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dc.contributor.authorStasiuk, Susan Josephine
dc.date.accessioned2010-07-23T01:58:29Z
dc.date.availableNO_RESTRICTIONen_US
dc.date.available2010-07-23T01:58:29Z
dc.date.issued2010
dc.identifier.urihttp://hdl.handle.net/10179/1485
dc.description.abstractParasitism, in nematodes, is a very successful life strategy which has evolved throughout the Nematoda phylum in several independent events. However, the genetic basis for parasitism remains unknown. Parastrongyloides trichosuri is a facultative parasitic nematode of the Australian brushtail possum. This parasite has retained the unusual ability to sample its environment at each generation, and make the developmental decision to develop either into a free-living nematode or, in response to environmental stress, develop into an infective larva, which must then seek out a host in order to complete its life cycle. The nematode model organism, Caenorhabditis elegans, also responds to environmental stresses by developing into a dauer larvae. The dauer hypothesis proposes that dauer larvae and infective larvae are homologous and that dauer larvae may be an evolutionary pre-adaptation that facilitated the evolution of parasitism in nematodes. One of the signalling pathways which control dauer larva development in C. elegans is the Insulin/IGF signalling pathway. Gene orthologues of the insulin/IGF signalling pathway were cloned from P. trichosuri: the daf-2 tyrosine kinase receptor, the age-1 phosphatidylinositol 3′ kinase and the daf-16 FOXO forkhead transcription factor. The expression profiles of these genes were characterized by q-PCR which determined that they were differentially expressed during the developmental switch to infective larva. Rescue by complementation showed that a P. trichosuri daf-16 transgene was able to recover both stress and developmental phenotypes in C. elegans daf mutants, suggesting it might perform an orthologous role in P. trichosuri. This research also demonstrated that the biology of P. trichosuri infective larvae and C. elegans dauer larvae are quite similar. Some of the environmental signals which control the free-living/infective larva developmental switch in P. trichosuri were characterized in this study and found to be similar to the environmental signals which trigger dauer larval development. These are: population density, food availability and temperature. There is a genetic component to the ability to respond to the environmental signals and inbred lines which display diverse developmental plasticity were isolated.en_US
dc.language.isoenen_US
dc.publisherMassey Universityen_US
dc.rightsThe Authoren_US
dc.subjectParastrongyloides trichosurien_US
dc.subjectAustralian brushtail possumen_US
dc.subjectInsulin/IGF signalling pathwayen_US
dc.subject.otherFields of Research::270000 Biological Sciences::270200 Geneticsen_US
dc.titleFunctional analysis of the insulin/IGF signalling pathway and the infective larva developmental switch in Parastrongyloides trichosuri : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Molecular Genetics at Massey University, Palmerston North, New Zealanden_US
dc.typeThesisen_US
thesis.degree.disciplineMolecular geneticsen_US
thesis.degree.grantorMassey Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophy (Ph.D.)en_US


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