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Karyotype variability in tropical maize sister inbred lines and hybrids compared with KYS standard line.

Mondin M, Santos-Serejo JA, Bertäo MR, Laborda P, Pizzaia D, Aguiar-Perecin ML - Front Plant Sci (2014)

Bottom Line: 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 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, Brazil.

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.

No MeSH data available.


Related in: MedlinePlus

Chromosomes 2 (A–D), 4 (E–G), and 5 (H,I) at pachytene stage from the 441311 × KYS hybrid (A,B,D,E,G,H) and KYS (C,F) and 444331 (I) lines. The homologues are completely synapsed in the hybrid, with exception of one cell in which a loop possibly resulting from a pairing failure occurred in a segment of the bivalent 2 (B). The arrowheads indicate the centromeres in carmine-stained chromosomes (A–C,E,F,H). FISH signals (red) of CentC and 5S rDNA probes on chromosome 2 (D), Cent4 and subtelomeric 4-12-1 clone (red) on chromosome 4 (G), and 4-12-1 on chromosome 5 (I) are displayed. Scale bars for carmine stained chromosomes and FISH images = 10 μm.
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Figure 5: Chromosomes 2 (A–D), 4 (E–G), and 5 (H,I) at pachytene stage from the 441311 × KYS hybrid (A,B,D,E,G,H) and KYS (C,F) and 444331 (I) lines. The homologues are completely synapsed in the hybrid, with exception of one cell in which a loop possibly resulting from a pairing failure occurred in a segment of the bivalent 2 (B). The arrowheads indicate the centromeres in carmine-stained chromosomes (A–C,E,F,H). FISH signals (red) of CentC and 5S rDNA probes on chromosome 2 (D), Cent4 and subtelomeric 4-12-1 clone (red) on chromosome 4 (G), and 4-12-1 on chromosome 5 (I) are displayed. Scale bars for carmine stained chromosomes and FISH images = 10 μm.

Mentions: The pachytene chromosomes of the 441311 × KYS hybrid were examined to investigate the pairing behavior of chromosomes 2 and 4. Carmine-stained chromosomes 2 and 4 from the 441311 and KYS lines and the respective hybrid (Figures 5A–C,E,F) were analyzed to compare their arm ratios. Chromosomes of the 444331 line were also included in this analysis (Table 3). The arm ratios of the chromosome 2 of 441311, 444331 and 4411311 × KYS were very similar (about 1.70), while in KYS (Figure 5C) it was 1.36, corresponding to data in the literature (Table 3; see review of KYS data in Anderson et al., 2003). The homologous chromosomes of the bivalent 2 were completely synapsed in all of the cells that were examined (Figure 5A), and in only one microsporocyte, a loop was detected (Figure 5B), suggesting the occurrence of a pairing failure in a chromosomal segment. The chromosome 4 arm ratios in 441311, 444331 and 4411311 × KYS were not similar (about 1.37 in the lines and 1.47 in the hybrid). Therefore, the centromeric position of the bivalent 4 appeared to be more variable among cells in the hybrid, but the pairing between homologues was complete (Figure 5E). The chromosome 4 arm ratio of KYS (Figure 5F) estimated in the present study was 1.63, which is also consistent with data in the literature. Therefore, the data showed that in the hybrid, the arm ratio value of chromosome 2 was similar to the one of the JD lines, while the chromosome 4 arm ratio was significantly different from the JD lines and intermediate between the parents (Table 3).


Karyotype variability in tropical maize sister inbred lines and hybrids compared with KYS standard line.

Mondin M, Santos-Serejo JA, Bertäo MR, Laborda P, Pizzaia D, Aguiar-Perecin ML - Front Plant Sci (2014)

Chromosomes 2 (A–D), 4 (E–G), and 5 (H,I) at pachytene stage from the 441311 × KYS hybrid (A,B,D,E,G,H) and KYS (C,F) and 444331 (I) lines. The homologues are completely synapsed in the hybrid, with exception of one cell in which a loop possibly resulting from a pairing failure occurred in a segment of the bivalent 2 (B). The arrowheads indicate the centromeres in carmine-stained chromosomes (A–C,E,F,H). FISH signals (red) of CentC and 5S rDNA probes on chromosome 2 (D), Cent4 and subtelomeric 4-12-1 clone (red) on chromosome 4 (G), and 4-12-1 on chromosome 5 (I) are displayed. Scale bars for carmine stained chromosomes and FISH images = 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4195276&req=5

Figure 5: Chromosomes 2 (A–D), 4 (E–G), and 5 (H,I) at pachytene stage from the 441311 × KYS hybrid (A,B,D,E,G,H) and KYS (C,F) and 444331 (I) lines. The homologues are completely synapsed in the hybrid, with exception of one cell in which a loop possibly resulting from a pairing failure occurred in a segment of the bivalent 2 (B). The arrowheads indicate the centromeres in carmine-stained chromosomes (A–C,E,F,H). FISH signals (red) of CentC and 5S rDNA probes on chromosome 2 (D), Cent4 and subtelomeric 4-12-1 clone (red) on chromosome 4 (G), and 4-12-1 on chromosome 5 (I) are displayed. Scale bars for carmine stained chromosomes and FISH images = 10 μm.
Mentions: The pachytene chromosomes of the 441311 × KYS hybrid were examined to investigate the pairing behavior of chromosomes 2 and 4. Carmine-stained chromosomes 2 and 4 from the 441311 and KYS lines and the respective hybrid (Figures 5A–C,E,F) were analyzed to compare their arm ratios. Chromosomes of the 444331 line were also included in this analysis (Table 3). The arm ratios of the chromosome 2 of 441311, 444331 and 4411311 × KYS were very similar (about 1.70), while in KYS (Figure 5C) it was 1.36, corresponding to data in the literature (Table 3; see review of KYS data in Anderson et al., 2003). The homologous chromosomes of the bivalent 2 were completely synapsed in all of the cells that were examined (Figure 5A), and in only one microsporocyte, a loop was detected (Figure 5B), suggesting the occurrence of a pairing failure in a chromosomal segment. The chromosome 4 arm ratios in 441311, 444331 and 4411311 × KYS were not similar (about 1.37 in the lines and 1.47 in the hybrid). Therefore, the centromeric position of the bivalent 4 appeared to be more variable among cells in the hybrid, but the pairing between homologues was complete (Figure 5E). The chromosome 4 arm ratio of KYS (Figure 5F) estimated in the present study was 1.63, which is also consistent with data in the literature. Therefore, the data showed that in the hybrid, the arm ratio value of chromosome 2 was similar to the one of the JD lines, while the chromosome 4 arm ratio was significantly different from the JD lines and intermediate between the parents (Table 3).

Bottom Line: 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 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, Brazil.

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.

No MeSH data available.


Related in: MedlinePlus