Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597361
Title: The developmental basis of allometry
Author: Castilho, L. V.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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Abstract:
This thesis investigates the role played by molecular signalling pathways in organ size determination in Drosophila melanogaster. First, the analysis of wing mosaics generated by mitotic recombination showed that both the insulin receptor InR and its downstream target chico have a strong and largely local autonomous reducing effect on wing size. Position of the mutant tissue in the mosaic wings determines the intensity of size deficits, since the posterior wing compartment is more severely affected than the anterior. A second insulin receptor was analysed and shown to perform no role in size determination. Additionally, the TGF-b/activin surface receptor babo causes much weaker size reductions, even though cells deficient for the gene have extreme difficulty to proliferate. This corroborates the idea that genes with an important role in cell proliferation do not necessary play a major role in determining final organ size. Finally, the small size phenotype of vein mutants (a member of the EGF pathway) was reassessed, and the results did not corroborate previous claims that the reduced size of vein mosaic wings is caused by an overall reduction of the wing. On the contrary (and consistently with the action of insulin and TGF-beta pathway genes), vein seems not to interfere with the size of adjacent non-vein regions of the mosaics. This adds a question mark to Garcia-Bellido's Entelechia model of wing development. A second issue addressed in this project is the known interaction between size and environmental factors. It is widely believed that the insulin pathway is responsible for converting nutrient availability into growth. Such hypothesis implies that the size of insulin pathway mutants should respond less than wildtype flies (or not respond at all) to starvation. Experiments showed that in fact chico and InR mutants do not respond to starvation, contrary to the intense size decrease observed in malnourished wildtype flies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.597361  DOI: Not available
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