MYB122 (At1g74080) is a nuclear R2R3-MYB transcription factor of subgroup 12, the glucosinolate-regulating MYB clade that also contains MYB28, MYB29 and MYB76 (aliphatic glucosinolates) and MYB34/ATR1 and MYB51/HIG1 (indolic glucosinolates). Its N-terminal R2R3 MYB repeats bind cis-regulatory promoter elements, and it positively regulates transcription of tryptophan-derived indolic glucosinolate (IG) biosynthetic genes such as CYP79B2/CYP79B3 and TSB1. Overexpression raises IG levels and causes high-auxin phenotypes, whereas loss of function lowers IG content; MYB122 acts partly redundantly with MYB34 and MYB51 (the triple mutant lacks IGs), with MYB122 playing an accessory role under standard conditions and a larger contribution under jasmonate/ethylene induction. By controlling CYP79B2/CYP79B3-dependent indole-3-acetaldoxime supply it also influences camalexin levels. Its expression is induced by pathogen-activated MPK3/MPK6-ERF6 signalling, camalexin-inducing stimuli, aphid feeding and copper; it associates with the jasmonate-regulated bHLH activators MYC2/MYC3/MYC4 and with the brassinosteroid-regulated repressor BES1. During infection by the hemibiotrophic fungus Colletotrichum higginsianum, MYB122 is induced specifically in epidermal cells at infection sites, and myb122 mutants are hypersusceptible, with larger lesions and accelerated branching of invasive hyphae, indicating a role in epidermal antifungal defense, presumably via IG-derived antimicrobial metabolites.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000976 transcription cis-regulatory region binding | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA machine-learning transfer of cis-regulatory region binding to an R2R3-MYB protein. MYB122 carries two HTH myb-type repeats with DNA-binding helix-turn-helix motifs and is supported by yeast one-hybrid promoter-binding data. Reason: Consistent with the R2R3-MYB DNA-binding domain architecture and with experimental eY1H promoter interactions (PMID:30356219, PMID:31806676) and promoter trans-activation of IG genes reported for the MYB34/MYB51/MYB122 group. Supporting Evidence: PMID:23580754 MYB34, MYB51, and MYB122, identified as regulators of the indolic glucosinolate biosynthetic pathway, exclusively trans-activate the promoters of TSB1, CYP79B2, and CYP79B3 |
| GO:0000976 transcription cis-regulatory region binding | IPI PMID:30356219 Transcriptional regulation of nitrogen-associated metabolism... | ACCEPT | Summary: Enhanced yeast one-hybrid (eY1H) interaction of MYB122 with the promoter of AT2G22810 in the nitrogen-metabolism transcriptional network screen. Reason: High-throughput eY1H directly assays binding of the TF to a promoter fragment; this supports the generic cis-regulatory region binding activity expected of an R2R3-MYB. Only the abstract is cached; the specific interaction is in the supplementary network data, which the TAIR curator used. The biological relevance of this particular promoter target to nitrogen metabolism is not established, but the binding activity itself is sound. 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. |
| GO:0000976 transcription cis-regulatory region binding | IPI PMID:31806676 A PXY-Mediated Transcriptional Network Integrates Signaling ... | ACCEPT | Summary: eY1H interaction of MYB122 with the promoter of AT2G34710 (PHABULOSA) in the PXY-mediated vascular transcriptional network screen. Reason: eY1H supports promoter (cis-regulatory region) binding by MYB122. As with the nitrogen network screen, the physiological significance of this target for vascular development is untested, but the molecular activity is consistent with the R2R3-MYB DNA-binding domain. Supporting Evidence: PMID:31806676 Here, we mapped a putative PXY-mediated transcriptional regulatory network comprising 690 transcription factor-promoter interactions PMID:31806676 We used high-throughput enhanced yeast one-hybrid (eY1H) assays |
| GO:0003700 DNA-binding transcription factor activity | ISS PMID:11118137 Arabidopsis transcription factors: genome-wide comparative a... | ACCEPT | Summary: Sequence-similarity based assignment from the genome-wide Arabidopsis transcription factor survey. MYB122 is an R2R3-MYB with two complete MYB repeats. Reason: Core molecular function. Beyond domain architecture, overexpression of MYB122 increases indolic glucosinolate levels and myb122 loss of function reduces them, consistent with MYB122 acting as a sequence-specific transcriptional activator of IG biosynthetic genes (as for its paralogs MYB34 and MYB51). Supporting Evidence: PMID:11118137 Arabidopsis dedicates over 5% of its genome to code for more than 1500 transcription factors PMID:17461791 Overexpression of MYB122, another close homologue of HIG1/MYB51, did not rescue the hig1-1 chemotype, but caused a high-auxin phenotype and increased levels of indolic glucosinolates in the wild-type. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular location (nucleus, ECO:0000305) mapped to GO. Reason: Expected location for an R2R3-MYB transcription factor; the glucosinolate MYBs carry an SV40-type nuclear localization signal motif. No direct localization study for MYB122 was found, but nucleus is the location where its core activity is executed. Supporting Evidence: PMID:23580754 These six MYB transcriptional factors, MYB28, MYB29, MYB76, MYB34, MYB51, and MYB122, might function in the nucleus due to an amino acid sequence acting as an SV40-type nuclear localization signal motif |
| GO:0005634 nucleus | ISM GO_REF:0000122 | ACCEPT | Summary: AtSubP sequence-based prediction of nuclear localization. Reason: Concordant with the TF function and the NLS motif noted for the glucosinolate MYB clade. |
| GO:0006355 regulation of DNA-templated transcription | TAS PMID:11118137 Arabidopsis transcription factors: genome-wide comparative a... | ACCEPT | Summary: Traceable author statement that MYB122, as a member of the Arabidopsis transcription factor complement, regulates transcription. Reason: Generic but correct process for a DNA-binding transcription factor. The more informative process, regulation of (indolic) glucosinolate biosynthesis, is proposed separately as a NEW annotation rather than replacing this general term. Supporting Evidence: PMID:11118137 Arabidopsis dedicates over 5% of its genome to code for more than 1500 transcription factors |
| GO:0006950 response to stress | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA machine-learning assignment of a very general stress-response process. Reason: Not wrong (MYB122 expression responds to biotic stresses such as aphid feeding and fungal infection, and it contributes to antifungal defense), but it is an uninformative high-level term; the specific roles are captured by defense response to fungus and the proposed glucosinolate regulation term. |
| GO:0009506 plasmodesma | HDA PMID:21533090 Arabidopsis plasmodesmal proteome. | MARK AS OVER ANNOTATED | Summary: Detection in a mass-spectrometry plasmodesmal (PD) proteome of 1341 proteins. Reason: MYB122 is a nuclear transcription factor; its presence in a PD-enriched cell wall fraction is most plausibly contamination, which the authors themselves estimate at about 35% of the list. MYB122 is not among the candidates validated by fluorescent fusion targeting. The annotation is not informative of MYB122 biology. Supporting Evidence: PMID:21533090 The size and content of the list indicates that the very sensitive technologies still reveal the presence of contaminant proteins but also that the list contains many proteins with known or inferred association with PD. |
| GO:0009625 response to insect | IEP PMID:23144921 Water stress and aphid feeding differentially influence meta... | KEEP AS NON CORE | Summary: MYB122 transcript levels were up-regulated by feeding of the specialist aphid Brevicoryne brassicae under all water regimes. Reason: Valid expression-pattern evidence that MYB122 transcription responds to insect (aphid) feeding, consistent with its role in IG regulation, but no functional requirement of MYB122 for aphid defense was shown. Supporting Evidence: PMID:23144921 Transcript levels of MYB122 were up-regulated as a result of feeding by B. brassicae in all water treatments. |
| GO:0050832 defense response to fungus | IDA PMID:37741284 Cell-type-specific responses to fungal infection in plants r... | ACCEPT | Summary: Single-cell transcriptomics of Arabidopsis leaves infected by Colletotrichum higginsianum showed MYB122 induced specifically in epidermal cells at infection sites; two independent myb122 T-DNA mutants were hypersusceptible, with larger lesions at 5 dpi and accelerated formation of branched secondary invasive hyphae in epidermal cells at 36-42 hpi. Reason: The full text (read from the article PDF; cache is abstract-only) shows a reproducible loss-of-function susceptibility phenotype with two alleles plus infection-site-specific induction, supporting involvement of MYB122 in antifungal defense. The evidence is really a mutant phenotype (IMP would be more apt than IDA), and the mechanism (elevated IG-derived antimicrobials in epidermis) is inferred, not measured. Consistent with the earlier finding that the myb34 myb51 myb122 triple mutant is susceptible to Plectosphaerella cucumerina via loss of IGs. This is the main biological process outcome of MYB122 activity and is retained as core. Supporting Evidence: PMID:37741284 emphasizing the contribution of the epidermis-expressed MYB122 to disease resistance PMID:26802248 MYB34/51/122 contribute to resistance toward P. cucumerina exclusively through IG biosynthesis |
| GO:0051707 response to other organism | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA machine-learning assignment of response to other organism. Reason: Correct but general; MYB122 is induced by fungal infection, Botrytis-activated MPK3/MPK6 signalling and aphid feeding. The specific defense role is captured by defense response to fungus. Supporting Evidence: PMID:27081184 MPK3/MPK6 regulate the expression of MYB51 and MYB122, two key regulators of IGS biosynthesis |
| GO:0010439 regulation of glucosinolate biosynthetic process | IMP PMID:24431192 MYB34, MYB51, and MYB122 distinctly regulate indolic glucosi... | NEW | Summary: MYB122 positively regulates indolic glucosinolate biosynthesis. Overexpression increases IG levels; myb122 single mutants have reduced IG levels and lose BR-mediated repression of IGs; the myb34 myb51 myb122 triple mutant is devoid of IGs. Reason: The TF itself performs the regulatory step (trans-activation of IG biosynthetic gene promoters such as CYP79B2/B3 and TSB1), so the participation test for a regulation term is met. Comparator check (QuickGO, Arabidopsis) - the subgroup-12 aliphatic glucosinolate regulators MYB28, MYB29 and MYB76 carry GO:0010439 by IMP, whereas MYB34 and MYB51 carry GO:0009759 indole glucosinolate biosynthetic process (acts_upstream_of_or_within, IMP); MYB122 has neither despite equivalent genetic evidence. No more specific "regulation of indole glucosinolate biosynthetic process" term exists in GO. MYB122's contribution is accessory relative to MYB34 and MYB51, but it is genetically demonstrable in single and combinatorial mutants. Supporting Evidence: PMID:24431192 MYB34, MYB51, and MYB122 act together to control the biosynthesis of I3M in shoots and roots, with MYB34 controlling biosynthesis of IGs mainly in the roots, MYB51 regulating biosynthesis in shoots, and MYB122 having an accessory role in the biosynthesis of IGs. PMID:24431192 The myb34 myb51 myb122 triple mutant is devoid of IGs, indicating that these three MYB factors are indispensable for IG production under standard growth conditions. PMID:17461791 Overexpression of MYB122, another close homologue of HIG1/MYB51, did not rescue the hig1-1 chemotype, but caused a high-auxin phenotype and increased levels of indolic glucosinolates in the wild-type. PMID:23580754 MYB34, MYB51 and MYB122 loss-of-function mutation all conferred reduced indolic glucosinolate levels. file:ARATH/MYB122/MYB122-deep-research-falcon.md primary function is positive transcriptional regulation of tryptophan-derived indole glucosinolate biosynthesis |
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Download this section (compressed HTML)Q: Does MYB122 promote epidermal resistance to C. higginsianum through indolic glucosinolate (PEN2/PEN3-dependent) products, camalexin, or other IAOx-derived metabolites, given that only the susceptibility phenotype (not metabolite levels) was measured in myb122 mutants?
Q: Is the C. higginsianum TAIR annotation (GO:0050832, IDA) better coded as IMP, since the evidence is a mutant susceptibility phenotype?
Q: Should a more specific GO term "regulation of indole glucosinolate biosynthetic process" be created to capture the distinct roles of MYB34, MYB51 and MYB122 versus the aliphatic regulators MYB28/MYB29/MYB76?
Q: Should MYB122 carry GO:1901183 positive regulation of camalexin biosynthetic process? Camalexin is reduced in myb51 myb122 and triple mutants via reduced IAOx supply (Frerigmann et al. 2015) and MYB122 promotes camalexin at P. syringae sites (Stahl et al. 2016), yet pathogen-induced camalexin is unaltered in the triple mutant (Frerigmann et al. 2016) and no single-mutant effect is reported.
Q: Which promoters does MYB122 bind directly in vivo, and how do its targets differ from MYB51, which is induced in vasculature rather than epidermis at infection sites?
Experiment: Compare IG, 4MI3G, camalexin and ICA levels in wild type, myb122 and complemented lines in infected leaf epidermis (epidermal peels or spatial metabolomics).
Hypothesis: myb122 mutants fail to accumulate indolic glucosinolates and their PEN2-dependent breakdown products in epidermal cells at C. higginsianum infection sites.
Type: cell-type-specific metabolite profiling
Experiment: Complement myb122 with an epidermis-specific promoter-driven MYB122 and test myb122 pen2 and myb122 cyp79b2 cyp79b3 combinations for additive versus epistatic susceptibility.
Hypothesis: The myb122 hypersusceptibility to C. higginsianum depends on IG metabolism.
Type: genetic complementation and epistasis
Experiment: Profile MYB122 genome-wide binding (tagged MYB122 under native promoter) in mock and C. higginsianum infected leaves.
Hypothesis: MYB122 directly binds promoters of CYP79B2, CYP79B3, TSB1 and CYP83B1 in infected epidermal cells.
Type: ChIP-seq / DAP-seq
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