Magnification in Drosophila: evidence for an inducible rDNA-specific recombination system

Komma, Donald J.; Atwood, K. C.

doi:10.1007/bf00280422

Cited by 10 publications

(8 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Finally, rapid changes in rDNA content have been documented in Drosophila 'bobbed' mutants, whose developmental defects are correlated with the loss of large numbers of rRNA genes from the NORs on either the X or Y chromosomes (Ritossa, 1976). Reversal of the bobbed phenotype can occur within several generations in certain genetic backgrounds and is correlated with the amplification (magnification) of the rDNA (Hawley and Tartof, 1985;Komma and Atwood, 1994;Ritossa, 1968). Therefore, it seems clear that NORs are dynamic regions of the genome where changes can occur rapidly.…”

Section: Changes Within the Rdna Of Nor2mentioning

confidence: 99%

Use of RFLPs larger than 100 kbp to map the position and internal organization of the nucleolus organizer region on chromosome 2 in Arabidopsis thaliana

et al. 1995

View full text Add to dashboard Cite

SummaryIn Arabidopsis thaliana ribosomel RNA genes (rRNA genes or rDNA) are grouped in two nucieolus organizer regions (NORs) that together comprise approximately 8% of the genome. The map positions of the NORs relative to other genetic markers are unknown. It was found that the restriction endonucleese Hindlll cuts once in some but not all rRNA genes to yield strain-specific RFLPs of 100-700 kb that could be visualized by pulsed-field gel electrophoresis and Southern blotting. The Hindlll RFLPs of the A. thaliana strains Columbia and Landsberg segregated among recombinant inbred lines derived from a cross between these two strains. Linkage analysis placed the NOR bearing the polymorphic Hindlll sites to the top of the upper arm of chromosome 2. The name NOR2 is suggested for this locus. HindUl-bearing rRNA genes ere interspersed with clusters of Hindlll-iess genes throughout NOR2. The observed clustering is most consistent with unequal crossing-over, or neerest-nelghbor gene conversion, as the mechanism(s) that spread rRNA gene variants throughout an NOR. No meiotic cross-over events yielding a 'hybrid' NOR with multiple RFLPs from both parents were observed among the 47 recombinant inbred lines examined. However, the appearance of novel HindUl profiles in approximately 40% of the recombinant inbred lines demonstrates that fluctuations in the distribution of rRNA gene variants occur frequently and can be readily detected on pulsedfield gels.

show abstract

Section: Changes Within the Rdna Of Nor2mentioning

confidence: 99%

Use of RFLPs larger than 100 kbp to map the position and internal organization of the nucleolus organizer region on chromosome 2 in Arabidopsis thaliana

et al. 1995

View full text Add to dashboard Cite

show abstract

“…Therefore, dual rDNA FISH result indicated that the copy number of 45S rDNA unit might be too low to detect on chromosomes at the cytogenetic level, even though there was the loci on the genome in this species or the plant strains used here. Several evidences of the intraspecifi c variation supported that unequal crossing over was the main mechanism involved in size changes of 45S rDNA sites (Butler and Metzenberg 1989;Komma and Atwood 1994). Determination of 45S rDNA locus in P. amaura, thus, would be possible by using other strains corrected from different population.…”

Section: Resultsmentioning

confidence: 99%

A cytogenetic study of Polytrias amaura (Poaceae)

et al. 2011

View full text Add to dashboard Cite

A karyomorphological characterization of Polytrias amaura (Poaceae) was performed using orcein staining, sequential fl uorescent staining with chromomycin A 3 (CMA) and 4',6-diamidino-2-phenylindole (DAPI), and fl uorescence in situ hybridization (FISH) method. The common somatic complement with 20 chromosomes were observed in all metaphase cells analyzed. Mitotic chromosomes in respective chromosome complement showed a gradual decrease in size from the largest to the smallest chromosomes. The largest and the smallest chromosome lengths at metaphase were 3.5 μm and 2.0 μm, respectively. The fl uorochromes of CMA and DAPI gave reproducible condensation pattern to every prometaphase chromosome, but not metaphse. Each chromosome displayed a characteristic condensation pattern, which was quite same between differential staining methods of GC-specifi c CMA and AT-specifi c DAPI. In FISH, two bright 5S rDNA signals were detected at interstitial region of the chromosomes.

show abstract

“…The number of ribosomal genes is supposed to be directly related to the size of the genome, but it can vary among species and even populations (CAPOSSELA et al 1992;MOSCONE et al 1995). It is known that the number of ribosomal genes could vary even very quickly in response to genetic or environmental stress (KOMMA and ATWOOD 1994;WATERS and SCHAAL 1996); moreover the activity of some rDNA clusters (NORs) could be regulated by evolutionary events or position effects (SCHUBERT and KUNZEL 1990). In the observed case, it seems that the change in the number of rDNA sites in the genome is associated to the artificial evolution consequent the domestication of cowpea.…”

Section: Discussionmentioning

confidence: 99%

Cytotaxonomic studies inVigna.IV. Variation of the number of active and silent rDNA sites inVigna unguiculatapopulations

Galasso¹,

Saponetti²,

Pignone³

1998

Caryologia

View full text Add to dashboard Cite

SUMMARY-Fluorescent in situ hybridization (FISH) using the pTa71 probe (18S 5.8S-25S rDNA) allowed the physical localization of the rRNA gene clusters on five chromosome pairs in mitotic metaphases of the reference line Tvx3236. Four pairs of these sites, showing high hybridization signal, colocalised with the chromosomal domains identified after Chromomycin A3 (CMA) fluorochrome staining, in telomeric regions. After staining with AgNO3, it was possible to ascertain that these sites had transcriptional activity. The fifth site, showing a lesser signal, had centromeric location and no transcriptional activity. In wild populations of Vigna unguiculata subsp. dekindtiana three major sites were detected with telomeric location and transcriptional activity. In two lines from Southern Italy six sites were observed: five were located telomerically and were genetically active, while the sixth was centromeric and had non activity. No variation was observed for the localization of the 5S rRNA gene clusteys. In all lines analysed it was possible to observe a strict topological correspondence between major rRNA genes sites and CMA stained heterocromatin. Moreover in all cases the regions so identified demonstrated transcriptional activity as assessed by the deposition of silver grains after AgNO3 staining. These results indicate that in cowpea the number of active r-DNA clusters is variable and might suggest that during the domestication/evolution of this crop an increase of these sites occurred.

show abstract

Magnification in Drosophila: evidence for an inducible rDNA-specific recombination system

Cited by 10 publications

References 16 publications

Use of RFLPs larger than 100 kbp to map the position and internal organization of the nucleolus organizer region on chromosome 2 in Arabidopsis thaliana

Use of RFLPs larger than 100 kbp to map the position and internal organization of the nucleolus organizer region on chromosome 2 in Arabidopsis thaliana

A cytogenetic study of Polytrias amaura (Poaceae)

Cytotaxonomic studies inVigna.IV. Variation of the number of active and silent rDNA sites inVigna unguiculatapopulations

Contact Info

Product

Resources

About