Abstract
Expression of four Arabidopsis (thale cress) genes corresponding to the small (ApS) and large subunits (ApL1, ApL2, ApL3) of ADP-glucose pyrophosphorylase (AGPase), a key enzyme of starch biosynthesis, was found to be profoundly and differentially regulated by sugar and light/dark exposures. Transcript levels of both ApL2 and ApL3, and to a lesser extent ApS, increased severalfold upon feeding sucrose or glucose to the detached leaves in the dark, whereas the mRNA content for ApL1 decreased under the same conditions. Glucose was, in general, less effective than sucrose in inducing regulation of AGPase genes, possibly due to observed limitations in its uptake when compared with sucrose uptake by detached leaves. Osmotic agents [sorbitol, poly(ethylene glycol)] had no effect on ApS, ApL2 and ApL3 transcript level, but they did mimic the effect of sucrose on ApL1 gene, suggesting that the latter is regulated by osmotic pressure rather than any particular sugar. For all the genes the sugar effect was closely mimicked by an exposure of the dark-pre-adapted leaves to the light. Under both dark and light conditions, sucrose fed to the detached leaves was found to be rapidly metabolized to hexoses and, to some extent, starch. Starch production reflected most probably an increase in substrate availability for AGPase reaction rather than being due to changes in AGPase protein content, since both the sugar feeding and light exposure had little or no effect on the activity of AGPase or on the levels of its small and large subunit proteins in leaf extracts. The data suggest tight translational or post-translational control, but they may also reflect spatial control of AGPase gene expression within a leaf. The sugar/light-dependent regulation of AGPase gene expression may represent a part of a general cellular response to the availability/allocation of carbohydrates during photosynthesis.
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Claims 13
Claim · model-written summary
Four Arabidopsis AGPase subunit genes were differentially regulated by sugar and light/dark exposures.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianat0 - Treatment
- sugar and light/dark exposurese2
- Gene
- ApL1, ApL2, ApL3e1
- Outcome
- Expression of four Arabidopsis (thale cress) genese1
- Direction
- regulatede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e1“Expression of four Arabidopsis (thale cress) genes corresponding to the small (ApS) and large subunits (ApL1, ApL2, ApL3)”
e2“was found to be profoundly and differentially regulated by sugar and light/dark exposures”
Claim · model-written summary
Feeding sucrose or glucose to detached leaves in the dark increased ApL2 and ApL3 transcript levels severalfold.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- feeding sucrose or glucose to the detached leaves in the darke3
- Gene
- ApL2 and ApL3e3
- Outcome
- Transcript levelse3
- Direction
- increased severalfolde3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e3“Transcript levels of both ApL2 and ApL3, and to a lesser extent ApS, increased severalfold upon feeding sucrose or glucose to the detached leaves in the dark”
Claim · model-written summary
Feeding sucrose or glucose to detached leaves decreased ApL1 mRNA content.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- feeding sucrose or glucose to the detached leavese3
- Gene
- ApL1e4
- Outcome
- mRNA contente4
- Direction
- decreasede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e3“Transcript levels of both ApL2 and ApL3, and to a lesser extent ApS, increased severalfold upon feeding sucrose or glucose to the detached leaves in the dark”
e4“whereas the mRNA content for ApL1 decreased under the same conditions”
Claim · model-written summary
Glucose was less effective than sucrose in inducing regulation of AGPase genes.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Glucosee5
- Gene
- AGPasee5
- Outcome
- inducing regulation of AGPase genese5
- Direction
- less effectivee5
- Comparator
- sucrosee5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e5“Glucose was, in general, less effective than sucrose in inducing regulation of AGPase genes”
Claim · model-written summary
Glucose uptake by detached leaves was limited compared with sucrose uptake.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Outcome
- uptakee6
- Qualifier
- observed limitations in its uptake when compared with sucrose uptake by detached leavese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e6“observed limitations in its uptake when compared with sucrose uptake by detached leaves”
Claim · model-written summary
Osmotic agents had no effect on ApS, ApL2 and ApL3 transcript levels.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Osmotic agentse7
- Gene
- ApS, ApL2 and ApL3e7
- Outcome
- transcript levele7
- Direction
- no effecte7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e7“Osmotic agents [sorbitol, poly(ethylene glycol)] had no effect on ApS, ApL2 and ApL3 transcript level”
Claim · model-written summary
Osmotic agents mimicked the effect of sucrose on ApL1 expression.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Osmotic agentse7
- Gene
- ApL1e2
- Outcome
- effect of sucrose on ApL1 genee2
- Direction
- mimice2
- Comparator
- sucrosee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e7“Osmotic agents [sorbitol, poly(ethylene glycol)] had no effect on ApS, ApL2 and ApL3 transcript level”
e2“they did mimic the effect of sucrose on ApL1 gene”
Claim · model-written summary
ApL1 is probably regulated by osmotic pressure rather than by any particular sugar.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Outcome
- the latter is regulatede3
- Qualifier
- osmotic pressure rather than any particular sugare3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e3“suggesting that the latter is regulated by osmotic pressure rather than any particular sugar”
Claim · model-written summary
Exposing dark-pre-adapted leaves to light closely mimicked the sugar effect on AGPase genes.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- exposure of the dark-pre-adapted leaves to the lighte4
- Outcome
- sugar effecte4
- Direction
- closely mimickede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e4“For all the genes the sugar effect was closely mimicked by an exposure of the dark-pre-adapted leaves to the light”
Claim · model-written summary
Sucrose fed to detached leaves was rapidly metabolized to hexoses and, to some extent, starch.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Compound
- sucrosee5
- Outcome
- rapidly metabolized to hexosese5
- Qualifier
- Under both dark and light conditionse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e5“Under both dark and light conditions, sucrose fed to the detached leaves was found to be rapidly metabolized to hexoses and, to some extent, starch”
Claim · model-written summary
Starch production probably reflected an increase in substrate availability for the AGPase reaction.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Outcome
- Starch productione6
- Qualifier
- increase in substrate availability for AGPase reactione6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e6“Starch production reflected most probably an increase in substrate availability for AGPase reaction rather than being due to changes in AGPase protein content”
Claim · model-written summary
Sugar feeding and light exposure had little or no effect on AGPase activity.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- sugar feeding and light exposuree7
- Gene
- AGPasee7
- Outcome
- activity of AGPasee7
- Direction
- little or no effecte7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e7“both the sugar feeding and light exposure had little or no effect on the activity of AGPase”
Claim · model-written summary
Sugar feeding and light exposure had little or no effect on the levels of AGPase small and large subunit proteins.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- sugar feeding and light exposuree7
- Outcome
- levels of its small and large subunit proteinse1
- Direction
- little or no effecte7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis thaliana (thale cress)”
e7“both the sugar feeding and light exposure had little or no effect on the activity of AGPase”
e1“or on the levels of its small and large subunit proteins in leaf extracts”
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