02785nas a2200193 4500008004100000245016100041210006900202260003000271300001100301490000600312520207600318100002802394700002602422700002602448700001902474700002602493700002102519856005102540 2011 eng d00aA Molecular Insight into Algal-Oomycete Warfare: cDNA Analysis of Ectocarpus siliculosus Infected with the Basal Oomycete Eurychasma dicksonii0 aMolecular Insight into AlgalOomycete Warfare cDNA Analysis of iE bPublic Library of Science ae245000 v63 a

Brown algae are the predominant primary producers in coastal habitats, and like land plants are subject to disease and parasitism. Eurychasma dicksonii is an abundant, and probably cosmopolitan, obligate biotrophic oomycete pathogen of marine brown algae. Oomycetes (or water moulds) are pathogenic or saprophytic non-photosynthetic Stramenopiles, mostly known for causing devastating agricultural and aquacultural diseases. Whilst molecular knowledge is restricted to crop pathogens, pathogenic oomycetes actually infect hosts from most eukaryotic lineages. Molecular evidence indicates that Eu. dicksonii belongs to the most early-branching oomycete clade known so far. Therefore Eu. dicksonii is of considerable interest due to its presumed environmental impact and phylogenetic position. Here we report the first large scale functional molecular data acquired on the most basal oomycete to date. 9873 unigenes, totalling over 3.5Mb of sequence data, were produced from Sanger-sequenced and pyrosequenced EST libraries of infected Ectocarpus siliculosus. 6787 unigenes (70%) were of algal origin, and 3086 (30%) oomycete origin. 57% of Eu. dicksonii sequences had no similarity to published sequence data, indicating that this dataset is largely unique. We were unable to positively identify sequences belonging to the RXLR and CRN groups of oomycete effectors identified in higher oomycetes, however we uncovered other unique pathogenicity factors. These included putative algal cell wall degrading enzymes, cell surface proteins, and cyclophilin-like proteins. A first look at the host response to infection has also revealed movement of the host nucleus to the site of infection as well as expression of genes responsible for strengthening the cell wall, and secretion of proteins such as protease inhibitors. We also found evidence of transcriptional reprogramming of E. siliculosus transposable elements and of a viral gene inserted in the host genome.

1 aGrenville-Briggs, Laura1 aGachon, Claire, M. M.1 aStrittmatter, Martina1 aSterck, Lieven1 aKüpper, Frithjof, C.1 avan West, Pieter uhttps://algaldiseases.myspecies.info/node/1701