Abstract
Reserve starch is an important plant product but the actual biosynthetic process is not yet fully understood. Potato (Solanum tuberosum) tuber discs from various transgenic plants were used to analyse the conversion of external sugars or sugar derivatives to starch. By using in vitro assays, a direct glucosyl transfer from glucose 1-phosphate to native starch granules as mediated by recombinant plastidial phosphorylase was analysed. Compared with labelled glucose, glucose 6-phosphate or sucrose, tuber discs converted externally supplied [(14)C]glucose 1-phosphate into starch at a much higher rate. Likewise, tuber discs from transgenic lines with a strongly reduced expression of cytosolic phosphoglucomutase, phosphorylase or transglucosidase converted glucose 1-phosphate to starch with the same or even an increased rate compared with the wild-type. Similar results were obtained with transgenic potato lines possessing a strongly reduced activity of both the cytosolic and the plastidial phosphoglucomutase. Starch labelling was, however, significantly diminished in transgenic lines, with a reduced concentration of the plastidial phosphorylase isozymes. Two distinct paths of reserve starch biosynthesis are proposed that explain, at a biochemical level, the phenotype of several transgenic plant lines.
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Claims 5
Claim · model-written summary
External glucose 1-phosphate entered starch at a much higher rate than three comparator sugars.
- Taxon
- Potato
Solanum tuberosumt0 - Treatment
- [(14)C]glucose 1-phosphatee0
- Outcome
- converted externally supplied [(14)C]glucose 1-phosphate into starche0
- Direction
- much highere0
- Comparator
- labelled glucose, glucose 6-phosphate or sucrosee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with labelled glucose, glucose 6-phosphate or sucrose, tuber discs converted externally supplied [(14)C]glucose 1-phosphate into starch at a much higher rate.”
t0“potato (Solanum tuberosum)”
Claim · model-written summary
Lines with reduced cytosolic enzyme expression retained or increased glucose 1-phosphate conversion.
- Taxon
- PotatoSolanum tuberosumt0
- Material
- transgenic linese0
- Outcome
- converted glucose 1-phosphate to starche0
- Direction
- same or even an increased ratee0
- Comparator
- wild-typee0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic lines with a strongly reduced expression of cytosolic phosphoglucomutase, phosphorylase or transglucosidase converted glucose 1-phosphate to starch with the same or even an increased rate compared with the wild-type”
t0“potato (Solanum tuberosum)”
Claim · model-written summary
Lines with reduced cytosolic and plastidial phosphoglucomutase showed similar conversion.
- Taxon
- potatoSolanum tuberosume0
- Material
- transgenic potato linese0
- Outcome
- Similar resultse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Similar results were obtained with transgenic potato lines possessing a strongly reduced activity of both the cytosolic and the plastidial phosphoglucomutase.”
Claim · model-written summary
Reduced plastidial phosphorylase concentration significantly diminished starch labelling.
- Taxon
- PotatoSolanum tuberosumt0
- Gene
- plastidial phosphorylase isozymese0
- Outcome
- Starch labellinge0
- Direction
- diminishede0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Starch labelling was, however, significantly diminished in transgenic lines, with a reduced concentration of the plastidial phosphorylase isozymes.”
t0“potato (Solanum tuberosum)”
Claim · model-written summary
The authors propose two paths of reserve starch biosynthesis.
- Taxon
- PotatoSolanum tuberosumt0
- Outcome
- reserve starch biosynthesise0
- Qualifier
- Two distinct pathse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Two distinct paths of reserve starch biosynthesis are proposed that explain, at a biochemical level, the phenotype of several transgenic plant lines.”
t0“potato (Solanum tuberosum)”
The same questions in other papers
glucose · quality: sugar starch · Solanum tuberosum (potato)Results agree
2 papers in the same direction as this paper
- positive
- positive
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.