title: Genome size, karyotype polymorphism and chromosomal evolution in Trypanosoma cruzi.
abstract: BACKGROUND
  The Trypanosoma cruzi genome was sequenced from a hybrid strain (CL Brener). However, high allelic variation and the repetitive nature of the genome have prevented the complete linear sequence of chromosomes being determined. Determining the full complement of chromosomes and establishing syntenic groups will be important in defining the structure of T. cruzi chromosomes. A large amount of information is now available for T. cruzi and Trypanosoma brucei, providing the opportunity to compare and describe the overall patterns of chromosomal evolution in these parasites.
  
  
  RESULTS
  The genome sizes, repetitive DNA contents, and the numbers and sizes of chromosomes of nine strains of T. cruzi from four lineages (TcI, TcII, TcV and TcVI) were determined. The genome of the TcI group was statistically smaller than other lineages, with the exception of the TcI isolate Tc1161 (José-IMT). Satellite DNA content was correlated with genome size for all isolates, but this was not accompanied by simultaneous amplification of retrotransposons. Regardless of chromosomal polymorphism, large syntenic groups are conserved among T. cruzi lineages. Duplicated chromosome-sized regions were identified and could be retained as paralogous loci, increasing the dosage of several genes. By comparing T. cruzi and T. brucei chromosomes, homologous chromosomal regions in T. brucei were identified. Chromosomes Tb9 and Tb11 of T. brucei share regions of syntenic homology with three and six T. cruzi chromosomal bands, respectively.
  
  
  CONCLUSIONS
  Despite genome size variation and karyotype polymorphism, T. cruzi lineages exhibit conservation of chromosome structure. Several syntenic groups are conserved among all isolates analyzed in this study. The syntenic regions are larger than expected if rearrangements occur randomly, suggesting that they are conserved owing to positive selection. Mapping of the syntenic regions on T. cruzi chromosomal bands provides evidence for the occurrence of fusion and split events involving T. brucei and T. cruzi chromosomes.
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Renata T
authors.initials: RT
authors.lastname: Souza
authors.forename: Fábio M
authors.initials: FM
authors.lastname: Lima
authors.forename: Roberto Moraes
authors.initials: RM
authors.lastname: Barros
authors.forename: Danielle R
authors.initials: DR
authors.lastname: Cortez
authors.forename: Michele F
authors.initials: MF
authors.lastname: Santos
authors.forename: Esteban M
authors.initials: EM
authors.lastname: Cordero
authors.forename: Jeronimo Conceiçao
authors.initials: JC
authors.lastname: Ruiz
authors.forename: Samuel
authors.initials: S
authors.lastname: Goldenberg
authors.forename: Marta M G
authors.initials: MM
authors.lastname: Teixeira
authors.forename: José Franco
authors.initials: JF
authors.lastname: da Silveira
mesh_terms: D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics*; D056915:DNA Copy Number Variations; D016054:DNA, Protozoan / Q000235:genetics; D004276:DNA, Satellite / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D019143:Evolution, Molecular; D059646:Genome Size; D018503:Genome, Protozoan / Q000235:genetics*; D059785:Karyotype; D011110:Polymorphism, Genetic; D013045:Species Specificity; D026801:Synteny; D014346:Trypanosoma brucei brucei; D014349:Trypanosoma cruzi / Q000145:classification / Q000235:genetics*
chemical_list: D016054:DNA, Protozoan; D004276:DNA, Satellite