rDNA site number polymorphism and NOR inactivation in natural populations ofAllium schoenoprasum

Garrido, Miguel Ángel Mesa; Jamilena, Manuel; Lozano, Rafael; Rejón, Carmelo Ruiz; Rejón, M. Ruíz; Parker, John

doi:10.1007/bf01429221

Cited by 18 publications

(10 citation statements)

References 15 publications

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“…Variation in the expression of 45S rDNA loci was also reported in H. chilensis (Cerbah et al, 1998a). In H. variegata, the polymorphism observed in the size of the rDNA site could have originated by unequal crossing-over or by amplification and transposition of single rDNA copies, as suggested for other plant species (Schubert and Wobus, 1985;Garrido et al, 1994). Cerbah et al (1998a) suggested that the main 45S rDNA site for the South American species is located on chromosome 3.…”

Section: Localization Of 45s and 5s Ribosomal Genesmentioning

confidence: 63%

Chromosomal organization and phylogenetic relationships in Hypochaeris species (Asteraceae) from Brazil

et al. 2005

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The association of cytogenetic and molecular techniques has contributed to the analysis of chromosome organization and phylogeny in plants. The fluorochrome GC-specific CMA 3 , fluorescent in situ hybridization (FISH) and RAPD (Random Amplified Polymorphic DNA) markers were used to investigate chromosome structure and genetic relationships in Hypochaeris (Asteraceae). Seven species native to South America, and two species introduced from Europe (H. glabra and Hypochaeris sp) were studied. FISH with rDNA probes identified one or two loci of 18S-5.8S-25S rDNA in the South American Hypochaeris species and one locus in the European species. Only one 5S rDNA locus was seen in all species studied. Blocks of GC-rich heterochromatin (CMA-positive bands) associated to 18S-5.8S-25SrDNA loci were detected in all species investigated. Co-location of 5S rDNA and CMA bands was also observed, except for three South American species and Hypochaeris sp. In two South American species, additional CMA bands not related to rDNA were observed on the long arm of chromosome 2, near to the centromere. Hypochaeris glabra exhibited additional CMA-positive signals distributed at pericentromeric regions, on the short arms of all chromosomes. A total of 122 RAPD markers were used to determine the genetic relationships among species. The level of polymorphism was very high, revealing two genetic groups comprising the South American and the European species, thus supporting a previous hypothesis of monophyly of the South American Hypochaeris species. The coefficients of genetic similarity between European and South American species were 0.35, on average. Polymorphism was also high within the two groups. The genetic associations observed with RAPD markers were consistent with chromosome characteristics. Species carrying similar distribution of 45S rDNA loci and CMA-positive signals were included in the same group revealed by RAPDs. Cytogenetic and molecular data support the view that not only chromosome rearrangements, but also changes in DNA sequence took place during the diversification of the South American Hypochaeris species.

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Section: Localization Of 45s and 5s Ribosomal Genesmentioning

confidence: 63%

Chromosomal organization and phylogenetic relationships in Hypochaeris species (Asteraceae) from Brazil

et al. 2005

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“…None of the American samples showed such an increase. On the other hand, in other crop species it has been reported that the number of ribosomal sites tends to rather diminish than increase during the evolution (MALUSZYNSKA and HESLOP-HARRISON 1993b;FUKUI et al 1994;GARRIDO et al 1994). It is also worth of notice that no variation for the position and number of the 5S rDNA sites is present (Figs.…”

Section: Discussionmentioning

confidence: 91%

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

Galasso¹,

Saponetti²,

Pignone³

1998

Caryologia

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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.

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“…The copy number and chromosomal location of rDNA could be rapidly changed in plant genomes (SCHUBERT and WOBUS 1985;RAI-NA and MUKAI 1999), and chromosomal rDNA distribution often varies among closely-related taxa, even if within species (GARRIDO et al 1994). Variation in the amount of rDNA genes has demonstrated to be on the basis of most of these polymorphisms, as revealed by in situ hybridization (WARBURTON and HENDERSON 1979;KING et al 1990;CASTRO et al 1998).…”

Section: Discussionmentioning

confidence: 99%

Distribution patterns of rDNAs and telomeres and chromosomal rearrangement between two cytotypes ofLysimachia mauritianaL. (Primulaceae)

et al. 2011

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-Two cytotypes of Lysimachia mauritiana collected from Japanese mainland (JM-type) and the Sakishima group (SR-type), located in the southernmost of the Ryukyu Archipelago of Japan, were cytogenetically analyzed. JM-and SR-types showed karyotype formulae of 2n=20(4m)=4m+2sm+4st+10t and 2n=18(6m)=6m+2sm+10t, respectively. In FISH analysis, a signal of 5S rDNA was observed at the interstitial region of long arm on a pair of t-chromosome in both cytotypes. On the other hand, different sizes of 45S rDNA signals were observed on the distal and proximal regions of m-, sm-, st-and t-chromosomes in JM-type, and of m-and t-chromosomes in SR-type. Also in SR-type, a tiny 45S rDNA signal was shown at the interstitial region of long arm on sm-chromosome. Telomere signals in two cytotypes appeared at both ends of all chromosomes, and at internal sites of certain chromosomes. The big telomere sequence signal at the proximal region coincided with the small 45S rDNA signal in JM-type. These results gave us a fusion/fi ssion hypothesis with two st-or one m-chromosome(s) for new intraspecifi c karyotype formation of JM-type or SR-type.

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rDNA site number polymorphism and NOR inactivation in natural populations ofAllium schoenoprasum

Cited by 18 publications

References 15 publications

Chromosomal organization and phylogenetic relationships in Hypochaeris species (Asteraceae) from Brazil

Chromosomal organization and phylogenetic relationships in Hypochaeris species (Asteraceae) from Brazil

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

Distribution patterns of rDNAs and telomeres and chromosomal rearrangement between two cytotypes ofLysimachia mauritianaL. (Primulaceae)

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