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INTER-KINGDOM EPIGENETICS: CHARACTERIZATION OF MAIZE B1 TANDEM REPEAT-MEDIATED SILENCING IN DROSOPHILA MELANOGASTER

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dc.contributor.author McEachern, Lori A.
dc.date.accessioned 2010-09-02T13:47:30Z
dc.date.available 2010-09-02T13:47:30Z
dc.date.issued 2010-09-02
dc.identifier.uri http://hdl.handle.net/10222/13036
dc.description.abstract Transgenic organisms are a valuable tool for studying epigenetics, as they provide significant insight into the evolutionary conservation of epigenetic control sequences, the interacting proteins, and the underlying molecular mechanisms. Paramutation is an epigenetic phenomenon in which the epigenetic status and expression level of one allele is heritably altered after pairing with another. At the b1 locus in maize, a control region consisting of seven 853 bp tandem repeats is required for paramutation. To study the conservation of the epigenetic mechanisms underlying maize b1 paramutation, I created transgenic Drosophila carrying the maize b1 control region flanked by FRT sites and adjacent to the Drosophila white reporter gene. The maize b1 tandem repeats caused epigenetic silencing in Drosophila, as white expression consistently increased following repeat removal. A single copy of the tandem repeat sequence was sufficient to cause silencing, and silencing strength increased as the number of repeats increased. Trans interactions, such as pairing-sensitive silencing, were also observed and appear to require a threshold number of b1 tandem repeats, similar to paramutation in maize. Analysis of transcription from the repeats showed that the b1 tandem repeats are transcribed from both strands in Drosophila, as they are in maize. Bidirectional transcription was found to extend to the regions flanking the repeats, and persisted in “repeats-out” transgenes following repeat removal. However, aberrant transcription was lost when a zero-repeat transgene was moved to a new genomic position, suggesting that it may be due to an epigenetic mark that is retained from the previous silenced state. A search for modifiers of b1 repeat-mediated silencing demonstrated that Polycomb group proteins are involved. Together, these results indicate considerable conservation of an epigenetic silencing process between the plant and animal kingdoms. Genomic imprinting is a related epigenetic process in which parent-specific epigenetic states are inherited and maintained in progeny. The conservation of epigenetic mechanisms was further explored via an in-depth review of the molecular mechanisms underlying genomic imprinting in plants, mammals and insects, and identification of potentially imprinted genes in Drosophila by microarray analysis. en_US
dc.language.iso en en_US
dc.subject Epigenetics en_US
dc.subject Drosophila melanogaster en_US
dc.subject Paramutation en_US
dc.subject Tandem repeats en_US
dc.subject Transcription en_US
dc.subject Silencing en_US
dc.subject Genomic imprinting en_US
dc.title INTER-KINGDOM EPIGENETICS: CHARACTERIZATION OF MAIZE B1 TANDEM REPEAT-MEDIATED SILENCING IN DROSOPHILA MELANOGASTER en_US
dc.date.defence 2010-08-19
dc.contributor.department Department of Biology en_US
dc.contributor.degree Doctor of Philosophy en_US
dc.contributor.external-examiner Dr. Lori Wallrath en_US
dc.contributor.graduate-coordinator Dr. Hal Whitehead en_US
dc.contributor.thesis-reader Dr. Bill Pohajdak en_US
dc.contributor.thesis-reader Dr. Ian Meinertzhagen en_US
dc.contributor.thesis-supervisor Dr. Vett Lloyd en_US
dc.contributor.ethics-approval Not Applicable en_US
dc.contributor.manuscripts Yes en_US
dc.contributor.copyright-release Yes en_US


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