Abstract
Sucrose (Suc)-phosphate synthase (SPS) plays a crucial role in the synthesis of Suc in photosynthetic and nonphotosynthetic tissues. Several isoforms of SPS exist in dicotyledonous plants that can be grouped into the different families A, B, and C. To explore whether functional differences between the SPS gene families might exist, we characterized a representative for each family from tobacco (Nicotiana tabacum). RNA-blot analysis revealed a distinct expression pattern for each of the three SPS genes. While the A-family member (NtSPSA) was found to be expressed in all tissues examined, expression of the B isoform (NtSPSB) was mainly confined to the reproductive organs and NtSPSC mRNA was exclusively detected in mature source leaves. We used RNA interference to assess the in planta function of NtSPSA and C. While silencing of NtSPSA had no detectable influence on leaf carbohydrate metabolism, reduction of NtSPSC led to an increase in leaf starch content by a factor of 3 to 8. Further analysis revealed that starch accumulation in NtSPSC-silenced plants was not due to an increased partitioning of carbon into starch, but rather showed that starch mobilization was impaired. The transgenic plants were unable to efficiently mobilize their transitory leaf starch during a prolonged period of darkness and accumulated maltose as a major intermediate of starch breakdown. NtSPSC mRNA level increased appreciably during the dark period while transcript levels of the other isoforms showed no diurnal changes. Together, these results suggest that NtSPSC is specifically involved in the synthesis of Suc during starch mobilization in the dark. The roles of the other SPS isoforms are discussed.
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Claims 12
Claim · model-written summary
NtSPSA was expressed in all tissues examined.
- Taxon
- tobacco
Nicotiana tabacume1 - Gene
- NtSPSAe0
- Outcome
- expressed in all tissues examinede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NtSPSA) was found to be expressed in all tissues examined”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
NtSPSB expression was mainly confined to reproductive organs.
- Taxon
- tobaccoNicotiana tabacume1
- Gene
- NtSPSBe0
- Outcome
- confined to the reproductive organse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NtSPSB) was mainly confined to the reproductive organs”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
NtSPSC mRNA was detected exclusively in mature source leaves.
- Taxon
- tobaccoNicotiana tabacume1
- Gene
- NtSPSCe0
- Outcome
- exclusively detected in mature source leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NtSPSC mRNA was exclusively detected in mature source leaves”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
Silencing NtSPSA had no detectable influence on leaf carbohydrate metabolism.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- silencing of NtSPSAe0
- Gene
- NtSPSAe0
- Outcome
- leaf carbohydrate metabolisme0
- Direction
- no detectable influencee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“silencing of NtSPSA had no detectable influence on leaf carbohydrate metabolism”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
Reducing NtSPSC increased leaf starch content by a factor of 3 to 8.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- reduction of NtSPSCe0
- Gene
- NtSPSCe0
- Outcome
- leaf starch contente0
- Direction
- increasee0
- Value
- a factor of 3 to 8e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reduction of NtSPSC led to an increase in leaf starch content by a factor of 3 to 8”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
Starch accumulation in NtSPSC-silenced plants did not result from increased carbon partitioning into starch.
- Taxon
- tobaccoNicotiana tabacume1
- Gene
- NtSPSCe0
- Outcome
- starch accumulatione0
- Qualifier
- not due to an increased partitioning of carbon into starche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“starch accumulation in NtSPSC-silenced plants was not due to an increased partitioning of carbon into starch”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
Starch mobilization was impaired in NtSPSC-silenced plants.
- Taxon
- tobaccoNicotiana tabacume2
- Treatment
- NtSPSC-silenced plantse1
- Outcome
- starch mobilizatione0
- Direction
- impairede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“starch mobilization was impaired”
e1“NtSPSC-silenced plants”
e2“tobacco (Nicotiana tabacum)”
Claim · model-written summary
Transgenic plants could not efficiently mobilize transient leaf starch during prolonged darkness.
- Taxon
- tobaccoNicotiana tabacume1
- Material
- transgenic plantse0
- Outcome
- mobilize their transitory leaf starche0
- Direction
- unable to efficiently mobilizee0
- Qualifier
- prolonged period of darknesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The transgenic plants were unable to efficiently mobilize their transitory leaf starch during a prolonged period of darkness”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
Transgenic plants accumulated maltose as a major starch-breakdown intermediate.
- Taxon
- tobaccoNicotiana tabacume2
- Material
- transgenic plantse1
- Outcome
- maltose as a major intermediate of starch breakdowne0
- Direction
- accumulatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“accumulated maltose as a major intermediate of starch breakdown”
e1“The transgenic plants”
e2“tobacco (Nicotiana tabacum)”
Claim · model-written summary
NtSPSC mRNA increased appreciably during darkness.
- Taxon
- tobaccoNicotiana tabacume1
- Gene
- NtSPSCe0
- Outcome
- mRNA levele0
- Direction
- increased appreciablye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NtSPSC mRNA level increased appreciably during the dark period”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
Transcript levels of the other SPS isoforms showed no diurnal changes.
- Taxon
- tobaccoNicotiana tabacume1
- Outcome
- transcript levels of the other isoformse0
- Direction
- no diurnal changese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transcript levels of the other isoforms showed no diurnal changes”
e1“tobacco (Nicotiana tabacum)”
Claim · model-written summary
NtSPSC is implicated specifically in sucrose synthesis during dark-period starch mobilization.
- Taxon
- tobaccoNicotiana tabacume1
- Gene
- NtSPSCe0
- Outcome
- synthesis of Suce0
- Qualifier
- during starch mobilization in the darke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NtSPSC is specifically involved in the synthesis of Suc during starch mobilization in the dark”
e1“tobacco (Nicotiana tabacum)”
The same questions in other papers
loss of function · quality: sugar starch · Nicotiana tabacum (tobacco)Results agree
2 papers in the same direction as this paper
- 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.