Nucleolus organizer regions in Drosophila species of the repleta group

Hennig, Wolfgang; Vogt, Peter H.; Jacob, Gabriele; Siegmund, Ingrid

doi:10.1007/bf00327630

Cited by 23 publications

(7 citation statements)

References 18 publications

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“…This observation is in accordance with previous results of Southem-blot analysis showing preferential replication (replicative dominance) of the D. simulans rDNA in the sima polytene nuclei (Mecheva & Semionov, 1990). Similar differences of the nucleolar organization of Drosophila species were observed earlier for the repleta group (Hennig et al, 1982). As might have been expected, in two other hybridsinsertion sequences only within the NOs and the mesi (D. melanogaster X D. simulans) and mema nucleoli (Semionov et al, 1986).…”

Section: Distribution Of Type I and Type Ii Insertions Along The Polysupporting

confidence: 60%

Localization of ribosomal DNA insertion elements in polytene chromosomes of Drosophila simulans, Drosophila mauritiana and their interspecific hybrids

Mecheva

Semionov

1992

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The locations of the ribosomal DNA (rDNA) insertion elements type I and type II along the polytene chromosomes of three Drosophila species of the melanogaster subgroup--D. simulans, D. mauritiana and D. melanogaster--have been compared. In situ hybridization has shown that the intragenomic distribution of type I as well as of type II insertions is different for these related species. In particular, we have revealed rDNA-free autosomal sites, containing type II element sequences within the D. simulans and D. mauritiana chromosomes. This finding confirms the ability of this type of insertion to transpose, as was demonstrated earlier for Bombyx mori. The appearance of the rDNA not associated with the nucleolar organizers, evident by additional nucleoli, occurred with species-specific frequency. At the same time, for all three species the pattern of such changes (an attachment of the nucleoli to varying sites of the chromosomes and the presence of ectopic contacts between them, a composition of the rDNA repeats in the nucleolar material not integrated at the nucleolar organizer) was similar. The number of additional nucleoli in the hybrid polytene nuclei corresponded to the value of the parental species exhibiting nucleolar replicative dominance.

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Section: Distribution Of Type I and Type Ii Insertions Along The Polysupporting

confidence: 60%

Localization of ribosomal DNA insertion elements in polytene chromosomes of Drosophila simulans, Drosophila mauritiana and their interspecific hybrids

Mecheva

Semionov

1992

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“…Because the rDNA units in D. ananassae are on the Y and 4th chromosomes (Roy et al 2005), we suggest that these variants represent sequence differences between the units on these chromosomes. Our data would predict that the rDNA units in D. mojanensis are also likely to be located on nonhomologous chromosomes, a situation proposed for several species of the repleta group (Hennig et al 1982).…”

Section: Genome Research 1893mentioning

confidence: 57%

Sequence variation within the rRNA gene loci of 12 Drosophila species

Stage¹,

Eickbush²

2007

Genome Res.

116

127

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Concerted evolution maintains at near identity the hundreds of tandemly arrayed ribosomal RNA (rRNA) genes and their spacers present in any eukaryote. Few comprehensive attempts have been made to directly measure the identity between the rDNA units. We used the original sequencing reads (trace archives) available through the whole-genome shotgun sequencing projects of 12 Drosophila species to locate the sequence variants within the 7.8-8.2 kb transcribed portions of the rDNA units. Three to 18 variants were identified in >3% of the total rDNA units from 11 species. Species where the rDNA units are present on multiple chromosomes exhibited only minor increases in sequence variation. Variants were 10-20 times more abundant in the noncoding compared with the coding regions of the rDNA unit. Within the coding regions, variants were three to eight times more abundant in the expansion compared with the conserved core regions. The distribution of variants was largely consistent with models of concerted evolution in which there is uniform recombination across the transcribed portion of the unit with the frequency of standing variants dependent upon the selection pressure to preserve that sequence. However, the 28S gene was found to contain fewer variants than the 18S gene despite evolving 2.5-fold faster. We postulate that the fewer variants in the 28S gene is due to localized gene conversion or DNA repair triggered by the activity of retrotransposable elements that are specialized for insertion into the 28S genes of these species.

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“…Although it was not shown that the integration site was telomeric, these results suggest some genetic instability of the satellite DNA arrays that may make them targets of transposable element insertions. It is also noteworthy that capture of nonhomologous DNA fragments can occur at the telomeres of the lower dipteran insect Anopheles gambiae, which also contains a complex satellite DNA (Biessmann et al 1996(Biessmann et al , 1998, and at several telomeres of D. neohydei (Hennig et al 1982), whose telomeric DNA sequences have not yet been identified.…”

Section: Discussionmentioning

confidence: 96%

A telomeric satellite in Drosophila virilis and its sibling species

et al. 2000

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Telomere elongation by telomerase is the most widespread mechanism among eukaryotes. However, alternative mechanisms such as homologous recombination between terminal satellite DNAs are probably used in lower dipteran insects and in some plants. Drosophila melanogaster uses the very unusual telomere elongation pathway of transposition of telomere-specific retrotransposable elements. The uniqueness of this telomere elongation mechanism raises the question of its origin. We, therefore, analyzed sequences located at telomeres of fairly distantly related Drosophila species, and in this paper we describe the characterization of complex satellite DNA sequences located at the telomeres of D. virilis and other species in the virilis group. We suggest an involvement of these DNA satellites in telomere elongation by homologous recombination similar to that found in lower dipterans. Our findings raise the possibility that telomere elongation by specific retrotransposons as found in D. melanogaster and its sibling species is a recent event in the evolution of dipteran insects.

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Nucleolus organizer regions in Drosophila species of the repleta group

Cited by 23 publications

References 18 publications

Localization of ribosomal DNA insertion elements in polytene chromosomes of Drosophila simulans, Drosophila mauritiana and their interspecific hybrids

Localization of ribosomal DNA insertion elements in polytene chromosomes of Drosophila simulans, Drosophila mauritiana and their interspecific hybrids

Sequence variation within the rRNA gene loci of 12 Drosophila species

A telomeric satellite in Drosophila virilis and its sibling species

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