Abstract
Sugars are necessary for plant growth and fruit development. Cucumber (Cucumis sativus L.) transports sugars, mainly raffinose family oligosaccharides (RFOs), in the vascular bundle. As the dominant sugars in cucumber fruit, glucose and fructose are derived from sucrose, which is the product of RFO hydrolysis by α-galactosidase (α-Gal). Here, we characterized the cucumber alkaline α-galactosidase 2 (CsAGA2) gene and found that CsAGA2 has undergone human selection during cucumber domestication. Further experiments showed that the expression of CsAGA2 increases gradually during fruit development, especially in fruit vasculature. In CsAGA2-RNA interference (RNAi) lines, fruit growth was delayed because of lower hexose production in the peduncle and fruit main vascular bundle (MVB). In contrast, CsAGA2-overexpressing (OE) plants displayed bigger fruits. Functional enrichment analysis of transcriptional data indicated that genes related to sugar metabolism, cell wall metabolism, and hormone signaling were significantly downregulated in the peduncle and fruit MVBs of CsAGA2-RNAi plants. Moreover, downregulation of CsAGA2 also caused negative feedback regulation on source leaves, which was shown by reduced photosynthetic efficiency, fewer plasmodesmata at the surface between mesophyll cell and intermediary cell (IC) or between IC and sieve element, and downregulated gene expression and enzyme activities related to phloem loading, as well as decreased sugar production and exportation from leaves and petioles. The opposite trend was observed in CsAGA2-OE lines. Overall, we conclude that CsAGA2 is essential for cucumber fruit set and development through mediation of sugar communication between sink strength and source activity.
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Claims 12
Claim · model-written summary
CsAGA2 underwent human selection in cucumber domestication.
- Taxon
- cucumber
Cucumis sativuse0 - Gene
- CsAGA2e0
- Outcome
- human selection during cucumber domesticatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CsAGA2 has undergone human selection during cucumber domestication”
Claim · model-written summary
CsAGA2 expression increased during fruit development, especially in fruit vasculature.
- Taxon
- cucumberCucumis sativust0
- Organ / stage
- fruit vasculaturee0
- Gene
- CsAGA2e0
- Outcome
- expression of CsAGA2e0
- Direction
- increasese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the expression of CsAGA2 increases gradually during fruit development, especially in fruit vasculature”
t0“cucumber”
Claim · model-written summary
CsAGA2 RNAi delayed fruit growth.
- Taxon
- cucumberCucumis sativust0
- Treatment
- CsAGA2-RNA interference (RNAi)e0
- Gene
- CsAGA2e0
- Outcome
- fruit growthe0
- Direction
- delayede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In CsAGA2-RNA interference (RNAi) lines, fruit growth was delayed because of lower hexose production in the peduncle and fruit main vascular bundle (MVB)”
t0“cucumber”
Claim · model-written summary
CsAGA2 RNAi lowered hexose production in peduncle and fruit vascular bundle.
- Taxon
- cucumberCucumis sativust0
- Organ / stage
- peduncle and fruit main vascular bundlee0
- Treatment
- CsAGA2-RNA interference (RNAi)e0
- Gene
- CsAGA2e0
- Outcome
- hexose productione0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In CsAGA2-RNA interference (RNAi) lines, fruit growth was delayed because of lower hexose production in the peduncle and fruit main vascular bundle (MVB)”
t0“cucumber”
Claim · model-written summary
CsAGA2 overexpression produced larger fruits.
- Taxon
- cucumberCucumis sativust0
- Treatment
- CsAGA2-overexpressing (OE)e0
- Gene
- CsAGA2e0
- Outcome
- fruitse0
- Direction
- biggere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CsAGA2-overexpressing (OE) plants displayed bigger fruits”
t0“cucumber”
Claim · model-written summary
Sugar metabolism, cell wall metabolism and hormone signaling genes were downregulated in RNAi fruit tissues.
- Taxon
- cucumberCucumis sativust0
- Material
- CsAGA2-RNAi plantse0
- Organ / stage
- peduncle and fruit MVBse0
- Outcome
- genes related to sugar metabolism, cell wall metabolism, and hormone signalinge0
- Direction
- downregulatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“genes related to sugar metabolism, cell wall metabolism, and hormone signaling were significantly downregulated in the peduncle and fruit MVBs of CsAGA2-RNAi plants”
t0“cucumber”
Claim · model-written summary
CsAGA2 downregulation reduced photosynthetic efficiency in source leaves.
- Taxon
- cucumberCucumis sativust0
- Organ / stage
- source leavese0
- Treatment
- downregulation of CsAGA2e0
- Gene
- CsAGA2e0
- Outcome
- photosynthetic efficiencye0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“downregulation of CsAGA2 also caused negative feedback regulation on source leaves, which was shown by reduced photosynthetic efficiency”
t0“cucumber”
Claim · model-written summary
CsAGA2 downregulation reduced plasmodesmata between mesophyll, intermediary and sieve cells.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- downregulation of CsAGA2e2
- Gene
- CsAGA2t0
- Outcome
- plasmodesmatae0
- Direction
- fewere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“fewer plasmodesmata at the surface between mesophyll cell and intermediary cell (IC) or between IC and sieve element”
t0“CsAGA2”
e1“CsAGA2 has undergone human selection during cucumber domestication”
e2“downregulation of CsAGA2 also caused negative feedback regulation on source leaves, which was shown by reduced photosynthetic efficiency”
Claim · model-written summary
Phloem loading gene expression and enzyme activity declined after CsAGA2 downregulation.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- downregulation of CsAGA2e2
- Gene
- CsAGA2t0
- Outcome
- gene expression and enzyme activities related to phloem loadinge0
- Direction
- downregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“downregulated gene expression and enzyme activities related to phloem loading”
t0“CsAGA2”
e1“CsAGA2 has undergone human selection during cucumber domestication”
e2“downregulation of CsAGA2 also caused negative feedback regulation on source leaves, which was shown by reduced photosynthetic efficiency”
Claim · model-written summary
Sugar production and export from leaves and petioles declined after CsAGA2 downregulation.
- Taxon
- cucumberCucumis sativuse1
- Organ / stage
- leaves and petiolese0
- Treatment
- downregulation of CsAGA2e2
- Gene
- CsAGA2t0
- Outcome
- sugar production and exportatione0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“decreased sugar production and exportation from leaves and petioles”
t0“CsAGA2”
e1“CsAGA2 has undergone human selection during cucumber domestication”
e2“downregulation of CsAGA2 also caused negative feedback regulation on source leaves, which was shown by reduced photosynthetic efficiency”
Claim · model-written summary
CsAGA2 overexpression showed the opposite source-leaf trend to RNAi.
- Taxon
- cucumberCucumis sativust0
- Material
- CsAGA2-OE linese0
- Outcome
- opposite trende0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The opposite trend was observed in CsAGA2-OE lines”
t0“cucumber”
Claim · model-written summary
CsAGA2 supports fruit set and development by mediating sugar communication between source and sink.
- Taxon
- cucumberCucumis sativuse0
- Gene
- CsAGA2e0
- Outcome
- fruit set and developmente0
- Qualifier
- mediation of sugar communication between sink strength and source activitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CsAGA2 is essential for cucumber fruit set and development through mediation of sugar communication between sink strength and source activity”
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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.