The kinetoplastids are unicellular flagellates that derive their name from the 'kinetoplast', a region within their single mitochondrion harboring its organellar genome of high DNA content, called kinetoplast (k) DNA. Some protein products of this mitochondrial genome are encoded as cryptogenes; their transcripts require editing to generate an open reading frame. This happens through RNA editing, whereby small regulatory guide (g)RNAs direct the proper insertion and deletion of one or more uridines at each editing site within specific transcript regions. An accurate perspective of the kDNA expansion and evolution of their unique uridine insertion/deletion editing across kinetoplastids has been difficult to achieve. Here, we resolved the kDNA structure and editing patterns in the early-branching kinetoplastid Trypanoplasma borreli and compare them with those of the well-studied trypanosomatids. We find that its kDNA consists of circular molecules of about 42 kb that harbor the rRNA and protein-coding genes, and 17 different contigs of approximately 70 kb carrying an average of 23 putative gRNA loci per contig. These contigs may be linear molecules, as they contain repetitive termini. Our analysis uncovered a putative gRNA population with unique length and sequence parameters that is massive relative to the editing needs of this parasite. We validated or determined the sequence identity of four edited mRNAs, including one coding for ATP synthase 6 that was previously thought to be missing. We utilized computational methods to show that the T. borreli transcriptome includes a substantial number of transcripts with inconsistent editing patterns, apparently products of non-canonical editing. This species utilizes the most extensive uridine deletion compared to other studied kinetoplastids to enforce amino acid conservation of cryptogene products, although insertions still remain more frequent. Finally, in three tested mitochondrial transcriptomes of kinetoplastids, uridine deletions are more common in the raw mitochondrial reads than aligned to the fully edited, translationally competent mRNAs. We conclude that the organization of kDNA across known kinetoplastids represents variations on partitioned coding and repetitive regions of circular molecules encoding mRNAs and rRNAs, while gRNA loci are positioned on a highly unstable population of molecules that differ in relative abundance across strains. Likewise, while all kinetoplastids possess conserved machinery performing RNA editing of the uridine insertion/deletion type, its output parameters are species-specific.

• Keywords
• ATPase 6, Euglenozoa, Maxicircle, Metakinetoplastina, Mitochondrion, RNA editing, U-indel editing, Uridine insertion/deletion editing, guide RNA,
• Publication type
• Journal Article MeSH

BACKGROUND: Trypanosoma theileri species complex includes parasites of Bovidae (cattle, sheep, goat, etc.) and Cervidae (deer) transmitted mainly by Tabanidae (horse flies and deerflies) and keds (Hippoboscidae). While morphological discrimination of species is challenging, two big clades, TthI and TthII, each containing parasites isolated from bovids and cervids, have been identified phylogenetically. To date, the development in the vector has been studied in detail only for the ked-transmitted sheep parasite T. melophagium (TthII), while the fate of trypanosomes in tabanids was described only briefly by light microscopy. METHODS: We collected infected tabanids of various species and identified trypanosomes by molecular phylogenetic analysis. The morphology and development of trypanosomes was studied using the combination of statistical analyses as well as light and electron microscopy. RESULTS: Two trypanosome species belonging to both TthI and TthII clades of the T. theileri complex were identified. The phylogenetic position of these two trypanosomes suggests that they parasitize deer. Both species were indiscernible by morphology in the vector and showed the same development in its intestine. In contrast to the previously described development of T. melophagium, both trypanosomes of tabanids only transiently infected midgut and settled mainly in the ileum, while pylorus and rectum were neglected. Meanwhile, the flagellates developing in the tabanid ileum (pyriform epimastigotes and metacyclic trypomastigotes) showed similarities to the corresponding stages in T. melophagium by morphology, mode of attachment to the host cuticle and formation of the fibrillar matrix surrounding the mass of developing parasites. In addition, for the first time to our knowledge we documented extraintestinal stages in these trypanosomes, located in the space between the epithelium and circular muscles. CONCLUSIONS: The development of different species of flagellates of the T. theileri complex in their insect vectors shows many similarities, which can be explained not only by their common origin, but also the same transmission mode, i.e. contamination of the oral mucosa with the gut content released after squashing the insect either by tongue or teeth. The observed differences (concerning primarily the distribution of developmental stages in the intestine) are associated rather with the identity of vectors than the phylogenetic position of parasites.

• Keywords
• Deerflies, Horseflies, Life cycle, Trypanosomes, Vector,
• MeSH
• Diptera * parasitology   MeSH
• Phylogeny MeSH
• Insect Vectors parasitology   MeSH
• Sheep MeSH
• Cattle MeSH
• Trypanosoma * MeSH
• Deer * parasitology   MeSH
• Animals MeSH
• Check Tag
• Cattle MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Leishmania spp. are important pathogens causing a vector-borne disease with a broad range of clinical manifestations from self-healing ulcers to the life-threatening visceral forms. Presence of Leishmania RNA virus (LRV) confers survival advantage to these parasites by suppressing anti-leishmanial immunity in the vertebrate host. The two viral species, LRV1 and LRV2 infect species of the subgenera Viannia and Leishmania, respectively. In this work we investigated co-phylogenetic patterns of leishmaniae and their viruses on a small scale (LRV2 in L. major) and demonstrated their predominant coevolution, occasionally broken by intraspecific host switches. Our analysis of the two viral genes, encoding the capsid and RNA-dependent RNA polymerase (RDRP), revealed them to be under the pressure of purifying selection, which was considerably stronger for the former gene across the whole tree. The selective pressure also differs between the LRV clades and correlates with the frequency of interspecific host switches. In addition, using experimental (capsid) and predicted (RDRP) models we demonstrated that the evolutionary variability across the structure is strikingly different in these two viral proteins.

• Keywords
• Leishmaniavirus, coevolution, phylogenomics,
• MeSH
• Leishmania virology   MeSH
• Leishmaniasis virology   MeSH
• Humans MeSH
• RNA, Viral analysis   MeSH
• RNA-Dependent RNA Polymerase genetics   MeSH
• RNA Viruses genetics   MeSH
• Capsid Proteins genetics   MeSH
• Viral Proteins genetics   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• RNA, Viral MeSH
• RNA-Dependent RNA Polymerase MeSH
• Capsid Proteins MeSH
• Viral Proteins MeSH

While numerous genomes of Leishmania spp. have been sequenced and analyzed, an understanding of the evolutionary history of these organisms remains limited due to the unavailability of the sequence data for their closest known relatives, Endotrypanum and Porcisia spp., infecting sloths and porcupines. We have sequenced and analyzed genomes of three members of this clade in order to fill this gap. Their comparative analyses revealed only minute differences from Leishmaniamajor genome in terms of metabolic capacities. We also documented that the number of genes under positive selection on the Endotrypanum/Porcisia branch is rather small, with the flagellum-related group of genes being over-represented. Most significantly, the analysis of gene family evolution revealed a substantially reduced repertoire of surface proteins, such as amastins and biopterin transporters BT1 in the Endotrypanum/Porcisia species when compared to amastigote-dwelling Leishmania. This reduction was especially pronounced for δ-amastins, a subfamily of cell surface proteins crucial in the propagation of Leishmania amastigotes inside vertebrate macrophages and, apparently, dispensable for Endotrypanum/Porcisia, which do not infect such cells.

• Keywords
• gene gain, gene loss, genome analysis, leishmaniinae,
• MeSH
• Phylogeny MeSH
• Leishmania major classification   genetics   MeSH
• Leishmania classification   genetics   MeSH
• Membrane Proteins genetics   MeSH
• Evolution, Molecular MeSH
• Protozoan Proteins genetics   MeSH
• Gene Expression Regulation MeSH
• Whole Genome Sequencing methods   MeSH
• Gene Expression Profiling MeSH
• Trypanosomatina classification   genetics   MeSH
• Virulence MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH
• Names of Substances
• Membrane Proteins MeSH
• Protozoan Proteins MeSH

Euglenozoa is a species-rich group of protists, which have extremely diverse lifestyles and a range of features that distinguish them from other eukaryotes. They are composed of free-living and parasitic kinetoplastids, mostly free-living diplonemids, heterotrophic and photosynthetic euglenids, as well as deep-sea symbiontids. Although they form a well-supported monophyletic group, these morphologically rather distinct groups are almost never treated together in a comparative manner, as attempted here. We present an updated taxonomy, complemented by photos of representative species, with notes on diversity, distribution and biology of euglenozoans. For kinetoplastids, we propose a significantly modified taxonomy that reflects the latest findings. Finally, we summarize what is known about viruses infecting euglenozoans, as well as their relationships with ecto- and endosymbiotic bacteria.

• Keywords
• Diplonemida, Euglenida, Kinetoplastida, microbial eukaryotes, phylogeny, systematics,
• MeSH
• Ecosystem MeSH
• Euglenozoa classification   genetics   physiology   virology   MeSH
• Phylogeny MeSH
• Mimiviridae pathogenicity   MeSH
• Symbiosis MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

Here we characterized the development of the trypanosomatid Blastocrithidia raabei in the dock bug Coreus marginatus using light and electron microscopy. This parasite has been previously reported to occur in the host hemolymph, which is rather typical for dixenous trypanosomatids transmitted to a plant or vertebrate with insect's saliva. In addition, C. marginatus has an unusual organization of the intestine, which makes it refractory to microbial infections: two impassable segments isolate the anterior midgut portion responsible for digestion and absorption from the posterior one containing symbiotic bacteria. Our results refuted the possibility of hemolymph infection, but revealed that the refractory nature of the host provokes very aggressive behavior of the parasite and makes its life cycle more complex, reminiscent of that in some dixenous trypanosomatids. In the pre-barrier midgut portion, the epimastigotes of B. raabei attach to the epithelium and multiply similarly to regular insect trypanosomatids. However, when facing the impassable constricted region, the parasites rampage and either fiercely break through the isolating segments or attack the intestinal epithelium in front of the barrier. The cells of the latter group pass to the basal lamina and accumulate there, causing degradation of the epitheliocytes and thus helping the epimastigotes of the former group to advance posteriorly. In the symbiont-containing post-barrier midgut segment, the parasites either attach to bacterial cells and produce cyst-like amastigotes (CLAs) or infect enterocytes. In the rectum, all epimastigotes attach either to the cuticular lining or to each other and form CLAs. We argue that in addition to the specialized life cycle B. raabei possesses functional cell enhancements important either for the successful passage through the intestinal barriers (enlarged rostrum and well-developed Golgi complex) or as food reserves (vacuoles in the posterior end).

• MeSH
• Microscopy, Electron MeSH
• Hemolymph parasitology   MeSH
• Heteroptera immunology   parasitology   MeSH
• Euglenozoa Infections immunology   parasitology   veterinary   MeSH
• Host-Parasite Interactions physiology   MeSH
• Disease Resistance MeSH
• Life Cycle Stages physiology   MeSH
• Intestinal Mucosa diagnostic imaging   parasitology   ultrastructure   MeSH
• Trypanosomatina growth & development   pathogenicity   ultrastructure   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

BACKGROUND: Amphibian trypanosomes were the first ever described trypanosomatids. Nevertheless, their taxonomy remains entangled because of pleomorphism and high prevalence of mixed infections. Despite the fact that the first species in this group were described in Europe, virtually none of the trypanosomes from European anurans was analyzed using modern molecular methods. METHODS: In this study, we explored the diversity and phylogeny of trypanosomes in true frogs from Europe using light microscopy and molecular methods. RESULTS: A comparison of observed morphotypes with previous descriptions allowed us to reliably identify three Trypanosoma spp., whereas the remaining two strains were considered to represent novel taxa. In all cases, more than one morphotype per blood sample was observed, indicating mixed infections. One hundred and thirty obtained 18S rRNA gene sequences were unambiguously subdivided into five groups, correspondent to the previously recognized or novel taxa of anuran trypanosomes. CONCLUSIONS: In this work we studied European frog trypanosomes. Even with a relatively moderate number of isolates, we were able to find not only three well-known species, but also two apparently new ones. We revealed that previous assignments of multiple isolates from distant geographical localities to one species based on superficial resemblance were unjustified. Our work also demonstrated a high prevalence of mixed trypanosome infections in frogs and proposed a plausible scenario of evolution of the genus Trypanosoma.

• Keywords
• Evolution, Frog trypanosomes, Mixed infections, Trypanosomatidae,
• MeSH
• Species Specificity MeSH
• Phylogeny * MeSH
• Genetic Variation MeSH
• Cloning, Molecular MeSH
• Polymerase Chain Reaction MeSH
• RNA, Protozoan genetics   MeSH
• RNA, Ribosomal, 18S genetics   MeSH
• Trypanosoma genetics   physiology   MeSH
• Anura blood   parasitology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czechoslovakia MeSH
• Ukraine MeSH
• Names of Substances
• RNA, Protozoan MeSH
• RNA, Ribosomal, 18S MeSH

The class Kinetoplastea encompasses both free-living and parasitic species from a wide range of hosts. Several representatives of this group are responsible for severe human diseases and for economic losses in agriculture and livestock. While this group encompasses over 30 genera, most of the available information has been derived from the vertebrate pathogenic genera Leishmaniaand Trypanosoma. Recent studies of the previously neglected groups of Kinetoplastea indicated that the actual diversity is much higher than previously thought. This article discusses the known segment of kinetoplastid diversity and how gene-directed Sanger sequencing and next-generation sequencing methods can help to deepen our knowledge of these interesting protists.

• MeSH
• Biodiversity * MeSH
• Biomarkers MeSH
• Databases, Genetic MeSH
• Phylogeny * MeSH
• Kinetoplastida classification   cytology   genetics   MeSH
• Metagenomics trends   MeSH
• DNA, Protozoan genetics   MeSH
• RNA, Protozoan genetics   MeSH
• RNA, Ribosomal, 18S genetics   MeSH
• DNA Barcoding, Taxonomic trends   MeSH
• Computational Biology MeSH
• High-Throughput Nucleotide Sequencing methods   MeSH
• Environment MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Biomarkers MeSH
• DNA, Protozoan MeSH
• RNA, Protozoan MeSH
• RNA, Ribosomal, 18S MeSH