The evolution of two Trypanosoma cruzi subgroups inferred from rRNA genes can be correlated with the interchange of American mammalian faunas in the Cenozoic and has implications to pathogenicity and host specificity
Mrs. Briones et al., The evolution of two Trypanosoma cruzi subgroups inferred from rRNA genes can be correlated with the interchange of American mammalian faunas in the Cenozoic and has implications to pathogenicity and host specificity, MOL BIOCH P, 104(2), 1999, pp. 219-232
The agent of Chagas disease, Trypanosoma cruzi, is divided into two highly
divergent genetic subgroups, lineages 1 and 2, which include all typed stra
ins isolated from humans, insect vectors, and sylvatic mammals. The evoluti
onary origin of these two T. cruzi lineages and the clinical importance of
their identification, have been the subject of intense debate. Here, using
molecular phylogenetic analysis, we found that the distance between the two
T. cruzi lineages is equivalent to the distance between genera Leishmania
and Endotrypanum. Also, we confirmed that T. rangeli is more closely relate
d to T. cruzi than to T. brucei using the rDNA sequence from a human strain
of T. rangeli. Phylogenetic trees based on small subunit rDNA sequences fu
rther suggest that the two T. cruzi lineages diverged between 88 and 37 mil
lion years (Myr) ago. We hypothesize that lineage 2 is indigenous to South
America while lineage 1 has been introduced to South America recently, alon
g with North American placental mammals, after the connection of the Americ
as in the Pliocene (5 Myr ago) or with caviomorph rodents and primates in t
he Oligocene (38 Myr ago). This would explain the preferential association
of T. cruzi lineage 2 with marsupials and of lineage 1 with human disease.
These two T. cruzi lineages are likely to be distinct species, or at least
subspecies, because of their different ecological and epidemiological trait
s and estimated long period of independent evolution. (C) 1999 Elsevier Sci
ence B.V. All rights reserved.