Discussion

Diplonemids (Diplonemea, Euglenozoa) are a sister group of euglenids - important in freshwater ecosystems - and kinetoplastid flagellates, which include highly pathogenic Trypanosoma and Leishmania spp. Both kinetoplastids and euglenids have long been recognized as virtually omnipresent and very species-rich, whereas diplonemids have remained largely unnoticed. They came into the spotlight only recently thanks to the Tara Oceans expedition, which revealed their global presence and extreme abundance in the world ocean. Indeed, diplonemids may comprise the 6th most abundant and 3rd most species-rich group of marine eukaryotes. However, until now, only few diplonemid species have been formally described. Goal of our study is to fill the enormous gap in our knowledge about this major player in the oceanic ecosystem and turn (at least) one strain into a genetically tractable system, which is a critical step towards functional studies of its genes. Our model species is Diplonema papillatum that can be easily cultivated axenically in the laboratory, reaches high density and grows in large volumes. We have already measured the cell viability and tested that D. papillatum is sensitive to multiple drugs that can be used as selectable markers. Recently, we are preparing a range of constructs that will be used to deliver DNA into this protist, so far not subjected to genetic manipulations.