Abstract
Partial submergence or treatment with either ethylene or gibberellin (GA) promotes rapid internodal growth in deepwater rice (Oryza sativa L.). Earlier work has shown that GA is the immediate hormonal signal for this growth response, which involves induction of the cell cycle at the G2/M phase transition and subsequent enhancement in the rate of DNA synthesis. In all eukaryotes, onset of mitosis is regulated by the p34cdc2/CDC28 protein kinase, whose activity is assayed by in vitro phosphorylation of histone H1. It was found that GA enhanced the activity of p34cdc2/CDC28-like histone H1 kinase in the intercalary meristem of rice internodes. The enzyme activity showed a sharp peak that correlated with a decrease in the population of cells in the G2 phase during the first 4 h of GA treatment but not with changes in DNA synthesis. The level of histone H1 kinase activity increased again when cell division activity in the intercalary meristem is known to be high. The expression of two cdc2 homologs was examined. The mRNA level of one of these, cdc2Os-2, was increased after 1 h of GA treatment, whereas the mRNA level of the other, cdc2Os-1, was not affected. Two cDNAs, cycOs1 and cycOs2, which show high homology to cyclin cDNAs, were cloned from rice. They share 75.1% sequence identity at the amino acid level, and both of them are encoded by mRNAs of 1.6 kb. Expression of the two corresponding cyclin genes was enhanced by GA, and the time course of the induction was compatible with a role for both cyclins in regulating the G2/M phase transition. The cyclins were expressed in the intercalary meristem and the elongation zone of the internode, but the GA-induced increase in transcript levels was restricted to the meristem only. The results support the hypothesis that induction of mitosis by GA is brought about by increased p34cdc2/CDC28 protein kinase activity, which may be the result of transcriptional activation of the cdc2Os-2, cycOs1 and cycOs2 genes.
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Claims 13
Claim · model-written summary
GA enhanced histone H1 kinase activity in the intercalary meristem.
- Taxon
- rice
Oryza sativae0 - Organ / stage
- intercalary meristeme0
- Treatment
- GAe0
- Gene
- p34cdc2/CDC28-like histone H1 kinasee0
- Outcome
- activity of p34cdc2/CDC28-like histone H1 kinasee0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“GA enhanced the activity of p34cdc2/CDC28-like histone H1 kinase in the intercalary meristem of rice internodes.”
Claim · model-written summary
An early kinase activity peak correlated with fewer G2 phase cells during the first four hours of GA treatment.
- Taxon
- riceOryza sativat0
- Treatment
- GA treatmente0
- Gene
- histone H1 kinaset0
- Outcome
- population of cells in the G2 phasee0
- Direction
- decreasee0
- Qualifier
- during the first 4 he0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The enzyme activity showed a sharp peak that correlated with a decrease in the population of cells in the G2 phase during the first 4 h of GA treatment but not with changes in DNA synthesis.”
t0“histone H1 kinase activity and the expression of cdc2 and cyclin genes during the induction of rapid growth in deepwater rice internodes”
Claim · model-written summary
The kinase activity peak did not correlate with DNA synthesis changes.
- Taxon
- riceOryza sativat0
- Treatment
- GA treatmente0
- Gene
- histone H1 kinaset0
- Outcome
- changes in DNA synthesise0
- Direction
- not withe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The enzyme activity showed a sharp peak that correlated with a decrease in the population of cells in the G2 phase during the first 4 h of GA treatment but not with changes in DNA synthesis.”
t0“histone H1 kinase activity and the expression of cdc2 and cyclin genes during the induction of rapid growth in deepwater rice internodes”
Claim · model-written summary
Histone H1 kinase activity rose again when meristem cell division activity was high.
- Taxon
- riceOryza sativat0
- Organ / stage
- intercalary meristeme0
- Outcome
- histone H1 kinase activitye0
- Direction
- increased againe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The level of histone H1 kinase activity increased again when cell division activity in the intercalary meristem is known to be high.”
t0“deepwater rice internodes”
Claim · model-written summary
GA increased cdc2Os-2 mRNA after one hour.
- Taxon
- riceOryza sativat0
- Treatment
- GA treatmente0
- Gene
- cdc2Os-2e0
- Outcome
- mRNA levele0
- Direction
- increasede0
- Qualifier
- after 1 he0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The mRNA level of one of these, cdc2Os-2, was increased after 1 h of GA treatment”
t0“deepwater rice internodes”
Claim · model-written summary
GA did not affect cdc2Os-1 mRNA.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the mRNA level of the other, cdc2Os-1, was not affected.”
t0“Gibberellin promotes histone H1 kinase activity and the expression of cdc2 and cyclin genes during the induction of rapid growth in deepwater rice internodes”
e1“The mRNA level of one of these, cdc2Os-2, was increased after 1 h of GA treatment”
Claim · model-written summary
Two rice cyclin homolog cDNAs, cycOs1 and cycOs2, were cloned.
- Taxon
- riceOryza sativae0
- Gene
- cycOs1 and cycOs2e0
- Outcome
- Two cDNAse0
- Comparator
- cyclin cDNAse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Two cDNAs, cycOs1 and cycOs2, which show high homology to cyclin cDNAs, were cloned from rice.”
Claim · model-written summary
cycOs1 and cycOs2 share 75.1% amino acid sequence identity.
- Taxon
- riceOryza sativat0
- Gene
- cycOs1 and cycOs2e1
- Outcome
- sequence identity at the amino acid levele0
- Value
- 75.1%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“They share 75.1% sequence identity at the amino acid level”
t0“Gibberellin promotes histone H1 kinase activity and the expression of cdc2 and cyclin genes during the induction of rapid growth in deepwater rice internodes”
e1“Two cDNAs, cycOs1 and cycOs2, which show high homology to cyclin cDNAs, were cloned from rice.”
Claim · model-written summary
Both cyclin homologs are encoded by 1.6 kb mRNAs.
- Taxon
- riceOryza sativat0
- Gene
- cyclin genest0
- Outcome
- mRNAse0
- Value
- 1.6 kbe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both of them are encoded by mRNAs of 1.6 kb.”
t0“Gibberellin promotes histone H1 kinase activity and the expression of cdc2 and cyclin genes during the induction of rapid growth in deepwater rice internodes”
Claim · model-written summary
GA enhanced expression of both cyclin genes.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Expression of the two corresponding cyclin genes was enhanced by GA”
t0“deepwater rice internodes”
Claim · model-written summary
The cyclins were expressed in the intercalary meristem and elongation zone.
- Taxon
- riceOryza sativat0
- Organ / stage
- intercalary meristem and the elongation zone of the internodee0
- Gene
- cyclinse0
- Outcome
- expressede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The cyclins were expressed in the intercalary meristem and the elongation zone of the internode”
t0“deepwater rice internodes”
Claim · model-written summary
GA induced increased cyclin transcripts only in the meristem.
- Taxon
- riceOryza sativat0
- Organ / stage
- meristeme0
- Treatment
- GAe0
- Gene
- cyclin genest0
- Outcome
- transcript levelse0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the GA-induced increase in transcript levels was restricted to the meristem only.”
t0“Gibberellin promotes histone H1 kinase activity and the expression of cdc2 and cyclin genes during the induction of rapid growth in deepwater rice internodes”
Claim · model-written summary
The authors propose GA induction of mitosis through increased p34cdc2/CDC28 kinase activity, potentially via transcriptional activation of cdc2Os-2, cycOs1 and cycOs2.
- Taxon
- riceOryza sativat0
- Treatment
- GAe0
- Gene
- p34cdc2/CDC28 protein kinasee0
- Outcome
- induction of mitosise0
- Qualifier
- transcriptional activation of the cdc2Os-2, cycOs1 and cycOs2 genese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“induction of mitosis by GA is brought about by increased p34cdc2/CDC28 protein kinase activity, which may be the result of transcriptional activation of the cdc2Os-2, cycOs1 and cycOs2 genes.”
t0“deepwater rice internodes”
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