Genetic structure and evolution of Trypanosoma cruzi, the agent of Chagas disease, as revealed by multiprimer RAPD analysis : clonality vs sexuality

#Trypanosoma cruzi$ natural populations have been shown to be highly heterogeneous and subdivided into a number of genetically distant clonal lineages. We have selected 21 highly resolutive primers, out of 120 tested, to analyse 50 stocks representative of the major genetic subdivisions of the parasite. Stocks were isolated from diverse hosts and from different geographic areas. Other trypanosomatids, including #Leishmania$ and #T. congolense$, were analysed in parallel in order to directly compare their genetic diversity with #T. cruzi$. The results show the marked genetic structuration of #T. cruzi$ in a few distinct genetic groups, confirming previous MLEE and RAPD data. These groups are interpreted as clonal lineages. RAPD markers specific for each group are numerous and will be used to develop probes for specific diagnostic purposes. The huge genetic heterogeneity of #T. cruzi$ is confirmed by the divergence between lineages of this parasite which is similar to that observed between species, and even species complexes, within the #Leishmania$ genus. The phylogenetic relationships between the #T. cruzi$ groups were investigated by multivariate and phylogenetic analysis. The monophyly of each group appears robust, but the hierarchical relationships between groups are problematic. Moreover, some groups display features that could be interpreted as the result of a hybridization event between strains of two other groups. These findings suggest the possibility of an evolutionary process involving both occasional recombination leading to new genotypes and clonal evolution of successful lineages. (Résumé d'auteur