title: Comparative chromosome painting in six species of Oligoryzomys (Rodentia, Sigmodontinae) and the karyotype evolution of the genus.
abstract: Oligoryzomys belongs to the tribe Oryzomyini, and contains about 22 species. Diploid numbers range from 2n = 44 in Oligoryzomys sp. 2 to 2n = 72 in O. utiaritensis and phylogenetic relationships are not well defined. The high morphological convergence leads to misidentification of taxonomic entities and the species are often identified by chromosomal characters. Until now, the genus has been studied only by classical cytogenetic approaches. To understand the chromosomal evolution of Oligoryzomys, we developed chromosome probes from a female of Oligoryzomys moojeni (OMO) with 2n = 70 and hybridized to other five Oligoryzomys species. The probes painted 31 segments on O. fornesi (OFO) with 2n = 62; 32 segments on O. microtis (OMI), 2n = 64; 33 segments on O. nigripes (ONI), 2n = 62 and on O. rupestris (ORU), 2n = 46; and 34 on Oligoryzomys sp. 2 (OSP), 2n = 44. OMO probes 4 and 5 showed a syntenic association in O. fornesi, O. microtis and O. nigripes and were also presented in the same pair, although disrupted, in O. rupestris and Oligoryzomys sp. 2. Concerning O. rupestris and Oligoryzomys sp. 2, species with the lowest diploid numbers of the genus, a total of 8 probes hybridized to 11 segments on the largest pair of ORU 1 and 9 probes hybridized to 12 segments on OSP 1. Also, OMO 6 painted three segments in ORU, corresponding to the proximal segment of ORU 2q, and the whole of ORU 19 and 20. In OSP, the segment corresponding to ORU 20 was homologous to OSP 1p. OMO X showed signals of hybridization in both X and Y chromosomes. Extensive chromosomal rearrangements, that could not be detected by classical cytogenetic techniques, such as pericentric inversions or repositioning of centromeres, Robertsonian rearrangements and tandem fusions/fissions, as well as gain/activation or loss/inactivation of centromeres and telomeric sequences have driven the huge genome reshuffling in these closely related species.
authors: Laboratório de Ecologia e Evolução, Instituto Butantan, São Paulo, São Paulo, Brazil.
authors: Camilla Bruno
authors: CB
authors: Di-Nizo
authors: Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil; Cambridge Resource Centre for Comparative Genomics, Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom; Instituto de Recursos Naturais-Universidade Federal de Itajubá, Itajubá, Minas Gerais, Brazil.
authors: Karen
authors: K
authors: Ventura
authors: Cambridge Resource Centre for Comparative Genomics, Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.
authors: Malcolm Andrew
authors: MA
authors: Ferguson-Smith
authors: Cambridge Resource Centre for Comparative Genomics, Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.
authors: Patricia Caroline Mary
authors: PC
authors: O'Brien
authors: Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
authors: Yatiyo
authors: Y
authors: Yonenaga-Yassuda
authors: Laboratório de Ecologia e Evolução, Instituto Butantan, São Paulo, São Paulo, Brazil.
authors: Maria José de J
authors: MJ
authors: Silva
mesh_terms: D000818:Animals; D001938:Brazil; D002503:Centromere / Q000235:genetics; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D020223:Chromosome Painting / Q000379:methods*; D033481:Chromosomes, Mammalian / Q000235:genetics*; D004171:Diploidy; D019143:Evolution, Molecular; D005260:Female; D005843:Geography; D007621:Karyotyping; D008297:Male; D010802:Phylogeny; D016205:Sigmodontinae / Q000145:classification / Q000235:genetics*; D013045:Species Specificity; D016615:Telomere / Q000235:genetics