TEMPERATURE-GRADIENT GEL-ELECTROPHORESIS (TGGE) ANALYSIS OF RIBOPRINTS FROM TRYPANOSOMA-CRUZI

To test the homogeneity of 18S sequences within Trypanosoma cruzi, rib oprint profiles were separated by temperature gradient gel electrophor esis (TGGE). Upon interpretation of melting curves of fragments within a riboprint profile, there appeared to be two 18S sequence types with in each stock examined. Two similar types were also observed within ou tgroup taxa Trypanosoma conorhini, Trypanosoma rangeli and Leishmania braziliensis. From DNA hybridization studies, these fragments were sho wn 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 phylogen etic inference, comparisons may be between paralogous and not ortholog ous copies of this region, such that, inferred relationships may merel y reflect a gene history. This seriously questions the current molecul ar phylogeny of these protozoa using 18S data.