Abstract
BACKGROUND: Starch is biosynthesised by a complex of enzymes including various starch synthases and starch branching and debranching enzymes, amongst others. The role of all these enzymes has been investigated using gene silencing or genetic knockouts, but there are few examples of overexpression due to the problems of either cloning large genomic fragments or the toxicity of functional cDNAs to bacteria during cloning. The aim of this study was to investigate the function of potato STARCH BRANCHING ENZYME II (SBEII) using overexpression in potato tubers. RESULTS: A hybrid SBEII intragene consisting of potato cDNA containing a fragment of potato genomic DNA that included a single intron was used in order to prevent bacterial translation during cloning. A population of 20 transgenic potato plants exhibiting SBEII overexpression was generated. Compared with wild-type, starch from these tubers possessed an increased degree of amylopectin branching, with more short chains of degree of polymerisation (DP) 6-12 and particularly of DP6. Transgenic lines expressing a GRANULE-BOUND STARCH SYNTHASE (GBSS) RNAi construct were also generated for comparison and exhibited post-transcriptional gene silencing of GBSS and reduced amylose content in the starch. Both transgenic modifications did not affect granule morphology but reduced starch peak viscosity. In starch from SBEII-overexpressing lines, the increased ratio of short to long amylopectin branches facilitated gelatinisation, which occurred at a reduced temperature (by up to 3°C) or lower urea concentration. In contrast, silencing of GBSS increased the gelatinisation temperature by 4°C, and starch required a higher urea concentration for gelatinisation. In lines with a range of SBEII overexpression, the magnitude of the increase in SBEII activity, reduction in onset of gelatinisation temperature and increase in starch swollen pellet volume were highly correlated, consistent with reports that starch swelling is greatly dependent upon the amylopectin branching pattern. CONCLUSION: This work reports the first time that overexpression of SBEII has been achieved in a non-cereal plant. The data show that overexpression of SBEII using a simple single-intron hybrid intragene is an effective way to modify potato starch physicochemical properties, and indicate that an increased ratio of short to long amylopectin branches produces commercially beneficial changes in starch properties such as reduced gelatinisation temperature, reduced viscosity and increased swelling volume.
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Claims 11
Claim · model-written summary
SBEII overexpression increased the degree of amylopectin branching in potato tuber starch compared with wild-type.
- Taxon
- potato
Solanum tuberosumt0 - Organ / stage
- tuberse2
- Treatment
- SBEII overexpressione1
- Gene
- SBEIIe1
- Outcome
- degree of amylopectin branchinge2
- Direction
- increasede2
- Comparator
- wild-typee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e1“A population of 20 transgenic potato plants exhibiting SBEII overexpression was generated”
e2“Compared with wild-type, starch from these tubers possessed an increased degree of amylopectin branching”
Claim · model-written summary
SBEII overexpression increased short amylopectin chains of DP 6-12, particularly DP6, compared with wild-type.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- SBEII overexpressione1
- Outcome
- short chains of degree of polymerisation (DP) 6-12e3
- Direction
- moree3
- Comparator
- wild-typee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e1“A population of 20 transgenic potato plants exhibiting SBEII overexpression was generated”
e2“Compared with wild-type, starch from these tubers possessed an increased degree of amylopectin branching”
e3“with more short chains of degree of polymerisation (DP) 6-12 and particularly of DP6”
Claim · model-written summary
Silencing of GBSS increased the gelatinisation temperature by 4°C.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- silencing of GBSSe7
- Gene
- GBSSe7
- Outcome
- gelatinisation temperaturee7
- Direction
- increasede7
- Value
- by 4°Ce7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e7“In contrast, silencing of GBSS increased the gelatinisation temperature by 4°C, and starch required a higher urea concentration for gelatinisation”
Claim · model-written summary
The GBSS RNAi construct reduced amylose content in the starch.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- GRANULE-BOUND STARCH SYNTHASE (GBSS) RNAi constructe4
- Gene
- GBSSe4
- Outcome
- amylose contente4
- Direction
- reducede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e4“Transgenic lines expressing a GRANULE-BOUND STARCH SYNTHASE (GBSS) RNAi construct were also generated for comparison and exhibited post-transcriptional gene silencing of GBSS and reduced amylose content in the starch”
Claim · model-written summary
Silencing of GBSS required a higher urea concentration for gelatinisation.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- silencing of GBSSe7
- Gene
- GBSSe7
- Outcome
- urea concentration for gelatinisatione7
- Direction
- highere7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e7“In contrast, silencing of GBSS increased the gelatinisation temperature by 4°C, and starch required a higher urea concentration for gelatinisation”
Claim · model-written summary
Both transgenic modifications did not affect starch granule morphology.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- Both transgenic modificationse5
- Outcome
- granule morphologye5
- Direction
- did not affecte5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e5“Both transgenic modifications did not affect granule morphology but reduced starch peak viscosity”
Claim · model-written summary
Both transgenic modifications reduced starch peak viscosity.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- Both transgenic modificationse5
- Outcome
- starch peak viscositye5
- Direction
- reducede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e5“Both transgenic modifications did not affect granule morphology but reduced starch peak viscosity”
Claim · model-written summary
Starch from SBEII-overexpressing lines gelatinised at a reduced temperature, by up to 3°C.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- SBEII-overexpressing linese6
- Outcome
- gelatinisatione6
- Direction
- reducede6
- Value
- by up to 3°Ce6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e6“In starch from SBEII-overexpressing lines, the increased ratio of short to long amylopectin branches facilitated gelatinisation, which occurred at a reduced temperature (by up to 3°C) or lower urea concentration”
Claim · model-written summary
Starch from SBEII-overexpressing lines gelatinised at a lower urea concentration.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- SBEII-overexpressing linese6
- Outcome
- urea concentratione6
- Direction
- lowere6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e6“In starch from SBEII-overexpressing lines, the increased ratio of short to long amylopectin branches facilitated gelatinisation, which occurred at a reduced temperature (by up to 3°C) or lower urea concentration”
Claim · model-written summary
Across lines with a range of SBEII overexpression, the increase in SBEII activity was highly correlated with reduced onset of gelatinisation temperature and increased starch swollen pellet volume.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- SBEII overexpressione1
- Outcome
- reduction in onset of gelatinisation temperature and increase in starch swollen pellet volumee1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e1“In lines with a range of SBEII overexpression, the magnitude of the increase in SBEII activity, reduction in onset of gelatinisation temperature and increase in starch swollen pellet volume were highly correlated”
Claim · model-written summary
A population of 20 transgenic potato plants with SBEII overexpression was generated.
- Taxon
- potatoSolanum tuberosumt0
- Outcome
- SBEII overexpressione1
- Value
- 20e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“potato tuber”
e1“A population of 20 transgenic potato plants exhibiting SBEII overexpression was generated”
The same questions in other papers
loss of function · molecular: metabolites · Solanum tuberosum (potato)Positive and negative results
12 papers in the same direction as this paper · 9 in the opposite direction
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See all 22 papers →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.