OsMADS3 (Q40704; gene MADS3/RAG; loci Os01g0201700 / LOC_Os01g10504) is the rice AGAMOUS ortholog - a C-class (AGAMOUS-lineage) MIKC-type MADS-box transcription factor. It is one of two duplicated rice AG-lineage C-class genes (with its paralog OsMADS58) that together control reproductive (inner-whorl) floral organ identity and floral meristem determinacy, the rice instantiation of the ABCDE / floral-quartet model of floral organ specification. Within the partitioned (subfunctionalized) duties of the two paralogs, OsMADS3 plays the more predominant role in repressing lodicule fate and in specifying stamen (whorl-3) identity, whereas OsMADS58 contributes more strongly to floral meristem determinacy and carpel morphogenesis. Genetically, loss of OsMADS3 (antisense lines and the T-DNA allele osmads3-3) causes almost all stamens to be homeotically transformed into lodicule-like organs and produces meristem-determinacy defects (increased carpel number, carpels-within-carpels); ectopic/overexpression of OsMADS3 conversely transforms lodicules into stamens. Mechanistically, OsMADS3 is a nuclear, sequence-specific DNA-binding transcription factor that acts through the MADS domain for DNA binding and the K-box for dimerization/higher-order MADS-complex (floral-quartet) assembly with SEP-like (E-class) partners. Beyond early organ identity, OsMADS3 has a later, stage-specific role in male reproductive development: it acts in late anther development by regulating reactive-oxygen-species (ROS) homeostasis, binding the MT-1-4b (metallothionein) promoter and inducing OsMT-I-4b to buffer ROS and promote tapetal programmed cell death. Unlike rice flowering-TIME regulators (e.g. GI, Hd3a), OsMADS3 is a genuine flower-development / floral-organ-identity gene; the SwissProt keyword-derived (SPKW, GO_REF:0000043) annotation to the generic "cell differentiation" (GO:0030154) therefore captured a real developmental role but at far too coarse a level, dropping the floral-organ-identity specificity that is the gene's actual function.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006357 regulation of transcription by RNA polymerase II | IBA GO_REF:0000033 | ACCEPT | Summary: IBA annotation propagated across the MADS-box / MEF2 transcription-factor phylogenetic group. OsMADS3 is a MIKC-type MADS-box transcription factor that regulates Pol II transcription of floral developmental target genes. Reason: Core, correct function. OsMADS3 is the rice AGAMOUS ortholog, a sequence-specific DNA-binding transcription factor that controls floral organ identity by regulating downstream gene expression; it directly binds and induces the MT-1-4b promoter during late anther development, demonstrating transcriptional-regulatory activity. The IBA term is at an appropriate level of specificity for the conserved MADS-box TF function. Supporting Evidence: file:ORYSJ/MADS3/MADS3-deep-research-falcon.md function as **DNA-binding dimers** and higher-order complexes that regulate developmental gene expression programs PMID:16326928 regulating the organ identity of stamens and carpels, the repression of A-class genes, and floral meristem determinacy |
| GO:0000978 RNA polymerase II cis-regulatory region sequence-specific DNA binding | IBA GO_REF:0000033 | ACCEPT | Summary: IBA annotation: OsMADS3 binds sequence-specific cis-regulatory DNA (CArG-box-type elements) via its MADS domain to regulate Pol II transcription of floral targets. Reason: Correct core molecular function. As a MADS-box protein OsMADS3 contains the canonical MADS domain (residues 1-61) that mediates sequence-specific DNA binding; it binds the MT-1-4b promoter directly. The IBA term captures the sequence-specific cis-regulatory DNA-binding activity at the right level of specificity for a MIKC-type floral transcription factor. Supporting Evidence: file:ORYSJ/MADS3/MADS3-deep-research-falcon.md function as **DNA-binding dimers** and higher-order complexes that regulate developmental gene expression programs file:ORYSJ/MADS3/MADS3-deep-research-falcon.md OsMADS3 is reported to **directly bind** the promoter of **MT-1–4b** |
| GO:0000977 RNA polymerase II transcription regulatory region sequence-specific DNA binding | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro (IPR033896, MEF2-like N-terminal region). Captures the same sequence-specific Pol II regulatory-region DNA-binding activity as the IBA annotation to the sibling term GO:0000978, at a slightly broader level. Reason: Consistent with the IBA annotation and with the documented MADS-domain DNA-binding activity of OsMADS3. The InterPro-derived term is correct; it overlaps the more precise cis-regulatory-region term (GO:0000978) but is not wrong. Duplicate / closely related sequence-specific DNA-binding terms with different evidence codes are acceptable. Supporting Evidence: file:ORYSJ/MADS3/MADS3-deep-research-falcon.md function as **DNA-binding dimers** and higher-order complexes that regulate developmental gene expression programs |
| GO:0003677 DNA binding | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro (MADS-box, IPR002100/IPR036879) for generic DNA binding. OsMADS3 binds DNA via its MADS domain. Reason: Correct but generic. OsMADS3 is a DNA-binding MADS-box transcription factor; "DNA binding" is a true high-level parent of its sequence-specific cis-regulatory DNA binding (GO:0000978 / GO:0000977). It is uninformative compared with the specific sequence-specific terms but is not incorrect, so it can be accepted as supporting computational evidence. Supporting Evidence: file:ORYSJ/MADS3/MADS3-deep-research-falcon.md function as **DNA-binding dimers** and higher-order complexes that regulate developmental gene expression programs |
| GO:0003700 DNA-binding transcription factor activity | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro (TF_Kbox, IPR002487). OsMADS3 is a DNA-binding transcription factor - its core molecular function. Reason: Core, correct molecular function. OsMADS3 is the rice AGAMOUS ortholog, a MIKC-type MADS-box transcription factor that binds DNA sequence-specifically and regulates transcription of floral developmental targets. The InterPro-derived TF-activity term is appropriate. Supporting Evidence: PMID:9869408 OsMADS3, is highly homologous to the members in the AGAMOUS (AG) family that is essential for the normal development of the internal file:ORYSJ/MADS3/MADS3-deep-research-falcon.md function as **DNA-binding dimers** and higher-order complexes that regulate developmental gene expression programs |
| GO:0005634 nucleus | IEA GO_REF:0000120 | ACCEPT | Summary: IEA annotation for nuclear localization (UniProtKB-SubCell SL-0191; InterPro IPR002487). Consistent with OsMADS3's function as a nuclear transcription factor. Reason: Correct cellular-component annotation. As a sequence-specific DNA-binding transcription factor, OsMADS3 acts in the nucleus; the UniProt entry assigns nuclear localization (by similarity), and the deep-research synthesis treats OsMADS3 as functioning in the nucleus. Direct fluorescent-tagging localization for OsMADS3 was not found in the accessible literature, but nuclear localization is well supported by its molecular function and family. Supporting Evidence: file:ORYSJ/MADS3/MADS3-deep-research-falcon.md OsMADS3 function is inferred to occur **in the nucleus** where it binds target promoters (e.g., MT-1-4b) |
| GO:0006355 regulation of DNA-templated transcription | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro (TF_Kbox, IPR002487) for generic regulation of DNA-templated transcription - a broad parent of the RNA-Pol-II-specific IBA term GO:0006357. Reason: Correct but broad. OsMADS3 regulates transcription of its floral developmental targets (e.g. it binds and induces the MT-1-4b promoter). "Regulation of DNA-templated transcription" is a true high-level parent of the more specific "regulation of transcription by RNA polymerase II" (GO:0006357, IBA). It is not wrong and provides consistent computational support; the RNA-Pol-II-specific term is the more informative one. Supporting Evidence: file:ORYSJ/MADS3/MADS3-deep-research-falcon.md function as **DNA-binding dimers** and higher-order complexes that regulate developmental gene expression programs file:ORYSJ/MADS3/MADS3-deep-research-falcon.md OsMADS3 is reported to **directly bind** the promoter of **MT-1–4b** |
| GO:0009791 post-embryonic development | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: IEA annotation from an ARBA machine-learning model (ARBA00029007). A very broad developmental grouping term that does not capture OsMADS3's specific role in floral organ identity. Reason: "Post-embryonic development" is an extremely generic, ML-derived process term that conveys almost no functional information. OsMADS3's actual developmental role is precisely defined: specification of stamen identity and floral organ identity, plus contribution to floral meristem determinacy. The specific floral terms (GO:0010097 specification of stamen identity, TAS; and GO:0048437 floral organ development, proposed below) fully capture the biology. The broad ARBA term is an over-annotation that adds nothing once the specific floral-development terms are present. Supporting Evidence: PMID:16326928 shows homeotic transformation of stamens into lodicules and ectopic development of lodicules in the second whorl file:ORYSJ/MADS3/MADS3-deep-research-falcon.md controlling reproductive organ identity and floral meristem determinacy |
| GO:0045944 positive regulation of transcription by RNA polymerase II | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro (MEF2-like N-terminal region, IPR033896). OsMADS3 acts as a transcriptional activator (UniProt keyword "Activator"); it directly induces the MT-1-4b promoter during late anther development. Reason: Supported. OsMADS3 is annotated by UniProt with the keyword "Activator", and the literature reports that it binds the MT-1-4b promoter and strongly induces OsMT-I-4b, a direct positive transcriptional-regulation activity. MADS-box C-class factors can both activate and repress targets, but a positive-regulation activity is genuinely documented, so the IEA term is acceptable. Supporting Evidence: file:ORYSJ/MADS3/MADS3-deep-research-falcon.md OsMADS3 is reported to **directly bind** the promoter of **MT-1–4b** (a metallothionein gene implicated in ROS scavenging), linking OsMADS3 transcriptional control to **ROS homeostasis** during late anther development |
| GO:0046983 protein dimerization activity | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro (MADS-box, IPR002100/IPR036879). MIKC-type MADS proteins dimerize (via the K-box) and assemble into higher-order floral-quartet complexes; OsMADS3 forms complexes with SEP-like (E-class) partners. Reason: Correct. The K-box domain (residues 87-178) mediates dimerization and higher-order complex formation, the structural basis of the floral-quartet model. OsMADS3 is reported to form complexes with SEP-like proteins (OsMADS1, OsMADS5, OsMADS24/8, OsMADS34, OsMADS45/7), and the K-box splice variation is interpreted as affecting protein-protein interaction capacity. Protein dimerization activity is a genuine, family-conserved molecular function. Supporting Evidence: file:ORYSJ/MADS3/MADS3-deep-research-falcon.md function as **DNA-binding dimers** and higher-order complexes that regulate developmental gene expression programs file:ORYSJ/MADS3/MADS3-deep-research-falcon.md OsMADS3 is described as acting via **protein complexes**, including interactions with **SEP-like MADS proteins** |
| GO:0048608 reproductive structure development | IEA GO_REF:0000117 | MODIFY | Summary: IEA annotation from an ARBA machine-learning model (ARBA00028277). Correct in essence (OsMADS3 acts in reproductive/floral development) but a broad parent term that does not capture its specific floral-organ-identity role. Reason: The essence is sound - OsMADS3 is a C-class floral homeotic gene that specifies reproductive (inner-whorl) organ identity - but "reproductive structure development" is a broad grouping term. The gene's documented role is more precisely the development and identity specification of floral organs (especially stamens). MODIFY to the more specific "floral organ development" (GO:0048437), which is accurate, non-obsolete, and complements the retained specific term GO:0010097 (specification of stamen identity). Proposed replacements: floral organ development Supporting Evidence: PMID:9869408 OsMADS3 belongs to the class C gene family of floral organ identity determination file:ORYSJ/MADS3/MADS3-deep-research-falcon.md controlling reproductive organ identity and floral meristem determinacy |
| GO:0010097 specification of stamen identity | TAS PMID:19820190 MOSAIC FLORAL ORGANS1, an AGL6-like MADS box gene, regulates... | ACCEPT | Summary: TAS annotation (AgBase) to the specific process "specification of stamen identity". This is the core biological process of OsMADS3 - the rice AGAMOUS ortholog and the predominant C-class specifier of stamen (whorl-3) identity. (The cited reference, PMID:19820190, is the OsMADS6/MFO1 AGL6-like paper; it documents MADS-box control of floral organ identity but does not itself characterize OsMADS3, so the strongest gene-specific support comes from the OsMADS3 loss-of-function literature.) Reason: This is the central, well-supported function of OsMADS3 and the most specific term in the annotation set. Loss-of-function evidence is decisive: antisense silencing and the T-DNA allele osmads3-3 cause almost all stamens to be homeotically transformed into lodicule-like organs, while overexpression transforms lodicules into stamens - the classic signature of a C-class stamen-identity specifier. OsMADS3 plays the more predominant role (vs its paralog OsMADS58) in repressing lodicule fate and specifying stamens. The term should be kept as a core function. Supporting Evidence: PMID:16326928 A knockout line of OSMADS3, in which the gene is disrupted by T-DNA insertion, shows homeotic transformation of stamens into lodicules PMID:11828031 As a consequence of the ectopic expression of the OsMADS3, lodicules were homeotically transformed into stamens PMID:9869408 the filaments of the transgenic plants were changed into thick and fleshy bodies, similar to lodicules file:ORYSJ/MADS3/MADS3-deep-research-falcon.md **Overexpression** of OsMADS3 can convert **lodicules to stamens** |
| GO:0030154 cell differentiation | IEA GO_REF:0000043 | MODIFY | Summary: SPKW (GO_REF:0000043) annotation derived from the UniProt keyword "Differentiation"; snapshot-only, removed in the current GOA release. OsMADS3 genuinely acts in a developmental program, but "cell differentiation" is far too generic - it drops all of the floral-organ-identity specificity that is the gene's actual function. Reason: Unlike rice flowering-TIME regulators (where a developmental keyword would be an over-annotation of a signalling protein), OsMADS3 IS a bona fide flower-development gene - the rice AGAMOUS ortholog and the predominant C-class specifier of stamen identity. So this is a MODIFY-to-specific case rather than a plain over-annotation: the keyword-derived "cell differentiation" (GO:0030154) is biologically in the right area but is so coarse that it conveys no information about WHAT differentiates. The precise, evidence-supported function is specification of floral-organ (stamen) identity: loss of OsMADS3 homeotically transforms stamens into lodicules and causes meristem-determinacy defects, while overexpression transforms lodicules into stamens. The annotation should therefore be retained but MODIFIED to the specific term "specification of stamen identity" (GO:0010097), which is already present in current GOA as a TAS annotation and captures the genuine biology that the retired generic keyword term only gestured at. (The broader "floral organ development", GO:0048437, and "floral meristem determinacy", GO:0010582, are also appropriate complementary terms; see core_functions and proposed_new_terms.) Net assessment: GOA's removal of the bare keyword term did not lose correct specific biology, because the specific stamen-identity term is independently annotated - but the generic keyword term itself was an over-coarse mapping that should be replaced rather than simply deleted. Proposed replacements: specification of stamen identity Supporting Evidence: PMID:16326928 A knockout line of OSMADS3, in which the gene is disrupted by T-DNA insertion, shows homeotic transformation of stamens into lodicules PMID:11828031 As a consequence of the ectopic expression of the OsMADS3, lodicules were homeotically transformed into stamens file:ORYSJ/MADS3/MADS3-deep-research-falcon.md **Overexpression** of OsMADS3 can convert **lodicules to stamens** |
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Download this section (compressed HTML)Q: Does OsMADS3 bind a defined CArG-box motif in rice target promoters (e.g. MT-1-4b), and what is the genome-wide set of direct OsMADS3 targets in developing stamens versus late anthers?
Suggested experts: Hiroaki Hirano
Q: How is the division of labour between OsMADS3 and OsMADS58 encoded - is it differential expression timing, differential SEP-partner (floral-quartet) composition, or both - and does the Ser109 K-box splice isoform alter partner choice?
Suggested experts: Martin M. Kater
Experiment: Perform ChIP-seq / DAP-seq for OsMADS3 in developing florets and late anthers to define its direct genome-wide targets and its DNA-binding motif, and test direct binding to the MT-1-4b promoter.
Hypothesis: OsMADS3 binds CArG-box elements in the promoters of stamen-identity and ROS-homeostasis genes (including MT-1-4b), acting as the direct transcriptional driver of these programs.
Type: genome-wide TF binding (ChIP-seq/DAP-seq) plus targeted promoter assay
Experiment: Reconstitute candidate OsMADS3 floral-quartet complexes in vitro / in planta (with B-class OsMADS2/OsMADS4 and SEP-like OsMADS1/OsMADS7/OsMADS8) and test higher-order complex assembly and cooperative DNA binding for the S109 vs delta-S109 K-box isoforms.
Hypothesis: OsMADS3 specifies stamen identity as part of a higher-order MADS quartet with B-class and SEP-like partners, and the K-box Ser109 splice variant modulates partner-interaction capacity and thus target selectivity.
Type: protein-protein interaction / DNA-binding biochemistry
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