Abstract
In vivo measurements of the enzymatic hydroxylation of the phytohormone (+)-abscisic acid to hormonally inactive (–)-phaseic acid in corn cell cultures revealed that (+)-abscisic acid 8′ hydroxylase activity was induced by (+)-abscisic acid treatment. This induction was blocked by the protein synthesis inhibitor cycloheximide and by the transcription inhibitor cordycepin. Following an induction treatment with abscisic acid, the amount of induced enzyme was measured by addition of both cycloheximide, to prevent further induction, and fresh abscisic acid as substrate for the induced enzyme. Phaseic acid production was related to the amount of enzyme induced. The experimental system was optimized for studying enzyme induction and the substrate specificity of the induced enzyme. The induced 8– hydroxylase was specific for (–)-abscisic acid, whereas the low basal activity also hydroxylated (–)-abscisic acid at the 7′ position to form 7′-hydroxy abscisic acid. After induction, the 8′ hydroxylase was rapidly degraded with a half-life of approximately 2 h. Phaseic and (′)-abscisic acid were weak inducers; however, the unstable oxidation product 8′-hydroxy abscisic acid exhibited 42% of the activity of (+)-abscisic acid. When corn cells were placed under water stress by increasing concentrations of mannitol in the culture medium, 8′ hydroxylase induction was suppressed. The experimental system described will be useful for further studies of the physiological and hormonal factors that modulate abscisic acid metabolism and for testing potential enzyme inhibitors and hormone analogues.
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Claims 11
Claim · model-written summary
Abscisic acid treatment induced its 8′ hydroxylase activity.
- Treatment
- (+)-abscisic acid treatmente0
- Gene
- (+)-abscisic acid 8′ hydroxylasee0
- Outcome
- 8′ hydroxylase activitye0
- Direction
- inducede0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“(+)-abscisic acid 8′ hydroxylase activity was induced by (+)-abscisic acid treatment”
t0“maize”
Claim · model-written summary
Cycloheximide blocked enzyme induction.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This induction was blocked by the protein synthesis inhibitor cycloheximide”
t0“maize”
Claim · model-written summary
Cordycepin blocked enzyme induction.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“and by the transcription inhibitor cordycepin”
t0“maize”
Claim · model-written summary
Phaseic acid production tracked induced enzyme amount.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phaseic acid production was related to the amount of enzyme induced.”
t0“maize”
Claim · model-written summary
Induced 8– hydroxylase was specific for (–)-abscisic acid.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The induced 8– hydroxylase was specific for (–)-abscisic acid”
t0“maize”
Claim · model-written summary
Low basal activity also hydroxylated (–)-abscisic acid at position 7′, forming 7′-hydroxy abscisic acid.
- Outcome
- 7′-hydroxy abscisic acide0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the low basal activity also hydroxylated (–)-abscisic acid at the 7′ position to form 7′-hydroxy abscisic acid”
t0“maize”
Claim · model-written summary
Induced hydroxylase degraded rapidly with an approximately 2 h half-life.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the 8′ hydroxylase was rapidly degraded with a half-life of approximately 2 h”
t0“maize”
Claim · model-written summary
Phaseic acid was a weak inducer.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phaseic and (′)-abscisic acid were weak inducers”
t0“maize”
Claim · model-written summary
(′)-abscisic acid was a weak inducer.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phaseic and (′)-abscisic acid were weak inducers”
t0“maize”
Claim · model-written summary
8′-hydroxy abscisic acid had 42% of (+)-abscisic acid induction activity.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“8′-hydroxy abscisic acid exhibited 42% of the activity of (+)-abscisic acid”
t0“maize”
Claim · model-written summary
Mannitol-induced water stress suppressed 8′ hydroxylase induction.
- Taxon
- corn
Zea mays subsp. mayse0 - Treatment
- increasing concentrations of mannitole0
- Outcome
- 8′ hydroxylase inductione0
- Direction
- suppressede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When corn cells were placed under water stress by increasing concentrations of mannitol in the culture medium, 8′ hydroxylase induction was suppressed.”
The same questions in other papers
cordycepin · molecular: expression · Zea mays (maize)Results agree
1 paper in the same direction as this paper
- negative
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.