Abstract
The importance of α-glucosidase in the endosperm starch metabolism of barley (Hordeum vulgare) seedlings is poorly understood. The enzyme converts maltose to glucose (Glc), but in vitro studies indicate that it can also attack starch granules. To discover its role in vivo, we took complementary chemical-genetic and reverse-genetic approaches. We identified iminosugar inhibitors of a recombinant form of an α-glucosidase previously discovered in barley endosperm (ALPHA-GLUCOSIDASE97 [HvAGL97]), and applied four of them to germinating grains. All four decreased the Glc-to-maltose ratio in the endosperm 10 d after imbibition, implying inhibition of maltase activity. Three of the four inhibitors also reduced starch degradation and seedling growth, but the fourth did not affect these parameters. Inhibition of starch degradation was apparently not due to inhibition of amylases. Inhibition of seedling growth was primarily a direct effect of the inhibitors on roots and coleoptiles rather than an indirect effect of the inhibition of endosperm metabolism. It may reflect inhibition of glycoprotein-processing glucosidases in these organs. In transgenic seedlings carrying an RNA interference silencing cassette for HvAgl97, α-glucosidase activity was reduced by up to 50%. There was a large decrease in the Glc-to-maltose ratio in these lines but no effect on starch degradation or seedling growth. Our results suggest that the α-glucosidase HvAGL97 is the major endosperm enzyme catalyzing the conversion of maltose to Glc but is not required for starch degradation. However, the effects of three glucosidase inhibitors on starch degradation in the endosperm indicate the existence of unidentified glucosidase(s) required for this process.
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Claims 13
Claim · model-written summary
Four inhibitors decreased the endosperm glucose-to-maltose ratio after 10 days.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaret0 - Organ / stage
- endosperme0
- Treatment
- All foure0
- Outcome
- Glc-to-maltose ratioe0
- Direction
- decreasede0
- Qualifier
- 10 d after imbibitione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“All four decreased the Glc-to-maltose ratio in the endosperm 10 d after imbibition”
t0“Barley Grains”
Claim · model-written summary
Three inhibitors reduced endosperm starch degradation.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- Three of the four inhibitorse0
- Outcome
- starch degradatione0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Three of the four inhibitors also reduced starch degradation and seedling growth”
t0“Barley Grains”
Claim · model-written summary
Three inhibitors reduced seedling growth.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- Three of the four inhibitorse0
- Outcome
- seedling growthe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Three of the four inhibitors also reduced starch degradation and seedling growth”
t0“Barley Grains”
Claim · model-written summary
The fourth inhibitor did not affect starch degradation or seedling growth.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- the fourthe0
- Outcome
- starch degradation and seedling growthe1
- Direction
- did not affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the fourth did not affect these parameters.”
e1“starch degradation and seedling growth”
t0“Barley Grains”
Claim · model-written summary
Amylase inhibition apparently did not explain reduced starch degradation.
- Taxon
- barleyHordeum vulgaret0
- Gene
- amylasese0
- Outcome
- Inhibition of starch degradatione0
- Qualifier
- apparently not due to inhibition of amylasese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inhibition of starch degradation was apparently not due to inhibition of amylases.”
t0“Barley Grains”
Claim · model-written summary
Inhibitors acted directly on roots and coleoptiles to inhibit seedling growth.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- roots and coleoptilese0
- Treatment
- inhibitorse0
- Outcome
- Inhibition of seedling growthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inhibition of seedling growth was primarily a direct effect of the inhibitors on roots and coleoptiles rather than an indirect effect of the inhibition of endosperm metabolism.”
t0“Barley Grains”
Claim · model-written summary
Seedling growth inhibition may reflect glycoprotein-processing glucosidase inhibition.
- Taxon
- barleyHordeum vulgaret0
- Gene
- glycoprotein-processing glucosidasese0
- Outcome
- Inhibition of seedling growthe1
- Qualifier
- may reflect inhibitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It may reflect inhibition of glycoprotein-processing glucosidases in these organs.”
e1“Inhibition of seedling growth”
t0“Barley Grains”
Claim · model-written summary
RNA interference lines had α-glucosidase activity reduced by up to 50%.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- RNA interference silencing cassette for HvAgl97e0
- Gene
- HvAgl97e0
- Outcome
- α-glucosidase activitye0
- Direction
- reducede0
- Value
- up to 50%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In transgenic seedlings carrying an RNA interference silencing cassette for HvAgl97, α-glucosidase activity was reduced by up to 50%.”
t0“Barley Grains”
Claim · model-written summary
RNA interference lines had a large decrease in glucose-to-maltose ratio.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- RNA interference silencing cassette for HvAgl97e1
- Outcome
- Glc-to-maltose ratioe0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was a large decrease in the Glc-to-maltose ratio in these lines”
e1“RNA interference silencing cassette for HvAgl97”
t0“Barley Grains”
Claim · model-written summary
RNA interference lines did not change starch degradation or seedling growth.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- RNA interference silencing cassette for HvAgl97e1
- Outcome
- starch degradation or seedling growthe0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no effect on starch degradation or seedling growth.”
e1“RNA interference silencing cassette for HvAgl97”
t0“Barley Grains”
Claim · model-written summary
HvAGL97 was inferred to be the major endosperm maltose-to-glucose enzyme.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- endosperme0
- Gene
- HvAGL97e0
- Outcome
- conversion of maltose to Glce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the α-glucosidase HvAGL97 is the major endosperm enzyme catalyzing the conversion of maltose to Glc”
t0“Barley Grains”
Claim · model-written summary
HvAGL97 was inferred unnecessary for starch degradation.
- Taxon
- barleyHordeum vulgaret0
- Gene
- HvAGL97e1
- Outcome
- starch degradatione0
- Qualifier
- not requirede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but is not required for starch degradation.”
e1“the α-glucosidase HvAGL97”
t0“Barley Grains”
Claim · model-written summary
The inhibitor results imply other unidentified glucosidases are needed for endosperm starch degradation.
- Taxon
- barleyHordeum vulgaret0
- Gene
- unidentified glucosidase(s)e0
- Outcome
- starch degradation in the endosperme0
- Qualifier
- required for this processe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the effects of three glucosidase inhibitors on starch degradation in the endosperm indicate the existence of unidentified glucosidase(s) required for this process.”
t0“Barley Grains”
The same questions in other papers
loss of function · quality: sugar starch · Hordeum vulgare (barley)Positive and negative results
2 papers in the same direction as this paper · 1 in the opposite direction
- positive
- negative
- 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.