| Evolution of the gene regulatory network controlling trunk segmentation in insects | |
Abstract/OtherAbstract
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The study of pattern formation in insects is the main source of our current understanding of the genetic processes underlying the development of an organism. Ontogeny has been thoroughly studied in the model organism Drosophila melanogaster, where a set of transcription factors and signaling molecules pattern the fly embryo through a segmentation gene cascade. Over the past 20 years, this model has been compared to different organisms throughout the Metazoa. Here I describe the functional analysis of genes and gene regulatory network controlling segmentation in the short germ beetle Tribolium castaneum. The hunchback gene is one of the major early determinants in the Drosophila segmentation cascade, where it serves an instructive role in patterning the entire body plan. In several insects, the role of hb in patterning body compartments (cardinal regions) is conserved. However, in hemimetabolous insects developing as short germs hb role has been reported to differ from the canonical gap function described in holometabolous insects. In the first chapter I describe the role of hb in Tribolium, a holometabolous insect developing as short germ. This analysis revealed that Tchb has an indirect effect in segmentation, mediated by other gap genes like giant, and a most likely a direct effect in the segment identity specification, by setting the anterior border of thoracic and abdominal Hox genes. This finding suggests an ancestral role of hb as a cardinal gene within insects and allows the reinterpretation of the canonical gap phenotype described in the fly. The expression analysis of ESTs in Tribolium identified a putative non-coding RNA showing a gap-like expression pattern during segmentation. In the second chapter I describe the functional analysis of this gene, named mille-pattes. This analysis defined Tcmlpt as a novel segmentation gene in Tribolium, which controlls trunk segmentation in a cross-regulatory network among gap genes and regulates the expression domains of Hox genes. Strikingly, mlpt does not code for a transcription factor, but instead, encodes several small peptides, which are conserved among mlpt homologues in various insects. As a model, the gene regulatory network controlling segmentation in Drosophila has been thoroughly tested in many other organisms, revealing a surprising plasticity of the developmental mechanism controlling segmentation among insects. In order to identify the regulatory interactions among the gap genes that are controlling segmentation in Tribolium, I further characterized the gap gene cross-regulatory network in Tribolium and their interaction with pair rule genes. This analysis provided a powerful data set on the regulatory interactions among gap genes and their interactions with pair rule genes in Tribolium. Finally, the concomitant characterization of segmentation genes presented in this thesis allowed the reinterpretation of the role of hunchback among insects, specially the canonical gap phenotype described for Tribolium and Drosophila. Furthermore, by studying the interactions between gap and Hox genes in Tribolium it was possible to propose a model for the regulation and function of TcAntp and for the regulation of the Hox genes along the AP axis in Tribolium. |
Authors
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Marques-Souza, Henrique |
Contributors
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Publication Detail
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Publisher : Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät. Institut für Genetik Type : Text.Thesis.Doctoral Format : application/pdf |
Date Detail
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2007 |
Subject
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Segmentierung, Insekten, Gapgene, Hoxgene, Netzwerke, Segmentation, Insect, Gap gene, Hox gene, Gene network, Life sciences |
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Source
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Copyright Information
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Copyright der Metadaten: Universität zu Köln |
Other Details
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Languages : eng |
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