TRANSPARENT TESTA GLABRA1 (TTG1) is an Arabidopsis WD40-repeat transcriptional coregulator/scaffold reused in multiple MYB-bHLH-WD40 complexes. TTG1 has no DNA-binding domain; instead, it binds bHLH/MYB partners to stabilize transcriptional regulatory complexes that control trichome initiation and patterning, root epidermal non-hair fate, seed coat proanthocyanidin and mucilage programs, and anthocyanin accumulation. Promoter targeting by TTG1-containing complexes occurs via the DNA-binding MYB and bHLH partners rather than through direct TTG1-DNA contact.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0009723 response to ethylene | IEP PMID:21427279 Auxin and ethylene induce flavonol accumulation through dist... | KEEP AS NON CORE | Summary: TTG1-related transcriptional networks respond to ethylene in flavonol/epidermal contexts. Reason: Ethylene response is a context-specific output of TTG1-associated transcriptional networks. |
| GO:0009733 response to auxin | IEP PMID:21427279 Auxin and ethylene induce flavonol accumulation through dist... | KEEP AS NON CORE | Summary: TTG1-related transcriptional networks respond to auxin in flavonol/epidermal contexts. Reason: Auxin response is a context-specific output of TTG1-associated transcriptional networks. |
| GO:0010026 trichome differentiation | IMP PMID:10402433 The TRANSPARENT TESTA GLABRA1 locus, which regulates trichom... | ACCEPT | Summary: TTG1 is required for trichome differentiation as the WD40 scaffold of the trichome MBW complex. Reason: Trichome differentiation is a core TTG1 biological role. Supporting Evidence: file:ARATH/TTG1/TTG1-deep-research-falcon.md encodes a WD40-repeat scaffold protein that functions primarily as the WD40 subunit of **MBW transcriptional activator complexes**. |
| GO:0032880 regulation of protein localization | IMP PMID:18434419 The TTG1-bHLH-MYB complex controls trichome cell fate and pa... | KEEP AS NON CORE | Summary: TTG1 and GL3 redistribution contributes to trichome patterning by trapping/depletion mechanisms. Reason: Regulation of protein localization is a supported mechanism but secondary to TTG1 scaffold/coregulator activity. |
| GO:0045165 cell fate commitment | IMP PMID:10402433 The TRANSPARENT TESTA GLABRA1 locus, which regulates trichom... | MODIFY | Summary: TTG1 is required for epidermal cell fate commitment, especially trichome and root non-hair fate. Reason: Plant epidermal cell fate specification is more informative than broad cell fate commitment. Proposed replacements: plant epidermal cell fate specification |
| GO:0090628 plant epidermal cell fate specification | IMP PMID:7813791 The TTG gene is required to specify epidermal cell fate and ... | ACCEPT | Summary: TTG1 specifies Arabidopsis epidermal cell fate through MYB-bHLH-WD40 complexes. Reason: Epidermal cell fate specification is a central TTG1 process. |
| GO:0003677 DNA binding | IDA PMID:18434419 The TTG1-bHLH-MYB complex controls trichome cell fate and pa... | MODIFY | Summary: DNA binding was measured for TTG1-containing complexes, but TTG1 is a WD40 scaffold without a DNA-binding domain. Reason: The original DNA-binding annotation should not be retained as direct TTG1 DNA binding; the DNA-contacting activity belongs to MYB/bHLH partners in the MBW complex, while TTG1 is better represented as a transcription coregulator. Proposed replacements: transcription coregulator activity |
| GO:0005515 protein binding | IPI PMID:11063707 GL3 encodes a bHLH protein that regulates trichome developme... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005515 protein binding | IPI PMID:12917293 A network of redundant bHLH proteins functions in all TTG1-d... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005515 protein binding | IPI PMID:14561633 A contradictory GLABRA3 allele helps define gene interaction... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005515 protein binding | IPI PMID:15255866 TT2, TT8, and TTG1 synergistically specify the expression of... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005515 protein binding | IPI PMID:18434419 The TTG1-bHLH-MYB complex controls trichome cell fate and pa... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005515 protein binding | IPI PMID:22334670 A single amino acid substitution in IIIf subfamily of basic ... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005515 protein binding | IPI PMID:24771765 Brassinosteroids control root epidermal cell fate via direct... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005515 protein binding | IPI PMID:28650476 CrY2H-seq: a massively multiplexed assay for deep-coverage i... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | MARK AS OVER ANNOTATED | Summary: TTG1 binds many MYB and bHLH partners as a WD40 scaffold, but generic protein binding does not describe the functional transcriptional coregulator role. Reason: The better curation is transcription coregulator/scaffold activity in MBW complexes; protein binding alone is over-generic. |
| GO:0005634 nucleus | IDA PMID:18434419 The TTG1-bHLH-MYB complex controls trichome cell fate and pa... | ACCEPT | Summary: The protein has nuclear localization consistent with its transcriptional regulatory role. Reason: Nuclear localization is the expected functional compartment for this transcriptional regulator. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: The protein has a cytoplasmic pool or predicted cytoplasmic localization in addition to nuclear MBW-complex activity. Reason: Cytoplasmic localization is supported for TTG1/mobile pools and does not conflict with nuclear transcriptional coregulator activity. |
| GO:0005737 cytoplasm | ISM GO_REF:0000122 | ACCEPT | Summary: The protein has a cytoplasmic pool or predicted cytoplasmic localization in addition to nuclear MBW-complex activity. Reason: Cytoplasmic localization is supported for TTG1/mobile pools and does not conflict with nuclear transcriptional coregulator activity. |
| GO:0005737 cytoplasm | IDA PMID:18547143 Two-dimensional patterning by a trapping/depletion mechanism... | ACCEPT | Summary: The protein has a cytoplasmic pool or predicted cytoplasmic localization in addition to nuclear MBW-complex activity. Reason: Cytoplasmic localization is supported for TTG1/mobile pools and does not conflict with nuclear transcriptional coregulator activity. Supporting Evidence: PMID:18547143 Both fusion proteins were found in the nucleus and in the cytoplasm (Figure 2F). |
| GO:0009963 positive regulation of flavonoid biosynthetic process | IC PMID:10402433 The TRANSPARENT TESTA GLABRA1 locus, which regulates trichom... | NEW | Summary: TTG1-containing MBW complexes activate anthocyanin and proanthocyanidin/flavonoid transcriptional programs. Reason: GOA captures TTG1 trichome and epidermal roles but omits the well-supported MBW role in positively regulating flavonoid biosynthetic outputs. Supporting Evidence: file:ARATH/TTG1/TTG1-deep-research-falcon.md TTG1-containing MBW combinations with MYBs **PAP1/PAP2/MYB113/MYB114** and bHLHs **GL3/EGL3/TT8** regulate anthocyanin accumulation through activation of late biosynthetic genes PMID:10402433 The TRANSPARENT TESTA GLABRA1 locus, which regulates trichome differentiation and anthocyanin biosynthesis in Arabidopsis, encodes a WD40 repeat protein. |
| GO:0003712 transcription coregulator activity | IC PMID:10402433 The TRANSPARENT TESTA GLABRA1 locus, which regulates trichom... | NEW | Summary: TTG1 is the non-DNA-binding WD40 scaffold/coregulator subunit of MBW transcriptional complexes. Reason: GOA currently represents TTG1 with generic protein binding and a misleading DNA-binding row, but the supported molecular role is transcriptional coregulator activity in MYB-bHLH-WD40 complexes. Supporting Evidence: file:ARATH/TTG1/TTG1-deep-research-falcon.md encodes a WD40-repeat scaffold protein that functions primarily as the WD40 subunit of **MBW transcriptional activator complexes**. PMID:18434419 The TTG1-bHLH-MYB complex controls trichome cell fate and patterning through direct targeting of regulatory loci. |
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Q: Can TTG1 annotations distinguish nucleus-localized transcriptional coregulator activity from cytoplasmic/mobile pools and hormone-regulated relocalization?
Experiment: Test TTG1 variants defective in GL3/TT8/MYB binding in trichome, root hair, anthocyanin, proanthocyanidin, and mucilage reporter assays to define partner-specific MBW functions.
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