scholarly journals Maize Chromosome Abnormalities and Breakage-Fusion-Bridge Cycles in Callus Cultures

2020 ◽  
Author(s):  
Margarida L.R. Aguiar-Perecin ◽  
Janay A. Santos-Serejo ◽  
José R. Gardingo ◽  
Mateus Mondin
Keyword(s):  
Dna Sequences ◽  
De Novo ◽  
Callus Cultures ◽  
Chromosome Abnormalities ◽  
Anaphase Bridges ◽  
C Banding ◽  
Chromosome Healing ◽  
Bfb Cycle ◽  
Chromosome Alterations

The maize karyotype was first characterized by the observation of pachytene chromosomes. The somatic chromosomes were identified by C-banding and FISH with repetitive DNA sequences. C-banding was useful for the identification of chromosome abnormalities in callus cultures. In the present review, we focus on the involvement of heterochromatic knobs on the occurrence of chromosome abnormalities in callus cultures. In a previous work we detected anaphase bridges resulting from delayed chromatid separation at knob regions and typical bridges derived from dicentric chromatids in cultures. The analysis of altered chromosomes showed they were derived from a chromatid-type breakage-fusion-bridge (BFB) cycle. Fluorescent in situ hybridization (FISH) showed signals of telomere sequences in the broken chromosome arm, thus giving evidence of de novo telomere formation on the broken chromosome end. Further observations of long- and short-term cultures have shown the presence of chromosome alterations derived from BFB cycles followed by chromosome healing. Additionally, the occurrence of unequal crossing over in a knob region was observed in callus culture. These results are of interest for studies on the mechanisms of chromosome alterations during evolution.

scholarly journals Breakage–fusion–bridge cycles and de novo telomere formation on broken chromosomes in maize callus cultures

Genome ◽  
2016 ◽  
Vol 59 (6) ◽  
pp. 367-378 ◽  
Author(s):  
Janay A. Santos-Serejo ◽  
Margarida L.R. Aguiar-Perecin
Keyword(s):  
De Novo ◽  
Chromosomal Evolution ◽  
Callus Cultures ◽  
Chromosome 7 ◽  
Telomeric Sequences ◽  
Chromosome Healing ◽  
Regenerated Plants ◽  
The Stability ◽  
Maize Callus

Breakpoints involved in chromosome alterations associated with heterochromatin have been detected in maize plants regenerated from callus culture. A cytogenetic analysis of plants regenerated from a maize callus was performed aiming to analyze the stability of a chromosome 7 bearing a deficiency-duplication (Df-Dp), which was interpreted as derived from a chromatid type breakage–fusion–bridge (BFB) cycle. The Df-Dp chromosome 7 was stable in mitotic and meiotic cells of the regenerated plants. Fluorescence in situ hybridization showed signals of telomeric sequences on the broken chromosome arm and provided evidence of de novo telomere formation. The stability of two types of altered chromosome 7 was investigated in C-banded metaphases from samples of the original callus that were collected during a period of 30–42 months after culture initiation. New alterations involving heterochromatic knobs of chromosomes 7 and 9 were observed. The aberrant chromosomes were stable in the subcultures, thus providing evidence of broken chromosome healing. The examination of anaphases showed the presence of bridges, which was consistent with the occurrence of BFB cycles. De novo telomere formation occurred in euchromatic and heterochromatic chromosome termini. The results point to events of chromosomal evolution that might occur in plants.

scholarly journals snRNA and Heterochromatin Formation Are Involved in DNA Excision during Macronuclear Development in Stichotrichous Ciliates

2005 ◽  
Vol 4 (11) ◽  
pp. 1934-1941 ◽  
Author(s):  
Stefan A. Juranek ◽  
Sina Rupprecht ◽  
Jan Postberg ◽  
Hans J. Lipps
Keyword(s):  
Dna Sequences ◽  
Chromatin Immunoprecipitation ◽  
De Novo ◽  
Histone H3 ◽  
Heterochromatin Formation ◽  
Macronuclear Development ◽  
Dna Elimination ◽  
Histone H3 Variant ◽  
Specific Sequences

ABSTRACT Several models for specific excision of micronucleus-specific DNA sequences during macronuclear development in ciliates exist. While the template-guided recombination model suggests recombination events resulting in specific DNA excision and reordering of macronucleus-destined sequences (MDS) guided by a template, there is evidence that an RNA interference-related mechanism is involved in DNA elimination in holotrichous ciliates. We describe that in the stichotrichous ciliate Stylonychia, snRNAs homologous to micronucleus-specific sequences are synthesized during macronuclear differentiation. Western and in situ analyses demonstrate that histone H3 becomes methylated at K9 de novo during macronuclear differentiation, and chromatin immunoprecipitation revealed that micronucleus-specific sequences are associated with methylated H3. To link both observations, expression of a PIWI homolog, member of the RNA-induced silencing complex, was silenced. In these cells, the methylated micronucleus-specific histone H3 variant “X” is still present in macronuclear anlagen and no K9 methylation of histone H3 is observed. We suggest that snRNA recruits chromatin-modifying enzymes to sequences to be excised. Based on our and earlier observations, we believe that this mechanism is not sufficient for specific excision of sequences and reordering of MDS in the developing macronucleus and propose a model for internal eliminated sequence excision and MDS reordering in stichotrichous ciliates.

Genome differentiation in Aegilops. 1. Distribution of highly repetitive DNA sequences on chromosomes of diploid species

Genome ◽  
1996 ◽  
Vol 39 (2) ◽  
pp. 293-306 ◽  
Author(s):  
Ekaterina D. Badaeva ◽  
Bernd Friebe ◽  
Bikram S. Gill
Keyword(s):  
In Situ Hybridization ◽  
Repetitive Dna ◽  
Dna Sequences ◽  
Repetitive Dna Sequences ◽  
Aegilops Species ◽  
D Genome ◽  
C Banding ◽  
Genome Differentiation ◽  
Highly Repetitive Dna

Genome differentiation in 12 diploid Aegilops species was analyzed using in situ hybridization with the highly repetitive DNA sequences pSc119 and pAs1 and C-banding. Chromosomes of all these diploid Aegilops species hybridized with the pSc119 probe; however, the level of hybridization and labeling patterns differed among genomes. Only four species (Ae. squarrosa, Ae. comosa, Ae. heldreichii, and Ae. uniaristata) showed distinct hybridization with pAs1. The labeling patterns were species-specific and chromosome-specific. Differences in in situ hybridization (ISH) patterns, also observed by C-banding, exist between the karyotypes of Ae. comosa and Ae. heldreichii, suggesting that they are separate, although closely related, subspecies. The S genome of Ae. spelioides was most similar to the B and G genomes of polyploid wheats on the basis of both C-banding and ISH patterns, but was different from other species of section Sitopsis. These species had different C-banding patterns but they were similar to each other and to Ae. mutica in the distribution of pSc119 hybridization sites. Two types of labeling were detected in Ae. squarrosa with the pAs1 probe. The first resembled that of the D-genome chromosomes of bread wheat, Triticum aestivum L. em. Thell., while the second was similar to the D genome of some of the polyploid Aegilops species. Relationships among diploid Aegilops species and the possible mechanisms of genome differentiation are discussed. Key words : wheat, Triticum, Aegilops, in situ hybridization, C-banding, evolution.

Sequential chromosome banding and in situ hybridization analysis

Genome ◽  
1993 ◽  
Vol 36 (4) ◽  
pp. 792-795 ◽  
Author(s):  
Jiming Jiang ◽  
Bikram S. Gill
Keyword(s):  
In Situ Hybridization ◽  
Dna Sequences ◽  
Acid Treatment ◽  
Chromosome Banding ◽  
Molecular Mapping ◽  
Genome Mapping ◽  
Genomic In Situ Hybridization ◽  
Metaphase Chromosomes ◽  
C Banding

Different combinations of chromosome N- or C-banding with in situ hybridization (ISH) or genomic in situ hybridization (GISH) were sequentially performed on metaphase chromosomes of wheat. A modified N-banding–ISH/GISH sequential procedure gave best results. Similarly, a modified C-banding – ISH/GISH procedure also gave satisfactory results. The variation of the hot acid treatment in the standard chromosome N- or C-banding procedures was the major factor affecting the resolution of the subsequent ISH and GISH. By the sequential chromosome banding – ISH/GISH analysis, multicopy DNA sequences and the breakpoints of wheat–alien translocations were directly allocated to specific chromosomes of wheat. The sequential chromosome banding– ISH/GISH technique should be widely applicable in genome mapping, especially in cytogenetic and molecular mapping of heterochromatic and euchromatic regions of plant and animal chromosomes.Key words: N-banding, C-banding, in situ hybridization, genomic in situ hybridization.

Distribution of telomeric repeats and their role in the healing of broken chromosome ends in wheat

Genome ◽  
1992 ◽  
Vol 35 (5) ◽  
pp. 844-848 ◽  
Author(s):  
Joanna E. Werner ◽  
Rama S. Kota ◽  
Bikram S. Gill ◽  
T. R. Endo
Keyword(s):  
In Situ Hybridization ◽  
De Novo ◽  
Wheat Chromosome ◽  
Variable Number ◽  
Mitotic Chromosomes ◽  
Telomeric Repeats ◽  
Telomeric Sequences ◽  
Chromosome Healing ◽  
Synthetic Probe

The distribution of the telomeric repeats in common wheat and their role in the healing of broken ends of deleted chromosomes was studied. In situ hybridization to mitotic chromosomes was carried out using a synthetic probe that was derived from the sequence of the telomeric repeats of Arabidopsis thaliana. Sites of hybridization were visualized as double dots at both ends of each wheat chromosome. Variation in the strength of the signal that was detected among chromosome arms might be due to the variable number of telomeric repeats of each chromosome end. While signals were absent on normal chromosomes at the pericentric and intercalary regions, hybridization sites were detected at the broken chromosome ends of all deleted chromosomes included in the study. All telocentric chromosomes of multitelocentric lines of 'Chinese Spring' showed a strong signal at the centromeric region. The results suggest that a de novo chromosome healing mechanism exists in wheat involving the addition of the telomeric sequences to the ends of broken chromosome. Further evidence indicated that the healing of broken ends is probably intrinsic to replication during gametogenesis.Key words: in situ hybridization, telomeric sequences, deleted chromosomes, chromosome healing, telosome.

Fluorescent in situ hybridization and C-banding analyses of highly repetitive DNA sequences in the heterochromatin of rye (Secale montanum Guss.) and wheat incorporating S. montanum chromosome segments

Genome ◽  
1995 ◽  
Vol 38 (4) ◽  
pp. 795-802 ◽  
Author(s):  
Angeles Cuadrado ◽  
Nicolás Jouve
Keyword(s):  
In Situ Hybridization ◽  
Repetitive Dna ◽  
Dna Sequences ◽  
Secale Cereale ◽  
Fluorescent In Situ Hybridization ◽  
Fish Analysis ◽  
C Banding ◽  
Translocation Breakpoints ◽  
Secale Montanum

The molecular characterization of C-banded regions of Secale montanum Guss. by means of in situ hybridization was performed in order to provide new information about their chromosome structure relative to cultivated rye, Secale cereale L. Accurate identification of individual chromosomes was achieved using simultaneous and (or) successive fluorescent in situ hybridization (FISH) and C-banding. FISH identification was performed using total rye DNA, three highly repetitive rye DNA sequences (pSc119.2, pSc74, and pSc34), and the ribosomal RNA probes pTa71 (18S, 5.8S, and 26S rDNA) and pTa794 (5S rDNA). FISH was also used to identify the chromosome segment involved in two spontaneous translocation lines recovered from a 'Chinese Spring' – S. montanum wheat–rye addition line. FISH analysis revealed the exact translocation breakpoints and allowed the identification of the transferred rye segments. The value of this type of analysis is discussed.Key words: Secale cereale, Secale montanum, rye, repetitive DNA, fluorescence in situ hybridization.

DNA sequence mapping in interphase and metaphase chromosomes by fluorescence in situ hybridization

1992 ◽  
Vol 50 (1) ◽  
pp. 496-497
Author(s):  
Barbara Trask ◽  
Susan Allen ◽  
Anne Bergmann ◽  
Mari Christensen ◽  
Anne Fertitta ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Dna Sequence ◽  
Dna Sequences ◽  
Dual Band ◽  
Nick Translation ◽  
Metaphase Chromosomes ◽  
Band Pass ◽  
Texas Red ◽  
Fluorescent Spot

Using fluorescence in situ hybridization (FISH), the positions of DNA sequences can be discretely marked with a fluorescent spot. The efficiency of marking DNA sequences of the size cloned in cosmids is 90-95%, and the fluorescent spots produced after FISH are ≈0.3 μm in diameter. Sites of two sequences can be distinguished using two-color FISH. Different reporter molecules, such as biotin or digoxigenin, are incorporated into DNA sequence probes by nick translation. These reporter molecules are labeled after hybridization with different fluorochromes, e.g., FITC and Texas Red. The development of dual band pass filters (Chromatechnology) allows these fluorochromes to be photographed simultaneously without registration shift.

scholarly journals HP1 drives de novo 3D genome reorganization in early Drosophila embryos

Nature ◽  
2021 ◽  
Author(s):  
Fides Zenk ◽  
Yinxiu Zhan ◽  
Pavel Kos ◽  
Eva Löser ◽  
Nazerke Atinbayeva ◽  
...  
Keyword(s):  
Genome Organization ◽  
Molecular Mechanisms ◽  
High Throughput Sequencing ◽  
De Novo ◽  
Early Embryo ◽  
Heterochromatin Protein ◽  
Chromosome Conformation ◽  
3D Genome ◽  
Genome Reorganization

AbstractFundamental features of 3D genome organization are established de novo in the early embryo, including clustering of pericentromeric regions, the folding of chromosome arms and the segregation of chromosomes into active (A-) and inactive (B-) compartments. However, the molecular mechanisms that drive de novo organization remain unknown1,2. Here, by combining chromosome conformation capture (Hi-C), chromatin immunoprecipitation with high-throughput sequencing (ChIP–seq), 3D DNA fluorescence in situ hybridization (3D DNA FISH) and polymer simulations, we show that heterochromatin protein 1a (HP1a) is essential for de novo 3D genome organization during Drosophila early development. The binding of HP1a at pericentromeric heterochromatin is required to establish clustering of pericentromeric regions. Moreover, HP1a binding within chromosome arms is responsible for overall chromosome folding and has an important role in the formation of B-compartment regions. However, depletion of HP1a does not affect the A-compartment, which suggests that a different molecular mechanism segregates active chromosome regions. Our work identifies HP1a as an epigenetic regulator that is involved in establishing the global structure of the genome in the early embryo.

scholarly journals Jacobsen syndrome and neonatal bleeding: report on two unrelated patients

2021 ◽  
Vol 47 (1) ◽  
Author(s):  
Gregorio Serra ◽  
Luigi Memo ◽  
Vincenzo Antona ◽  
Giovanni Corsello ◽  
Valentina Favero ◽  
...  
Keyword(s):  
Developmental Delay ◽  
De Novo ◽  
Comparative Genomic ◽  
Fish Analysis ◽  
Variable Degree ◽  
Jacobsen Syndrome ◽  
Contiguous Gene ◽  
Clinical Consequences ◽  
11Q Deletion

Abstract Introduction In 1973, Petrea Jacobsen described the first patient showing dysmorphic features, developmental delay and congenital heart disease (atrial and ventricular septal defect) associated to a 11q deletion, inherited from the father. Since then, more than 200 patients have been reported, and the chromosomal critical region responsible for this contiguous gene disorder has been identified. Patients’ presentation We report on two unrelated newborns observed in Italy affected by Jacobsen syndrome (JBS, also known as 11q23 deletion). Both patients presented prenatal and postnatal bleeding, growth and developmental delay, craniofacial dysmorphisms, multiple congenital anomalies, and pancytopenia of variable degree. Array comparative genomic hybridization (aCGH) identified a terminal deletion at 11q24.1-q25 of 12.5 Mb and 11 Mb, in Patient 1 and 2, respectively. Fluorescent in situ hybridization (FISH) analysis of the parents documented a de novo origin of the deletion for Patient 1; parents of Patient 2 refused further genetic investigations. Conclusions Present newborns show the full phenotype of JBS including thrombocytopenia, according to their wide 11q deletion size. Bleeding was particularly severe in one of them, leading to a cerebral hemorrhage. Our report highlights the relevance of early diagnosis, genetic counselling and careful management and follow-up of JBS patients, which may avoid severe clinical consequences and lower the mortality risk. It may provide further insights and a better characterization of JBS, suggesting new elements of the genotype-phenotype correlations.

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