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dc.contributor.advisorAkam, Michael
dc.contributor.advisorTelford, Max
dc.contributor.authorCyrus-Kent, Chloë
dc.description.abstractA major goal of evolutionary developmental biology is to explore mechanisms and events underlying evolution of the myriad body plan morphologies expressed both genetically and phenotypically within the animal kingdom. Arthropods exhibit an astounding array of morphological diversity both within and between representative sub-phyla, thus providing an ideal phylum through which to address questions of body plan innovation and diversification. Major arthropod groups are recognised and defined by the distinct form and number of articulated appendages present along the antero-posterior axis of their segmented bodies. A great deal is known about the developmental genetics of limb development in the model insect Drosophila melanogaster, added to which, much comparative gene expression data and a growing body of functional genetic data is emerging for other arthropod species. Arthropod limb primordia are consistently marked by expression of the homeobox gene Distal-less (Dll), and the focus of this thesis is to compare signalling mediated by early Dll regulatory genes activity along antero-posterior and dorso-ventral embryonic axes during limb specification in Drosophila, with the activity of their orthologs in the widely disparate chelicerate, the spider mite Tetranychus urticae – interpreting new data with that available for other arthropods. Having made a detailed study of spider mite embryonic (and post-embryonic) development, to provide a basis for understanding mRNA transcription and protein activity patterns, I confirmed typical expression of Tetranychus Dll in prosomal limb primordia. I obtained limited results for the candidate antero-posterior positioning genes wingless and engrailed, although one of the two engrailed paralogs I identified is reportedly expressed in posterior segmental compartments, consistent with possible conservation of Engrailed-Wingless interactions in metameric patterning and positive regulation of Dll in arthropod limb specification. In Drosophila, wingless-dependent Dll transcription is restricted along the dorso-ventral axis by dorsal Dpp-mediated and ventral EGFR-mediated signalling gradients. Based on data from Tetranychus and other arthropods, neither dorsal nor ventral signalling regimes appear conserved outside the Drosophila system. Dll suppression in fly abdominal segments occurs due to powerful Hox (Ubx/AbdA) repression of the early Dll cis-regulatory element; this is discussed in relation to the independently evolved limbless chelicerate opisthosoma, informed by hypothetical scenarios of cis (regulatory DNA) and trans (coding sequence) evolution. Given practical difficulties and limitations encountered while working with spider mites, I offer a final assessment of the place of Tetranychus urticae as a non-model, and yet still valuable chelicerate species to consider carrying into the exciting future of evolutionary developmental biology.en_GB
dc.description.sponsorshipThis doctoral research work was supported by the Biotechnology and Biological Sciences Research Council, the Newton Trust and Corpus Christi College Cambridge.en_GB
dc.rightsAttribution 2.0 UK: England & Walesen
dc.subjectappendage developmenten_GB
dc.subjectlimb developmenten_GB
dc.subjectspider miteen_GB
dc.subjectTetranychus urticaeen_GB
dc.subjectmodel organismen_GB
dc.subjectbody planen_GB
dc.subjectevolutionary developmental biologyen_GB
dc.subjectgenetic regulationen_GB
dc.subjectregulatory elementsen_GB
dc.subjectantibody stainen_GB
dc.subjectin situ hybridisationen_GB
dc.titleAppendage development and early Distal-less regulation in arthropods: A study of the chelicerate Tetranychus urticae (Acarida)en_GB
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.publisher.institutionUniversity of Cambridgeen_GB
dc.publisher.departmentDepartment of Zoologyen_GB
dc.publisher.departmentSchool of Biological Sciencesen_GB
dc.publisher.departmentCorpus Christi Collegeen_GB

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Attribution 2.0 UK: England & Wales
Except where otherwise noted, this item's licence is described as Attribution 2.0 UK: England & Wales