Transposons, also known as transposable elements (TEs), are genetic elements capable of changing their location in the genome and amplifying in number. Because of their ability to cause mutations in the host genome, often with detrimental consequences to the host, yet avoid being eliminated by natural selection, transposons have been labeled selfish elements or genomic parasites. However, the advent of genomics has allowed the identification of numerous instances where transposons have played a crucial role in host genome evolution. In this thesis, I evaluate the extent to which transposons have influenced the genomes of their hosts, with an emphasis on plant genomes. I review the present knowledge of different mechanisms by which this is achieved and provide examples to illustrate them. Next, I tackle the problem of annotating transposons in the completed genomic sequence of domestic rice by comparing RepeatMasker, the standard approach used in transposon annotation, with an alternative approach employing hidden Markov models. In addition, I perform a genome-wide analysis of gene fragment capture by rice Mutator-like transposons. I conclude that, while this is a widespread phenomenon in rice, it is unlikely to represent a major force in generating novel protein-coding genes. Nevertheless, the duplicated gene fragments that are transcribed may playa role in the regulation of host genes they arose from via an RNAi-like mechanism. Finally, I conduct an in silico analysis of a gene family derived from a domesticated Mutator-like transposase, called MUSTANG (MUG), in conjunction with an experimental characterization of the MUG family in Arabidopsis. The results of the study indicate that the MUG family arose in a common ancestor of flowering plants and that the Arabidopsis genes AtMUG1 and/or AtMUG2 may act as global regulators of mitochondrial function. I conclude that our appreciation of the role of transposons in host function and evolution will undoubtedly continue to grow as our understanding of these processes deepens.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.115687 |
| Date | January 2008 |
| Creators | Juretic, Nikoleta. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 003133175, proquestno: AAINR66313, Theses scanned by UMI/ProQuest. |
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