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P G Cionini

Publications and source records attributed to P G Cionini.

15 recordsLinked to original sources
PubMed2000

The chromosome complement of Olea europaea L.: characterization by differential staining of the chromatin and in-situ hybridization of highly repeated DNA sequences.

The chromosome complement of olive (Olea europaea L.) has been characterized by differential staining of the chromatin and chromosomal localization of highly repeated DNA sequences and ribosomal cistrons. DAPI staining produces different-sized positive bands in various locations on all the chromosomes. By combining this band pattern with the results obtained from cytological hybridization of OeTaq80, OeTaq178, and OeGEM86 DNA tandem repeats, most of the pairs can be distinguished from each other, in spite of the large number of chromosomes (2n = 46), their small size and similar morphology. Different tandem-repeated DNA sequences may be contained into single heterochromatic chromosome regions, even though there are regions where repeats of only one family are present. OeTaq80- and OeGEM86-related DNA sequences are rather specific to the heterochromatin at the chromosome ends, while most sequences related to the longer OeTaq178 probe are confined to interstitial heterochromatin. Some exceptions suggest that major chromosomal rearrangements occurred during genome evolution. Polymorphism, which may differentiate olive cultivars, was observed within chromosome pairs I, V, and VII.

Chromatin↗
PubMed1999

A family of dispersed repeats in the genome of Vicia faba: structure, chromosomal organization, redundancy modulation, and evolution.

A family of repeated DNA sequences of about 1200 bp in length and bordered by well-conserved, 18 bp inverted repeats (VfB family) was found in the nuclear genome of Vicia faba. The structure, chromosomal organization, redundancy modulation and evolution of these sequences were investigated. They are enriched in A+T base pairs (about 40% G+C) and lack any obvious internally repeated motif. A 64%-73% nucleotide sequence identity was found when pairwise comparisons between VfB sequences were carried out (average 69%). Direct repeats were not found to flank the inverted repeats that border these DNA sequences. The results obtained by hybridizing VfB repeats to Southern blots of V. faba genomic DNA digested with EcoRI indicated that these DNA elements are interspersed in the genome. The appearance of bands in these Southern blots and comparison of the structure of the sequences that flank different VfB elements showed that these repeats might be part of other, longer repeated DNA sequences. A high degree of dispersion throughout the genome was confirmed by cytological hybridization, which showed VfB sequences to be scattered along the length of all chromosomes and to be absent or rare only at heterochromatic chromosomal regions. These sequences contribute to intraspecific alterations of genomic size. Indeed, dot-blot hybridizations proved that their redundancy, which is positively correlated with the overall amount of nuclear DNA in each accession, varies between V. faba land races (27x10(3)-230x10(3) copies per 1C DNA). Southern blot hybridization of VfB repeats to restriction endonuclease-digested genomic DNAs of V. faba, V. narbonensis, V. sativa, Phaseolus coccineus, Populus deltoides, and Triticum durum revealed nucleotide sequence homology of these DNA elements, whatever the stringency conditions, only to the DNAs of Vicia species, and to a reduced extent to the DNAs of V. narbonensis and V. sativa compared with that of V. faba. It is concluded that VfB repeats might be descended from mobile DNA elements and contribute to change genomic size and organization during evolution.

Base Composition↗
PubMed1999

Amount and organization of the heterochromatin in Olea europaea and related species.

The amount and spatial organization of the heterochromatin in nuclei of the shoot meristem and the frequency in the nuclear DNA of sequences belonging to a family of tandem repeats were investigated in cultivars of Olea europaea and related species. Significant differences between Olea species and between cultivars of O. europaea were observed: (i) in the spatial organization of the heterochromatin in interphase nuclei as determined by the number and surface area of the chromocentres; (ii) in genome size; and (iii) in the amount of condensed chromatin as measured by cytophotometry carried out at different thresholds of optical density. DNA elements belonging to a family of tandem repeats about 80 bp in length (OeTaq80 repeats) were isolated from the genomic DNA of an olive cultivar. It was shown: (i) by nucleotide sequence comparisons, that these repeats display variability in structure even within the same array, where different elements may share no more than 74% homology; (ii) by in situ hybridization, that OeTaq80-related DNA sequences are mainly localized in the heterochromatin at the chromosome ends; (iii) by dot-blot hybridization experiments, that these sequences are highly represented in the genome of all the olive cultivars and the majority of Olea species studied, and that their frequency may differ significantly even between olive cultivars; and (iv) by calculating the copy number of OeTaq80-related sequences per haploid (1C) genome, that the redundancy of these DNA elements may differ significantly between the genomes tested. It is suggested that the inter- and intraspecific changes in the nuclear and genomic traits observed can contribute to the understanding of the phylogenetic relationships between Olea species and in defining parameters to be exploited in varietal identification within cultivated olives.

Base Sequence↗
PubMed1995

FokI DNA repeats in the genome of Vicia faba: species specificity, structure, redundancy modulation, and nuclear organization.

Tandemly repeated DNA sequences about 60 bp in length, which may be isolated by digestion with FokI restriction endonuclease, were studied by means of molecular and cytological hybridization in Vicia faba and other Vicia species. The results obtained can be summarized as follows: (i) FokI repeats are almost species specific to V. faba, since they hybridize to a minimum extent to genomic DNA of only two out of five related species; (ii) these tandemly repeated elements display variability in structure even within one and the same array, where different repeats may share not more than 71% homology; (iii) their redundancy in the genome of V. faba is remarkably high and varies largely between land races (copy numbers per haploid, 1C, genome range from 21.51 x 10(6) to 5.39 x 10(6)); (iv) FokI repeats are clustered in differing amounts in each subtelocentric pair of the chromosome complement and are missing or present in a nondetectable amount in the submetacentric pair; (vi) chromosome regions that bear these repeats associate closely to varying degrees in interphase nuclei. These results are discussed in relation to possible functional roles that tandemly repeated DNA sequences such as the FokI elements might play.

Base Sequence↗
PubMed1991

Structure and chromosomal localization of DNA sequences related to ribosomal subrepeats in Vicia faba.

Subrepeating sequences of 325 bp found in the ribosomal intergenic spacer (IGS) of Vicia faba and responsible for variations in the length of the polycistronic units for rRNA were isolated and used as probes for in situ hybridization. Hybridization occurs at many regions of the metaphase chromosomes besides those bearing rRNA genes, namely chromosome ends and all the heterochromatic regions revealed by enhanced fluorescence after quinacrine staining. The DNA homologous to the 325 bp repeats that does not reside in the IGS was isolated, cloned and sequenced. It is composed of tandemly arranged 336 bp elements, each comprising two highly related 168 bp sequences. This structure is very similar to that of the IGS repeats and ca. 75% nucleotide sequence identity can be observed between these and the 168 bp doublets. The most obvious difference lies in the deletion, in the former, of a 14 bp segment from one of the two related sequences. It is hypothesized that the IGS repeats are derived from the 336 bp elements and have been transposed to ribosomal cistrons from other genome fractions. The possible relations between these sequences and others with similar structural features found in other species are discussed.

Base Sequence↗
PubMed1986

Amplification of nuclear DNA sequences during induced plant cell dedifferentiation.

Cell dedifferentiation has been induced in Vicia faba roots by removing the whole meristem (decapitation). When centrifuged to equilibrium in CsCl density gradient, the DNA from dedifferentiating tissues forms a heavier satellite, not occurring in the DNA from differentiated tissues. Most of the radioactivity after [3H]thymidine feeding is found in the satellite DNA. Its sequences have a well defined nuclear localization, as shown by in situ hybridization experiments. These results indicate amplification of G + C-rich nuclear DNA sequences during cell dedifferentiation.

Cell Differentiation↗
PubMed1984

In situ evaluation of the functional state of chromatin by means of Quinacrine Mustard staining and time-resolved fluorescence microscopy.

A pulsed laser microfluorometer with high spatial and temporal resolution was employed to study the functional state of chromatin, using Quinacrine Mustard as the fluorescent probe. Corresponding segments of polytene chromosomes of embryo suspensor cells of Phaseolus coccineus and parenchymal cells of Helianthus tuberosus, in phases not involving DNA synthesis, were selected as models. The fluorescence decay time turned out to be a discriminating parameter for the chromatin fractions of differing functional engagement. The results were interpreted on the basis of a different accessibility of the DNA to the intercalating agent, as a result of the different structural situation of the chromatin. This fact determines modifications of the energy transfer rates between dye molecules in different quantum efficiency conditions, which results in variations of fluorescence decay times.

Chromatin↗
PubMed1982

Cytological localization of inverted repeated DNA sequences in Vicia faba.

Inverted repeated DNA sequences have been isolated from sheared Vicia faba DNA by hydroxylapatite column chromatography, treated with nuclease S1, tritiated by the nick translation method and hybridized in situ on squashes of Vicia faba root tips. Silver grains appear grouped in a rather limited portion of interphase nuclei and form a sort of band across them. The central regions of metaphase chromosomes are preferentially labeled, labeling being excluded from telomeres, centromeres and secondary constrictions. These results are briefly discussed in relation to those obtained in other species and the functional significance of inverted repeats.

DNA↗
PubMed1979

Employment of bis-intercalating dyes for the "in situ" study of DNA composition.

Spectrofluorometric characteristics of DNA-RO4 complexes have been studied in order to evaluate the possibility of employment of RO4 (a bis-intercalating dye) for the determination of the DNA base composition. The results have shown the usefulness of this compound for DNA with AT percentage between 30% and 60%. RO4 has been also applied to the study of the chromosome banding mechanism.

Aminoacridines↗
PubMed1977

Cytological localization of the genes for the four classes of ribosomal RNA (25S, 18S, 5.8S and 5S) in polytene chromosomes of Phaseolus coccineus.

Homologous tritiated 25S, 18S and 5.8S rRNAs were used separately for in situ hybridization to the polytene chromosomes of the embryo suspensor cells of phaseolus coccineus. Hybridization occurred at the same chromosomal sites which were labeled in previous in situ hybridization experiments with 25 + 18S rRNAs in the same material (Avanzi et al., 1972), namely: nucleolus organizing system (satellite, nucleolar constriction and organizer) of chromosome pairs I (S1) and V (S2), proximal heterochromatic segment of the long arm of chromosome pair I, and terminal heterochromatic segment of chromosome pair II. Competition hybridization experiments confirmed for P. coccineus the high sequence homology between 25S and 18S rRNA already known for other plants. Homologous 125I-5S rRNA was found to hybridize to three sites in the polytene chromosomes of P. coccineus: the proximal heterochromatic segment in the long arm of chromosome pair I (which also bears the sequences complementary to 25S, 18S and 5.8S RNAs), most of the proximal heterochromatic segment plus a small portion of adjoining euchromatin in the long arm of chromosome pair VI and the large intercalary heterochromatic segment in the same chromosome pair. Simultaneous labeling of the two 5S RNA sites in chromosome VI was quite rare (3%), the rule being labelling of one site to the exclusion of the other, with a labeling frequency of 43.7% and 53.3% for sites no. 1 and no. 2 respectively. These results are interpreted as being due to differential hybridizability of chromosomal sites such as described in other materials.

Chromosome Mapping↗