Kinetoplastid flagellates are known for several unusual features, one of which is their complex mitochondrial genome, known as kinetoplast (k) DNA, composed of mutually catenated maxi- and minicircles. Trypanosoma lewisi is a member of the Stercorarian group of trypanosomes which is, based on human infections and experimental data, now considered a zoonotic pathogen. By assembling a total of 58 minicircle classes, which fall into two distinct categories, we describe a novel type of kDNA organization in T. lewisi. RNA-seq approaches allowed us to map the details of uridine insertion and deletion editing events upon the kDNA transcriptome. Moreover, sequencing of small RNA molecules enabled the identification of 169 unique guide (g) RNA genes, with two differently organized minicircle categories both encoding essential gRNAs. The unprecedented organization of minicircles and gRNAs in T. lewisi broadens our knowledge of the structure and expression of the mitochondrial genomes of these human and animal pathogens. Finally, a scenario describing the evolution of minicircles is presented.
Trypanosoma lewisi is a cosmopolitan parasite that has always been considered specific for rats, Rattus spp. (1,2). However, cases of atypical human trypanosomiasis caused by this trypanosome have been reported (3–11). Among them, one patient died from a T. lewisi infection, sending out the message that this form of trypanosomiasis could also be fatal (8). Even more worrying, it has been demonstrated that T. lewisi is resistant to lysis by normal human serum (12). Clearly, gaining more basic knowledge and a better understanding of this neglected zoonotic pathogen is timely.
Li S-J., Zhang X., Lukeš J., Li B.-Q., Wang J.F., Qu L-H., Hide G., Lai D-H., Lun Z.R. 2020: Novel organization of mitochondrial minicircles andguide RNAs in the zoonotic pathogen Trypanosoma lewisi. Nucleic Acids Research 48: 9747–9761. [IF=11.501]