Kinetoplastids are a diverse group of flagellates which exhibit editing by insertion/deletion of U’s in the mitochondrial mRNAs. Some mRNAs require editing to build most of their coding sequences, a process known as pan-editing. Evidence suggests that pan-editing is an ancestral feature in kinetoplastids. Here, we investigate how the transition from non-edited to pan-edited states occurred. The mitochondrial mRNAs and protein sequences from nine kinetoplastids and related groups (diplonemids, euglenids, and jakobids) were analyzed. RNA editing increased protein hydrophobicity to extreme values by introducing U’s in the second codon position, despite the absence of editing preferences related to codon position. In addition, hydrophobicity was maintained by purifying selection in species that lost editing by retroposition of the fully edited mRNA. Only a few hydrophobic to hydrophilic amino acid changes were inferred for such species. In the protein secondary structure, these changes occurred spatially close to other hydrophilic residues. The analysis of coevolving sites showed that multiple changes are required together for hydrophobicity to be lost, which suggest the proteins are locked into extended hydrophobicity. Finally, an analysis of the NAD7 protein-protein interactions showed they can also influence hydrophobicity increase in the protein and where editing can occur in the mRNA. In conclusion, our results suggest that protein hydrophobicity has influenced editing site selection and how editing expanded in mRNAs. In effect, the hydrophobicity increase was entrenched by a neutral ratchet moved by a mutational pressure to introduce U’s, thus helping to explain both RNA editing increase and, possibly, persistence.
Trypanosomes are a group of parasitic flagellates with medical and veterinary importance. Despite many species having been described in this genus, little is known about many of them. Here, we report a genetic and morphological characterization of trypanosomatids isolated from wild mammals from the Argentine Chaco region. Parasites were morphologically and ultrastructurally characterized by light microscopy and transmission electron microscopy. Additionally, 18s rRNA and gGAPDH genes were sequenced and analyzed using maximum likelihood and Bayesian inference. Morphological characterization showed clear characteristics associated with the Trypanosoma genus. The genetic characterization demonstrates that the studied isolates have identical sequences and a pairwise identity of 99% with Trypanosoma lainsoni, which belongs to the clade of lizards and snakes/rodents and marsupials. To date, this species had only been found in the Amazon region. Our finding represents the second report of T. lainsoni and the first record for the Chaco region. Furthermore, we ultrastructurally described for the first time the species. Finally, the host range of T. lainsoni was expanded (Leopardus geoffroyi, Carenivora, Felidae; and Calomys sp., Rodentia, Cricetidae), showing a wide host range for this species.
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