title: Karyotypic evolution of ribosomal sites in buffalo subspecies and their crossbreed.
abstract: DOMESTIC BUFFALOES ARE DIVIDED INTO TWO GROUP BASED ON CYTOGENETIC CHARACTERISTICS AND HABITATS: the "river buffaloes" with 2n = 50 and the "swamp buffaloes", 2n = 48. Nevertheless, their hybrids are viable, fertile and identified by a 2n = 49. In order to have a better characterization of these different cytotypes of buffaloes, and considering that NOR-bearing chromosomes are involved in the rearrangements responsible for the karyotypic differences, we applied silver staining (Ag-NOR) and performed fluorescent in situ hybridization (FISH) experiments using 18S rDNA as probe. Metaphases were obtained through blood lymphocyte culture of 21 individuals, including river, swamp and hybrid cytotypes. Ag-NOR staining revealed active NORs on six chromosome pairs (3p, 4p, 6, 21, 23, 24) in the river buffaloes, whereas the swamp buffaloes presented only five NOR-bearing pairs (4p, 6, 20, 22, 23). The F1 cross-breed had 11 chromosomes with active NORs, indicating expression of both parental chromosomes. FISH analysis confirmed the numerical divergence identified with Ag-NOR. This result is explained by the loss of the NOR located on chromosome 4p in the river buffalo, which is involved in the tandem fusion with chromosome 9 in this subspecies. A comparison with the ancestral cattle karyotype suggests that the NOR found on the 3p of the river buffalo may have originated from a duplication of ribosomal genes, resulting in the formation of new NOR sites in this subspecies.
authors: Universidade Federal do Pampa , Campus São Gabriel , São Gabriel, RS , Brazil .
authors: Tiago Marafiga
authors: TM
authors: Degrandi
authors: Faculty of Science , University of the Republic , Montevideo , Uruguay .
authors: Sebastian
authors: S
authors: Pita
authors: Faculty of Science , University of the Republic , Montevideo , Uruguay .
authors: Yanina
authors: Y
authors: Panzera
authors: Laboratório de Cultura de Tecidos e Citogenética , Institute Evandro Chagas , Ananindeua, PA , Brazil . ; Instituto de Ciências Exatas e Naturais , Faculdade de Ciências Naturais , Universidade Federal do Pará , Belém, PA , Brazil .
authors: Edivaldo Herculano C
authors: EH
authors: de Oliveira
authors: Empresa Brasileira de Pesquisa Agropecuária , Amazônia Oriental , Belém, PA , Brazil .
authors: José Ribamar Felipe
authors: JR
authors: Marques
authors: Empresa Brasileira de Pesquisa Agropecuária , Amazônia Oriental , Belém, PA , Brazil .
authors: Marivaldo Rodrigues
authors: MR
authors: Figueiró
authors: Instituto de Ciências Exatas e Naturais , Faculdade de Ciências Naturais , Universidade Federal do Pará , Belém, PA , Brazil .
authors: Larissa Coêlho
authors: LC
authors: Marques
authors: Universidade Federal do Pampa , Campus São Gabriel , São Gabriel, RS , Brazil .
authors: Lucia
authors: L
authors: Vinadé
authors: Universidade Federal do Pampa , Campus São Gabriel , São Gabriel, RS , Brazil .
authors: Ricardo José
authors: RJ
authors: Gunski
authors: Universidade Federal do Pampa , Campus São Gabriel , São Gabriel, RS , Brazil .
authors: Analía Del Valle
authors: Adel V
authors: Garnero
keywords: 18S rDNA; Bubalus bubalis; FISH