title: Evaluation of Trypanosoma cruzi hybrid stocks based on chromosomal size variation.
abstract: Although all classical lines of evidence point to the fact that Trypanosoma cruzi has a predominantly clonal evolution, accumulating data show that some T. cruzi stocks are the result of hybridisation events. We evaluated whether chromosomal polymorphism would give evolutionary information on hybrid isolates. Twenty-three coding sequences were mapped on the chromosomes of nine parasite stocks, four of which are putative hybrids (CL Brener and rDNA group 1/2). Phenetic analyses of karyotype data were based on the absolute chromosomal size difference index (aCSDI), a method that assumes that the genomic distance between two organisms is the sum of the size differences between their homologous chromosomes. aCSDI-based dendrograms obtained from a variable number of probes (3-18 probes) defined in all the cases three clusters: two corresponding, respectively, to T. cruzi I and T. cruzi II groups; and a third one, to rDNA group 1/2. CL Brener was alternatively positioned in T. cruzi II or rDNA group 1/2 clusters. Three clusters were also observed in the dendrogram constructed with restriction fragment length polymorphism (RFLP) data from 18 probes. The topology of the chromosome and RFLP dendrograms is similar, with a significant correlation coefficient (r=0.86062; P<0.0001), supporting a strong structuring of the clusters. This study also revealed that hybrid stocks have a larger proportion of two different-sized homologous chromosomes, as compared with non-hybrid strains. Overall, our results show that chromosomes are valuable characters for identification of evolutionary groups, in particular, T. cruzi hybrid organisms.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Avenida Professor Lineu Prestes, 748, CEP 05508-000, São Paulo SP, Brazil.
authors.forename: Aurélio
authors.initials: A
authors.lastname: Pedroso
authors.forename: Elisa
authors.initials: E
authors.lastname: Cupolillo
authors.forename: Bianca
authors.initials: B
authors.lastname: Zingales
mesh_terms: D000818:Animals; D002678:Chimera; D002875:Chromosomes / Q000737:chemistry / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D019143:Evolution, Molecular; D014644:Genetic Variation; D007621:Karyotyping; D010802:Phylogeny; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D014349:Trypanosoma cruzi / Q000235:genetics*