ABCE model of floral organ identity (MADS floral quartets)

In the eudicot flower, four concentric whorls of organs (sepals, petals, stamens and carpels) get their identities from overlapping homeotic gene activities, as described by the ABC model and its later ABCE extension. In Arabidopsis thaliana the A function is supplied by APETALA1 (AP1, a MIKC-type MADS-domain transcription factor) and APETALA2 (AP2, an AP2/ERF-domain transcriptional repressor). The B function is supplied by the obligate MADS heterodimer APETALA3/PISTILLATA (AP3/PI) and the C function by AGAMOUS (AG). The E function is supplied redundantly by the four SEPALLATA MADS proteins (SEP1-SEP4). A alone specifies sepals (whorl 1), A+B petals (whorl 2), B+C stamens (whorl 3) and C carpels (whorl 4). E activity is required for B and C function: sep1 sep2 sep3 flowers make only sepals, and sep1 sep2 sep3 sep4 flowers make only leaf-like organs. At the molecular level, the floral quartet model proposes that each organ identity is set by a distinct tetrameric MADS complex. Two MADS dimers bind two CArG boxes and loop the DNA between them, with SEP proteins (above all SEP3) acting as the tetramerization hub. Expressing A or C together with B and E genes is enough to turn leaves into petal-like or stamen-like organs. A and C are mutually antagonistic. AP2 confines AG to the inner two whorls by recruiting the TOPLESS/HDA19 co-repressor, while AG excludes AP1 from the inner whorls. The SEP3-AG tetramer also terminates the floral meristem after carpel initiation. Floral meristem identity (LEAFY, AP1 meristem function, CAULIFLOWER, FRUITFULL, TERMINAL FLOWER1) is a separate, upstream module. LEAFY is cited here only as an activator of the B and C genes. The D-class ovule identity genes (STK/SHP) and the downstream organ differentiation programs are also outside this boundary.

MODULE:floral_organ_identity_abceDRAFTCONCRETEDevelopmental Processmodules/floral_organ_identity_abce.yaml
specification of floral organ identityGO:0010093
PMID:1685111
Genetic interactions among floral homeotic genes of Arabidopsis.
Classic ABC field model: AP2 acts in the two outer whorls, AP3/PI in whorls two and three, and AG in the two inner whorls. AP2 and AG act antagonistically.
the products of these homeotic genes are each active in fields occupying two adjacent whorls, AP2 in the two outer whorls, PI and AP3 in whorls two and three, and AG in the two inner whorls
PMID:10821278
B and C floral organ identity functions require SEPALLATA MADS-box genes.
The SEP genes define the E function required for B and C activity.
Here we show that the activities of the B and C organ-identity genes require the activities of three closely related and functionally redundant MADS-box genes, SEPALLATA1/2/3 (SEP1/2/3).
PMID:15530395
The SEP4 gene of Arabidopsis thaliana functions in floral organ and meristem identity.
SEP4 adds to the E function. Quadruple sep mutants convert all floral organs, including sepals, into leaf-like organs.
floral organs are converted into leaf-like organs in sep1 sep2 sep3 sep4 quadruple mutants, indicating the involvement of all four SEP genes in the development of sepals.
PMID:11206550
Complexes of MADS-box proteins are sufficient to convert leaves into floral organs.
ABC proteins form ternary and quaternary complexes through SEP3, and these complexes are sufficient to convert leaves into petaloid or staminoid organs.
Our findings indicate that the formation of ternary and quaternary complexes of ABC proteins may be the molecular basis of the ABC model
PMID:11231153
Conversion of leaves into petals in Arabidopsis.
SEP plus A and B genes are sufficient for petal identity.
Here we show that the combined action of the SEP genes, together with the A and B genes, is sufficient to convert leaves into petals.
PMID:27624831
MADS-domain transcription factors and the floral quartet model of flower development: linking plant development and evolution.
Review of the floral quartet model.
The floral quartet model of floral organ specification poses that different tetramers of MIKC-type MADS-domain transcription factors control gene expression and hence the identity of floral organs during development.
PMID:22238427
Characterization of MADS-domain transcription factor complexes in Arabidopsis flower development.
AP1, AP3, PI, AG and SEP3 form complexes in floral tissue in vivo.
five major floral homeotic MADS-domain proteins (AP1, AP3, PI, AG, and SEP3) interact in floral tissues as proposed in the "floral quartet" model.

Boundary: the upstream floral meristem identity module (LFY, AP1 meristem role, CAL, FUL, TFL1) and the D-class ovule identity complexes (STK, SHP1/2 with SEP) are excluded. AP1 appears here only in its A-class organ identity role. The annoton MF terms follow the gene reviews' core_functions. AP2 and AP3 currently carry the generic GO:0003700 in their reviews (the AP3 and PI reviews are still INITIALIZED). No Arabidopsis GO-CAM models contain these genes (gocams/index.tsv checked). PANTHER family ids are not asserted.

11Nodes
6Parts
1Variant Sets
4Variants
13Annotons
4Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:floral_organ_identity_abce deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Function consistency and core coverage

9 gene-function check(s) reflected in core functions · 0 conflict(s) · 0 evidence or coverage gap(s) (13 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

AnnotonParticipantFunctionAssessment
ap1_a_class_tf AP1
UniProtKB:P35631
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
ap2_a_class_repressor AP2
UniProtKB:P47927
Gene 		DNA-binding transcription factor activity
GO:0003700 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
ap3_b_class_tf AP3
UniProtKB:P35632
Gene 		DNA-binding transcription factor activity
GO:0003700 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
pi_b_class_tf PI
UniProtKB:P48007
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
ag_c_class_tf AG
UniProtKB:P17839
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
sep3_e_class_hub SEP3
UniProtKB:O22456
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
sep1_e_class SEP1
UniProtKB:P29382
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
sep2_e_class SEP2
UniProtKB:P29384
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
sep4_e_class SEP4
UniProtKB:P29383
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
sepal_quartet_tf PROTEIN_COMPLEX
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
petal_quartet_tf PROTEIN_COMPLEX
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
stamen_quartet_tf PROTEIN_COMPLEX
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
carpel_quartet_tf PROTEIN_COMPLEX
Gene 		DNA-binding transcription factor activity, RNA polymerase II-specific
GO:0000981 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.

Feedback loops (advisory, prose-driven: a regulator counts as "feedback" when its own description says so)

✓ every negative regulator described as feedback has an upstream edge closing the loop.

  • ap2_a_class_repressor ⊣ c_function [input]
    ap2_a_class_repressor is a negative regulator with no upstream edge (not described as feedback)
  • c_function ⊣ ap1_a_class_tf [input]
    c_function is a negative regulator with no upstream edge (not described as feedback)

Gene-review completeness (9/9 grounded genes reviewed)

9 complete review(s) · 6 with deep research · 0 missing review · 3 reviewed but lacking deep research

Gene Review Complete Deep research
AG P17839 ✓ ✓ ✓
AP1 P35631 ✓ ✓ ✓
AP2 P47927 ✓ ✓ ✓
AP3 P35632 ✓ ✓ ✓
PI P48007 ✓ ✓ ✓
SEP1 P29382 ✓ ✓ ✗
SEP2 P29384 ✓ ✓ ✗
SEP3 O22456 ✓ ✓ ✓
SEP4 P29383 ✓ ✓ ✗

Details

Context
Arabidopsis thalianaNCBITaxon:3702
nucleusGO:0005634
ABCE floral organ identity specificationDevelopmental Processfloral_organ_identity_abce

Combinatorial specification of the four floral organ identities by A (AP1, AP2), B (AP3/PI), C (AG) and E (SEP1-4) homeotic transcription factors acting as whorl-specific MADS tetramers, with A-C mutual antagonism setting the boundary between perianth and reproductive whorls.

specification of floral organ identityGO:0010093
Context
Arabidopsis thalianaNCBITaxon:3702
nucleusGO:0005634

Connections

ap2_a_class_repressor -> c_function Negatively Regulates
AP2 keeps AG transcriptionally inactive in whorls 1 and 2. In ap2 mutants, AG RNA is found in all whorls.
PMID:1675158
Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product.
AG RNA spreads to all whorls in ap2 mutants.
In ap2 mutant flowers, AG RNA is present in the organ primordia of all floral whorls.
PMID:20876650
On reconciling the interactions between APETALA2, miR172 and AGAMOUS with the ABC model of flower development.
AP2 and AG are antagonistic A- and C-class genes.
APETALA2 ( AP2 ) and AGAMOUS ( AG ) represent A- and C-class genes that act in an antagonistic fashion to specify perianth and reproductive organs, respectively.
ap2_a_class_repressor -> b_function Negatively Regulates
AP2 also sets the expression borders of AP3 and PI (and SEP3) through TOPLESS/HDA19.
PMID:23034631
APETALA2 negatively regulates multiple floral organ identity genes in Arabidopsis by recruiting the co-repressor TOPLESS and the histone deacetylase HDA19.
AP2 regulates expression borders of B-class and E-class genes.
also regulates the expression borders of the B-class genes APETALA3 and PISTILLATA, and the E-class gene SEPALLATA3
c_function -> ap1_a_class_tf Negatively Regulates
AG prevents AP1 RNA accumulation in the two inner whorls, completing A-C mutual antagonism.
PMID:7506995
Regulation of the arabidopsis floral homeotic gene APETALA1.
AG excludes AP1 from whorls 3 and 4.
the organ identity gene AGAMOUS prevents AP1 RNA accumulation in the two inner whorls of wild-type flowers
The A, B, C and E proteins are the subunits from which the whorl-specific quartet complexes assemble. The E-class SEP proteins enter as tetramerization partners rather than as regulators of B and C activity, which is why B and C organ identity genetically requires SEP function.
PMID:10821278
B and C floral organ identity functions require SEPALLATA MADS-box genes.
B and C activities require SEP1/2/3.
the activities of the B and C organ-identity genes require the activities of three closely related and functionally redundant MADS-box genes
Part 1: homeotic class activities (A, B, C, E transcription factors)
Floral homeotic class activitiesModulehomeotic_class_activities

The individual gene-product activities that make up each homeotic class. All except AP2 are MIKC-type MADS-domain transcription factors that bind CArG boxes as dimers and assemble into tetramers.

Part 1: A function
A function (AP1, AP2)Regulatory Stepa_function

A function specifies sepals alone and petals together with B. AP1 is a MADS-domain factor that also acts earlier in floral meristem identity (a separate module). AP2 is an AP2/ERF-domain repressor that confines AG to the inner whorls. AP2 protein is itself limited by miR172.

Annotons

AP1: A-class MADS transcription factor
ap1_a_class_tf
Participant: Gene Product: AP1
Gene Product:
AP1UniProtKB:P35631

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of sepal identityGO:0010096 specification of petal identityGO:0010095

Locations

nucleusGO:0005634

A-class MADS factor in the sepal (AP1-SEP) and petal (AP1-SEP-AP3-PI) quartets; binds CArG boxes as a homodimer or in heteromeric complexes.

PMID:8643482
Dimerization specificity of Arabidopsis MADS domain homeotic proteins APETALA1, APETALA3, PISTILLATA, and AGAMOUS.
AP1 homodimers bind CArG boxes.
only AP1 homodimers, AG homodimers, and AP3/PI heterodimers are capable of binding to CArG-box sequences
AP2: A-class AP2/ERF-domain transcriptional repressor
ap2_a_class_repressor
Participant: Gene Product: AP2
Gene Product:
AP2UniProtKB:P47927

Function

DNA-binding transcription factor activityGO:0003700

Processes

specification of floral organ identityGO:0010093

Locations

nucleusGO:0005634

Represses AG (and sets the expression borders of AP3, PI and SEP3) in the outer whorls by recruiting TOPLESS and HDA19.

PMID:23034631
APETALA2 negatively regulates multiple floral organ identity genes in Arabidopsis by recruiting the co-repressor TOPLESS and the histone deacetylase HDA19.
AP2 represses C, B and E genes via TOPLESS/HDA19.
We show that AP2 represses its target genes by physically recruiting the co-repressor TOPLESS and the histone deacetylase HDA19.
Part 2: B function
B function (AP3/PI obligate heterodimer)Regulatory Stepb_function

AP3 and PI bind DNA only as an AP3/PI heterodimer. They specify petals with A and stamens with C. In ap3 or pi mutants, petals become sepals and stamens become carpels.

Annotons

AP3: B-class MADS transcription factor
ap3_b_class_tf
Participant: Gene Product: AP3
Gene Product:
AP3UniProtKB:P35632

Function

DNA-binding transcription factor activityGO:0003700

Processes

specification of petal identityGO:0010095 specification of stamen identityGO:0010097

Locations

nucleusGO:0005634

Obligate heterodimer partner of PI; B-class subunit of petal and stamen quartets.

PMID:8643482
Dimerization specificity of Arabidopsis MADS domain homeotic proteins APETALA1, APETALA3, PISTILLATA, and AGAMOUS.
Only the AP3/PI heterodimer, not either homodimer, binds CArG boxes.
only AP1 homodimers, AG homodimers, and AP3/PI heterodimers are capable of binding to CArG-box sequences
PI: B-class MADS transcription factor
pi_b_class_tf
Participant: Gene Product: PI
Gene Product:
PIUniProtKB:P48007

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of petal identityGO:0010095 specification of stamen identityGO:0010097

Locations

nucleusGO:0005634

Obligate heterodimer partner of AP3; B-class subunit of petal and stamen quartets.

PMID:1685111
Genetic interactions among floral homeotic genes of Arabidopsis.
pi mutants convert petals to sepals and stamens to carpels.
Homeotic conversions are petals to sepals and stamens to carpels
Part 3: C function
C function (AG)Regulatory Stepc_function

AG specifies stamens with B and carpels alone, and terminates the floral meristem. In ag mutants, stamens become petals and a new flower arises in place of the gynoecium.

Annotons

AG: C-class MADS transcription factor
ag_c_class_tf
Participant: Gene Product: AG
Gene Product:
AGUniProtKB:P17839

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of stamen identityGO:0010097 specification of carpel identityGO:0010094 floral meristem determinacyGO:0010582

Locations

nucleusGO:0005634

C-class subunit of the stamen (AP3-PI-AG-SEP) and carpel (AG-SEP) quartets. The SEP3-AG tetramer activates KNU and CRC to terminate the floral meristem.

PMID:1685111
Genetic interactions among floral homeotic genes of Arabidopsis.
ag mutants transform stamens to petals and make an indeterminate inner flower.
cause petals to develop instead of stamens and another flower to arise in place of the gynoecium
PMID:29562355
Tetramerization of MADS family transcription factors SEPALLATA3 and AGAMOUS is required for floral meristem determinacy in Arabidopsis.
The SEP3-AG heterotetramer activates KNU and CRC for determinacy.
The heterotetramer formed by SEP3 and the MADS protein, AGAMOUS, is necessary to activate two target genes, KNUCKLES and CRABSCLAW
Part 4: E function (redundant SEPALLATA hub)
E function (SEP1-SEP4)Regulatory Stepe_function

The four SEPALLATA MADS proteins act redundantly as tetramerization partners for A, B and C proteins. SEP3 is the dominant hub, and its K3 subdomain can confer tetramer formation on AP3/PI. SEP1, SEP2 and SEP4 each contribute but are masked by redundancy. SEP4 is also needed for sepal identity and adds to floral meristem identity.

Annotons

SEP3: E-class MADS tetramerization hub
sep3_e_class_hub
Participant: Gene Product: SEP3
Gene Product:
SEP3UniProtKB:O22456

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of floral organ identityGO:0010093 floral meristem determinacyGO:0010582

Locations

nucleusGO:0005634

Principal E-class subunit. It heterodimerizes with AP1, AP3/PI and AG, drives tetramerization and is sufficient to loop DNA in quartet-like complexes in vitro.

PMID:19276203
Reconstitution of 'floral quartets' in vitro involving class B and class E floral homeotic proteins.
SEP3 K3 subdomain confers tetramerization; SEP3-AP3-PI complexes form preferentially.
Domain-deletion and domain-swapping experiments indicate that the subdomain K3 of SEP3 is involved in tetramer formation and is sufficient to confer the ability of tetramer formation to AP3 and PI.
SEP1: redundant E-class MADS factor
sep1_e_class
Participant: Gene Product: SEP1
Gene Product:
SEP1UniProtKB:P29382

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of floral organ identityGO:0010093

Locations

nucleusGO:0005634

Redundant E-class partner; binds CArG DNA as a dimer and heterodimerizes with AG.

PMID:10821278
B and C floral organ identity functions require SEPALLATA MADS-box genes.
sep1 sep2 sep3 triple mutants form only sepals.
Triple mutant Arabidopsis plants lacking the activity of all three SEP genes produce flowers in which all organs develop as sepals.
SEP2: redundant E-class MADS factor
sep2_e_class
Participant: Gene Product: SEP2
Gene Product:
SEP2UniProtKB:P29384

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of floral organ identityGO:0010093

Locations

nucleusGO:0005634

Redundant E-class partner; isolated as an AG K-domain interactor (AGL4).

PMID:9418042
Specific interactions between the K domains of AG and AGLs, members of the MADS domain family of DNA binding proteins.
AGL2 (SEP1), AGL4 (SEP2) and AGL9 (SEP3) interact with the AG K domain.
These clones each encode one of four highly related MADS domain proteins: AGL2, AGL4, AGL6 and AGL9.
SEP4: E-class MADS factor (sepal identity, meristem identity)
sep4_e_class
Participant: Gene Product: SEP4
Gene Product:
SEP4UniProtKB:P29383

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of floral organ identityGO:0010093

Locations

nucleusGO:0005634

Redundant E-class factor that, unlike SEP1-3, is needed for sepal (whorl 1) identity in the quadruple-mutant background.

PMID:15530395
The SEP4 gene of Arabidopsis thaliana functions in floral organ and meristem identity.
SEP4 contributes to all organ types and to meristem identity.
SEP4 contributes to the development of petals, stamens, and carpels in addition to sepals and that it plays an important role in meristem identity.
Part 2: whorl-specific MADS quartet complexes
Whorl-specific floral quartet complexesModulewhorl_quartets

Combinations of the class activities as tetrameric MADS complexes, one per whorl. The compositions follow the floral quartet model. The stamen and carpel quartets (and the SEP3-AP3-PI-containing petal and stamen complexes) have biochemical support in vitro and in vivo. The sepal quartet composition remains a model inference.

Variant set: Floral quartet by whorl by floral whorl / organ type (One Or More)

The variants are spatially exclusive organ programs within one flower, not alternatives for one step. Each whorl realizes one of them, and the flower as a whole realizes all four.

Sepal quartet (A + E; whorl 1)Protein Complexsepal_quartet

Proposed AP1-AP1-SEP-SEP tetramer. Sepal identity needs A and SEP4 (SEP1-4 redundantly). In sep1 sep2 sep3 sep4 mutants, sepals become leaf-like.

specification of sepal identityGO:0010096

Annotons

AP1-SEP sepal-identity complex
sepal_quartet_tf
Participant: Protein Complex: AP1-SEP MADS tetramer (proposed)
Protein Complex:
AP1-SEP MADS tetramer (proposed)
Active units:
AP1
Participant: Gene Product: AP1
Gene Product:
AP1UniProtKB:P35631
Role: A-class DNA-binding subunit
SEP4 (with SEP1-3)
Participant: Gene Product: SEP4
Gene Product:
SEP4UniProtKB:P29383
Role: E-class tetramerization subunit

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of sepal identityGO:0010096
PMID:15530395
The SEP4 gene of Arabidopsis thaliana functions in floral organ and meristem identity.
All four SEP genes are involved in sepal development.
indicating the involvement of all four SEP genes in the development of sepals
Petal quartet (A + B + E; whorl 2)Protein Complexpetal_quartet

AP1-SEP-AP3-PI tetramer. A + B + SEP is sufficient to convert leaves into petals.

specification of petal identityGO:0010095

Annotons

AP1-SEP3-AP3-PI petal-identity complex
petal_quartet_tf
Participant: Protein Complex: AP1-SEP3-AP3-PI MADS tetramer
Protein Complex:
AP1-SEP3-AP3-PI MADS tetramer
Active units:
AP1
Participant: Gene Product: AP1
Gene Product:
AP1UniProtKB:P35631
Role: A-class subunit
SEP3
Participant: Gene Product: SEP3
Gene Product:
SEP3UniProtKB:O22456
Role: E-class tetramerization hub
AP3
Participant: Gene Product: AP3
Gene Product:
AP3UniProtKB:P35632
Role: B-class subunit (with PI)
PI
Participant: Gene Product: PI
Gene Product:
PIUniProtKB:P48007
Role: B-class subunit (with AP3)

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of petal identityGO:0010095
PMID:11206550
Complexes of MADS-box proteins are sufficient to convert leaves into floral organs.
Ectopic PI+AP3+AP1 or PI+AP3+SEP3 converts leaves into petaloid organs.
35S::PI;35S::AP3;35S::SEP3, are transformed into petaloid organs
Stamen quartet (B + C + E; whorl 3)Protein Complexstamen_quartet

AP3-PI-AG-SEP tetramer. PI+AP3+SEP3+AG converts leaves into staminoid organs.

specification of stamen identityGO:0010097

Annotons

AP3-PI-AG-SEP3 stamen-identity complex
stamen_quartet_tf
Participant: Protein Complex: AP3-PI-AG-SEP3 MADS tetramer
Protein Complex:
AP3-PI-AG-SEP3 MADS tetramer
Active units:
AP3
Participant: Gene Product: AP3
Gene Product:
AP3UniProtKB:P35632
Role: B-class subunit (with PI)
PI
Participant: Gene Product: PI
Gene Product:
PIUniProtKB:P48007
Role: B-class subunit (with AP3)
AG
Participant: Gene Product: AG
Gene Product:
AGUniProtKB:P17839
Role: C-class subunit
SEP3
Participant: Gene Product: SEP3
Gene Product:
SEP3UniProtKB:O22456
Role: E-class tetramerization hub

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of stamen identityGO:0010097
PMID:11206550
Complexes of MADS-box proteins are sufficient to convert leaves into floral organs.
Ectopic PI+AP3+SEP3+AG converts leaves into staminoid organs.
those of 35S::PI;35S::AP3;35S::SEP3;35S::AG are transformed into staminoid organs
Carpel quartet (C + E; whorl 4)Protein Complexcarpel_quartet

AG-AG-SEP-SEP tetramer. It specifies carpels and also terminates the floral meristem through KNU and CRC.

specification of carpel identityGO:0010094 floral meristem determinacyGO:0010582

Annotons

AG-SEP3 carpel-identity and determinacy complex
carpel_quartet_tf
Participant: Protein Complex: AG-SEP3 MADS tetramer
Protein Complex:
AG-SEP3 MADS tetramer
Active units:
AG
Participant: Gene Product: AG
Gene Product:
AGUniProtKB:P17839
Role: C-class DNA-binding subunit
SEP3
Participant: Gene Product: SEP3
Gene Product:
SEP3UniProtKB:O22456
Role: E-class tetramerization hub

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981

Processes

specification of carpel identityGO:0010094 floral meristem determinacyGO:0010582
PMID:29562355
Tetramerization of MADS family transcription factors SEPALLATA3 and AGAMOUS is required for floral meristem determinacy in Arabidopsis.
SEP3-AG heterotetramer is needed for determinacy targets.
SEP3 heterotetramer formation is required for correct termination of the floral meristem