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Ribosomal DNA clusters and telomeric (TTAGG)n repeats in blue butterflies (Lepidoptera, Lycaenidae) with low and high chromosome numbers.

Vershinina AO, Anokhin BA, Lukhtanov VA - Comp Cytogenet (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Zoological Institute, Russian Academy of Sciences, Universitetskaya emb. 1, St. Petersburg 199034, Russia.

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.

No MeSH data available.


Related in: MedlinePlus

Localization of FISH signals on telomeres (red) and rDNA clusters (green) in squash chromosome preparations of seven species of Polyommatus (subgenus Agrodiaetus). Chromosomes are counterstained with DAPI. Note telomeric signals of different intensity. 1–7 one 18S rDNA cluster is found 8 two 18S rDNA clusters are found 1Polyommatus (Agrodiaetus) caeruleus, MII 2–3Polyommatus (Agrodiaetus) hamadanensis, MI cells from two different populations with different karyotypes (n=19 and n=21 accordingly) 4Polyommatus (Agrodiaetus) karindus, MII 5Polyommatus (Agrodiaetus) morgani, MI 6Polyommatus (Agrodiaetus) peilei, MII 7Polyommatus (Agrodiaetus) pfeifferi, MII 8Polyommatus (Agrodiaetus) sennanensis, MII. The inset in the upper right corner shows twice enlarged image of rDNA-carrying chromosomes.
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Figure 1: Localization of FISH signals on telomeres (red) and rDNA clusters (green) in squash chromosome preparations of seven species of Polyommatus (subgenus Agrodiaetus). Chromosomes are counterstained with DAPI. Note telomeric signals of different intensity. 1–7 one 18S rDNA cluster is found 8 two 18S rDNA clusters are found 1Polyommatus (Agrodiaetus) caeruleus, MII 2–3Polyommatus (Agrodiaetus) hamadanensis, MI cells from two different populations with different karyotypes (n=19 and n=21 accordingly) 4Polyommatus (Agrodiaetus) karindus, MII 5Polyommatus (Agrodiaetus) morgani, MI 6Polyommatus (Agrodiaetus) peilei, MII 7Polyommatus (Agrodiaetus) pfeifferi, MII 8Polyommatus (Agrodiaetus) sennanensis, MII. The inset in the upper right corner shows twice enlarged image of rDNA-carrying chromosomes.

Mentions: In all karyotypes weak and strong telomeric signals were present (Figs 1–8). The chromosomes of blue butterflies are very small and some of them are at the limit of the resolving power of light microscopy. For this reason, TTAGG signals in some cases could not be distinguished from background noise. Unlike the telomere probes, rDNA probes produced strong signals of different intensity. The chromosomal distribution pattern of telomeric repeats was similar in all seven species, the exact location of telomeres (terminal or interstitial) was impossible to identify since the meiotic chromosomes were extremely contracted. The distribution pattern of 18S rDNA signals varied markedly showing two different variants – with one or two rDNA-carrying bivalents in MI karyotype and, correspondingly, with one or two rDNA-carrying chromosomes in MII karyotype. All chromosome numbers were found to coincide with previously published karyotype data for seven studied species (Lukhtanov et al. 2005, Kandul et al. 2007). In two Polyommatus (Agrodiaetus) hamadanensis populations intraspecific chromosomal polymorphism has been discovered.


Ribosomal DNA clusters and telomeric (TTAGG)n repeats in blue butterflies (Lepidoptera, Lycaenidae) with low and high chromosome numbers.

Vershinina AO, Anokhin BA, Lukhtanov VA - Comp Cytogenet (2015)

Localization of FISH signals on telomeres (red) and rDNA clusters (green) in squash chromosome preparations of seven species of Polyommatus (subgenus Agrodiaetus). Chromosomes are counterstained with DAPI. Note telomeric signals of different intensity. 1–7 one 18S rDNA cluster is found 8 two 18S rDNA clusters are found 1Polyommatus (Agrodiaetus) caeruleus, MII 2–3Polyommatus (Agrodiaetus) hamadanensis, MI cells from two different populations with different karyotypes (n=19 and n=21 accordingly) 4Polyommatus (Agrodiaetus) karindus, MII 5Polyommatus (Agrodiaetus) morgani, MI 6Polyommatus (Agrodiaetus) peilei, MII 7Polyommatus (Agrodiaetus) pfeifferi, MII 8Polyommatus (Agrodiaetus) sennanensis, MII. The inset in the upper right corner shows twice enlarged image of rDNA-carrying chromosomes.
© Copyright Policy - creative-commons-attribution
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488964&req=5

Figure 1: Localization of FISH signals on telomeres (red) and rDNA clusters (green) in squash chromosome preparations of seven species of Polyommatus (subgenus Agrodiaetus). Chromosomes are counterstained with DAPI. Note telomeric signals of different intensity. 1–7 one 18S rDNA cluster is found 8 two 18S rDNA clusters are found 1Polyommatus (Agrodiaetus) caeruleus, MII 2–3Polyommatus (Agrodiaetus) hamadanensis, MI cells from two different populations with different karyotypes (n=19 and n=21 accordingly) 4Polyommatus (Agrodiaetus) karindus, MII 5Polyommatus (Agrodiaetus) morgani, MI 6Polyommatus (Agrodiaetus) peilei, MII 7Polyommatus (Agrodiaetus) pfeifferi, MII 8Polyommatus (Agrodiaetus) sennanensis, MII. The inset in the upper right corner shows twice enlarged image of rDNA-carrying chromosomes.
Mentions: In all karyotypes weak and strong telomeric signals were present (Figs 1–8). The chromosomes of blue butterflies are very small and some of them are at the limit of the resolving power of light microscopy. For this reason, TTAGG signals in some cases could not be distinguished from background noise. Unlike the telomere probes, rDNA probes produced strong signals of different intensity. The chromosomal distribution pattern of telomeric repeats was similar in all seven species, the exact location of telomeres (terminal or interstitial) was impossible to identify since the meiotic chromosomes were extremely contracted. The distribution pattern of 18S rDNA signals varied markedly showing two different variants – with one or two rDNA-carrying bivalents in MI karyotype and, correspondingly, with one or two rDNA-carrying chromosomes in MII karyotype. All chromosome numbers were found to coincide with previously published karyotype data for seven studied species (Lukhtanov et al. 2005, Kandul et al. 2007). In two Polyommatus (Agrodiaetus) hamadanensis populations intraspecific chromosomal polymorphism has been discovered.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Zoological Institute, Russian Academy of Sciences, Universitetskaya emb. 1, St. Petersburg 199034, Russia.

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.

No MeSH data available.


Related in: MedlinePlus