GLABRA1 (GL1/AtMYB0) is a nuclear R2R3-MYB transcription factor that specifies shoot epidermal trichome fate in Arabidopsis. With GL3/EGL3 bHLH partners and the WD40 protein TTG1, GL1 activates developmental regulators including GL2 and TTG2 and mobile R3-MYB inhibitors including CPC and ETC1, coupling trichome differentiation to spacing. DELLA and JAZ repressors modulate this transcriptional module in response to gibberellin and jasmonate.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0001708 cell fate specification | IMP PMID:12244266 Roles of the GLABROUS1 and TRANSPARENT TESTA GLABRA Genes in... | MODIFY | Summary: GL1 specifies epidermal/trichome precursor fate rather than cell fate specification in general. Reason: Plant epidermal cell fate specification is the better-supported process. Proposed replacements: plant epidermal cell fate specification Supporting Evidence: PMID:12244266 the constitutive expression of both GL1 and R in the same plant caused trichomes to develop on all shoot epidermal surfaces. |
| GO:0009740 gibberellic acid mediated signaling pathway | TAS PMID:9625690 Gibberellins promote trichome formation by Up-regulating GLA... | KEEP AS NON CORE | Summary: GL1 is a transcriptional effector of gibberellin-regulated trichome initiation. Reason: GA-dependent GL1 transcription and gl1 epistasis support this pathway context (PMID:9625690); later DELLA-GL1 interaction evidence (PMID:24659329) strengthens a direct hormone-to-transcription link. Retain as non-core, consistently with jasmonate signaling. Supporting Evidence: PMID:9625690 In the double mutant the gl1-1 glabrous phenotype is epistatic to the spy-5 phenotype, suggesting that GL1 acts downstream of the GA signal transduction pathway. PMID:24659329 DELLAs and JAZs interact with bHLH factors (EGL3 and GL3) and MYB factor (GL1), essential components of the WD-repeat/bHLH/MYB complex, to repress their transcription activity |
| GO:0009867 jasmonic acid mediated signaling pathway | IMP PMID:21551388 The Jasmonate-ZIM-domain proteins interact with the WD-Repea... | KEEP AS NON CORE | Summary: Jasmonate pathway regulators modulate the GL1-containing MBW complex during trichome initiation. Reason: JA regulation is a context-specific upstream modulation of the trichome MBW module rather than GL1 core molecular function. Supporting Evidence: PMID:21551388 the JA-induced trichome initiation was disrupted in gl1 and the gl3 egl3 double mutant. |
| GO:0010026 trichome differentiation | IMP PMID:21551388 The Jasmonate-ZIM-domain proteins interact with the WD-Repea... | ACCEPT | Summary: GL1 promotes Arabidopsis trichome differentiation as part of the MBW transcriptional complex. Reason: Trichome differentiation is a core biological process for GL1. Supporting Evidence: PMID:21551388 the JA-induced trichome initiation was disrupted in gl1 and the gl3 egl3 double mutant. |
| GO:0010154 fruit development | IMP PMID:3793867 Cytotoxic and enterotoxic activities of Campylobacter jejuni... | MARK AS OVER ANNOTATED | Summary: GOA cites PMID:3793867 (an unrelated Campylobacter plasmid paper); the intended source is very probably PMID:33955486 (Arteaga et al. 2021), which links a structural GL1 mutation to natural trichome formation on fruits and pedicels. That is fruit-surface trichome patterning, not a role in fruit growth or maturation. Reason: The identification of PMID:33955486 as the intended paper is a strong inference, not TAIR-confirmed. TAIR made exactly three GO:0010154 annotations with PMID:3793867, to TCL1, GL1 and TRY, all on 20210127, and Arteaga et al. 2021 functionally characterized exactly these three MYB loci in fruit trichome patterning. The phenotype is ectopic epidermal trichome development on the fruit (carpel/silique) surface and pedicel, controlled by the MBW/R3-MYB trichome patterning network. It does not show a GL1 role in gynoecium or silique growth, morphogenesis or maturation. The fruit-development term is therefore a low-information, over-broad reading of a trichome-patterning phenotype, and the underlying biology is already captured by the GL1 trichome differentiation and patterning terms. The original GOA reference id is retained. Supporting Evidence: PMID:33955486 Functional characterization of these three loci revealed cis-regulatory mutations in TRICHOMELESS1 and TRIPTYCHON, as well as a structural mutation in GLABRA1. PMID:33955486 Here we examined natural populations of Arabidopsis (Arabidopsis thaliana) that develop trichomes in fruits and pedicels, phenotypes previously not reported in the Arabidopsis genus. PMID:33955486 Hence, GL1 overexpression produced by doubling the number of natural GL1 alleles is sufficient to trigger the development of trichomes in fruits, in the absence of the repression mediated by TCL1 and TRY . |
| 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: Loss of GL1 affects the subcellular distribution of GL3. Reason: The protein-localization effect is a patterning mechanism output rather than GL1 core molecular function. Supporting Evidence: PMID:18434419 The loss of TTG1 and GL1 through mutation, affects the subcellular distribution of GL3. |
| GO:0048629 trichome patterning | IMP PMID:12244266 Roles of the GLABROUS1 and TRANSPARENT TESTA GLABRA Genes in... | ACCEPT | Summary: GL1 participates in the MBW regulatory circuit controlling trichome spacing and patterning. Reason: Trichome patterning is a central experimentally supported GL1 biological role. Supporting Evidence: PMID:12244266 the constitutive expression of both GL1 and R in the same plant caused trichomes to develop on all shoot epidermal surfaces. |
| GO:2000039 regulation of trichome morphogenesis | IMP PMID:21551388 The Jasmonate-ZIM-domain proteins interact with the WD-Repea... | ACCEPT | Summary: GL1 regulates trichome morphogenesis through MBW-dependent transcriptional programs. Reason: Regulation of trichome morphogenesis is supported and closely related to GL1 core trichome function. Supporting Evidence: PMID:21551388 the JA-induced trichome initiation was disrupted in gl1 and the gl3 egl3 double mutant. |
| GO:0003677 DNA binding | IEA GO_REF:0000117 | MODIFY | Summary: GL1 functions as a promoter-binding transcription factor; generic DNA binding is too broad. Reason: Use transcription cis-regulatory region binding to capture promoter/regulatory DNA binding by the transcription factor. Proposed replacements: transcription cis-regulatory region binding |
| GO:0003677 DNA binding | IDA PMID:18434419 The TTG1-bHLH-MYB complex controls trichome cell fate and pa... | MODIFY | Summary: GL1 functions as a promoter-binding transcription factor; generic DNA binding is too broad. Reason: Use transcription cis-regulatory region binding to capture promoter/regulatory DNA binding by the transcription factor. Proposed replacements: transcription cis-regulatory region binding Supporting Evidence: PMID:18434419 In vivo binding of the R2R3-MYB protein GLABRA1 (GL1) to the promoters of GLABRA2 (GL2), TRANSPARENT TESTA GLABRA2 (TTG2), CAPRICE (CPC) and ENHANCER OF TRIPTYCHON AND CAPRICE1 (ETC1) establishes that these genes are major transcriptional targets for the TTG1-bHLH-MYB regulatory complex. |
| GO:0003700 DNA-binding transcription factor activity | ISS PMID:11118137 Arabidopsis transcription factors: genome-wide comparative a... | ACCEPT | Summary: GL1 is a DNA-binding transcription factor regulating gene expression programs. Reason: Direct in vivo occupancy of GL2, TTG2, CPC and ETC1 promoters supports the sequence-specific transcriptional-regulator assignment, independently of the source classification (PMID:18434419). Supporting Evidence: PMID:18434419 In vivo binding of the R2R3-MYB protein GLABRA1 (GL1) to the promoters of GLABRA2 (GL2), TRANSPARENT TESTA GLABRA2 (TTG2), CAPRICE (CPC) and ENHANCER OF TRIPTYCHON AND CAPRICE1 (ETC1) establishes that these genes are major transcriptional targets for the TTG1-bHLH-MYB regulatory complex. |
| GO:0003700 DNA-binding transcription factor activity | TAS PMID:9625690 Gibberellins promote trichome formation by Up-regulating GLA... | ACCEPT | Summary: GL1 is a DNA-binding transcription factor regulating gene expression programs. Reason: Direct in vivo occupancy of GL2, TTG2, CPC and ETC1 promoters supports the sequence-specific transcriptional-regulator assignment, independently of the source classification (PMID:18434419). Supporting Evidence: PMID:18434419 In vivo binding of the R2R3-MYB protein GLABRA1 (GL1) to the promoters of GLABRA2 (GL2), TRANSPARENT TESTA GLABRA2 (TTG2), CAPRICE (CPC) and ENHANCER OF TRIPTYCHON AND CAPRICE1 (ETC1) establishes that these genes are major transcriptional targets for the TTG1-bHLH-MYB regulatory complex. |
| GO:0005515 protein binding | IPI PMID:11063707 GL3 encodes a bHLH protein that regulates trichome developme... | REMOVE | Summary: GL3 directly interacts with GL1 in yeast and plant overexpression assays; GL1-TTG1 direct binding was not detected in the yeast assay. Reason: GL3 directly interacts with GL1 in yeast and plant overexpression assays; GL1-TTG1 direct binding was not detected in the yeast assay. Remove the uninformative generic protein-binding annotation while retaining this interaction evidence. This does not reject the interaction, and interaction alone does not establish a distinct molecular activity beyond the supported functions reviewed elsewhere. Supporting Evidence: PMID:11063707 Yeast two-hybrid assays indicate that GL3 participates in physical interactions with GL1, TTG1, and itself, but that GL1 and TTG1 do not interact. |
| GO:0005515 protein binding | IPI PMID:12917293 A network of redundant bHLH proteins functions in all TTG1-d... | REMOVE | Summary: EGL3 interacts with GL1 in the redundant bHLH network supporting trichome initiation. Reason: EGL3 interacts with GL1 in the redundant bHLH network supporting trichome initiation. Remove the uninformative generic protein-binding annotation while retaining this interaction evidence. This does not reject the interaction, and interaction alone does not establish a distinct molecular activity beyond the supported functions reviewed elsewhere. Supporting Evidence: PMID:12917293 Yeast two-hybrid and plant overexpression studies show that EGL3, like GL3, interacts with TTG1, the myb proteins GL1, PAP1 and 2, CPC and TRY |
| GO:0005515 protein binding | IPI PMID:14561633 A contradictory GLABRA3 allele helps define gene interaction... | REMOVE | Summary: The gl3-sst allele reduces interaction with GL1; TRY inhibits GL1-GL3 association, and functional GFP-GL1 localizes to trichome nuclei. Reason: The gl3-sst allele reduces interaction with GL1; TRY inhibits GL1-GL3 association, and functional GFP-GL1 localizes to trichome nuclei. Remove the uninformative generic protein-binding annotation while retaining this interaction evidence. This does not reject the interaction, and interaction alone does not establish a distinct molecular activity beyond the supported functions reviewed elsewhere. Supporting Evidence: PMID:14561633 Yeast interaction assays comparing GL3 with gl3-sst proteins show that the mutant protein interaction with GL1 and TTG1 is decreased by 75% and 50%, respectively |
| GO:0005515 protein binding | IPI PMID:15584952 Comparison of TRY and the closely related At1g01380 gene in ... | REMOVE | Summary: The R3-MYB inhibitor At1g01380 inhibits GL1-GL3 interaction; altered GL1-GL3 affinity in gl3-sst is associated with trichome clustering. Reason: The R3-MYB inhibitor At1g01380 inhibits GL1-GL3 interaction; altered GL1-GL3 affinity in gl3-sst is associated with trichome clustering. Remove the uninformative generic protein-binding annotation while retaining this interaction evidence. This does not reject the interaction, and interaction alone does not establish a distinct molecular activity beyond the supported functions reviewed elsewhere. Supporting Evidence: PMID:15584952 At1g01380 protein can inhibit the interaction between the positive trichome regulators GL1 and GL3 |
| GO:0005515 protein binding | IPI PMID:21551388 The Jasmonate-ZIM-domain proteins interact with the WD-Repea... | REMOVE | Summary: JAZ repressors bind the GL1-containing transcriptional module, connecting jasmonate-dependent relief of repression to trichome initiation. Reason: JAZ repressors bind the GL1-containing transcriptional module, connecting jasmonate-dependent relief of repression to trichome initiation. Remove the uninformative generic protein-binding annotation while retaining this interaction evidence. This does not reject the interaction, and interaction alone does not establish a distinct molecular activity beyond the supported functions reviewed elsewhere. Supporting Evidence: PMID:21551388 JAZ proteins interact with bHLH (Transparent Testa8, Glabra3 [GL3], and Enhancer of Glabra3 [EGL3]) and R2R3 MYB transcription factors (MYB75 and Glabra1) |
| GO:0005515 protein binding | IPI PMID:24659329 Arabidopsis DELLA and JAZ proteins bind the WD-repeat/bHLH/M... | REMOVE | Summary: DELLA and JAZ repressors bind GL1 and bHLH partners, coupling GA and JA signaling to activation of trichome developmental transcription. Reason: DELLA and JAZ repressors bind GL1 and bHLH partners, coupling GA and JA signaling to activation of trichome developmental transcription. Remove the uninformative generic protein-binding annotation while retaining this interaction evidence. This does not reject the interaction, and interaction alone does not establish a distinct molecular activity beyond the supported functions reviewed elsewhere. Supporting Evidence: PMID:24659329 DELLAs and JAZs interact with bHLH factors (EGL3 and GL3) and MYB factor (GL1), essential components of the WD-repeat/bHLH/MYB complex, to repress their transcription activity |
| GO:0005515 protein binding | IPI PMID:32844153 Quantitative insight into the combinatorial interactions wit... | REMOVE | Summary: Purified-protein quartz-crystal microbalance experiments measure GL1 association with GL3 and PAP1; these in vitro affinities do not establish an anthocyanin biosynthetic role for GL1. Reason: Purified-protein quartz-crystal microbalance experiments measure GL1 association with GL3 and PAP1; these in vitro affinities do not establish an anthocyanin biosynthetic role for GL1. Remove the uninformative generic protein-binding annotation while retaining this interaction evidence. This does not reject the interaction, and interaction alone does not establish a distinct molecular activity beyond the supported functions reviewed elsewhere. Supporting Evidence: PMID:32844153 Dissociation constants were measured by applying nonlinear fit on Langmuir formula (Fig 1D), resulting in the dissociation constants (KD) of GL3 and GL1, GL3 and PAP1, and PAP1 and GL1, which were 9.53 ± 7.52 µM, 0.29 ± 0.20 µM, and 0.049 ± 0.04 µM, respectively (average of three independent experiments) |
| GO:0006355 regulation of DNA-templated transcription | IEA GO_REF:0000108 | MODIFY | Summary: GL1 regulates transcription as part of its core function, but the parent term is broad. Reason: Regulation of transcription by RNA polymerase II is the better process context for a plant nuclear transcription factor. Proposed replacements: regulation of transcription by RNA polymerase II |
| GO:0030154 cell differentiation | IEA GO_REF:0000117 | MODIFY | Summary: GL1 affects epidermal cell differentiation, but the annotation is too broad. Reason: Plant epidermal cell fate specification is the more informative supported process. Proposed replacements: plant epidermal cell fate specification |
| GO:0048731 system development | IEA GO_REF:0000117 | MODIFY | Summary: The broad developmental inference reflects the trichome differentiation program controlled by GL1. Reason: Narrow the electronic development assignment to the experimentally supported trichome differentiation process. Proposed replacements: trichome differentiation |
| GO:0090558 plant epidermis development | IEA GO_REF:0000117 | ACCEPT | Summary: GL1 affects plant epidermis development through trichome cell fate regulation. Reason: Trichome cell-fate specification is a core function within epidermis development. A broader true parent of the core process is not a peripheral function merely because it is broad. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: Functional GFP-tagged GL1 localizes to trichome nuclei. Reason: Direct localization evidence from PMID:14561633 supports the nuclear compartment, independently of the source inference or TAS citation. Supporting Evidence: PMID:14561633 Analysis of plants expressing functional GFP-tagged versions of GL1, GL3 and TRY show that the proteins are localized in trichome nuclei. |
| GO:0005634 nucleus | ISM GO_REF:0000122 | ACCEPT | Summary: Functional GFP-tagged GL1 localizes to trichome nuclei. Reason: Direct localization evidence from PMID:14561633 supports the nuclear compartment, independently of the source inference or TAS citation. Supporting Evidence: PMID:14561633 Analysis of plants expressing functional GFP-tagged versions of GL1, GL3 and TRY show that the proteins are localized in trichome nuclei. |
| GO:0005634 nucleus | TAS PMID:9625690 Gibberellins promote trichome formation by Up-regulating GLA... | ACCEPT | Summary: Functional GFP-tagged GL1 localizes to trichome nuclei. Reason: Direct localization evidence from PMID:14561633 supports the nuclear compartment, independently of the source inference or TAS citation. Supporting Evidence: PMID:14561633 Analysis of plants expressing functional GFP-tagged versions of GL1, GL3 and TRY show that the proteins are localized in trichome nuclei. |
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Download this section (compressed HTML)Q: Should GL1 DNA-binding rows be normalized to transcription cis-regulatory region binding when direct promoter-binding evidence is available?
Q: Should hormone-context annotations for GL1 be represented as regulation of the trichome MBW module rather than GL1 acting in hormone signaling pathways?
Experiment: Perform GL1 ChIP-seq or CUT&RUN in young leaf primordia together with rapid GL1 perturbation RNA-seq to separate direct trichome regulatory targets from downstream epidermal phenotypes.
Hypothesis: Acute GL1 perturbation changes directly occupied trichome-regulator transcripts before secondary epidermal responses.
Type: Time-resolved chromatin occupancy and transcriptomics
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