Temperature gradient gel electrophoresis (TGGE) analysis of riboprints from Trypanosoma cruzi

To test the homogeneity of 18S sequences within Trypanosoma cruzi, riboprint profiles were separated by temperature gradient gel electrophoresis (TGGE). Upon interpretation of melting curves of fragments within a riboprint profile, there appeared to be two 18S sequence types within each stock examined. Two similar types were also observed within outgroup taxa Trypanosoma conorhini, Trypanosoma rangeli and Leishmania braziliensis. From DNA hybridization studies, these fragments were shown to have homology to the 18S V1 region. There are therefore two 18S V1 regions, differing in sequence, present in all taxa examined. When only a single 18S sequence is used to represent each taxa for phylogenetic inference, comparisons may be between paralogous and not orthologous copies of this region, such that, inferred relationships may merely reflect a gene history. This seriously questions the current molecular phylogeny of these protozoa using 18S data.