Abstract
Water deficit at the early post-pollination stage in cereal grains decreases endosperm cell division and, in turn, decreases the capacity for storage material accumulation. Post-mitotic replication of nuclear DNA (endoreduplication) may also play a role in stress effects. To gain a better understanding of the extent to which cell proliferation and endoreduplication are affected by water deficit, nuclear numbers and size were examined in endosperms of maize (Zea mays L.) by flow cytometry and the transcript levels of genes which have recognized roles in the cell cycle were quantified. Water deficit from 5-13 d after pollination (DAP) decreased the rate of endosperm cell division by 90% and inhibited [3H]-thymidine incorporation into DNA from 9-13 DAP. The proportion of nuclei engaging in endoreduplication and nuclear DNA content increased steadily from 9-13 DAP in controls, but water deficit initially increased the proportion of endoreduplicating nuclei at 9 DAP, then halted further entry into endoreduplication and S-phase cycling from 9-13 DAP. Transcript levels of alpha-tubulin, and the S-phase gene products histone H3 and PCNA were not affected by water deficit until 13 DAP, whereas those of ZmCdc2, a cyclin dependent kinase (CDK) with regulatory roles in mitosis, were inhibited substantially from 9-13 DAP. Cell proliferation and associated processes were inhibited at initial stages of the stress episode, whereas endoreduplication and associated S-phase processes were not inhibited until the stress was more advanced. It was concluded that endosperm mitosis has greater sensitivity than endoreduplication to water deficit.
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Claims 9
Claim · model-written summary
Water deficit decreased endosperm cell division rate by 90%.
- Treatment
- Water deficit from 5-13 d after pollination (DAP)e0
- Outcome
- rate of endosperm cell divisione0
- Direction
- decreasede0
- Value
- 90%e0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Water deficit from 5-13 d after pollination (DAP) decreased the rate of endosperm cell division by 90%”
t0“maize endosperm”
Claim · model-written summary
Water deficit inhibited thymidine incorporation into DNA from 9 to 13 DAP.
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inhibited [3H]-thymidine incorporation into DNA from 9-13 DAP”
t0“maize endosperm”
Claim · model-written summary
In controls, endoreduplicating nuclear proportion and DNA content increased from 9 to 13 DAP.
- Outcome
- proportion of nuclei engaging in endoreduplication and nuclear DNA contente0
- Direction
- increased steadilye0
- Qualifier
- 9-13 DAP in controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The proportion of nuclei engaging in endoreduplication and nuclear DNA content increased steadily from 9-13 DAP in controls”
t0“maize endosperm”
Claim · model-written summary
Water deficit initially increased the endoreduplicating nuclear proportion at 9 DAP.
- Treatment
- water deficite0
- Outcome
- proportion of endoreduplicating nucleie0
- Direction
- increasede0
- Qualifier
- 9 DAPe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“water deficit initially increased the proportion of endoreduplicating nuclei at 9 DAP”
t0“maize endosperm”
Claim · model-written summary
Water deficit then halted entry into endoreduplication and S-phase cycling.
- Outcome
- further entry into endoreduplication and S-phase cyclinge0
- Direction
- haltede0
- Qualifier
- 9-13 DAPe0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“then halted further entry into endoreduplication and S-phase cycling from 9-13 DAP”
t0“maize endosperm”
Claim · model-written summary
Alpha-tubulin transcript levels were unaffected until 13 DAP.
- Treatment
- water deficite0
- Gene
- alpha-tubuline0
- Outcome
- Transcript levels of alpha-tubuline0
- Direction
- not affectede0
- Qualifier
- until 13 DAPe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcript levels of alpha-tubulin, and the S-phase gene products histone H3 and PCNA were not affected by water deficit until 13 DAP”
t0“maize endosperm”
Claim · model-written summary
Histone H3 and PCNA transcript levels were unaffected until 13 DAP.
- Treatment
- water deficite0
- Gene
- histone H3 and PCNAe0
- Outcome
- Transcript levels of alpha-tubulin, and the S-phase gene products histone H3 and PCNAe0
- Direction
- not affectede0
- Qualifier
- until 13 DAPe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcript levels of alpha-tubulin, and the S-phase gene products histone H3 and PCNA were not affected by water deficit until 13 DAP”
t0“maize endosperm”
Claim · model-written summary
ZmCdc2 transcripts were inhibited substantially from 9 to 13 DAP.
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“those of ZmCdc2, a cyclin dependent kinase (CDK) with regulatory roles in mitosis, were inhibited substantially from 9-13 DAP”
t0“maize endosperm”
Claim · model-written summary
Endosperm mitosis was more sensitive to water deficit than endoreduplication.
- Treatment
- water deficite0
- Outcome
- endosperm mitosise0
- Direction
- greater sensitivitye0
- Comparator
- endoreduplicatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“endosperm mitosis has greater sensitivity than endoreduplication to water deficit”
t0“maize endosperm”
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Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.