Saprolegnia parasitica is one of the most devastating animal pathogenic oomycetes causing massive economic losses every year worldwide. The disease – saprolegniosis, is characterised by the appearance of white cotton-like spots on the skin, fins and gills of freshwater fish, leading to its death by haemodilution. More efficient control methods will be derived from a better understanding of S. parasitica, but inefficient transformation protocols currently are limiting the basic molecular knowledge This thesis describes the first application of transient gene silencing in S. parasitica. A gene that codes for a putative tyrosinase from S. parasitica, SpTyr, was selected to investigate the suitability of the RNAi technique to functionally characterise genes. Transient gene silencing can be used to functionally characterise genes in S. parasitica. In order to infect a host organism S. parasitica needs to attach to it. We found that detachment of S. parasitica cysts requires strength 3 times higher when compared to other Saprolegnia spp. I also demonstrate through functional genomics that a gene, SPRG_018636, that encodes for a fibronectin protein is involved in spine formation. Aquacultures often use, as a method of sterilisation, UV systems. This method has proven to be efficient against bacteria, virus and protozoa. However, we studied the effect of UVB and UVC on the growth of several oomycetes including S. parasitica and Saprolegnia diclina and it was found that S. parasitica is UV resistant. Key players from the resistance mechanism were not identified but significant knowledge was acquired on recovery from UV damage. Small steps were taken towards the development of a stable transformation protocol with the work on this thesis. Nevertheless, further studies will be necessary to accomplish this goal. Functional characterisation of a homolog of PiNuk7 found in S. parasitica genome was performed. This protein unlike Phytophthora infestans homolog did not translocate into the host cell.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:635976 |
| Date | January 2014 |
| Creators | Saraiva, Marcia |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225277 |
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