This is particularly expected for innate immunity genes, as they represent the first line of host defence against pathogens. I will present different cases of how some of these genes and the pathways they trigger have been targeted by natural selection, in its different forms and intensities. I will also illustrate how these findings are helping to delineate genes that are important for host defence, with respect to those exhibiting higher immunological redundancy, and to increase our understanding of how past selection has had an impact on disease susceptibility in modern populations.
Contact person: Anja Hoerger <hoerger"at"bio.lmu.de>
