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Chromosomal size variation in Trypanosoma cruzi is mainly progressive and is evolutionarily informative

Published online by Cambridge University Press:  30 July 2002

J. HENRIKSSON
Affiliation:
Department of Medical Genetics, Uppsala University, Biomedical Center, Box 589, S-751 23 Uppsala, Sweden
J. C. DUJARDIN
Affiliation:
Laboratory of Protozoology, Institute of Tropical Medicine ‘Prince Leopold’, Nationalestraat 155, B-2000 Antwerpen 1, Belgium
C. BARNABÉ
Affiliation:
Génétique des Maladies Infectieuses, UMR CNRS/IRD 9926, IRD, BP5045, F-34032 Montpellier Cedex, France
S. BRISSE
Affiliation:
Eijkman-Winkler Institute, University Medical Centre Utrecht, AZU G04.614, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
G. TIMPERMAN
Affiliation:
Laboratory of Protozoology, Institute of Tropical Medicine ‘Prince Leopold’, Nationalestraat 155, B-2000 Antwerpen 1, Belgium
J. VENEGAS
Affiliation:
Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Casilla 70086, Santiago-7, Chile
U. PETTERSSON
Affiliation:
Department of Medical Genetics, Uppsala University, Biomedical Center, Box 589, S-751 23 Uppsala, Sweden
M. TIBAYRENC
Affiliation:
Génétique des Maladies Infectieuses, UMR CNRS/IRD 9926, IRD, BP5045, F-34032 Montpellier Cedex, France
A. SOLARI
Affiliation:
Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Casilla 70086, Santiago-7, Chile

Abstract

The evolutionary significance of chromosome size polymorphism was explored in a representative panel of 26 Trypanosoma cruzi stocks. We tested a progressive model (aCSDI) assuming that the larger the size difference between homologous chromosomes, the more divergent the parasites are. This was contrasted with a non-progressive model (Jaccard's distance), in which any chromosome size difference has the same weight. ACSDI-based dendrograms were very similar to those built-up from multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD) data: structuring in 2 major lineages (T. cruzi I and T. cruzi II) and 5 small subdivisions within T. cruzi II was identical, and branching was very similar. Furthermore, a significant correlation (P<0·001) was observed between aCSDI and phenetic distances calculated from MLEE and RAPD data. In contrast, analysis of chromosome size polymorphism with Jaccard's distance generated dendrograms with relatively long branches, causing most branching points to cluster close together, which generates statistically uncertain branching points. Our results thus support a model of progressive chromosome size-variation and show that despite an extensive polymorphism, chromosomal sizes constitute valuable characters for evolutionary analyses. Furthermore, our data are consistent with the clonal evolution model previously proposed for T. cruzi.

Type
Research Article
Copyright
2002 Cambridge University Press

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