UGT73C5 (At2g36800; also DOGT1, ZOG3) is a family 1 UDP-glycosyltransferase (GT1, PANTHER PTHR48047:SF153) of the UGT73C group, a seven-member clade of Arabidopsis thaliana in which six genes lie in a tandem array on chromosome 2. It uses UDP-glucose to glucosylate hydroxyl groups on structurally diverse small molecules. In planta it is the enzyme responsible for 23-O-glucosylation of the brassinosteroids brassinolide and castasterone in seedlings: silencing abolishes detectable brassinolide-23-O-glucoside, and overexpression lowers endogenous brassinosteroid levels and produces a brassinosteroid-deficient dwarf phenotype that is rescued by applied brassinosteroid, consistent with a role in hormone inactivation and homeostasis. It also glucosylates the C-3 hydroxyl of the Fusarium trichothecene mycotoxin deoxynivalenol (and 15-acetyl-deoxynivalenol), which inactivates the toxin, and overexpression increases deoxynivalenol tolerance; the gene is induced by deoxynivalenol and weakly by salicylic acid, jasmonate and ethylene precursor. In vitro screens show additional, weaker O-glucosylation of trans-zeatin, dihydrozeatin, cis-zeatin and quercetin (7-O and 4'-O). Expression is highest in the vasculature and root tip of young seedlings and increases in elongating hypocotyls. Its subcellular location has not been determined directly; the predicted single transmembrane helix sits within the soluble GT-B fold typical of the family, and the protein has been detected in leaf microsomal fractions.
Definition: Catalysis of the transfer of a glucosyl group from UDP-glucose to the 23-hydroxy group of a brassinosteroid such as brassinolide or castasterone, forming a brassinosteroid 23-O-beta-D-glucoside.
Justification: UGT73C5 is the principal brassinolide/castasterone 23-O-glucosyltransferase in Arabidopsis seedlings, and no GO molecular function term describes brassinosteroid glucosylation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005783 endoplasmic reticulum | HDA PMID:28887381 Global Analysis of Membrane-associated Protein Oligomerizati... | KEEP AS NON CORE | Summary: High-throughput identification of UGT73C5 in cholate-solubilised leaf microsomal fractions profiled by size-exclusion chromatography and LC/MS. Reason: The protein was detected in a proteome-scale microsomal profiling study; the gene is not discussed in the main text and the ER assignment rests on fraction co-behaviour. Family 1 plant UGTs are generally regarded as soluble enzymes, and peripheral association with endomembranes is plausible but untested by any targeted localisation of UGT73C5. Retained as a non-core, high-throughput location. Supporting Evidence: PMID:28887381 Here we combined cell fractionation of Arabidopsis leaves with nondenaturing detergent solubilization and LC/MS-based profiling of size exclusion chromatography fractions |
| GO:0008194 UDP-glycosyltransferase activity | IDA PMID:12970342 Detoxification of the Fusarium mycotoxin deoxynivalenol by a... | MODIFY | Summary: UGT73C5 (DOGT1) transfers glucose from UDP-glucose to the C-3 hydroxyl of deoxynivalenol. Reason: The activity is correct but the donor shown is specifically UDP-glucose, so the more specific GO:0035251 UDP-glucosyltransferase activity (an is_a descendant of GO:0008194, already carried by this gene via IBA) is warranted. No GO term for deoxynivalenol 3-O-glucosyltransferase activity was found. Proposed replacements: UDP-glucosyltransferase activity Supporting Evidence: PMID:12970342 catalyzes the transfer of glucose from UDP-glucose to the hydroxyl group at carbon 3 of deoxynivalenol |
| GO:0008194 UDP-glycosyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapping from the UDP-glucuronosyl/UDP-glucosyltransferase domain (IPR002213). Reason: The domain-based inference is correct, but experimental data on this protein establish UDP-glucose as the donor, so the specific child term GO:0035251 is preferred, consistent with the IDA row for the same term. Proposed replacements: UDP-glucosyltransferase activity Supporting Evidence: file:ARATH/UGT73C5/UGT73C5-uniprot.txt DR InterPro; IPR002213; UDP_glucos_trans. PMID:12970342 catalyzes the transfer of glucose from UDP-glucose to the hydroxyl group at carbon 3 of deoxynivalenol |
| GO:0009507 chloroplast | ISM GO_REF:0000122 | REMOVE | Summary: AtSubP sequence-based prediction of chloroplast localisation. Reason: No transit peptide or plastid-targeting feature is recorded for UGT73C5, no proteomic or imaging study places it in plastids, and its characterised substrates (brassinosteroids, deoxynivalenol, zeatin) are conjugated outside the plastid in the cited work. The only experimental location data come from leaf microsomes. The chloroplast call is an unsupported prediction. Supporting Evidence: PMID:28887381 Here we combined cell fractionation of Arabidopsis leaves with nondenaturing detergent solubilization and LC/MS-based profiling of size exclusion chromatography fractions |
| GO:0016020 membrane | IEA GO_REF:0000044 | MARK AS OVER ANNOTATED | Summary: UniProt subcellular-location mapping from "Membrane; Single-pass membrane protein", itself an inference (ECO:0000305) from a predicted helix at residues 146-162. Reason: The integral-membrane claim rests only on a hydrophobicity-predicted helix (ECO:0000255) located inside the N-terminal Rossmann-like domain of the GT-B fold shared by family 1 UGTs, which are typically soluble. Microsomal detection (PMID:28887381) is compatible with peripheral association, so membrane is not impossible, but an integral single-pass topology is not supported. Supporting Evidence: file:ARATH/UGT73C5/UGT73C5-uniprot.txt SUBCELLULAR LOCATION: Membrane {ECO:0000305}; Single-pass membrane file:ARATH/UGT73C5/UGT73C5-uniprot.txt DR CDD; cd03784; GT1_Gtf-like; 1. |
| GO:0016131 brassinosteroid metabolic process | IDA PMID:16214889 The UGT73C5 of Arabidopsis thaliana glucosylates brassinoste... | ACCEPT | Summary: UGT73C5 glucosylates brassinolide and castasterone at the 23-OH in planta and in yeast; silencing abolishes detectable brassinolide-23-O-glucoside in seedlings and overexpression lowers endogenous brassinosteroids. Reason: UGT73C5 catalyses the conjugation step itself, so it does the work of this metabolic process. Feeding experiments, heterologous expression and RNAi together show it is the principal brassinolide 23-O-glucosyltransferase in seedlings. The downstream inference that glucosylation inactivates brassinosteroids is supported but stated by the authors to be not conclusive, so a more specific homeostasis or inactivation term is not proposed. Supporting Evidence: PMID:16214889 The UGT73C5 of Arabidopsis thaliana catalyses 23-O-glucosylation of the BRs brassinolide (BL) and castasterone PMID:16214889 in the transgenic lines silenced in UGT73C5 expression, no 23-O-glucoside was detected PMID:16214889 Heterologous expression of UGT73C5 in yeast also indicated that, on feeding BL or CS, only the 23- O -glucosides were formed |
| GO:0035251 UDP-glucosyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBD at PTN008730368, seeded by six Arabidopsis UGTs including UGT73C5 (AT2G36800) itself. Reason: UGT73C5 has direct experimental evidence for transfer of glucose from UDP-glucose, and it is one of the seeds of the PAINT node, so the IBA records that the donor specificity is inherited across the clade. PAINT propagated only this donor-level activity from the node and none of UGT73C5's acceptor-specific terms (zeatin, quercetin, brassinosteroid), which is consistent with acceptor specificity varying among members. This is the correct level for the core molecular function. Supporting Evidence: PMID:12970342 catalyzes the transfer of glucose from UDP-glucose to the hydroxyl group at carbon 3 of deoxynivalenol file:interpro/panther/PTHR48047/PTHR48047-paint.tsv AGI_LocusCode:AT2G36790|AGI_LocusCode:AT2G36800|AGI_LocusCode:AT3G53160 file:ARATH/UGT73C5/UGT73C5-uniprot.txt DR PANTHER; PTHR48047:SF153; UDP-GLYCOSYLTRANSFERASE 73C5-RELATED; 1. |
| GO:0046527 glucosyltransferase activity | IDA PMID:16214889 The UGT73C5 of Arabidopsis thaliana glucosylates brassinoste... | MODIFY | Summary: Glucosylation of brassinolide and castasterone at the 23-OH in planta and in yeast. Reason: Correct but general. The glucose donor for UGT73C5 is UDP-glucose (PMID:12970342), so GO:0035251 UDP-glucosyltransferase activity, an is_a child of GO:0046527 already carried by this gene, is the appropriate term. A brassinosteroid 23-O-glucosyltransferase activity term does not exist and is proposed under proposed_new_terms. Proposed replacements: UDP-glucosyltransferase activity Supporting Evidence: PMID:16214889 The UGT73C5 of Arabidopsis thaliana catalyses 23-O-glucosylation of the BRs brassinolide (BL) and castasterone PMID:12970342 catalyzes the transfer of glucose from UDP-glucose to the hydroxyl group at carbon 3 of deoxynivalenol |
| GO:0046527 glucosyltransferase activity | IEA GO_REF:0000117 | MODIFY | Summary: ARBA machine-learning assignment of glucosyltransferase activity. Reason: True but general; experimental data establish UDP-glucose as donor, so GO:0035251 is preferred, consistent with the IDA row for the same term. The ARBA rule itself is not used as evidence. Proposed replacements: UDP-glucosyltransferase activity Supporting Evidence: PMID:12970342 catalyzes the transfer of glucose from UDP-glucose to the hydroxyl group at carbon 3 of deoxynivalenol |
| GO:0050403 trans-zeatin O-beta-D-glucosyltransferase activity | IDA PMID:15342621 N-glucosylation of cytokinins by glycosyltransferases of Ara... | KEEP AS NON CORE | Summary: In a screen of 105 recombinant Arabidopsis UGTs, UGT73C5 was one of three enzymes forming O-glucosides of trans-zeatin and dihydrozeatin. Reason: The recombinant activity is directly demonstrated and the term matches it, so the annotation stands. There is no evidence that UGT73C5 contributes to cytokinin O-glucoside pools in planta (the gene is not induced by cytokinin), and its established in vivo roles are brassinosteroid and mycotoxin glucosylation, so this substrate-promiscuity activity is non-core. Supporting Evidence: PMID:15342621 UGT85A1, UGT73C5, and UGT73C1 recognized trans-zeatin and dihydrozeatin, which have an available hydroxyl group for glucosylation and formed the O-glucosides file:ARATH/UGT73C5/UGT73C5-uniprot.txt Not induced by cytokinin treatment. |
| GO:0050502 cis-zeatin O-beta-D-glucosyltransferase activity | IDA PMID:15342621 N-glucosylation of cytokinins by glycosyltransferases of Ara... | KEEP AS NON CORE | Summary: In vitro O-glucosylation of cis-zeatin reported for recombinant UGT73C5. Reason: The cached abstract names only trans-zeatin and dihydrozeatin, but the curated UniProt function statement, tied to this paper, records in vitro activity on cis-zeatin; the curator saw the full text, so the activity is accepted. As with trans-zeatin, physiological relevance has not been shown, so it is non-core. Supporting Evidence: file:ARATH/UGT73C5/UGT73C5-uniprot.txt Active in vitro on cis-zeatin, dihydrozeatin-9-N-Glc, and olomoucine. |
| GO:0071456 cellular response to hypoxia | HEP PMID:31519798 Integrative Analysis from the Epigenome to Translatome Uncov... | MARK AS OVER ANNOTATED | Summary: Transcript/translatome change of UGT73C5 in a genome-wide survey of seedlings exposed to hypoxia and reoxygenation. Reason: The evidence is an expression change in a genome-scale profiling study in which UGT73C5 is not discussed individually. Responsiveness of a transcript does not show that the enzyme performs any part of the hypoxia response, and no functional link between UGT73C5 and low-oxygen adaptation has been reported. The gene is broadly stress-inducible (deoxynivalenol, salicylic acid, jasmonate, ethylene). Supporting Evidence: PMID:31519798 we performed a survey spanning the epigenome to translatome of Arabidopsis (Arabidopsis thaliana) seedlings in response to hypoxia and reoxygenation |
| GO:0080044 quercetin 7-O-glucosyltransferase activity | IDA PMID:15352060 Arabidopsis glycosyltransferases as biocatalysts in fermenta... | KEEP AS NON CORE | Summary: Low quercetin 7-O-glucosylation by recombinant UGT73C5 in a 91-enzyme regioselectivity screen. Reason: The activity was observed in vitro and is recorded by UniProt as low. There is no evidence that UGT73C5 glucosylates flavonols in planta. Kept as a non-core substrate-promiscuity activity. Supporting Evidence: PMID:15352060 discovered 29 that are capable of glucosylating the substrate file:ARATH/UGT73C5/UGT73C5-uniprot.txt Possesses low quercetin 7-O-glucosyltransferase |
| GO:0080046 quercetin 4'-O-glucosyltransferase activity | IDA PMID:15352060 Arabidopsis glycosyltransferases as biocatalysts in fermenta... | KEEP AS NON CORE | Summary: Low quercetin 4'-O-glucosylation by recombinant UGT73C5 in vitro. Reason: As for the 7-O activity, this is a low in vitro activity from a regioselectivity screen without in planta support; non-core. Supporting Evidence: PMID:15352060 discovered 29 that are capable of glucosylating the substrate file:ARATH/UGT73C5/UGT73C5-uniprot.txt and 4'-O-glucosyltransferase activities in vitro. |
| GO:0098754 detoxification | IDA PMID:12970342 Detoxification of the Fusarium mycotoxin deoxynivalenol by a... | ACCEPT | Summary: UGT73C5 glucosylates deoxynivalenol at C-3; the glucoside no longer inhibits in vitro translation, and overexpression in Arabidopsis increases tolerance to deoxynivalenol. Reason: UGT73C5 itself catalyses the inactivating conjugation, so it performs the detoxification step rather than being merely required for it. The activity was shown biochemically, in yeast and by overexpression in planta, and the gene is rapidly induced by the toxin. The contribution of endogenous UGT73C5 to resistance during Fusarium infection has not been tested genetically. Supporting Evidence: PMID:12970342 Using a wheat germ extract-coupled transcription/translation system we have shown that this enzymatic reaction inactivates the mycotoxin PMID:12970342 Constitutive overexpression in Arabidopsis leads to enhanced tolerance against deoxynivalenol |
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Download this section (compressed HTML)Q: Does loss of UGT73C5 (or combined loss of UGT73C5 and UGT73C6) alter endogenous brassinosteroid levels and growth, given that single RNAi lines show only subtle hypocotyl phenotypes?
Q: Does endogenous UGT73C5 contribute to deoxynivalenol detoxification during Fusarium infection, or only when overexpressed?
Q: Is UGT73C5 cytosolic, peripherally associated with the ER, or integral to a membrane via the predicted 146-162 helix?
Experiment: Generate ugt73c5 ugt73c6 CRISPR double mutants and measure endogenous brassinosteroids, brassinosteroid glucosides after feeding, and hypocotyl and rosette growth.
Hypothesis: UGT73C5 and UGT73C6 act redundantly in brassinosteroid inactivation.
Type: genetic and metabolite profiling
Experiment: Image a functional UGT73C5-fluorescent protein fusion with ER and cytosolic markers and test carbonate/detergent extraction of microsomal UGT73C5.
Hypothesis: UGT73C5 is a soluble cytosolic enzyme.
Type: subcellular localization
Experiment: Infect ugt73c5 mutants with a deoxynivalenol-producing Fusarium strain and quantify deoxynivalenol-3-O-glucoside and disease symptoms.
Hypothesis: Endogenous UGT73C5 limits deoxynivalenol damage during infection.
Type: pathogen assay
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