Abstract
Abnormal mitosis occurs in maize tapetum, producing binucleate cells that later disintegrate, following a pattern of programmed cell death. FISH allowed us to observe chromosome nondisjunction and micronucleus formation in binucleate cells, using DNA probes specific to B chromosomes (B's), knobbed chromosomes, and the chromosome 6 (NOR) of maize. All chromosome types seem to be involved in micronucleus formation, but the B's form more micronuclei than do knobbed chromosomes and knobbed chromosomes form more than do chromosomes without knobs. Micronuclei were more frequent in 1B plants and in a genotype selected for low B transmission rate. Nondisjunction was observed in all types of FISH-labeled chromosomes. In addition, unlabeled bridges and delayed chromatids were observed in the last telophase before binucleate cell formation, suggesting that nondisjunction might occur in all chromosomes of the maize complement. B nondisjunction is known to occur in the second pollen mitosis and in the endosperm, but it was not previously reported in other tissues. This is also a new report of nondisjunction of chromosomes of the normal set (A's) in tapetal cells. Our results support the conclusion that nondisjunction and micronucleus formation are regular events in the process of the tapetal cell death program, but B's strongly increase A chromosome instability.
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Claims 12
Claim · model-written summary
Abnormal mitosis in maize tapetum produced binucleate cells that later disintegrated.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abnormal mitosis occurs in maize tapetum, producing binucleate cells that later disintegrate”
Claim · model-written summary
All chromosome types appeared involved in micronucleus formation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All chromosome types seem to be involved in micronucleus formation”
e1“in maize tapetum”
Claim · model-written summary
B chromosomes formed more micronuclei than knobbed chromosomes.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the B's form more micronuclei than do knobbed chromosomes”
e1“in maize tapetum”
Claim · model-written summary
Knobbed chromosomes formed more micronuclei than chromosomes without knobs.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“knobbed chromosomes form more than do chromosomes without knobs”
e1“micronuclei”
e2“chromosome 6 (NOR) of maize”
Claim · model-written summary
Micronuclei were more frequent in 1B plants.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Micronuclei were more frequent in 1B plants”
e1“in maize tapetum”
Claim · model-written summary
Micronuclei were more frequent in a genotype selected for low B transmission.
- Material
- a genotype selected for low B transmission ratee0
- Outcome
- Micronucleie0
- Direction
- more frequente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Micronuclei were more frequent in 1B plants and in a genotype selected for low B transmission rate”
e1“in maize tapetum”
Claim · model-written summary
Nondisjunction occurred in all FISH-labeled chromosome types.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nondisjunction was observed in all types of FISH-labeled chromosomes”
e1“in maize tapetum”
Claim · model-written summary
Unlabeled bridges and delayed chromatids occurred before binucleate-cell formation.
- Organ / stage
- last telophase before binucleate cell formatione0
- Outcome
- unlabeled bridges and delayed chromatidse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“unlabeled bridges and delayed chromatids were observed in the last telophase before binucleate cell formation”
e1“in maize tapetum”
Claim · model-written summary
The authors inferred nondisjunction may affect all chromosomes in the maize complement.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“suggesting that nondisjunction might occur in all chromosomes of the maize complement”
Claim · model-written summary
The study newly reports nondisjunction of normal A chromosomes in tapetal cells.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a new report of nondisjunction of chromosomes of the normal set (A's) in tapetal cells”
e1“in maize tapetum”
Claim · model-written summary
The authors conclude nondisjunction and micronucleus formation regularly accompany tapetal cell death.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nondisjunction and micronucleus formation are regular events in the process of the tapetal cell death program”
e1“in maize tapetum”
Claim · model-written summary
B chromosomes strongly increased A chromosome instability.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“B's strongly increase A chromosome instability”
e1“in maize tapetum”