FT is an Arabidopsis PEBP-family protein that acts as a mobile flowering signal and transcriptional coactivator. It is produced in leaf phloem companion cells and moves through the phloem to the shoot apex, where association with FD-class bZIP transcription factors promotes expression of floral identity genes such as AP1. Its movement is regulated by proteins including FTIP1; FT is the transported signal rather than the transporter. FT occurs in nuclear and cytoplasmic pools, and ER-associated FT has been observed in transient localization experiments. Biochemical lipid-overlay and liposome assays show preferential binding to phosphatidylcholine rather than phosphatidylethanolamine, despite the historical PEBP family name. PC-binding-site mutations and changes in PC composition affect flowering activity. FT also has a cell-autonomous role in guard-cell stomatal opening, distinct from its long-distance floral signaling role.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: FT has a nuclear pool that functions with FD-class transcription factors. Reason: PMID:16099979 and curated localization establish nuclear FT. Independent full-text PMID:22529749 also detects nuclear FT:RFP in transiently transformed N. benthamiana cells. Retain the nuclear location without treating that heterologous localization as a native meristem-only assay. Supporting Evidence: file:ARATH/FT/FT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000269|PubMed:16099979}. Nucleus PMID:22529749 FT:RFP was also localized in the nucleus |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: FT also occupies a cytoplasmic pool. Reason: Curated experimental localization from PMID:16099979 supports cytoplasm. This pool is compatible with synthesis, intracellular trafficking and movement of the floral signal; no narrower cytosolic compartment is forced from an assay reported simply as cytoplasm. Supporting Evidence: file:ARATH/FT/FT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000269|PubMed:16099979}. Nucleus |
| GO:0005783 endoplasmic reticulum | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: FT has an observed ER-associated localization in a transport-partner assay. Reason: Full PMID:22529749 reports transient FT:RFP and FTIP1:GFP colocalization at ER connected to the nuclear envelope in N. benthamiana leaf epidermal cells. Retain the real organelle observation as context-dependent/non-core; do not reject it merely because transcriptional coactivation occurs in the nucleus. The experiment does not establish that FT is an integral ER membrane protein or resolve an ER subcompartment. Supporting Evidence: PMID:22529749 both FTIP1:GFP and FT:RFP were colocalized to ER connected to the nuclear envelope |
| GO:0009908 flower development | IEA GO_REF:0000043 | MODIFY | Summary: Specify the positive effect of FT on floral development. Reason: FT acts with FD at the shoot apex to activate AP1 and initiate floral development (PMID:16099979). The supported role is positive regulation, already represented by the target-specific GO:0009911 experimental rows. Replacing flower development with its positive regulation is a lateral correction of causal role, not an is_a/part_of descendant refinement or a claim that FT itself supplies floral tissue structure. Proposed replacements: positive regulation of flower development Supporting Evidence: PMID:16099979 FD and FT are interdependent partners through protein interaction and act at the shoot apex to promote floral transition and to initiate floral development through transcriptional activation of a floral meristem identity gene, APETALA1 (AP1). |
| GO:0030154 cell differentiation | IEA GO_REF:0000043 | MODIFY | Summary: Express the developmental claim as promotion of floral development. Reason: The keyword-derived differentiation claim lacks a specified cell lineage. Primary evidence directly establishes activation of floral identity through FT/FD; replace the generic developmental mapping with the existing positive regulation of flower development term. This is role/scope refinement rather than denial of a true claim for being broad. Proposed replacements: positive regulation of flower development Supporting Evidence: PMID:16099979 FD and FT are interdependent partners through protein interaction and act at the shoot apex to promote floral transition and to initiate floral development through transcriptional activation of a floral meristem identity gene, APETALA1 (AP1). |
| GO:0005515 protein binding | IPI PMID:16099979 FD, a bZIP protein mediating signals from the floral pathway... | REMOVE | Summary: FT-FD association is functionally informative, but bare binding is not. Reason: The molecular interaction and coactivation are represented by the independently reassessed specific FT binding and coactivator proposals. Remove only the uninformative GO:0005515 row under policy, not the experimentally demonstrated FD association. Supporting Evidence: PMID:16099979 FD and FT are interdependent partners through protein interaction and act at the shoot apex to promote floral transition and to initiate floral development through transcriptional activation of a floral meristem identity gene, APETALA1 (AP1). |
| GO:0005515 protein binding | IPI PMID:17189287 Molecular basis of late-flowering phenotype caused by domina... | REMOVE | Summary: Ectopic FWA binds FT and inhibits its flowering activity. Reason: The paper directly demonstrates FWA-FT interaction and uses ectopic FWA as an inhibitor of FT. This does not make FT a transcriptional inhibitor or give it the activity of its binding partner. Remove generic binding under policy while preserving this source-specific interaction. Supporting Evidence: PMID:17189287 Yeast two-hybrid analysis and in vitro pull-down assay showed that FWA protein can specifically interact with FT protein. |
| GO:0005515 protein binding | IPI PMID:19656342 Genetic and spatial interactions between FT, TSF and SVP dur... | REMOVE | Summary: FT interacts with bZIP partners also recognized by TSF. Reason: The primary study assays the common bZIP interactions in yeast and distinguishes photoperiodic phenotypes. Retain that mechanistic evidence in the specific binding/coactivation account; remove bare protein binding as uninformative, not as false. Supporting Evidence: PMID:19656342 TSF and FT have similar biochemical functions by showing that they interact in yeast with the same bZIP transcription factors. |
| GO:0005515 protein binding | IPI PMID:29259105 Characterization of Multiple C2 Domain and Transmembrane Reg... | REMOVE | Summary: MCTP association concerns regulated FT trafficking. Reason: The full study assays FTIP1/MCTP domains and FT interaction. The cargo interaction does not establish a new FT-enabled transport activity; remove bare binding without denying the physical interaction or MCTP transport mechanism. Supporting Evidence: file:ARATH/FT/FT-uniprot.txt Interacts with FTIP1/MCTP1 in phloem companion cells (PubMed:22529749, PubMed:29259105). |
| GO:0010022 meristem determinacy | IGI PMID:30943325 Genetic interactions reveal the antagonistic roles of FT/TSF... | ACCEPT | Summary: FT participates in determining reproductive meristem fate. Reason: The source compares ft tsf, tfl1 and combined genotypes, tissue-specific expression and grafting. Meristem phenotype depends on the balance and location of FT/TSF versus TFL1, not simply flowering time. Retain this experimentally resolved developmental function without asserting that endogenous FT universally terminates every inflorescence. Supporting Evidence: PMID:30943325 Plants overexpressing FT or TSF (or both FT and TFL1) generated a terminal flower, as did tfl1-20 mutants. |
| GO:0005515 protein binding | IPI PMID:22529749 FTIP1 is an essential regulator required for florigen transp... | REMOVE | Summary: FT binds its transport regulator FTIP1. Reason: Full primary data support the FT-FTIP1 interaction in phloem companion cells. FTIP1 mediates export while FT is the mobile cargo/signal. Remove uninformative bare binding without assigning the transporter's activity to FT. Supporting Evidence: PMID:22529749 FTIP1 is required for FT export from companion cells to sieve elements |
| GO:0010119 regulation of stomatal movement | IMP PMID:21737277 FLOWERING LOCUS T regulates stomatal opening. | KEEP AS NON CORE | Summary: FT regulates stomatal opening in guard cells. Reason: Guard-cell overexpression and the ft-1 loss-of-function allele establish a cell-autonomous stomatal role. Retain this secondary function; FT is not itself the plasma-membrane proton pump or phototropin kinase. Supporting Evidence: PMID:21737277 Transgenic plants overexpressing FT in guard cells showed open stomata, whereas a loss-of-function FT allele, ft-1, exhibited closed stomata and failed to activate the H(+)-ATPase in response to blue light. |
| GO:0009909 regulation of flower development | IGI PMID:20626659 Arabidopsis BLADE-ON-PETIOLE1 and 2 promote floral meristem ... | MODIFY | Summary: Specify the positive effect of FT on floral development. Reason: The original term already describes regulation of flower development. Independent FT/FD-dependent activation of AP1 (PMID:16099979) and the existing FT flowering phenotypes support the positive direction, captured by the already-present GO:0009911. The accessible evidence supports that sign without assigning uninspected assay details from the original PMID:20626659 interaction study. Proposed replacements: positive regulation of flower development Supporting Evidence: PMID:16099979 FD and FT are interdependent partners through protein interaction and act at the shoot apex to promote floral transition and to initiate floral development through transcriptional activation of a floral meristem identity gene, APETALA1 (AP1). |
| GO:0005515 protein binding | IPI PMID:16099980 Integration of spatial and temporal information during flora... | REMOVE | Summary: FT-FD complex formation activates floral identity genes. Reason: This physical interaction is retained by the specific functional claims. Bare protein binding is removed under policy; the removal does not negate complex formation or its transcriptional output. Supporting Evidence: PMID:16099980 A complex of FT and FD proteins in turn can activate floral identity genes such as APETALA1 (AP1). |
| GO:0005634 nucleus | IDA PMID:16099979 FD, a bZIP protein mediating signals from the floral pathway... | ACCEPT | Summary: FT has a nuclear pool that functions with FD-class transcription factors. Reason: PMID:16099979 and curated localization establish nuclear FT. Independent full-text PMID:22529749 also detects nuclear FT:RFP in transiently transformed N. benthamiana cells. Retain the nuclear location without treating that heterologous localization as a native meristem-only assay. Supporting Evidence: file:ARATH/FT/FT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000269|PubMed:16099979}. Nucleus PMID:22529749 FT:RFP was also localized in the nucleus |
| GO:0005737 cytoplasm | IDA PMID:16099979 FD, a bZIP protein mediating signals from the floral pathway... | ACCEPT | Summary: FT also occupies a cytoplasmic pool. Reason: Curated experimental localization from PMID:16099979 supports cytoplasm. This pool is compatible with synthesis, intracellular trafficking and movement of the floral signal; no narrower cytosolic compartment is forced from an assay reported simply as cytoplasm. Supporting Evidence: file:ARATH/FT/FT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000269|PubMed:16099979}. Nucleus |
| GO:0048573 photoperiodism, flowering | IEP PMID:17446353 FT protein movement contributes to long-distance signaling i... | ACCEPT | Summary: FT carries photoperiodic flowering information from leaves to the apex. Reason: Native Arabidopsis phloem-expression and grafting experiments establish long-distance movement of FT protein coupled to floral induction. FT is a signal component, not a direct photoreceptor; the cited experiment does not rely on the separately retracted FT-mRNA movement paper. Supporting Evidence: PMID:17446353 FT fusion proteins expressed specifically in phloem cells move to the apex and move long distances between grafted plants. PMID:17446353 FT protein acts as a long-distance signal that induces Arabidopsis flowering. |
| GO:0008429 phosphatidylethanolamine binding | ISS PMID:10583961 Activation tagging of the floral inducer FT. | MODIFY | Summary: Correct the lipid specificity from phosphatidylethanolamine to phosphatidylcholine. Reason: The original 1999 ISS claim reflects PEBP-family similarity, not a direct FT lipid assay. Purified Arabidopsis FT binds PC in lipid-overlay and liposome assays, whereas PE gives no significant binding under those tested conditions (PMID:24698997). Binding-site mutagenesis corroborates PC recognition (PMID:31726375). Replace the substrate-specific activity with GO:0031210; the family name is not evidence of PE specificity. Proposed replacements: phosphatidylcholine binding Supporting Evidence: PMID:24698997 In particular no signals were found for binding to PE, even if PE was spotted at higher concentrations PMID:24698997 We concluded that FT is a PC-binding protein in vitro. PMID:31726375 PC binding was significantly compromised for FTm1 and FTm3 but not FTm2 and FTm4 |
| GO:0009911 positive regulation of flower development | IMP PMID:10583960 A pair of related genes with antagonistic roles in mediating... | ACCEPT | Summary: FT positively regulates flowering. Reason: The source reports delayed flowering after loss of FT and precocious flowering after overexpression. Combined with FT/FD transcriptional activation, this supports FT participation in the promotive regulatory process rather than mere necessity as an inert substrate. Supporting Evidence: PMID:10583960 Loss of FT causes delay in flowering, whereas overexpression of FT results in precocious flowering independent of CO or photoperiod. PMID:16099979 FD and FT are interdependent partners through protein interaction and act at the shoot apex to promote floral transition and to initiate floral development through transcriptional activation of a floral meristem identity gene, APETALA1 (AP1). |
| GO:0009911 positive regulation of flower development | IMP PMID:10583961 Activation tagging of the floral inducer FT. | ACCEPT | Summary: Activation-tagged FT promotes floral induction. Reason: The source isolates FT by activation tagging and places it downstream of CONSTANS and alongside LFY. Its regulatory participation is independently resolved by FT/FD-dependent activation of AP1, so the positive process claim is retained. Supporting Evidence: PMID:10583961 FLOWERING LOCUS T (FT), which acts in parallel with the meristem-identity gene LEAFY (LFY) to induce flowering of Arabidopsis, was isolated by activation tagging. PMID:16099980 A complex of FT and FD proteins in turn can activate floral identity genes such as APETALA1 (AP1). |
| GO:0140297 DNA-binding transcription factor binding | IPI PMID:16099979 FD, a bZIP protein mediating signals from the floral pathway... | NEW | Summary: Retain the inherited specific FT transcription-factor-binding proposal. Reason: PMID:16099979 directly establishes functional interaction between FT and the bZIP transcription factor FD; curated evidence also identifies FDP. This specifies the otherwise uninformative binding rows. GO:0140297 and GO:0003713 are not ancestor/descendant terms in the inspected live ontology: one records partner recognition, the other a demonstrated transcriptional effect. No new process claim or autonomous DNA-binding activity is inferred. Supporting Evidence: PMID:16099979 FD and FT are interdependent partners through protein interaction and act at the shoot apex to promote floral transition and to initiate floral development through transcriptional activation of a floral meristem identity gene, APETALA1 (AP1). file:ARATH/FT/FT-uniprot.txt Interacts with FD/BZIP14 and FDP/BZIP27 (PubMed:16099979, PubMed:16099980). |
| GO:0003713 transcription coactivator activity | IPI PMID:16099980 Integration of spatial and temporal information during flora... | NEW | Summary: Retain the inherited FT transcription-coactivator proposal. Reason: The FT-FD complex activates AP1 and FT/FD are interdependent for floral induction. Thus FT contributes to the transcriptional step through a DNA-binding factor, rather than being an inert transported substrate or itself a DNA-binding transcription factor. The proposal has functional support beyond physical binding alone and is not an ancestor/descendant duplicate of GO:0140297. Supporting Evidence: PMID:16099980 A complex of FT and FD proteins in turn can activate floral identity genes such as APETALA1 (AP1). PMID:16099979 FD and FT are interdependent partners through protein interaction and act at the shoot apex to promote floral transition and to initiate floral development through transcriptional activation of a floral meristem identity gene, APETALA1 (AP1). |
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Download this section (compressed HTML)Q: How do the PC molecular species bound to native FT affect its transport versus transcriptional coactivation at the meristem?
Q: What is the native stoichiometry and partner composition of Arabidopsis FT transcriptional complexes across leaf and shoot-apex cell types?
Experiment: Compare native-expression PC-binding mutants for graft-transmissible movement, FD-complex association, target transcription and flowering, while measuring PC species in matched tissues.
Hypothesis: PC-binding-site changes affect FT coactivation independently of long-distance transport.
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