MYB51 (HIGH INDOLIC GLUCOSINOLATE 1, HIG1; At1g18570) is a nuclear R2R3-MYB transcription factor of subgroup 12 that activates the genes of tryptophan-derived (indolic) glucosinolate biosynthesis, including tryptophan-pathway genes such as ASA1 and the core-structure genes CYP79B2/B3 and CYP83B1. It acts together with bHLH partners of subgroup IIIe (MYC2/bHLH06, MYC3, MYC4, bHLH04, bHLH05), which are required for its activity. Among the three indolic glucosinolate MYBs (MYB34, MYB51, MYB122) MYB51 is the main regulator in shoots and the central one under salicylic acid and ethylene signalling; the triple mutant lacks indolic glucosinolates. MYB51 is induced by touch, wounding, MAMPs (flg22), insects and pathogens, and acts downstream of ethylene signalling to supply the 4-methoxy-indol-3-ylmethyl glucosinolate needed for PEN2-dependent, flg22-triggered callose deposition and for antibacterial, antifungal and anti-herbivore defenses. Its promoter is active in rosette leaves and trichomes, and during Colletotrichum higginsianum infection its induction at infection sites is confined to vasculature cells.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000976 transcription cis-regulatory region binding | IPI PMID:30356219 Transcriptional regulation of nitrogen-associated metabolism... | ACCEPT | Summary: IPI annotation from the enhanced yeast one-hybrid (eY1H) nitrogen-associated transcriptional regulatory network of Gaudinier et al. 2018, recording binding of MYB51 to the promoter of locus AT3G61830 (WITH/FROM). Reason: The cached publication is abstract-only, so the specific MYB51-promoter interaction cannot be checked here; the curator saw the network data. Binding to cis-regulatory regions of target genes is the expected molecular function of an R2R3-MYB with two intact HTH Myb repeats, and is independently supported by the ability of MYB51 to trans-activate glucosinolate gene promoters [PMID:25049362]. The individual target is from a high-throughput screen and is not part of MYB51's characterised regulon, but the molecular function term itself is correct. Supporting Evidence: PMID:30356219 Here we present a transcriptional regulatory network and twenty-one transcription factors that regulate the architecture of root and shoot systems in response to changes in nitrogen availability. PMID:25049362 The MYBs could induce the transcription of all tested promoters of GSL biosynthetic pathway in trans, indicating a direct role of MYB51 in the binding and activation of GSL biosynthesis genes. |
| GO:0000976 transcription cis-regulatory region binding | IPI PMID:31806676 A PXY-Mediated Transcriptional Network Integrates Signaling ... | ACCEPT | Summary: IPI annotation from the eY1H PXY-mediated vascular transcriptional regulatory network (690 TF-promoter interactions), recording binding of MYB51 to the promoter of locus AT1G68810 (WITH/FROM). Reason: MYB51 is not discussed in the main text of the cached paper; the interaction is in the network supplementary data that the curator used. As for the other eY1H annotation, the molecular function (binding of transcription cis-regulatory regions) is correct for this R2R3-MYB, although the individual vascular target is a screen result of unknown physiological relevance. Supporting Evidence: PMID:31806676 Here, we mapped a putative PXY-mediated transcriptional regulatory network comprising 690 transcription factor-promoter interactions in Arabidopsis |
| GO:0003700 DNA-binding transcription factor activity | ISS PMID:11118137 Arabidopsis transcription factors: genome-wide comparative a... | ACCEPT | Summary: Sequence-based assignment of MYB51 as a DNA-binding transcription factor from the genome-wide catalogue of Arabidopsis transcription factors. Reason: MYB51 has the two HTH Myb-type DNA-binding repeats of R2R3-MYB factors, localises to the nucleus, and experimentally activates promoters of indolic glucosinolate genes [PMID:17461791, PMID:25049362]. DNA-binding transcription factor activity is correct; a more specific activator term is proposed as NEW below. Supporting Evidence: PMID:17461791 HIG1/MYB51 was shown to activate promoters of indolic glucosinolate biosynthetic genes leading to increased accumulation of indolic glucosinolates. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: Nuclear localisation mapped from the UniProt subcellular location, which is backed by experimental evidence (ECO:0000269, PMID:17461791). Reason: Nuclear localisation is expected for a transcription factor and is recorded experimentally in UniProt; MYB51 acts in nuclear complexes with bHLH partners [PMID:25049362]. Supporting Evidence: PMID:25049362 BiFC reveals an interaction of indolic MYB51, MYB34 and MYB122 but also of MYB28 and MYB29 with bHLH05 and bHLH04. |
| GO:0005634 nucleus | ISM GO_REF:0000122 | ACCEPT | Summary: AtSubP sequence-based prediction of nuclear localisation. Reason: Consistent with the experimentally supported nuclear localisation recorded by UniProt and with the transcription-factor function of MYB51. |
| GO:0006355 regulation of DNA-templated transcription | IEA GO_REF:0000108 | ACCEPT | Summary: Inter-ontology inference from DNA-binding transcription factor activity. Reason: Correct, if general. MYB51 is a transcriptional activator of glucosinolate and tryptophan pathway genes [PMID:17461791, PMID:19095898]; the specific process-level role is captured by regulation of glucosinolate biosynthetic process. Supporting Evidence: PMID:19095898 ASA1 gene expression was also induced by Flg22 treatment (Table S1A), and this up-regulation was dependent on MYB51 (Table 1A). |
| GO:0009617 response to bacterium | IMP PMID:23073694 Metabolic and transcriptomic changes induced in Arabidopsis ... | KEEP AS NON CORE | Summary: myb51 mutants were among glucosinolate/camalexin pathway mutants that failed to mount Pseudomonas fluorescens SS101-induced resistance to P. syringae pv. tomato. Reason: The mutant phenotype is genuine, and MYB51 acts upstream of the response by controlling supply of indolic glucosinolates. This is an indirect, downstream physiological consequence of MYB51's core regulatory function, so it is kept as non-core. Supporting Evidence: PMID:23073694 Subsequent bioassays with seven Arabidopsis mutants ( myb51 , cyp79B2cyp79B3 , cyp81F2 , pen2 , cyp71A12 , cyp71A13 , and myb28myb29 ) disrupted in the biosynthesis pathways for these plant secondary metabolites showed that camalexin and glucosinolates are indeed required for the induction of Pst resistance by Pf .SS101 . |
| GO:0009625 response to insect | IEP PMID:23144921 Water stress and aphid feeding differentially influence meta... | KEEP AS NON CORE | Summary: MYB51 transcript levels increased after aphid feeding (Myzus persicae, Brevicoryne brassicae) on Arabidopsis. Reason: Expression-based (IEP) annotation that is consistent with MYB51's role in inducible indolic glucosinolate production; MYB51 overexpression also reduced herbivory by Spodoptera exigua [PMID:17461791]. A real but peripheral, stimulus-response aspect rather than the core regulatory function. Supporting Evidence: PMID:23144921 Notably, expression of genes encoding indolyl and aliphatic glucosinolate biosynthesis transcription factors responded differentially to aphid feeding in A. thaliana, with increased MYB51 and decreased MYB76. PMID:17461791 HIG1/MYB51 overexpression reduced insect herbivory as revealed by dual-choice assays with the generalist lepidopteran herbivore, Spodoptera exigua. |
| GO:0009682 induced systemic resistance | IMP PMID:23073694 Metabolic and transcriptomic changes induced in Arabidopsis ... | MARK AS OVER ANNOTATED | Summary: myb51 mutants failed to show rhizobacterium (P. fluorescens SS101)-induced resistance to P. syringae pv. tomato. Reason: The GO definition of induced systemic resistance specifies a response to non-pathogenic bacteria that does not depend upon salicylic acid signalling, whereas the same paper explicitly shows that the Pf.SS101-induced response is salicylic-acid dependent and not JA/ET dependent. MYB51's contribution is also indirect, through indolic glucosinolate supply. The phenotype is better covered by the retained (non-core) response to bacterium annotation from the same paper. Supporting Evidence: PMID:23073694 Transcriptomic analysis and bioassays with specific Arabidopsis mutants revealed that, unlike many other rhizobacteria, the Pf .SS101 -induced resistance response to Pst is dependent on salicylic acid signaling and not on jasmonic acid and ethylene signaling. |
| GO:0009759 indole glucosinolate biosynthetic process | IMP PMID:17461791 The transcription factor HIG1/MYB51 regulates indolic glucos... | MODIFY | Summary: Loss of HIG1/MYB51 lowers glucosinolate levels and gain of function raises indolic glucosinolates; MYB51 trans-activates promoters of indolic glucosinolate pathway genes. Reason: The phenotype is robust and central to MYB51 biology, but MYB51 is a transcription factor and does not catalyse any step of indolic glucosinolate biosynthesis; the enzymes (CYP79B2/B3, CYP83B1, SUR1, UGT74B1, SOT16) carry the biosynthetic process term. The appropriate process for MYB51 is regulation of glucosinolate biosynthetic process (GO:0010439); GO currently has no positive or indole-specific child of this term. Proposed replacements: regulation of glucosinolate biosynthetic process Supporting Evidence: PMID:17461791 HIG1/MYB51 was shown to activate promoters of indolic glucosinolate biosynthetic genes leading to increased accumulation of indolic glucosinolates. PMID:17461791 The corresponding loss-of-function mutant hig1-1 contained low levels of glucosinolates. PMID:24431192 MYB51 is the central regulator of IG synthesis upon SA and ET signaling |
| GO:0042742 defense response to bacterium | IMP PMID:19095898 Glucosinolate metabolites required for an Arabidopsis innate... | KEEP AS NON CORE | Summary: Clay et al. 2009 placed MYB51 downstream of ethylene signalling and upstream of indolic glucosinolate biosynthesis in flg22-triggered immunity; glucosinolate-dependent callose deposition contributes to restriction of P. syringae growth. Reason: Bacterial growth data for myb51 are in the supplementary figures, which the curator had; the cached text supports MYB51 being required for the flg22-induced, glucosinolate-dependent callose response that restricts bacterial growth. MYB51 acts upstream by supplying 4-methoxy-indol-3-ylmethyl glucosinolate, so this is a genuine but indirect, non-core annotation. Supporting Evidence: PMID:19095898 S1) was significantly reduced in myb51 mutants (Table 1A), indicating that MYB51 up-regulates IGS biosynthesis in response to Flg22. PMID:19095898 suggesting that glucosinolate-dependent callose deposition most likely contributes to MAMP-induced growth suppression of PtoDC3000 |
| GO:0052544 defense response by callose deposition in cell wall | IMP PMID:19095898 Glucosinolate metabolites required for an Arabidopsis innate... | KEEP AS NON CORE | Summary: myb51-1 and myb51-2 mutants are impaired in flg22-induced callose deposition. Reason: Directly supported by mutant phenotypes. MYB51 acts upstream (ethylene -> MYB51 -> indolic glucosinolate synthesis -> PEN2/PEN3-dependent callose), not as part of the callose deposition machinery, so the annotation is retained as non-core with its acts_upstream_of_or_within qualifier. Supporting Evidence: PMID:19095898 as well as two transcription factor mutants myb51-1 and myb51-2, were impaired in the Flg22-induced callose response PMID:19095898 Since ASA1 expression is Et-inducible, these data suggest that MYB51 functions downstream of Et signaling and that MYB51 most likely mediates at least some transcriptional responses to Et signaling. |
| GO:0001228 DNA-binding transcription activator activity, RNA polymerase II-specific | IDA PMID:25049362 bHLH05 is an interaction partner of MYB51 and a novel regula... | NEW | Summary: MYB51 trans-activates promoters of glucosinolate biosynthetic genes (ASA1, CYP79B3, CYP83B1) in cultured Arabidopsis cells, and gain of function increases expression of these genes and indolic glucosinolate levels. Reason: The existing annotations record only the generic DNA-binding transcription factor activity. Trans-activation assays and the activation-tagging phenotype show that MYB51 is a transcriptional activator of its targets, and no repressor activity has been reported. Supporting Evidence: PMID:25049362 The MYBs could induce the transcription of all tested promoters of GSL biosynthetic pathway in trans, indicating a direct role of MYB51 in the binding and activation of GSL biosynthesis genes. PMID:17461791 HIG1/MYB51 was shown to activate promoters of indolic glucosinolate biosynthetic genes leading to increased accumulation of indolic glucosinolates. |
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Download this section (compressed HTML)Q: Does MYB51 directly regulate camalexin biosynthesis under specific conditions (UV, AgNO3), given that camalexin is reduced in myb51-containing double mutants but pathogen-induced camalexin is not compromised in the myb34/51/122 triple mutant?
Q: What is the function of vasculature-restricted MYB51 induction at fungal infection sites (C. higginsianum), compared with the epidermal induction of MYB122?
Q: Which cis-element does MYB51 bind in indolic glucosinolate gene promoters, and is DNA binding dependent on its bHLH partners?
Experiment: ChIP-seq or DAP-seq of MYB51 (alone and with bHLH05) to define its direct target promoters and binding motif.
Hypothesis: MYB51 directly binds promoters of ASA1, CYP79B2/B3 and CYP83B1.
Experiment: Cell-type-specific complementation of myb51 (vasculature vs epidermis promoters) and infection with C. higginsianum and P. cucumerina, measuring fungal growth and indolic glucosinolate levels.
Hypothesis: Vascular MYB51 contributes to restricting fungal spread independently of epidermal MYB122.
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