GA3OX1 (GA4, AtGA3ox1; At1g15550) encodes a gibberellin 3beta-hydroxylase (GA 3-oxidase), a soluble 2-oxoglutarate- and Fe(II)-dependent dioxygenase that catalyses the final step of bioactive gibberellin biosynthesis, converting GA9 to GA4 (preferred substrate) and GA20 to GA1 by regiospecific 3beta-hydroxylation. ga4 mutants are semi-dwarfs that accumulate GA9 and lack 3beta-hydroxylated GAs. With its paralog GA3ox2, GA3OX1 supplies bioactive GA during vegetative growth and seed germination, where both are expressed in the cortex and endodermis of the embryo axis. GA3OX1 transcription is strongly feedback-repressed by bioactive GA (a direct DELLA target; requires the AT-hook protein AGF1) and induced by red light in imbibed seeds via phytochrome-dependent removal of the repressor PIL5.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: Yeast two-hybrid interaction from a large-scale phytohormone protein network screen (partner is a nuclear regulator or transcription factor). Reason: Removal does not mean the interaction is false. Bare 'protein binding' from a binary Y2H screen is uninformative; no functional consequence for GA 3-oxidase activity has been shown and the partners (BRX, TIFY8, SPT, ESR2, TCP23, TOE2, IAA28) are nuclear regulators with no established link to GA3ox1 enzyme function. Not retained as a core function. |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: Yeast two-hybrid interaction from a large-scale phytohormone protein network screen (partner is a nuclear regulator or transcription factor). Reason: Removal does not mean the interaction is false. Bare 'protein binding' from a binary Y2H screen is uninformative; no functional consequence for GA 3-oxidase activity has been shown and the partners (BRX, TIFY8, SPT, ESR2, TCP23, TOE2, IAA28) are nuclear regulators with no established link to GA3ox1 enzyme function. Not retained as a core function. |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: Yeast two-hybrid interaction from a large-scale phytohormone protein network screen (partner is a nuclear regulator or transcription factor). Reason: Removal does not mean the interaction is false. Bare 'protein binding' from a binary Y2H screen is uninformative; no functional consequence for GA 3-oxidase activity has been shown and the partners (BRX, TIFY8, SPT, ESR2, TCP23, TOE2, IAA28) are nuclear regulators with no established link to GA3ox1 enzyme function. Not retained as a core function. |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: Yeast two-hybrid interaction from a large-scale phytohormone protein network screen (partner is a nuclear regulator or transcription factor). Reason: Removal does not mean the interaction is false. Bare 'protein binding' from a binary Y2H screen is uninformative; no functional consequence for GA 3-oxidase activity has been shown and the partners (BRX, TIFY8, SPT, ESR2, TCP23, TOE2, IAA28) are nuclear regulators with no established link to GA3ox1 enzyme function. Not retained as a core function. |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: Yeast two-hybrid interaction from a large-scale phytohormone protein network screen (partner is a nuclear regulator or transcription factor). Reason: Removal does not mean the interaction is false. Bare 'protein binding' from a binary Y2H screen is uninformative; no functional consequence for GA 3-oxidase activity has been shown and the partners (BRX, TIFY8, SPT, ESR2, TCP23, TOE2, IAA28) are nuclear regulators with no established link to GA3ox1 enzyme function. Not retained as a core function. |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: Yeast two-hybrid interaction from a large-scale phytohormone protein network screen (partner is a nuclear regulator or transcription factor). Reason: Removal does not mean the interaction is false. Bare 'protein binding' from a binary Y2H screen is uninformative; no functional consequence for GA 3-oxidase activity has been shown and the partners (BRX, TIFY8, SPT, ESR2, TCP23, TOE2, IAA28) are nuclear regulators with no established link to GA3ox1 enzyme function. Not retained as a core function. |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: Yeast two-hybrid interaction from a large-scale phytohormone protein network screen (partner is a nuclear regulator or transcription factor). Reason: Removal does not mean the interaction is false. Bare 'protein binding' from a binary Y2H screen is uninformative; no functional consequence for GA 3-oxidase activity has been shown and the partners (BRX, TIFY8, SPT, ESR2, TCP23, TOE2, IAA28) are nuclear regulators with no established link to GA3ox1 enzyme function. Not retained as a core function. |
| GO:0005737 cytoplasm | ISM GO_REF:0000122 | ACCEPT | Summary: Predicted cytoplasmic localization. Reason: GA 3-oxidases are soluble cytosolic dioxygenases. Supporting Evidence: PMID:22533671 In higher plants, GAs are synthesized by the action of terpene cyclases, cytochrome P450 mono-oxygenases and 2-oxoglutarate-dependent dioxygenases localized, respectively, in plastids, the endomembrane system and the cytosol. |
| GO:0005737 cytoplasm | TAS PMID:9701576 Gibberellin dose-response regulation of GA4 gene transcript ... | ACCEPT | Summary: Author statement of cytoplasmic localization. Reason: Consistent with the cytosolic location of the late GA dioxygenases. Supporting Evidence: PMID:22533671 In higher plants, GAs are synthesized by the action of terpene cyclases, cytochrome P450 mono-oxygenases and 2-oxoglutarate-dependent dioxygenases localized, respectively, in plastids, the endomembrane system and the cytosol. |
| GO:0009416 response to light stimulus | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Response to light stimulus propagated in the GA3ox clade. Reason: GA3ox1 transcription is induced by red light via phytochrome (partly through degradation of PIL5) during seed germination; a regulatory property, not the core function. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: PANTHER:PTN004134051 SUPPORTS TRANSFER GA3ox clade node seeded by Arabidopsis GA3ox1/GA3ox2, both light-induced in imbibed seeds. AGI_LocusCode:AT1G80340 SUPPORTS TRANSFER GA3ox2 (GA4H), red-light induced via phyB. Supporting Evidence: PMID:9836749 We show that expression of both GA4 and GA4H genes in imbibed seeds was induced within 1 hr after a brief red (R) light treatment. PMID:17449805 inhibits seed germination by repressing GIBBERELLIN 3beta-HYDROXYLASE1 (GA3ox1) and GA3ox2 |
| GO:0009639 response to red or far red light | IEP PMID:17010113 Regulation of hormone metabolism in Arabidopsis seeds: phyto... | KEEP AS NON CORE | Summary: Expression responds to red/far-red light in seeds (phytochrome-regulated hormone metabolism study). Reason: Phytochrome regulation of GA3ox1 expression is well documented; non-core regulatory response. Supporting Evidence: PMID:9836749 We show that expression of both GA4 and GA4H genes in imbibed seeds was induced within 1 hr after a brief red (R) light treatment. |
| GO:0009686 gibberellin biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: GA3ox1 catalyses the final step producing bioactive GA4 (from GA9) and GA1 (from GA20). Reason: Conserved role of the GA3ox clade. Supporting Evidence: PMID:9625708 thereby confirming that GA4 encodes a GA 3beta-hydroxylase |
| GO:0009686 gibberellin biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: GA3ox1 catalyses the final step producing bioactive GA4 (from GA9) and GA1 (from GA20). Reason: Consistent with experimental evidence. Supporting Evidence: PMID:9625708 thereby confirming that GA4 encodes a GA 3beta-hydroxylase |
| GO:0009686 gibberellin biosynthetic process | IMP PMID:2236013 Endogenous gibberellins in Arabidopsis thaliana and possible... | ACCEPT | Summary: ga4 mutants have reduced 3beta-hydroxylated GAs and accumulate GA9. Reason: Genetic evidence. Supporting Evidence: PMID:2236013 The GA4 gene encodes, therefore, a protein with 3 beta-hydroxylation activity. PMID:2236013 It is concluded that the reduced levels of the 3 beta-hydroxy-GAs, GA1 and GA4, are the cause of the semidwarf growth habit of both mutants. |
| GO:0009686 gibberellin biosynthetic process | TAS PMID:15923331 The involvement of gibberellin 20-oxidase genes in phytochro... | ACCEPT | Summary: GA3ox1 catalyses the final step producing bioactive GA4 (from GA9) and GA1 (from GA20). Reason: Consistent with experimental evidence. Supporting Evidence: PMID:9625708 thereby confirming that GA4 encodes a GA 3beta-hydroxylase |
| GO:0009739 response to gibberellin | IEP PMID:15927942 Contribution of gibberellins to the formation of Arabidopsis... | KEEP AS NON CORE | Summary: GA-responsive expression of GA biosynthetic genes in developing seeds (seed coat study; abstract centres on GA20ox2/3 and GA3ox4). Reason: The cached abstract does not mention GA3ox1, but GA feedback repression of GA3ox1 is independently well established (PMID:9701576, PMID:17277098); retained as non-core regulatory response. Supporting Evidence: PMID:17277098 Here, we found that only the AtGA3ox1 among the AtGA3ox family of Arabidopsis (Arabidopsis thaliana) is under the regulation of GA-negative feedback. |
| GO:0009739 response to gibberellin | IEP PMID:17277098 AGF1, an AT-hook protein, is necessary for the negative feed... | KEEP AS NON CORE | Summary: Only GA3ox1 among the AtGA3ox family is under GA-negative feedback; AGF1 binds the feedback cis-element. Reason: Genuine transcriptional response; part of GA homeostasis, non-core. Supporting Evidence: PMID:17277098 Here, we found that only the AtGA3ox1 among the AtGA3ox family of Arabidopsis (Arabidopsis thaliana) is under the regulation of GA-negative feedback. |
| GO:0009739 response to gibberellin | IEP PMID:17933900 Global analysis of della direct targets in early gibberellin... | KEEP AS NON CORE | Summary: GA3ox1 is among early GA-repressed, DELLA-induced direct DELLA targets. Reason: Genuine feedback response; non-core. Supporting Evidence: PMID:17933900 Several DELLA targets encode GA biosynthetic enzymes and GA receptors, indicating direct involvement of DELLA in feedback regulation. |
| GO:0009740 gibberellic acid mediated signaling pathway | TAS PMID:9701576 Gibberellin dose-response regulation of GA4 gene transcript ... | MARK AS OVER ANNOTATED | Summary: GA3ox1 produces bioactive GA; it is a feedback target but not a component of the GA signaling pathway. Reason: Hormone biosynthesis is upstream of signal transduction; the process role is captured by gibberellin biosynthetic process. Supporting Evidence: PMID:9701576 Here we show that active GAs regulate GA4 transcript abundance in a dose-dependent manner |
| GO:0010114 response to red light | IEP PMID:17449805 PIL5, a phytochrome-interacting bHLH protein, regulates gibb... | KEEP AS NON CORE | Summary: PIL5, degraded upon phytochrome activation by red light, represses GA3ox1, so GA3ox1 expression rises in red light. Reason: Indirect regulatory response of expression; non-core. Supporting Evidence: PMID:17449805 inhibits seed germination by repressing GIBBERELLIN 3beta-HYDROXYLASE1 (GA3ox1) and GA3ox2 PMID:9836749 We show that expression of both GA4 and GA4H genes in imbibed seeds was induced within 1 hr after a brief red (R) light treatment. |
| GO:0016707 gibberellin 3-beta-dioxygenase activity | IBA GO_REF:0000033 | ACCEPT | Summary: GA 3beta-dioxygenase activity conserved in the GA3ox clade. Reason: Experimentally supported on the target. Supporting Evidence: PMID:9625708 thereby confirming that GA4 encodes a GA 3beta-hydroxylase |
| GO:0016707 gibberellin 3-beta-dioxygenase activity | IDA PMID:9625708 Function and substrate specificity of the gibberellin 3beta-... | ACCEPT | Summary: Recombinant GA4 protein 3beta-hydroxylates GA9 and GA20 to GA4 and GA1, preferring GA9. Reason: Core activity (RHEA:68996, RHEA:10104). Supporting Evidence: PMID:9625708 thereby confirming that GA4 encodes a GA 3beta-hydroxylase PMID:9625708 GA9 was the preferred substrate, with a Michaelis value of 1 microm compared with 15 microm for GA20. |
| GO:0016707 gibberellin 3-beta-dioxygenase activity | IEA GO_REF:0000120 | ACCEPT | Summary: EC/Rhea mapping. Reason: Matches experimental evidence. Supporting Evidence: PMID:9625708 thereby confirming that GA4 encodes a GA 3beta-hydroxylase |
| GO:0016707 gibberellin 3-beta-dioxygenase activity | IMP PMID:2236013 Endogenous gibberellins in Arabidopsis thaliana and possible... | ACCEPT | Summary: GA profiling of ga4 mutants indicates loss of 3beta-hydroxylation. Reason: Genetic evidence consistent with the enzyme activity. Supporting Evidence: PMID:2236013 The GA4 gene encodes, therefore, a protein with 3 beta-hydroxylation activity. |
| GO:0016707 gibberellin 3-beta-dioxygenase activity | TAS PMID:9701576 Gibberellin dose-response regulation of GA4 gene transcript ... | ACCEPT | Summary: Author statement that GA4 encodes GA 3beta-hydroxylase. Reason: Consistent with direct enzyme assays. Supporting Evidence: PMID:9701576 Arabidopsis GA4 gene transcripts encode GA 3beta-hydroxylase, an enzyme that catalyzes the conversion of inactive to active GAs. |
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Download this section (compressed HTML)Q: Do the nuclear regulators detected as GA3ox1 interactors in high-throughput yeast two-hybrid screens (e.g. BRX, TCP23, IAA28) affect GA3ox1 localization or activity in planta, or are these interactions non-physiological?
Experiment: Test selected Y2H partners by co-immunoprecipitation from native tissues and measure GA4 formation in corresponding mutant backgrounds.
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