Significance: Kinetoplastids are a group of protists with unique morphology and molecular features. Many have developed a parasitic lifestyle and are economically and medically important causative agents of serious crop, animal, and human diseases. Evolutionarily, Paratrypanosoma confusum sits between parasitic trypanosomatids and free-living bodonids and therefore is uniquely informative for study of the emergence of parasitism. It is morphologically very flexible, as it forms three distinct life stages that can be studied separately. Particularly interesting is the haptomonad stage in which it rebuilds its flagellum into an extensive adhesive plaque. As an adaptation to parasitism, Paratrypanosoma lost a plethora of enzymes involved in breakdown of macromolecules and the capacity of receptor-mediated endocytosis but has gained surface proteins and membrane transporters to obtain nutrients from the host.

Summary: The mitochondrial DNA of diplonemid and kinetoplastid protists is known for its suite of bizarre features, including the presence of concatenated circular molecules, extensive trans‐splicing and various forms of RNA editing. Here we report on the existence of another remarkable characteristic: hyper‐inflated DNA content. We estimated the total amount of mitochondrial DNA in four kinetoplastid species (Trypanosoma brucei, Trypanoplasma borreli, Cryptobia helicis, and Perkinsela sp.) and the diplonemid Diplonema papillatum. Staining with 4′,6‐diamidino‐2‐phenylindole and RedDot1 followed by color deconvolution and quantification revealed massive inflation in the total amount of DNA in their organelles. This was further confirmed by electron microscopy. The most extreme case is the ∼260 Mbp of DNA in the mitochondrion of Diplonema, which greatly exceeds that in its nucleus; this is, to our knowledge, the largest amount of DNA described in any organelle. Perkinsela sp. has a total mitochondrial DNA content ~6.6× greater than its nuclear genome. This mass of DNA occupies most of the volume of the Perkinsela cell, despite the fact that it contains only six protein‐coding genes. Why so much DNA? We propose that these bloated mitochondrial DNAs accumulated by a ratchet‐like process. Despite their excessive nature, the synthesis and maintenance of these mtDNAs must incur a relatively low cost, considering that diplonemids are one of the most ubiquitous and speciose protist groups in the ocean. © 2018 The Authors. IUBMB Life published by Wiley Periodicals, Inc. on behalf of International Union of Biochemistry and Molecular Biology., 70(12):1267–1274, 2018

Parasitic protists of the genus Cytauxzoon are detected in wide range of wild and domestic felids. Bobcats are confirmed reservoir of C. felis in North America, while domestic cats are susceptible hosts suffering from severe or fatal illness. Cytauxzoon infections are mainly reported from American felids and recently, several sub-clinical and clinical findings were reported from European, Asian and African felids. In 2014 a collection of organs of 4 Eurasian lynx and 12 wild cats from 11 Romanian localities was carried out to determine the prevalence and genetic diversity of Cytauxzoon sp. We detected overall high prevalence of 62.5 % in both species of wild felids; 50 % in wild cats and 100 % in Eurasian lynx. The phylogenetic analysis indicates two distinct clades of Cytauxzoon in felids, with all of our sequences clustering with sequences of Cytauxzoon sp. /C. manul from Palaearctic felids. Further studies, development of new genetic markers and experimental transmission studies are required f...

Ticks, notorious blood-feeders and disease-vectors, have lost a part of their genetic complement encoding haem biosynthetic enzymes and are, therefore, dependent on the acquisition and distribution of host haem. Solute carrier protein SLC48A1, aka haem-responsive gene 1 protein (HRG1), has been implicated in haem transport, regulating the availability of intracellular haem. HRG1 transporter has been identified in both free-living and parasitic organisms ranging from unicellular kinetoplastids, nematodes, up to vertebrates. However, an HRG1 homologue in the arthropod lineage has not yet been identified. We have identified a single HRG1 homologue in the midgut transcriptome of the tick Ixodes ricinus, denoted as Ir HRG, and have elucidated its role as a haem transporter. Data from haem biosynthesis-deficient yeast growth assays, systemic RNA interference and the evaluation of gallium protoporphyrin IX-mediated toxicity through tick membrane feeding clearly show that Ir HRG is the bona fide tetrapyrrole transporter. We argue that during evolution, ticks profited from retaining a functional hrg1 gene in the genome because its protein product facilitates host haem escort from intracellularly digested haemoglobin, rendering haem bioavailable for a haem-dependent network of enzymes.