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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060
EISSN: 1678-8060
Vol. 94, No. s1, 1999, pp. 189-193
Bioline Code: oc99158
Full paper language: English
Document type: Research Article
Document available free of charge

Memórias do Instituto Oswaldo Cruz, Vol. 94, No. s1, 1999, pp. 189-193

 en Genetic Diversity and Genetic Exchange in Trypanosoma cruzi: Dual Drug-resistant "Progeny" from Episomal Transformants
JR Stothard; IA Frame & MA Miles

Abstract

Extensive characterisation of Trypanosoma cruzi by isoenzyme phenotypes has separated the species into three principal zymodeme groups, Z1, Z2 and Z3, and into many individual zymodemes. There is marked diversity within Z2. A strong correlation has been demonstrated between the strain clusters determined by isoenzymes and those obtained using random amplified polymorphic DNA (RAPD) profiles. Polymorphisms in ribosomal RNA genes, in mini-exon genes, and microsatellite fingerprinting indicate the presence of at least two principal T.cruzi genetic lineages. Lineage 1 appears to correspond with Z2 and lineage 2 with Z1. Z1 (lineage 2) is associated with Didelphis. Z2 (lineage 1) may be associated with a primate host. Departures from Hardy-Weinberg equilibrium and linkage disequilibrium indicate that propagation of T.cruzi is predominantly clonal. Nevertheless, two studies show putative
homozygotes and heterozygotes circulating sympatrically: the allozyme frequencies for phosphoglucomutase, and hybrid RAPD profiles suggest that genetic exchange may be a current phenomenon in some T.cruzi transmission cycles. We were able to isolate dual drug-resistant T.cruzi biological clones following copassage of putative parents carrying single episomal drug-resistant markers. A multiplex PCR confirmed that dual drug-resistant clones carried both episomal plasmids. Preliminary karyotype analysis suggests that recombination may not be confined to the extranuclear genome.

Keywords
Trypanosoma cruzi - genetic diversity - genetic exchange - transfection

 
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