title: Interstitial telomeric sites and Robertsonian translocations in species of Ipheion and Nothoscordum (Amaryllidaceae).
abstract: The genera Nothoscordum and Ipheion (Allioideae, Amaryllidaceae) are cytologically characterized by a dysploid series with variable numbers of metacentric and acrocentric chromosomes typical of karyotypes rearranged by Robertsonian translocations (RT). Since they have large chromosomes, low diploid numbers, and possess two telomeric motifs [the vertebrate-type (TTAGGG) n and the Arabidopsis-type (TTTAGGG) n ] they are suitable for investigating the occurrence and possible role of interstitial telomeric sites (ITS) associated with RT. We analyzed the distributions of telomeric sites in 12 species of Nothoscordum and Ipheion and found that both telomeric probes colocalized in all chromosome termini. Cloning and sequencing PCR products obtained using both telomeric primers simultaneously revealed long stretches of (TTAGGG) n and (TTTAGGG) n sequences together with degenerated telomeric sequences. Most acrocentric chromosomes have a 45S rDNA site at the terminal region of the short arms adjacent to the most distal telomeric sites. Telomeric signals were found at all chromosome ends, but ITS were also detected in a few proximal and subterminal regions in some Nothoscordum species. Although RT are common in this group of plants, our findings suggest that proximal positioning of telomeric motifs are not necessarily related to that kind of rearrangement. Rather, transposition of telomeric sequences followed by amplification, could better explain the presence of (TTAGGG) n and (TTTAGGG) n repeats at those sites. Furthermore, a few small interstitial sites found in some Nothoscordum species indicate that dispersion of these sequences was not restricted to the proximal region.
authors: Laboratory of Plant Cytogenetics and Evolution, Centro de Ciências Biológicas, Department of Botany, Federal University of Pernambuco, Rua Nelson Chaves S/N, Cidade Universitária, Recife, PE, 50670-420, Brazil. lgrsouza@hotmail.com.
authors: Gustavo
authors: G
authors: Souza
authors: Laboratory of Cytogenetics and Plant Diversity, Department of General Biology, State University of Londrina, Londrina, Paraná, Brazil.
authors: Andre L L
authors: AL
authors: Vanzela
authors: Laboratory of Genetics, Department of Plant Biology, Faculty of Agronomy, University of the Republic, Montevideo, Uruguay.
authors: Orfeo
authors: O
authors: Crosa
authors: Laboratory of Plant Cytogenetics and Evolution, Centro de Ciências Biológicas, Department of Botany, Federal University of Pernambuco, Rua Nelson Chaves S/N, Cidade Universitária, Recife, PE, 50670-420, Brazil.
authors: Marcelo
authors: M
authors: Guerra
mesh_terms: D001483:Base Sequence; D032461:Chromosomes, Plant / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D059785:Karyotype; D019668:Liliaceae / Q000235:genetics*; D008969:Molecular Sequence Data; D012335:RNA, Ribosomal / Q000235:genetics; D017422:Sequence Analysis, DNA; D016615:Telomere / Q000235:genetics*; D014178:Translocation, Genetic
chemical_list: D018744:DNA, Plant; D012335:RNA, Ribosomal; C088179:RNA, ribosomal, 45S
keywords: 45S rDNA; Asparagales; Interstitial telomeric sites; Ipheion; Nothoscordum; Robertsonian translocations