Molecular characterization of the short interspersed repetitive element SIRE in the six discrete typing units (DTUs) of Trypanosoma cruzi.

Repetitive sequences constitute an important proportion of the Trypanosoma cruzi genome; hence, they have been used as molecular markers and as amplification targets to identify the parasite presence via PCR. In this study, a molecular characterization of the SIRE repetitive element was performed in the six discrete typing units (DTUs) of T. cruzi. The results evidenced that this element, located in multiple chromosomes, was interspersed in the genome of all DTUs of the parasite. The presence of several motifs implicated in element insertion, duplication, and functionality suggests that SIRE could be an active element in the parasite genome. Of interest, there were SIRE specific Alu I fragments that allowed to discriminate DTU I from the others DTUs. Moreover, an UPGMA phenetic tree constructed from fragment sharing Southern blot data showed that T. cruzi I isolates conform a cluster separated from the T. cruzi II-VI isolates. When the relative number of SIRE copies was determined, a variation from 105 to 2,000 copies per haploid genome was observed among the different isolates without kept a DTU-relationship. In all, these findings suggest that SIRE sequence is a good target for parasite DNA amplification.