Abstract
Brassinosteroids (BRs) induce various growth responses when applied exogenously to plant tissues, and the analysis of biosynthetic mutants reveals an essential role for plant growth and development. Only a few BR-regulated genes have been identified so far, and the corresponding gene products are assumed to be involved in cell elongation. The present study shows that BR growth responses are linked to the regulation of carbohydrate metabolism by induction of the mRNA for the key enzyme of an apoplastic phloem-unloading pathway. Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected. This enhanced enzyme activity was shown to correlate with the induction of the mRNA of extracellular invertase Lin6, whereas the mRNA levels of the other three extracellular invertase isoenzymes were not affected. The induction level induced by different BRs correlates with their growth-promoting activity. The physiological significance of this regulation is further supported by the low concentrations and short incubation times required to induce Lin6 mRNA. This regulatory mechanism results in an elevated uptake of sucrose via the hexose monomers, and thus an increased supply of carbohydrates to the BR-treated cells. Experiments with tomato seedlings showed that the localized BR-dependent growth response of the hypocotyl elongation zone was accompanied by a specific induction of Lin6 mRNA that is restricted to the corresponding tissues. This study demonstrates a role of BRs in tissue-specific source/sink regulation.
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Claims 9
Claim · model-written summary
Brassinosteroids elevated cell-wall-bound invertase activity in tomato suspension cells.
- Taxon
- tomato
Solanum lycopersicume1 - Organ / stage
- suspension culture cellse1
- Treatment
- Addition of BRse1
- Gene
- cell-wall-bound invertasee1
- Outcome
- activity of cell-wall-bound invertasee1
- Direction
- elevatese1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected”
Claim · model-written summary
Brassinosteroids did not affect intracellular invertase activities in tomato suspension cells.
- Taxon
- tomatoSolanum lycopersicume1
- Organ / stage
- suspension culture cellse1
- Treatment
- Addition of BRse1
- Outcome
- intracellular invertase activitiese1
- Direction
- not affectede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected”
Claim · model-written summary
Enhanced invertase activity correlated with induction of extracellular invertase Lin6 mRNA.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- Addition of BRse1
- Gene
- extracellular invertase Lin6e2
- Outcome
- induction of the mRNAe2
- Direction
- increaseinferrede2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected”
e2“This enhanced enzyme activity was shown to correlate with the induction of the mRNA of extracellular invertase Lin6”
Claim · model-written summary
Brassinosteroids left the mRNA levels of the other three extracellular invertase isoenzymes unaffected.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- Addition of BRse1
- Gene
- extracellular invertasee3
- Outcome
- the mRNA levels of the other three extracellular invertase isoenzymese3
- Direction
- not affectede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected”
e3“the mRNA levels of the other three extracellular invertase isoenzymes were not affected”
Claim · model-written summary
The induction level by different brassinosteroids correlated with their growth-promoting activity.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- different BRse4
- Outcome
- growth-promoting activitye4
- Direction
- increaseinferrede4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected”
e4“The induction level induced by different BRs correlates with their growth-promoting activity”
Claim · model-written summary
Low concentrations and short incubation times were enough to induce Lin6 mRNA in tomato.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- low concentrations and short incubation timese5
- Gene
- Lin6e5
- Outcome
- Lin6 mRNAe5
- Direction
- inducee5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected”
e5“The physiological significance of this regulation is further supported by the low concentrations and short incubation times required to induce Lin6 mRNA”
Claim · model-written summary
The regulatory mechanism elevates sucrose uptake via hexose monomers and supplies more carbohydrate to BR-treated cells.
- Taxon
- tomatoSolanum lycopersicume1
- Compound
- sucrosee6
- Outcome
- uptake of sucrose via the hexose monomerse6
- Direction
- elevatede6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected”
e6“This regulatory mechanism results in an elevated uptake of sucrose via the hexose monomers, and thus an increased supply of carbohydrates to the BR-treated cells”
Claim · model-written summary
In tomato seedlings, the BR-dependent growth response of the hypocotyl elongation zone was accompanied by specific induction of Lin6 mRNA restricted to those tissues.
- Taxon
- tomato seedlingsSolanum lycopersicume7
- Organ / stage
- hypocotyl elongation zonee7
- Gene
- Lin6e7
- Outcome
- induction of Lin6 mRNAe7
- Direction
- increaseinferrede7
- Qualifier
- restricted to the corresponding tissuese7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“Experiments with tomato seedlings showed that the localized BR-dependent growth response of the hypocotyl elongation zone was accompanied by a specific induction of Lin6 mRNA that is restricted to the corresponding tissues”
Claim · model-written summary
Brassinosteroids have a role in tissue-specific source/sink regulation in tomato.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- BRse2
- Outcome
- source/sink regulatione2
- Qualifier
- tissue-specifice2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell-wall-bound invertase, whereas the intracellular invertase activities were not affected”
e2“This study demonstrates a role of BRs in tissue-specific source/sink regulation”
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