<p><i>Saprolegnia parasitica</i> and <i>Aphanomyces astaci </i>are parasitic water moulds belonging to the Oomycetes. Despite their importance as parasites they are very little studied at the molecular level and the work described in this thesis was aimed at increasing the molecular knowledge of these organisms by cloning and characterising genes of potential importance for reproduction and pathogenicity.</p><p>Stage-specific transcripts from<i> Saprolegnia parasitica</i> were isolated by differential display RT-PCR. One of the markers, <i>puf1 </i>encodes a putative mRNA binding protein which may be involved in post-transcriptional regulation of gene expression. <i>S. parasitica puf1 </i>is expressed exclusively in spore cysts that have not been determined for germination or repeated zoospore emergence indicating that the cyst stage has two phases, of about equal duration, which are physiologically and transcriptionally distinct. A similar expression pattern is observed in <i>Aphanomyces </i>spp. with different regulation of spore development and in the transcript is detected in both primary and secondary cysts.</p><p>A putative chitinase <i>AaChi1</i>, was cloned from the crayfish plague fungus, <i>Aphanomyces astaci. </i>Analysis of chitinase activity and <i>AaChi1</i> expression showed that chitinase in <i>A. astaci </i>is constitutively expressed in growing and sporulating mycelia, but absent in zoospores, a pattern which reflects the infectious life cycle of <i>A. astaci</i>. This expression pattern is conserved between the four known genotypes of <i>A. astaci</i>, in contrast to saprophytic and fish-pathogenic <i>Aphanomyces </i>spp. </p><p>Genetic and physiological analysis were conducted on five strains of <i>Aphanomyces, </i>isolated from suspected outbreaks of crayfish plague in Spain and Italy. The strains are not virulent against freshwater crayfish, and RAPD PCR and ITS sequence analysis show that they are unrelated to the crayfish plague fungus, <i>A. astaci.</i></p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-1592 |
| Date | January 2001 |
| Creators | Andersson, Gunnar |
| Publisher | Uppsala University, Comparative Physiology, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1104-232X ; 680 |
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