Pathogens of brown algae: culture studies of Anisolpidium ectocarpii and A. rosenvingei reveal that the Anisolpidiales are uniflagellated oomycetes |
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Authors: | Claire MM Gachon Martina Strittmatter Yacine Badis Kyle I Fletcher Pieter Van West Dieter G Müller |
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Institution: | 1. The Scottish Association for Marine Science, Culture Collection for Algae and Protozoa, Scottish Marine Institute, Oban, Argyll PA37 1QA, UKclaire.gachon@sams.ac.uk;3. The Scottish Association for Marine Science, Culture Collection for Algae and Protozoa, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK;4. Aberdeen Oomycete Laboratory, Institute of Medical Sciences, University of Aberdeen, Foresterhill, AB25 2ZD, UK;5. Fachbereich Biologie, Universit?t Konstanz, D-78457 Konstanz, Germany |
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Abstract: | Using laboratory cultures, we have documented the life cycle of Anisolpidium ectocarpii, a pathogen of Ectocarpus and other filamentous brown algae, and presented preliminary observations on Anisolpidium rosenvingei, a pathogen of Pylaiella littoralis. Consistent with earlier reports, the zoospores of both species have a single anterior flagellum, which justified the placement of Anisolpidium amongst the Hyphochytriales (Hyphochytridiomycota). We have also shown that A. ectocarpii can complete its infection cycle in a broad selection of species from various brown algal orders, whereas A. rosenvingei seemingly exhibits a strict specificity for unilocular sporangia of P. littoralis. Unexpectedly, nuclear (18S rRNA) and mitochondrial (cox1, cox2) markers regroup A. ectocarpii and A. rosenvingei, into a hitherto unrecognized monophyletic clade within the oomycetes (Oomycota), most closely related to the Olpidiopsidales. The Anisolpidium genus is therefore entirely distinct from the Hyphochytridiomycota and represents the first confirmed instance of an anteriorly uniciliate oomycete. Finally, we suggest that a valid morphological criterion to separate true hyphochytrids from oomycetes is the timing of zoospore cleavage. Given the evidence, we propose to transfer the Anisolpidiales from the Hyphochytriales to the Oomycetes. |
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Keywords: | 18S rRNA Anisolpidiales cox1 cox2 Ectocarpus host range Hyphochytriales Pylaiella |
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