Trypanosomatids (Euglenozoa) are a diverse group of unicellular flagellates predominately infecting insects (monoxenous species) or circulating between insects and vertebrates or plants (dixenous species). Monoxenous trypanosomatids harbor a wide range of RNA viruses belonging to the families Narnaviridae, Totiviridae, Qinviridae, Leishbuviridae, and a putative group of tombus-like viruses. Here, we focus on the subfamily Blastocrithidiinae, a previously unexplored divergent group of monoxenous trypanosomatids comprising two related genera: Obscuromonas and Blastocrithidia. Members of the genus Blastocrithidia employ a unique genetic code, in which all three stop codons are repurposed to encode amino acids, with TAA also used to terminate translation. Obscuromonas isolates studied here bear viruses of three families: Narnaviridae, Qinviridae, and Mitoviridae. The latter viral group is documented in trypanosomatid flagellates for the first time. While other known mitoviruses replicate in the mitochondria, those of trypanosomatids appear to reside in the cytoplasm. Although no RNA viruses were detected in Blastocrithidia spp., we identified an endogenous viral element in the genome of B. triatomae indicating its past encounter(s) with tombus-like viruses.

Central European Institute of Technology Masaryk University Brno 625 00 Czechia

Department of Parasitology Faculty of Science Charles University BIOCEV Vestec 252 50 Czechia

Department of Parasitology Faculty of Science Charles University Prague 128 00 Czechia

Division of Infectious Diseases Department of Medicine University of Alberta Edmonton Alberta T6G 2G3 Canada

Faculty of Science University of South Bohemia České Budějovice 370 05 Czechia

Institute of Parasitology Biology Centre Czech Academy of Sciences České Budějovice 370 05 Czechia

Life Science Research Centre Faculty of Science University of Ostrava Ostrava 710 00 Czechia

National Center for Biotechnology Information NLM National Institutes of Health Bethesda 20894 USA

The Shmunis School of Biomedicine and Cancer Research Tel Aviv University Tel Aviv 39040 Israel

Zoological Institute of the Ruian Academy of Sciences St Petersburg 199034 Russia

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