Seminar of the Department of Microbiology

Development of phytomyxean parasites and their effect on different hosts

Michaela Hittorf - PhD Candidate, AG Neuhauser

28.04.2022, 11:00 - Join online



Phytomyxea are obligatory intracellular parasites belonging to the supergroup Rhizaria and are divided into two main clades: the terrestrial Plasmodiophorida and the marine Phagomyxida. The most investigated species is Plasmodiophora brassicae, the causal agent of clubroot disease in Brassicaceae, responsible for serious crop losses. Disease management is difficult and there is no effective control strategy yet. Little is known about other Phytomyxea, whose hosts include plants and oomycetes on land; and brown algae and diatoms in the sea. Phytomyxean life cycles and infection mechanisms seem to be consistent despite the outstanding phylogenetic distance separating their hosts. The aim of my thesis is to get a better understanding of the phytomyxean – host interactions, by comparing the parasite development and its influence on host growth in plants and brown algae. Among host growth processes, endoreduplication has been found to be important for the accommodation of plant symbionts such as nematodes, mycorrhizal fungi, viruses, oomycetes and bacteria. P. brassicae also induces endoreduplication in infected plant cells. Using two pathosystems, one involving P. brassicae and plants; and a second involving the marine phytomyxean Maullinia ectocarpii and marine brown algae we try to investigate if induced endoreduplication is: 1) a conserved feature within the clade Phytomyxea; 2) present also in non-plant hosts. In order to do so we used fluorescence microscopy coupled with nuclear staining and Fluorescence In Situ Hybridization to visualize endoreduplication-related increase in nuclear size. Additionally, we are gathering further evidence on endoreduplication by ploidy measurement and differential expression data on cell-cycle related genes. To further expand on Phytomyxid life-cycles and diversity, we also present here first molecular data for the neglected species Hillenburgia radicalis, a phytomyxean species infecting Poa sp. roots. We re-characterize and expand its life cycle; and contextualize it with that of other Phytomyxea.

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