title: The Cytoskeleton Architecture of Algivorous Protoplast Feeders (Viridiraptoridae, Rhizaria) Indicates Actin-Guided Perforation of Prey Cell Walls.
abstract: Several distantly related, phagotrophic microeukaryotes share the remarkable ability to perforate foreign cell walls in a well-defined pattern to acquire protoplast material as food. The underlying cellular processes, especially the local application of cell wall degrading agents, are still unexplored. We examined the distribution of F-actin and alpha-tubulin in the algivorous, viridiraptorid amoeboflagellates Orciraptor agilis and Viridiraptor invadens over their life histories using phalloidin conjugates and immunolocalization. During attack, both species form distinctive, F-actin-rich structures at the contact zone to the algal prey cell, which exactly match the species-specific cell wall perforations and resemble invadopodia and podosome rosettes of mammalian cells to a certain extent. Furthermore, F-actin is involved in the extraction of plastid material by Orciraptor and in prey cell invasion by Viridiraptor (here, F-actin localizes to a characteristic hyaline channel, which surrounds the streaming cytoplasm). The digestive-reproductive stages of viridiraptorids display a highly ordered microtubular cytoskeleton, whereas distinct phalloidin-positive actin structures could not be detected. We discuss the presumed function of F-actin during perforation and penetration of the algal cell wall by viridiraptorids, and compare the cytoskeleton architecture of these protoplast feeders to amoeboflagellates from different eukaryotic supergroups.
authors.affiliation: Department of Botany, Cologne Biocenter, University of Cologne, Zülpicher Str. 47b, 50674 Cologne, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Busch
authors.affiliation: Department of Botany, Cologne Biocenter, University of Cologne, Zülpicher Str. 47b, 50674 Cologne, Germany. Electronic address: shess@magniflash.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hess
mesh_terms: D000199:Actins / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D056907:Cercozoa / Q000166:cytology*; D003599:Cytoskeleton / Q000378:metabolism*; D020387:Food Chain; D015800:Protozoan Proteins / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism*
chemical_list: D000199:Actins; D015800:Protozoan Proteins; D014404:Tubulin
keywords: Orciraptor; Viridiraptor; amoeboflagellate.; invasion; lysopodium; phalloidin