Universität Innsbruck

Seminar of the Department of Microbiology

You are how you eat: the role of phagocytosis in phytomyxid-host interactions



Andrea Garvetto - Postdoc - Microbiology - UIBK - AG Neuhauser

23.03.2023, 11:00 - Hybrid

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Phytomyxea, including the agriculturally impactful Plasmodiophora brassicae, are intracellular biotrophic parasites infecting plants and stramenopiles. They belong to the clade Rhizaria, where phagotrophy is one of the main mode of nutrition. Phagocytosis is a complex trait of eukaryotes and, although well documented for free-living unicellular eukaryotes and specific cellular types of animals, data on phagocytosis in intracellular, biotrophic parasites are scant. Phagocytosis, where parts of the host cell are consumed at once, is seemingly at odds with intracellular biotrophy. Here we provide evidence that phagotrophy is part of the nutritional strategy of Phytomyxea, using morphological and genetic data (including a novel transcriptome of the brown algae parasite Maullinia ectocarpii). We document intracellular phagocytosis in P. brassicae and M. ectocarpii by transmission electron microscopy (TEM) and fluorescent in situ hybridization. Our investigations confirm molecular signatures of phagocytosis in Phytomyxea and hint at a small specialised subset of genes used for intracellular phagocytosis. Microscopic evidence confirms the existence of intracellular phagocytosis, which in Phytomyxea targets primarily host organelles. Phagocytosis seems to coexist with the manipulation of host physiology typical of “traditional” biotrophic interactions. Our findings resolve long debated questions on the feeding behaviour of Phytomyxea, suggesting an unrecognised role for phagocytosis in biotrophic interactions.