Abstract
To gain insight into the synthesis and functions of enzymes of starch metabolism in leaves of Arabidopsis L. Heynth, Affymetrix microarrays were used to analyze the transcriptome throughout the diurnal cycle. Under the conditions employed, transitory leaf starch is degraded progressively during a 12-h dark period, and then accumulates during the following 12-h light period. Transcripts encoding enzymes of starch synthesis changed relatively little in amount over 24 h except for two starch synthases, granule bound starch synthase and starch synthase II, which increased appreciably during the transition from dark to light. The increase in RNA encoding granule-bound starch synthase may reflect the extensive destruction of starch granules in the dark. Transcripts encoding several enzymes putatively involved in starch breakdown showed a coordinated decline in the dark followed by rapid accumulation in the light. Despite marked changes in their transcript levels, the amounts of some enzymes of starch metabolism do not change appreciably through the diurnal cycle. Posttranscriptional regulation is essential in the maintenance of amounts of enzymes and the control of their activities in vivo. Even though the relationships between transcript levels, enzyme activity, and diurnal metabolism of starch metabolism are complex, the presence of some distinctive diurnal patterns of transcripts for enzymes known to be involved in starch metabolism facilitates the identification of other proteins that may participate in this process.
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Claims 7
Claim · model-written summary
Leaf starch fell during darkness and accumulated in light.
Verbatim
e0“transitory leaf starch is degraded progressively during a 12-h dark period, and then accumulates during the following 12-h light period.”
e1“Arabidopsis L. Heynth”
Claim · model-written summary
Most starch synthesis enzyme transcripts changed little over 24 h.
Verbatim
e0“Transcripts encoding enzymes of starch synthesis changed relatively little in amount over 24 h”
e1“Arabidopsis L. Heynth”
Claim · model-written summary
Granule bound starch synthase and starch synthase II transcripts increased at dark-to-light transition.
Verbatim
e0“granule bound starch synthase and starch synthase II, which increased appreciably during the transition from dark to light.”
e1“Arabidopsis L. Heynth”
Claim · model-written summary
Several starch breakdown enzyme transcripts declined in dark and accumulated rapidly in light.
Verbatim
e0“Transcripts encoding several enzymes putatively involved in starch breakdown showed a coordinated decline in the dark followed by rapid accumulation in the light.”
e1“Arabidopsis L. Heynth”
Claim · model-written summary
Amounts of some starch metabolism enzymes changed little despite transcript changes.
Verbatim
e0“Despite marked changes in their transcript levels, the amounts of some enzymes of starch metabolism do not change appreciably through the diurnal cycle.”
e1“Arabidopsis L. Heynth”
Claim · model-written summary
Authors infer posttranscriptional regulation maintains enzyme abundance and controls activity.
- Taxon
- Arabidopsis L. Heynthe1
- Outcome
- maintenance of amounts of enzymes and the control of their activitiese0
- Qualifier
- Posttranscriptional regulatione0
Not reportedDirection
Verbatim
e0“Posttranscriptional regulation is essential in the maintenance of amounts of enzymes and the control of their activities in vivo.”
e1“Arabidopsis L. Heynth”
Claim · model-written summary
Distinctive transcript patterns help identify other proteins in starch metabolism.
Verbatim
e0“the presence of some distinctive diurnal patterns of transcripts for enzymes known to be involved in starch metabolism facilitates the identification of other proteins that may participate in this process.”
e1“Arabidopsis L. Heynth”