Molecular mechanisms during food acquisition and gliding locomotion in viridiraptorid amoeboflagellates - a transcriptomic study of Orciraptor agilis (Cercozoa, Rhizaria)

• Applicant: Professor Dr. Sebastian Hess
• Subject Area: Plant Biochemistry and Biophysics ; Evolutionary Cell and Developmental Biology (Zoology)
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 283693520

The Viridiraptoridae is a recently discovered family of phagotrophic freshwater flagellates, whose members have the ability to penetrate the cell walls of green algae in order to exploit their cell content as food. The key ability of these highly specialised 'protoplast feeders' is the local degradation of cellulosic cell wall polymers, which takes place in a well-defined and species-specific pattern. The subsequent food uptake, i.e. the extraction of the algal plastid or the invasion of the algal cell, involves changes in cytoskeletal architecture and function. Between feeding events, mobile viridiraptorid cells display flagella-based gliding motility, a still poorly studied locomotory process known from flagellates of diverse phylogenetic affiliation. Cell wall perforation, prey cell invasion and gliding motility are three fascinating, yet unexplored phenomena in viridiraptorids. Therefore, I intend to explore 1) cell wall degrading enzymes, 2) actin-binding proteins, and 3) motor proteins interacting with microtubules in the viridiraptorid Orciraptor agilis. This will be done with a comparative transcriptomic approach and a selection of biochemical methods. My aim is to shed light on the underlying molecular machinery of the above mentioned processes with a focus on carbohydrate-active enzymes involved in cell wall lysis. With this proposal I expect to provide experimental evidence for enzymatic cell wall degradation in unicellular 'protoplast feeders' with genetic and biochemical methods, to characterise candidate enzymes, and to explore the repertoire of structural and force-generating cytoskeletal proteins involved in feeding and locomotion. Besides specific insights into the functioning of viridiraptorids, this work should also contribute to enhance genomic knowledge about the yet understudied eukaryotic supergroup Rhizaria in general.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professor Dr. Alastair Simpson