Evolution of Trypanosoma cruzi: clarifying hybridisations, mitochondrial introgressions and phylogenetic relationships between major lineages

Abstract

Several different models of Trypanosoma cruzi evolution have been proposed. These models suggest that scarce events of genetic exchange occurred during the evolutionary history of this parasite. In addition, the debate has focused on the existence of one or two hybridisation events during the evolution of T. cruzi lineages. Here, we reviewed the literature and analysed available sequence data to clarify the phylogenetic relationships among these different lineages. We observed that TcI, TcIII and TcIV form a monophyletic group and that TcIII and TcIV are not, as previously suggested, TcI-TcII hybrids. Particularly, TcI and TcIII are sister groups that diverged around the same time that a widely distributed TcIV split into two clades (TcIVS and TcIVN). In addition, we collected evidence that TcIII received TcIVS kDNA by introgression on several occasions. Different demographic hypotheses (surfing and asymmetrical introgression) may explain the origin and expansion of the TcIII group. Considering these hypotheses, genetic exchange should have been relatively frequent between TcIII and TcIVS in the geographic area in which their distributions overlapped. In addition, our results support the hypothesis that two independent hybridisation events gave rise to TcV and TcVI. Consequently, TcIVS kDNA was first transferred to TcIII and later to TcV and TcVI in TcII/TcIII hybridisation events.

Genetic diversity of Trypanosoma cruzi in bats, and multilocus phylogenetic and phylogeographical analyses supporting Tcbat as an independent DTU (discrete typing unit)

“…Tomasini and Diosque, 2015).288 isolates of all DTUs resulted in a phylogenetic tree supporting Tcbat closest to TcI (sister groups), whereas290 TcII was corroborated as the most basal lineage and TcIII-TcVI clustered together in a clade with a complex 291 branching pattern -the topology B(Fig. 4A).…”

Evidence of hybridization, mitochondrial introgression and biparental inheritance of the kDNA minicircles in Trypanosoma cruzi I

“…The three strains also gave us the possibility to address kDNA inheritance in hybrids. Maxicircle inheritance is assumed to be uniparental according to previous results in hybrid DTUs TcV and TcVI, since they share maxicircles with TcIII but not with TcII [31,38]. We were unable to address the hypothesis of uniparental inheritance of maxicircles because the DNA fragments analyzed here were identical among the three strains.…”

“…Parasexuality appears to be infrequent in nature, although it could not be discarded from a population genomic study where several aneuploid stock were observed [20]. Despite this hybrid DTUs such as TcV and TcVI showed heterozygous patterns more compatible with meiosis and gamete fusion than with the model of parasexuality [24,38,57]. An expected result of the parasexual model is the existence of strains with high degrees of aneuploidy.…”

“…In T. cruzi, mito-nuclear discordance is clearly observed in TcIII. According to nuclear loci, TcIII is nearly related to TcI; although maxicircle sequences cluster TcIII with TcIV from South America [31,38]. In addition, mito-nuclear discordance was also observed within TcI [39][40][41].…”

Pathogen Species Identification from Metagenomes in Ancient Remains: the Challenge of Identifying Human Pathogenic Species of Trypanosomatidae Via Bioinformatic Tools

“…In Bolivia and Peru, strains belonging to the DTU I and DTU V clades are the main T. cruzi strains isolated, followed by strains of DTUs IV, III and VI [10]. The knowledge of the complex evolutionary history of T. cruzi, which involved genetic exchanges [11], and the existence of hybrid DTUs will certainly benefit from the identification of the infecting strains at the DTU level from this ancient DNA material. Insight into the circulating strains in these mummies would generate important elements for the calibration of such a dynamically evolving scenario.…”