Abstract
Maize karyotype variability has been extensively investigated. The identification of maize somatic and pachytene chromosomes has improved with the development of fluorescence in situ hybridization (FISH) using tandemly repeated DNA sequences as probes. We identified the somatic chromosomes of sister inbred lines that were derived from a tropical flint maize population (Jac Duro [JD]), and hybrids between them, using FISH probes for the 180-bp knob repeat, centromeric satellite (CentC), centromeric satellite 4 (Cent4), subtelomeric clone 4-12-1, 5S ribosomal DNA and nucleolus organizing region DNA sequences. The observations were integrated with data based on C-banded mitotic metaphases and conventional analysis of pachytene chromosomes. Heterochromatic knobs visible at pachynema were coincident with C-bands and 180-bp FISH signals on somatic chromosomes, and most of them were large. Variation in the presence of some knobs was observed among lines. Small 180-bp knob signals were invariant on the short arms of chromosomes 1, 6, and 9. The subtelomeric 4-12-1 signal was also invariant and useful for identifying some chromosomes. The centromere location of chromosomes 2 and 4 differed from previous reports on standard maize lines. Somatic chromosomes of a JD line and the commonly used KYS line were compared by FISH in a hybrid of these lines. The pairing behavior of chromosomes 2 and 4 at pachytene stage in this hybrid was investigated using FISH with chromosome-specific probes. The homologues were fully synapsed, including the 5S rDNA and CentC sites on chromosome 2, and Cent4 and subtelomeric 4-12-1 sites on chromosome 4. This suggests that homologous chromosomes could pair through differential degrees of chromatin packaging in homologous arms differing in size. The results contribute to current knowledge of maize global diversity and also raise questions concerning the meiotic pairing of homologous chromosomes possibly differing in their amounts of repetitive DNA.
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Claims 8
Claim · model-written summary
In maize, heterochromatic knobs visible at pachynema were coincident with C-bands and 180-bp FISH signals on somatic chromosomes.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize karyotype variability has been extensively investigated”
e1“Heterochromatic knobs visible at pachynema were coincident with C-bands and 180-bp FISH signals on somatic chromosomes, and most of them were large”
Claim · model-written summary
Most heterochromatic knobs in maize were large.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize karyotype variability has been extensively investigated”
e1“Heterochromatic knobs visible at pachynema were coincident with C-bands and 180-bp FISH signals on somatic chromosomes, and most of them were large”
Claim · model-written summary
Presence of some knobs varied among maize lines.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize karyotype variability has been extensively investigated”
e2“Variation in the presence of some knobs was observed among lines”
Claim · model-written summary
Small 180-bp knob signals were invariant on the short arms of maize chromosomes 1, 6 and 9.
- Organ / stage
- short arms of chromosomes 1, 6, and 9e3
- Outcome
- Small 180-bp knob signalse3
- Qualifier
- invariante3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize karyotype variability has been extensively investigated”
e3“Small 180-bp knob signals were invariant on the short arms of chromosomes 1, 6, and 9”
Claim · model-written summary
The subtelomeric 4-12-1 signal in maize was invariant and useful for identifying some chromosomes.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize karyotype variability has been extensively investigated”
e4“The subtelomeric 4-12-1 signal was also invariant and useful for identifying some chromosomes”
Claim · model-written summary
The centromere location of maize chromosomes 2 and 4 differed from previous reports on standard maize lines.
- Outcome
- centromere location of chromosomes 2 and 4e5
- Comparator
- previous reports on standard maize linese5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize karyotype variability has been extensively investigated”
e5“The centromere location of chromosomes 2 and 4 differed from previous reports on standard maize lines”
Claim · model-written summary
In a maize hybrid, the homologues were fully synapsed at pachytene, including the 5S rDNA and CentC sites on chromosome 2 and the Cent4 and subtelomeric 4-12-1 sites on chromosome 4.
- Outcome
- The homologues were fully synapsede6
- Qualifier
- including the 5S rDNA and CentC sites on chromosome 2e6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize karyotype variability has been extensively investigated”
e6“The homologues were fully synapsed, including the 5S rDNA and CentC sites on chromosome 2, and Cent4 and subtelomeric 4-12-1 sites on chromosome 4”
Claim · model-written summary
Homologous maize chromosomes could pair through differential degrees of chromatin packaging in homologous arms differing in size.
- Outcome
- homologous chromosomes could paire7
- Qualifier
- differential degrees of chromatin packaging in homologous arms differing in sizee7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize karyotype variability has been extensively investigated”
e7“This suggests that homologous chromosomes could pair through differential degrees of chromatin packaging in homologous arms differing in size”