On the origin of TSAR: morphology, diversity and phylogeny of Telonemia

• Published in: Open biology Vol. 12; no. 3; p. 210325
• Main Authors: Tikhonenkov, Denis V, Jamy, Mahwash, Borodina, Anastasia S, Belyaev, Artem O, Zagumyonnyi, Dmitry G, Prokina, Kristina I, Mylnikov, Alexander P, Burki, Fabien, Karpov, Sergey A
• Format: Journal Article
• Language: English
• Published: England Royal Society 01.03.2022; The Royal Society
• Subjects: 18S rDNA; Biological Evolution; Eukaryotic Cells; evolution; Life Sciences; microbial diversity; Phylogeny; protists; Stramenopiles; telonemids; ultrastructure; protists; 18S rDNA; evolution; microbial diversity; ultrastructure; telonemids
• ISSN: 2046-2441; 2046-2441
• DOI: 10.1098/rsob.210325

Telonemia is a poorly known major phylum of flagellated eukaryotes with a unique combination of morphological traits. Phylogenomics recently revealed the phylogenetic position of telonemids as sister to SAR, one of the largest groups of eukaryotes, comprising Stramenopiles, Alveolata and Rhizaria. Due to this key evolutionary position, investigations of telonemids are of critical importance for elucidating the origin and diversification of an astounding diversity of eukaryotic forms and life strategies. To date, however, only two species have been morphologically characterized from Telonemia, which do not represent this genetically very diverse group. In this study, we established cultures for six new telonemid strains, including the description of five new species and a new genus. We used these cultures to update the phylogeny of Telonemia and provide a detailed morphological and ultrastructural investigation. Our data elucidate the origin of TSAR from flagellates with complex morphology and reconstruction of the ancestral structure of stramenopiles, alveolates and rhizarians, and their main synapomorphic characters. Since telonemids are a common component of aquatic environments, the features of their feeding, behaviour and ecological preferences observed in clonal cultures and the results of global metabarcoding analysis contribute to a deeper understanding of organization of microbial food webs.