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Title: Gene silencing and development in Phytophthora infestans
Author: Walker, C.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2007
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In order to investigate whether epigenetics plays a role in P. infestans, the expression patterns of genes involved in transcriptional and post-transcriptional gene silencing were investigated and several were found to be up-regulated in both pre-infection stages and in planta. A histone deacetylase (Pi-HDA1) was selected for functional characterization using RNA interference (RNAi). Silencing Pi-HDA1 produced large aberrant zoospores indicating that it may be required for development. In addition silencing of Pi-HDA1 resulted in reactivation of INF1 production in inf1-transgenic silenced strains, therefore suggesting that Pi-HDA1 may be directly involved in the silencing of inf1 in inf1-transgenic silenced strains. In addition an RNA helicase, Pi-RNH1 was also found to be specifically up-regulated in zoospores. Pi-RNH1-silenced strains produced large aberrant zoospores that had undergone partial cleavage and often had multiple flagella on their surface. The Pi-RNH1-silenced zoospores were also sensitive to osmotic pressure and they often ruptured upon release from the sporangia. These findings indicate that Pi-RNH1 has a major function in zoospore development. In addition the mechanism of internuclear gene silencing was further investigated. In P. infestans internuclear gene silencing is a process where silencing is transmitted from nucleus to nucleus in heterokaryotic strains. Previously it was demonstrated that internuclear gene silencing is a transcriptional silencing process. In several eukaryotes transcriptional silencing has been shown to involve methylation of cytosines. Methylation sensitive sequencing was performed and it was concluded that DNA methylation is not involved in transcriptional silencing in P. infestans. In solution hybridization assays provided preliminary evidence that small RNAs may be the diffusible factor responsible for the spread of silencing.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available