Abstract
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.
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Claims 6
Claim · model-written summary
The deficient duplicated chromosome 7 was stable in mitosis and meiosis.
- Outcome
- Df-Dp chromosome 7 was stable in mitotic and meiotic cellse0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Df-Dp chromosome 7 was stable in mitotic and meiotic cells of the regenerated plants.”
t0“maize callus cultures”
Claim · model-written summary
Telomeric signals on the broken arm evidenced new telomere formation.
- Outcome
- de novo telomere formatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fluorescence in situ hybridization showed signals of telomeric sequences on the broken chromosome arm and provided evidence of de novo telomere formation.”
t0“maize callus cultures”
Claim · model-written summary
New alterations involved heterochromatic knobs of chromosomes 7 and 9.
- Outcome
- New alterations involving heterochromatic knobs of chromosomes 7 and 9e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“New alterations involving heterochromatic knobs of chromosomes 7 and 9 were observed.”
t0“maize callus cultures”
Claim · model-written summary
Aberrant chromosomes remained stable in subcultures, supporting broken chromosome healing.
- Outcome
- aberrant chromosomes were stable in the subculturese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The aberrant chromosomes were stable in the subcultures, thus providing evidence of broken chromosome healing.”
t0“maize callus cultures”
Claim · model-written summary
Anaphase bridges were present, consistent with breakage fusion bridge cycles.
- Outcome
- presence of bridgese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The examination of anaphases showed the presence of bridges, which was consistent with the occurrence of BFB cycles.”
t0“maize callus cultures”
Claim · model-written summary
New telomeres formed at euchromatic and heterochromatic termini.
- Outcome
- De novo telomere formatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“De novo telomere formation occurred in euchromatic and heterochromatic chromosome termini.”
t0“maize callus cultures”