37 research outputs found

    Molecular mechanisms of environmental signal reception in mouth-form and dauer polyphenism in Pristionchus pacificus

    Get PDF
    Entwicklungsplastizität beschreibt die Fähigkeit eines Genoms, unterschiedliche Phänotypen in unterschiedlichen Umgebungen auszubilden. Obwohl das Phänomen oft in der Natur vorkommt sind die genetischen Mechanismen sowie die Gewebe, die dafür verantwortlich sind, Signal aus der Umwelt in den Entwicklungsprozess zu integrieren, noch nicht genügend erforscht. Diskrete Fälle von Entwicklungsplastizität, auch Polyphänismen genannt, eignen sich aufgrund der klaren Beziehung zwischen Umweltsginal und ausgebildetem Phänotyp sowie der einfachen Identifizierung des Phänotypen besonders gut für die Erforschung der molekularen Steuerung von Entwicklungsplastizität. Das am umfassendsten beschriebene Regulationsnetzwerk eines Polyphänismus unterliegt der Bildung von Dauerlarven im Modellorganismus Caenorhabditis elegans. Um die allgemeinen Prinzipien polyphäner Regulation zu verstehen, bedarf es jedoch eines vergleichenden Ansatzes. Auch bei Pristionchus pacificus, einer Spezies von Fadenwürmern aus der Familie der Diplogastridae, tritt der Polyphänismus der Dauerlarven auf; zudem verfügt die Spezies über einen weiteren Polyphänismus der Mundform (fleischfressende und bakterienfressende Morphe). Das Netzwerk an genetischen Schaltpunkten dieses Polyphänismus wurde bereits gut untersucht, doch eine detaillierte Beschreibung der molekularen Prozesse an den für Sinnesreize verantwortlichen Zilien blieb bislang noch aus. In dieser Arbeit untersuche ich die rezeptiven Mechanismen, die der Integration von Signalen aus der Umweltbei der Entwicklung der Polyphänismen in P. pacificus zugrundeliegen. Das erste Projekt untersuchte die Entwicklung und Rolle der primären Zilien in P. pacificus mithilfe eines Kandidatengen Ansatzes. Obwohl die Entwicklung primärer Zilien in P. pacificus und C. elegans größtenteils konserviert ist, konnten wir beschreiben, wie P. pacificus’ Dauerlarven in kontrastierender Weise durch rezeptive molekularen Pfade reguliert werden, die in den sensorischen Zilien ausgedrückt werden.Damit werden frühere Befunde untermauert, die die Divergenz der Chemotaxis-Präferenzen zwischen C. elegans und P. pacificus Dauerlarven und die Entdeckung des Käfer-Sex-Pheromon-Rezeptors OBI-1 in P. pacificus zeigten. Unsere Studie konkretisiert damit frühere Spekulationen über die schnelle Entwicklung molekularer Signalwege von Polyphänismen zwischen verschiedenen Arten. Die Entdeckung des Mundform-Phänotyps bei Mutanten, denen die sensorischen Flimmerhärchen völlig fehlen, motivierte das Screening auf den Mundform-Phänotyp bei zuvor erzeugten Mutanten der Komponenten der sensorischen Flimmerhärchen. Dies führte zur Entdeckung unterschiedlicher Rollen einzelner Komponenten bei der Regulierung des Mundform-Polyphänismus, wobei der anterograde Transport vermutlich die Hauptrolle bei der Bildung des fleischfressenden Morphs spielt. Das zweite große Projekt verwendete eine EMS-Mutagenese, um die rezeptiven Wege zu untersuchen, die Umgebungstemperatur in die Ausbildung des Mundform-Dimorphismus integrieren, was zur Entdeckung des sensorischen Zilien-assoziierten-cGMP-Signalweges führte, dessen Rolle zuvor in C. elegans’ Dauerlarven beschrieben wurde. Interessanterweise weisen Mutanten dieses Signalweges, wie auch im Fall des vollständigen Verlustes der Zilien, eine gegensätzliche Rolle bei der Dauerpolyphenese in C. elegans und P. pacificus auf. Beide Projekte zeigen, dass verschiedene Umweltreize, die die Mundform beeinflussen, weit upstream durch pleiotrope rezeptive Moleküle integriert werden. Diese Arbeit liefert eine umfassende vergleichende Beschreibung der molekularen Signalwege oberhalb der genetischen Schalter, die den Mundform-Polyphenismus bei P. pacificus regulieren.Developmental plasticity is the ability of a genome to change its phenotype across heterogeneous environments. Although it is a common phenomenon in nature, the receptive molecular pathways and sensory tissues which integrate environmental signals into development are not well investigated yet. Discrete cases of phenotypic plasticity, commonly known as polyphenisms, are particularly useful for the investigation of molecular regulation of developmentally plastic traits due to the clear relationship between environmental signals and phenotypes as well as due to easy identification of distinct phenotypes. The most comprehensive network of polyphenism regulation is found in dauer polyphenism in the model organism Caenorhabditis elegans. Primary cilia of sensory neurons have a major role in the perception of the environmental stimuli which regulate dauer formation in C. elegans. However, a comparative approach is necessary to explore general principles. The diplogastrid nematode Pristionchus pacificus shares a dauer polyphenism with C. elegans, and has an additional polyphenism of mouth-structures (carnivorous and bacteriovorus morph). While the switch network of mouth-form polyphenism is well investigated, the molecular machinery of sensory cilia has not been investigated so far. This thesis addresses the role of far upstream molecular pathways, which integrate aspects of the environment into development. The first major project included an investigation of the development and role of primary sensory cilia in P. pacificus through a candidate approach. Results showed that, while the development of sensory cilia is highly conserved between C. elegans and P. pacificus, dauers in P. pacificus are regulated in a contrasting manner by the receptive molecular pathways expressed in the sensory cilia in P. pacificus and C. elegans. These results, advance previous findings, which showed the divergence in chemotaxis preferences between the two species’ respective dauers and the discovery of the beetle sex pheromone receptor OBI-1 in P. pacificus. Our study fleshes out previous speculations that the receptive molecular pathways of polyphenism evolve fast between different species. The discovery of mouth-form phenotype in mutants completely lacking sensory cilia motivated the screen for mouth-form phenotype across previously generated mutants of the components of sensory cilia, which led to discovery of contrasting roles of individual components in mouth-form polyphenism regulation, with anterograde transport presumably having the strongest role in the formation of the carnivorous morph. The second major project used an unbiased approach via EMS mutagenesis to investigate the receptive pathways which integrate temperature into mouth-form dimorphism which resulted in the discovery of sensory cilia associated-cGMP signalling pathway, a role similar to what has previously been described in the dauer polyphenism in C. elegans. Interestingly, as in the case of complete loss of cilia, mutants of this pathway have a contrasting role in dauer formation between C. elegans and P. pacificus. Both projects showed that different environmental stimuli relevant for determining the mouth-form are integrated far upstream through pleiotropic receptive molecules. This thesis provides a comprehensive comparative description of molecular pathways that regulate mouth-form polyphenism in P. pacificus

    The evolution of language: Proceedings of the Joint Conference on Language Evolution (JCoLE)

    Get PDF

    Probabilidades Variacionales y Propensiones del Desarrollo: Un Estudio Filosófico del Azar en la Variación Evolutiva

    Get PDF
    Tesis inédita de la Universidad Complutense de Madrid, Facultad de Filosofía, leída el 09/11/2020The ongoing debate over a possible extension of the explanatory corpus of evolutionary biology touches many aspects of philosophical interest, among which is the role that chance plays in its models and explanations. In particular, how evolutionary variation relates to chance seems to differ under the classical and the evo-devo perspectives. While some tools of the philosophy of probability and chance have been incorporated into important aspects of evolutionary biology, this discrepancy has not been considered from this perspective. In this dissertation, Iintend to bridge part of this gap by endorsing a conception of chance in the generation of evolutionary variation that is the result of incorporating several conceptual tools from the philosophy of probability and chance into different views over the nature of evolutionary variation. My aim is to clarify the distinct roles that chance in variation plays in the field of evo-devo as compared with classical evolutionary genetics. I depart from the construction of a suitable philosophical framework about the representative role of probabilities in evolutionary disciplines and the type of explanatory causes that are responsible for them...El actual debate sobre una posible extensión del corpus explicativo de la biología evolutiva recoge muchos aspectos de interés filosófico, entre los que se encuentra el rol del azar en sus modelos y explicaciones. En particular, la relación entre la variación evolutiva y el azar parece ser muy distinto bajo las perspectivas clásica y dela evo-devo. Mientras que algunas herramientas de la filosofía de la probabilidad y el azar han sido incorporadas en aspectos importantes de la biología evolutiva, esta disparidad no ha sido considerada desde esta perspectiva. En esta tesis, mi intención es aliviar parcialmente esta carencia defendiendo una noción de azar en la generación de la variación evolutiva que es el resultado de incorporar varias herramientas conceptuales de la filosofía de la probabilidad a distintas perspectivas sobre su naturaleza. Mi objetivo es clarificar los distintos roles que el azar en la variación juega en el campo de la evo-devo en comparación con la genética evolutiva clásica. Comienzo con la construcción de un marco filosófico que considera el rol representativo de la probabilidad en las disciplinas evolutivas y el tipo de causas explicativas que son responsables de ella...Fac. de FilosofíaTRUEunpu

    How to build a biological machine using engineering materials and methods

    Get PDF
    We present work in 3D printing electric motors from basic materials as the key to building a self-replicating machine to colonise the Moon. First, we explore the nature of the biological realm to ascertain its essence, particularly in relation to the origin of life when the inanimate became animate. We take an expansive view of this to ascertain parallels between the biological and the manufactured worlds. Life must have emerged from the available raw material on Earth and, similarly, a self-replicating machine must exploit and leverage the available resources on the Moon. We then examine these lessons to explore the construction of a self-replicating machine using a universal constructor. It is through the universal constructor that the actuator emerges as critical. We propose that 3D printing constitutes an analogue of the biological ribosome and that 3D printing may constitute a universal construction mechanism. Following a description of our progress in 3D printing motors, we suggest that this engineering effort can inform biology, that motors are a key facet of living organisms and illustrate the importance of motors in biology viewed from the perspective of engineering (in the Feynman spirit of "what I cannot create, I cannot understand")

    The genetic basis of sexual antagonism in Drosophila melanogaster

    Get PDF
    The divergent reproductive roles of males and females generate sexually antagonistic selection, with different trait values favoured in each sex. Responses to these selective pressures are however constrained by the sexes’ shared genome, leading to ’sexual antagonism, where, at a given locus, opposing alleles are favoured in males and females. Sexual antagonism is a taxonomically widespread and evolutionarily important phenomenon, but the identity and characteristics of the genetic loci underlying it remain almost entirely unknown. This thesis combines experimentation, bioinformatics and theory to identify, characterise, and explore the evolution of sexually antagonistic loci. In the introduction (chapter 1), I review the literature and integrate underlying theory and key empirical findings. I then identify the first putative antagonistic variants across the Drosophila melanogaster genome by comparing the sequences of haplotypes with contrasting sex-specific fitness profiles (chapter 2). I find a substantial excess of candidate SNPs, beyond the null expectation, and show that these SNPs are a non-random subset of the genetic variation in the LHM population. In chapter 3, I characterise the functional properties of antagonistic loci using a suite of bioinformatic analyses. Here, a prominent role of gene regulation emerges. I further describe an evolve-and-resequence experiment conducted to investigate the evolution of sexually antagonistic loci under sex-limited selection (chapter 4). Here, I was able to verify a subset of the sexually antagonistic loci identified in chapter 2. In chapter 5, I build a theoretical model to investigate when and where sexually antagonistic alleles invade in gene regulatory cascades. I find sexually antagonistic polymorphism can be displaced to higher levels of the regulatory hierarchy from where it initially arises. In the general discussion (chapter 6), I place these findings into context and provide a perspective on future research prospects
    corecore