title: Ribosomal DNA clusters and telomeric (TTAGG)n repeats in blue butterflies (Lepidoptera, Lycaenidae) with low and high chromosome numbers.
abstract: Ribosomal DNA clusters and telomeric repeats are important parts of eukaryotic genome. However, little is known about their organization and localization in karyotypes of organisms with holocentric chromosomes. Here we present first cytogenetic study of these molecular structures in seven blue butterflies of the genus Polyommatus Latreille, 1804 with low and high chromosome numbers (from n=10 to n=ca.108) using fluorescence in situ hybridization (FISH) with 18S rDNA and (TTAGG) n telomeric probes. FISH with the 18S rDNA probe showed the presence of two different variants of the location of major rDNA clusters in Polyommatus species: with one or two rDNA-carrying chromosomes in haploid karyotype. We discuss evolutionary trends and possible mechanisms of changes in the number of ribosomal clusters. We also demonstrate that Polyommatus species have the classical insect (TTAGG) n telomere organization. This chromosome end protection mechanism probably originated de novo in small chromosomes that evolved via fragmentations.
authors.affiliation: Zoological Institute, Russian Academy of Sciences, Universitetskaya emb. 1, St. Petersburg 199034, Russia.
authors.forename: Alisa O
authors.initials: AO
authors.lastname: Vershinina
authors.affiliation: Zoological Institute, Russian Academy of Sciences, Universitetskaya emb. 1, St. Petersburg 199034, Russia.
authors.forename: Boris A
authors.initials: BA
authors.lastname: Anokhin
authors.affiliation: Zoological Institute, Russian Academy of Sciences, Universitetskaya emb. 1, St. Petersburg 199034, Russia ; Department of Entomology, St. Petersburg State University, Universitetskaya emb. 7/9, St. Petersburg 199034, Russia.
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Lukhtanov
keywords: Lycanidae; chromosome; karyotype evolution; ribosomal DNA; taxonomy; telomeres