AM1 (Protein AMEIOTIC 1; UniProt C0RWW9) is a plant-specific, meiocyte-restricted nuclear/chromatin-associated regulatory protein that acts as a master switch for meiotic entry and early prophase I progression in maize. It has no defined enzymatic reaction or transporter substrate; instead it behaves as a chromosome-associated regulator (~780 aa, ~85.6 kDa, with predicted coiled-coil domains) that establishes meiosis-specific chromosome structure, licenses cohesin/axis loading and recombination-machinery installation, and governs the leptotene-to-zygotene transition (Pawlowski et al. 2009, PMID:19204280). In strong loss-of-function am1 alleles, premeiotic cells that should become meiocytes instead execute mitosis-like (equational) divisions - including formation of a preprophase band - rather than meiosis, so AM1 is required to commit cells to the meiotic program. A separation-of-function allele (am1-praI, R358W) produces protein at near-wild-type levels but with defective chromatin localization, entering meiosis yet arresting at the leptotene/zygotene transition; this defines a second, distinct prophase-progression role. AM1 is experimentally required for telomere bouquet formation, homologous chromosome pairing, AFD1(Rec8 cohesin)/ASY1 axis-component loading, DSB formation in strong alleles, and RAD51 focus installation (wild-type ~500 RAD51 foci/nucleus at mid-zygotene vs none in am1-1 or am1-praI). Immunolocalization shows diffuse nuclear signal in premeiotic interphase, chromatin-associated puncta in leptotene/early zygotene, and pericentromeric persistence into pachytene. am1 mutants are male-sterile because male meiosis arrests at leptotene. AM1 is the maize ortholog of Arabidopsis SWI1/DYAD and rice OsAM1, defining a conserved plant meiotic-initiation family (InterPro IPR044221 DYAD/AMEIOTIC1). Because AM1 acts in the mitosis-to-meiosis switch and EARLY prophase I, its genuine biology is captured by the specific meiotic process terms; the retired SwissProt-keyword-derived terms "cell division" and "chromosome segregation" are over-broad / mis-placed for this early-prophase regulator.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: IEA annotation mapped from the UniProt subcellular-location vocabulary (SL-0191, Nucleus). AM1 is a nuclear protein, directly confirmed by immunolocalization in maize male meiocytes. Reason: Correct and consistent with direct experimental evidence. UniProt records the subcellular location as Nucleus with the note that AM1 is diffuse in the nucleus during meiotic initiation, and Pawlowski et al. (2009) showed by immunolocalization that AM1 is a nuclear protein throughout early meiosis [PMID:19204280]. This computational subcellular-location mapping duplicates the IDA annotation to the same term and is at the right level of specificity. Supporting Evidence: PMID:19204280 The AM1 protein is diffuse in the nucleus during the initiation of meiosis file:MAIZE/AM1/AM1-deep-research-falcon.md Premeiotic interphase:** diffuse **nuclear** signal |
| GO:0005694 chromosome | IEA GO_REF:0000044 | ACCEPT | Summary: IEA annotation mapped from the UniProt subcellular-location vocabulary (SL-0468, Chromosome). AM1 binds chromatin in early meiotic prophase I, confirmed experimentally. Reason: Correct. UniProt records "Chromosome" as a subcellular location with the note that AM1 binds to chromatin in early meiotic prophase I [PMID:19204280]. Pawlowski et al. (2009) showed AM1 localizes as chromatin-associated puncta/elongated patches in leptotene/early zygotene and persists at pericentromeric regions. This computational mapping duplicates the IDA annotation to the same term; both are accepted. Supporting Evidence: PMID:19204280 binds to chromatin in early meiotic prophase I file:MAIZE/AM1/AM1-deep-research-falcon.md Leptotene / early zygotene:** **chromatin-associated** puncta and elongated patches |
| GO:0007131 reciprocal meiotic recombination | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro (IPR044221, DYAD/AMEIOTIC1). AM1 is required for the initiation and progression of meiotic recombination, supported by direct maize evidence. Reason: Supported by both the InterPro family signature and direct experimental evidence. The UniProt FUNCTION statement explicitly states AM1 is "Required for homologous chromosome pairing, and initiation and progression of meiotic recombination" [PMID:19204280]. In am1 mutants the recombination program fails to install: wild-type meiocytes show ~500 RAD51 foci per nucleus at mid-zygotene, whereas no RAD51 foci are detected in am1-1 or am1-praI. The IBA/IEA term is at an appropriate level of specificity for AM1's role in enabling reciprocal (crossover) recombination. Supporting Evidence: PMID:19204280 all meiotic processes require am1, including expression of meiosis-specific genes, establishment of the meiotic chromosome structure, meiosis-specific telomere behavior, meiotic recombination, pairing, synapsis file:MAIZE/AM1/AM1-deep-research-falcon.md wild type, RAD51 foci peak at about **500 ± 47 per nucleus** at mid-zygotene (**n = 9**), while **no RAD51 foci** were detected in either *am1-1* or *am1-praI*. |
| GO:0051177 meiotic sister chromatid cohesion | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: IEA annotation from InterPro (IPR044221, DYAD/AMEIOTIC1). AM1 is required upstream of meiotic cohesin loading - AFD1 (the maize Rec8 cohesin homolog) and the axis protein ASY1 fail to localize in am1 mutants - so the gene contributes to establishing meiotic cohesion, but this is a permissive/upstream role rather than a direct cohesion activity. Reason: The annotation is biologically reasonable but reflects an upstream, permissive role rather than AM1 being a cohesion component itself. AM1 is required for chromatin localization of AFD1 (the maize REC8/Rec8 meiotic cohesin) and ASY1, which are absent or strongly reduced in am1-1 [PMID:19204280]; thus loss of AM1 indirectly disrupts meiotic sister chromatid cohesion. AM1 is not a cohesin or cohesin-loading enzyme - it is a chromatin-associated regulator that licenses the broader meiotic chromosome program of which cohesion is one part. The term is correct as a downstream-of-AM1 consequence but is best classified as non-core; the core biology is the meiotic-entry / chromosome- structure / recombination program. Supporting Evidence: file:MAIZE/AM1/AM1-deep-research-falcon.md AFD1 (Rec8 homolog)** and **ASY1** chromatin localization are absent or strongly reduced in *am1-1* file:MAIZE/AM1/AM1-deep-research-falcon.md AM1 is required upstream of multiple prophase structures |
| GO:0051321 meiotic cell cycle | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro (IPR044221, DYAD/AMEIOTIC1). AM1 is a core regulator of the meiotic cell cycle - specifically the mitosis-to-meiosis transition and early prophase I. Reason: Core, well-supported function and the most appropriate broad process term for AM1. In strong am1 alleles, cells that should become meiocytes instead execute mitosis-like (equational) divisions rather than meiosis, demonstrating that AM1 is required to commit cells to and progress through the meiotic cell cycle [PMID:19204280]. The InterPro family signature for the DYAD/AMEIOTIC1 group correctly assigns this term. It duplicates the IMP annotation to the same term; both are accepted as core. Supporting Evidence: file:MAIZE/AM1/AM1-deep-research-falcon.md in strong loss-of-function *am1* alleles, cells that should become meiocytes instead execute **mitosis-like (equational) divisions** rather than normal meiosis. file:MAIZE/AM1/AM1-deep-research-falcon.md AM1 is a core regulator of this transition |
| GO:0005634 nucleus | IDA PMID:19204280 Maize AMEIOTIC1 is essential for multiple early meiotic proc... | ACCEPT | Summary: IDA annotation from Pawlowski et al. (2009): AM1 is diffuse in the nucleus during meiotic initiation and binds chromatin in early prophase I. Directly confirmed by immunolocalization in maize meiocytes. Reason: Strongly supported core localization. Immunolocalization in maize male meiocytes shows a diffuse nuclear AM1 signal in premeiotic interphase, consistent with the UniProt subcellular location [PMID:19204280]. Nuclear localization is the expected compartment for a chromatin-associated meiotic regulator. This IDA is the primary experimental basis for the duplicate IEA nucleus annotation. Supporting Evidence: PMID:19204280 The AM1 protein is diffuse in the nucleus during the initiation of meiosis file:MAIZE/AM1/AM1-deep-research-falcon.md Premeiotic interphase:** diffuse **nuclear** signal |
| GO:0005694 chromosome | IDA PMID:19204280 Maize AMEIOTIC1 is essential for multiple early meiotic proc... | ACCEPT | Summary: IDA annotation from Pawlowski et al. (2009): AM1 binds chromatin in early meiotic prophase I, forming chromatin-associated puncta and persisting at pericentromeric regions. Directly demonstrated by immunolocalization. Reason: Strongly supported core localization. AM1 localizes as chromatin-associated puncta and elongated patches in leptotene/early zygotene and persists at pericentromeric regions into pachytene; the separation-of-function am1-praI allele produces protein that fails to localize properly to chromatin, linking chromatin association to prophase progression [PMID:19204280]. The chromosome/chromatin localization is integral to AM1's mechanism. Supporting Evidence: PMID:19204280 binds to chromatin in early meiotic prophase I file:MAIZE/AM1/AM1-deep-research-falcon.md signal largely disappears from bulk chromatin but **persists at pericentromeric regions** |
| GO:0051321 meiotic cell cycle | IMP PMID:19204280 Maize AMEIOTIC1 is essential for multiple early meiotic proc... | ACCEPT | Summary: IMP annotation from Pawlowski et al. (2009), the foundational AMEIOTIC1 paper. am1 affects the transition to meiosis and progression through early meiotic prophase; loss of am1 diverts premeiotic cells into mitosis. This is the core biological process. Reason: This is AM1's core, experimentally demonstrated biological process. The am1 gene "affects the transition to meiosis and progression through the early stages of meiotic prophase in maize", and in most am1 mutants premeiotic cells enter mitosis instead of meiosis [PMID:19204280]. The IMP is directly supported by the loss-of-function (disruption) phenotype - male meiosis arrested at leptotene, causing sterility. The broad "meiotic cell cycle" term is appropriate; more specific child processes (mitotic- to-meiotic switching, meiotic chromosome organization, homologous chromosome pairing) are proposed below as more precise complementary terms. Supporting Evidence: PMID:19204280 the ameiotic1 (am1) gene, which affects the transition to meiosis and progression through the early stages of meiotic prophase in maize PMID:19204280 in most am1 mutants premeiotic cells enter mitosis instead of meiosis. |
| GO:0051301 cell division | IEA GO_REF:0000043 | MARK AS OVER ANNOTATED | Summary: SPKW (GO_REF:0000043) annotation derived from the UniProt keyword "Cell division"; snapshot-only, removed in the current GOA release. AM1's role is meiosis-specific (commitment to and progression through the meiotic cell cycle), not generic cell division. Reason: GOA's removal of this annotation was JUSTIFIED. "Cell division" is an over-broad, uninformative process term produced by keyword mapping. AM1 is a meiosis-specific regulator: it acts in the mitosis-to-meiosis transition and early prophase I, and in strong am1 alleles premeiotic cells that fail to commit to meiosis instead undergo mitosis-like (equational) divisions [PMID:19204280]. The gene's genuine biology is precisely captured by the retained specific term "meiotic cell cycle" (GO:0051321, IDA/IMP); a blanket "cell division" term adds no information and obscures the meiosis-restricted function. This is a general-as-specific over-annotation; removal is appropriate. Tier A. Supporting Evidence: file:MAIZE/AM1/AM1-deep-research-falcon.md in strong loss-of-function *am1* alleles, cells that should become meiocytes instead execute **mitosis-like (equational) divisions** rather than normal meiosis. PMID:19204280 the ameiotic1 (am1) gene, which affects the transition to meiosis and progression through the early stages of meiotic prophase in maize |
| GO:0007059 chromosome segregation | IEA GO_REF:0000043 | REMOVE | Summary: SPKW (GO_REF:0000043) annotation derived from the UniProt keyword "Chromosome partition"; snapshot-only, removed in the current GOA release. AM1 acts in EARLY prophase I (leptotene-to-zygotene transition, pairing, recombination initiation); because am1 mutants arrest at leptotene, chromosomes never reach the meiotic divisions where segregation occurs, so "chromosome segregation" is mis-placed/over-broad rather than a demonstrated AM1 function. Reason: GOA's removal of this annotation was JUSTIFIED. AM1 functions strictly in meiotic entry and early prophase I - telomere bouquet formation, homologous chromosome pairing, chromosome axis/cohesion establishment, and recombination initiation up to the leptotene-zygotene transition [PMID:19204280]. The disruption phenotype is male meiosis arrested at leptotene, so in am1 mutants chromosomes never progress to metaphase/anaphase where chromosome segregation takes place; segregation is therefore never reached as a direct AM1-dependent event. No segregation defect or segregation machinery role is attributed to AM1 in the primary literature or the deep research. Any cohesion-related contribution is already (and more precisely) covered by the retained "meiotic sister chromatid cohesion" term (GO:0051177), which concerns cohesin establishment in prophase rather than the segregation process. The keyword-derived "chromosome segregation" term is a process mis-placement and should be removed rather than retained. Tier A. Supporting Evidence: PMID:19204280 the ameiotic1 (am1) gene, which affects the transition to meiosis and progression through the early stages of meiotic prophase in maize file:MAIZE/AM1/AM1-deep-research-falcon.md the *am1-praI* allele allows meiotic entry but causes arrest at/near the **leptotene/zygotene (L/Z) transition** file:MAIZE/AM1/AM1-deep-research-falcon.md AM1 acts in the nucleus at the **mitosis→meiosis switch** and again at a distinct **leptotene–zygotene progression checkpoint** |
| GO:0051728 cell cycle switching, mitotic to meiotic cell cycle | IMP PMID:19204280 Maize AMEIOTIC1 is essential for multiple early meiotic proc... | NEW | Summary: AM1 is the master switch that commits premeiotic cells to the meiotic cell cycle; in its absence cells enter mitosis instead of meiosis. This specific mitotic-to-meiotic switching process is not represented in current GOA and better captures AM1's primary function than the generic "meiotic cell cycle". Reason: The defining phenotype of am1 mutants is failure of the mitosis-to-meiosis switch: in most am1 mutants premeiotic cells enter mitosis instead of meiosis, and strong alleles show mitotic microtubule patterns including a preprophase band [PMID:19204280]. GO:0051728 "cell cycle switching, mitotic to meiotic cell cycle" (defined as the process in which a cell switches cell cycle mode from mitotic to meiotic division) precisely describes AM1's role and is more informative than the parent "meiotic cell cycle". IMP is justified by the loss-of-function phenotype. Supporting Evidence: PMID:19204280 in most am1 mutants premeiotic cells enter mitosis instead of meiosis. file:MAIZE/AM1/AM1-deep-research-falcon.md Several strong *am1* alleles show a **mitotic microtubule pattern**, including presence of the **preprophase band (PPB)** |
| GO:0070192 chromosome organization involved in meiotic cell cycle | IMP PMID:19204280 Maize AMEIOTIC1 is essential for multiple early meiotic proc... | NEW | Summary: AM1 builds the proper meiosis-specific chromosome structure at the beginning of meiosis, licensing cohesin/axis assembly. This meiotic chromosome-organization process captures AM1's chromatin-structuring role more precisely than the generic terms currently present. Reason: The UniProt FUNCTION statement states AM1 "Plays a fundamental role in building the proper chromosome structure at the beginning of meiosis", and Pawlowski et al. (2009) show AM1 is required for establishment of the meiotic chromosome structure and for loading of AFD1(Rec8 cohesin) and ASY1 [PMID:19204280]. GO:0070192 "chromosome organization involved in meiotic cell cycle" precisely captures this chromatin- structuring function. IMP is justified by the am1 loss-of-function chromosome-structure defects. Supporting Evidence: file:MAIZE/AM1/AM1-deep-research-falcon.md AM1 as a plant-specific protein required for meiotic initiation and early prophase I file:MAIZE/AM1/AM1-deep-research-falcon.md AFD1 (Rec8 homolog)** and **ASY1** chromatin localization are absent or strongly reduced in *am1-1* |
| GO:0007129 homologous chromosome pairing at meiosis | IMP PMID:19204280 Maize AMEIOTIC1 is essential for multiple early meiotic proc... | NEW | Summary: AM1 is required for homologous chromosome pairing; in am1-1 the telomere bouquet is absent and homolog pairing fails. This specific pairing process is part of AM1's early-prophase role and is not currently represented in GOA. Reason: The UniProt FUNCTION statement explicitly states AM1 is "Required for homologous chromosome pairing" [PMID:19204280], and the deep research records that in am1-1 the telomere bouquet is absent and homolog pairing fails (persistent unpaired FISH signals). GO:0007129 "homologous chromosome pairing at meiosis" precisely captures this defect. IMP is justified by the am1-1 pairing-failure phenotype. Supporting Evidence: PMID:19204280 establishment of the meiotic chromosome structure, meiosis-specific telomere behavior, meiotic recombination, pairing, synapsis file:MAIZE/AM1/AM1-deep-research-falcon.md the telomere bouquet is absent and telomeres remain scattered; homolog pairing fails, with FISH showing persistent unpaired signals. |
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Download this section (compressed HTML)Q: What is the biochemical activity of AM1 at the molecular level - does the DYAD/AMEIOTIC1 family act as a chromatin scaffold/adaptor, and does it (like Arabidopsis SWI1/DYAD) protect meiotic cohesin by antagonizing a WAPL-like cohesin-release pathway?
Suggested experts: Wojciech P. Pawlowski, W. Zacheus Cande
Q: How does AM1 chromatin localization (lost in am1-praI) mechanistically license the leptotene-to-zygotene transition - which downstream factors does AM1 recruit or stabilize at the meiotic chromosome axis?
Suggested experts: Chung-Ju Rachel Wang
Q: Does AM1 have any role in female (megaspore) meiosis distinct from its male meiotic-entry function, given allele-specific female phenotypes?
Suggested experts: Inna N. Golubovskaya
Experiment: Perform AM1 chromatin immunoprecipitation (ChIP-seq) and proximity-labeling (TurboID) proteomics in staged maize meiocytes to identify AM1 chromatin-binding sites and interacting partners during the leptotene-to-zygotene transition.
Hypothesis: AM1 acts as a chromatin scaffold that recruits/stabilizes meiotic axis and cohesin components (AFD1/Rec8, ASY1) at early prophase chromosomes.
Type: ChIP-seq and proximity-labeling proteomics in meiocytes
Experiment: Reconstruct the am1-praI (R358W) chromatin-localization defect with a panel of point mutants across the conserved aa 324-436 region and assay AM1 chromatin binding, AFD1/ASY1 loading and RAD51 focus formation.
Hypothesis: Chromatin association of AM1 (disrupted by R358W) is specifically required for prophase I progression and recombination-machinery installation, separable from the meiotic-entry function.
Type: structure-function point-mutant complementation in maize
Experiment: Cross am1 with mutants in candidate cohesin-release/anti-cohesion factors (a maize WAPL homolog) to test whether AM1 protects meiotic cohesin, and quantify AFD1 retention on prophase chromosomes.
Hypothesis: AM1, like SWI1/DYAD in Arabidopsis, maintains meiotic chromosome architecture by antagonizing premature cohesin removal.
Type: genetic epistasis and cohesin-retention cytology
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