Abstract
Sucrose transporters of the SUT4 clade show dual targeting to both the plasma membrane as well as to the vacuole. Previous investigations revealed a role for the potato sucrose transporter StSUT4 in flowering, tuberization, shade avoidance response, and ethylene production. Down-regulation of StSUT4 expression leads to early flowering, tuberization under long days, far-red light insensitivity, and reduced diurnal ethylene production. Sucrose export from leaves was increased and a phase-shift of soluble sugar accumulation in source leaves was observed, arguing for StSUT4 to be involved in the entrainment of the circadian clock. Here, we show that StSUT4, whose transcripts are highly unstable and tightly controlled at the post-transcriptional level, connects components of the ethylene and calcium signalling pathway. Elucidation of the StSUT4 interactome using the split ubiquitin system helped to prove direct physical interaction between the sucrose transporter and the ethylene receptor ETR2, as well as with the calcium binding potato calmodulin-1 (PCM1) protein, and a calcium-load activated calcium channel. The impact of calcium ions on transport activity and dual targeting of the transporter was investigated in detail. For this purpose, a reliable esculin-based transport assay was established for SUT4-like transporters. Site-directed mutagenesis helped to identify a diacidic motif within the seventh transmembrane spanning domain that is essential for sucrose transport activity and targeting, but not required for calcium-dependent inhibition. A link between sucrose, calcium and ethylene signalling has been previously postulated with respect to pollen tube growth, shade avoidance response, or entrainment of the circadian clock. Here, we provide experimental evidence for the direct interconnection of these signalling pathways at the molecular level by direct physical interaction of the main players.
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Claims 6
Claim · model-written summary
StSUT4 physically interacts directly with the ethylene receptor ETR2.
- Taxon
- potato
Solanum tuberosume0 - Gene
- ethylene receptor ETR2e1
- Outcome
- direct physical interactione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Previous investigations revealed a role for the potato sucrose transporter StSUT4 in flowering, tuberization, shade avoidance response, and ethylene production”
e1“direct physical interaction between the sucrose transporter and the ethylene receptor ETR2”
Claim · model-written summary
StSUT4 physically interacts directly with the calcium-binding potato calmodulin-1 (PCM1) protein.
- Taxon
- potatoSolanum tuberosume0
- Gene
- potato calmodulin-1 (PCM1)e2
- Outcome
- direct physical interactione2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Previous investigations revealed a role for the potato sucrose transporter StSUT4 in flowering, tuberization, shade avoidance response, and ethylene production”
e2“direct physical interaction between the sucrose transporter and the ethylene receptor ETR2, as well as with the calcium binding potato calmodulin-1 (PCM1) protein, and a calcium-load activated calcium channel”
Claim · model-written summary
StSUT4 physically interacts directly with a calcium-load activated calcium channel.
- Taxon
- potatoSolanum tuberosume0
- Gene
- calcium-load activated calcium channele2
- Outcome
- direct physical interactione2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Previous investigations revealed a role for the potato sucrose transporter StSUT4 in flowering, tuberization, shade avoidance response, and ethylene production”
e2“direct physical interaction between the sucrose transporter and the ethylene receptor ETR2, as well as with the calcium binding potato calmodulin-1 (PCM1) protein, and a calcium-load activated calcium channel”
Claim · model-written summary
A reliable esculin-based transport assay was established for SUT4-like transporters.
- Taxon
- potatoSolanum tuberosume0
- Compound
- esculine4
- Outcome
- reliable esculin-based transport assaye4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Previous investigations revealed a role for the potato sucrose transporter StSUT4 in flowering, tuberization, shade avoidance response, and ethylene production”
e4“a reliable esculin-based transport assay was established for SUT4-like transporters”
Claim · model-written summary
Site-directed mutagenesis identified a diacidic motif in the seventh transmembrane domain as essential for sucrose transport activity and targeting.
- Taxon
- potatoSolanum tuberosume0
- Treatment
- Site-directed mutagenesise5
- Gene
- diacidic motif within the seventh transmembrane spanning domaine5
- Outcome
- sucrose transport activity and targetinge5
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Previous investigations revealed a role for the potato sucrose transporter StSUT4 in flowering, tuberization, shade avoidance response, and ethylene production”
e5“Site-directed mutagenesis helped to identify a diacidic motif within the seventh transmembrane spanning domain that is essential for sucrose transport activity and targeting”
Claim · model-written summary
The diacidic motif is not required for calcium-dependent inhibition of StSUT4.
- Taxon
- potatoSolanum tuberosume0
- Treatment
- Site-directed mutagenesise5
- Gene
- diacidic motif within the seventh transmembrane spanning domaine5
- Outcome
- calcium-dependent inhibitione6
- Direction
- not requirede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Previous investigations revealed a role for the potato sucrose transporter StSUT4 in flowering, tuberization, shade avoidance response, and ethylene production”
e5“Site-directed mutagenesis helped to identify a diacidic motif within the seventh transmembrane spanning domain that is essential for sucrose transport activity and targeting”
e6“but not required for calcium-dependent inhibition”
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