Abstract
Spatiotemporal patterns of DNA replication have been described for yeast and many types of cultured animal cells, frequently after cell cycle arrest to aid in synchronization. However, patterns of DNA replication in nuclei from plants or naturally developing organs remain largely uncharacterized. Here we report findings from 3D quantitative analysis of DNA replication and endoreduplication in nuclei from pulse-labeled developing maize root tips. In both early and middle S phase nuclei, flow-sorted on the basis of DNA content, replicative labeling was widely distributed across euchromatic regions of the nucleoplasm. We did not observe the perinuclear or perinucleolar replicative labeling patterns characteristic of middle S phase in mammals. Instead, the early versus middle S phase patterns in maize could be distinguished cytologically by correlating two quantitative, continuous variables, replicative labeling and DAPI staining. Early S nuclei exhibited widely distributed euchromatic labeling preferentially localized to regions with weak DAPI signals. Middle S nuclei also exhibited widely distributed euchromatic labeling, but the label was preferentially localized to regions with strong DAPI signals. Highly condensed heterochromatin, including knobs, replicated during late S phase as previously reported. Similar spatiotemporal replication patterns were observed for both mitotic and endocycling maize nuclei. These results revealed that maize euchromatin exists as an intermingled mixture of two components distinguished by their condensation state and replication timing. These different patterns might reflect a previously described genome organization pattern, with "gene islands" mostly replicating during early S phase followed by most of the intergenic repetitive regions replicating during middle S phase.
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Claims 9
Claim · model-written summary
Early and middle S-phase maize nuclei had widely distributed euchromatic replication labeling.
- Organ / stage
- root tipse0
- Outcome
- replicative labeling was widely distributed across euchromatic regions of the nucleoplasme1
- Qualifier
- early and middle S phase nucleie1
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“developing maize root tips”
e1“In both early and middle S phase nuclei, flow-sorted on the basis of DNA content, replicative labeling was widely distributed across euchromatic regions of the nucleoplasm.”
Claim · model-written summary
Maize middle S-phase nuclei lacked mammalian-style perinuclear or perinucleolar replication patterns.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“developing maize root tips”
e1“We did not observe the perinuclear or perinucleolar replicative labeling patterns characteristic of middle S phase in mammals.”
Claim · model-written summary
Replication label and DAPI staining distinguished early from middle S phase in maize.
- Outcome
- early versus middle S phase patternse0
- Qualifier
- replicative labeling and DAPI staininge0
- Comparator
- early versus middle S phasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the early versus middle S phase patterns in maize could be distinguished cytologically by correlating two quantitative, continuous variables, replicative labeling and DAPI staining.”
Claim · model-written summary
Early S-phase maize nuclei preferentially labeled weak-DAPI euchromatic regions.
- Organ / stage
- Early S nucleie1
- Outcome
- euchromatic labeling preferentially localized to regions with weak DAPI signalse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“developing maize root tips”
e1“Early S nuclei exhibited widely distributed euchromatic labeling preferentially localized to regions with weak DAPI signals.”
Claim · model-written summary
Middle S-phase maize nuclei preferentially labeled strong-DAPI euchromatic regions.
- Organ / stage
- Middle S nucleie1
- Outcome
- label was preferentially localized to regions with strong DAPI signalse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“developing maize root tips”
e1“Middle S nuclei also exhibited widely distributed euchromatic labeling, but the label was preferentially localized to regions with strong DAPI signals.”
Claim · model-written summary
Highly condensed heterochromatin including knobs replicated during late S phase.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“developing maize root tips”
e1“Highly condensed heterochromatin, including knobs, replicated during late S phase as previously reported.”
Claim · model-written summary
Mitotic and endocycling maize nuclei showed similar replication patterns.
- Outcome
- Similar spatiotemporal replication patternse1
- Qualifier
- both mitotic and endocycling maize nucleie1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize nuclei”
e1“Similar spatiotemporal replication patterns were observed for both mitotic and endocycling maize nuclei.”
Claim · model-written summary
Maize euchromatin consists of intermingled components differentiated by condensation and replication timing.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize euchromatin exists as an intermingled mixture of two components distinguished by their condensation state and replication timing.”
Claim · model-written summary
The authors hypothesize early gene-island replication followed by middle-S replication of repetitive intergenic regions.
- Outcome
- different patternse1
- Qualifier
- "gene islands" mostly replicating during early S phase followed by most of the intergenic repetitive regions replicating during middle S phasee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize euchromatin”
e1“These different patterns might reflect a previously described genome organization pattern, with "gene islands" mostly replicating during early S phase followed by most of the intergenic repetitive regions replicating during middle S phase.”