| Aspect | Key findings | Evidence type | Quantitative data (if available) | Key references with year + DOI URL |
|---|---|---|---|---|
| Definition/concept | **Direct maize evidence:** AM1 in maize corresponds to **AMEIOTIC1**, the product of UniProt **C0RWW9**, a plant-specific meiotic regulator required for the mitosis-to-meiosis transition and early prophase I progression. It is not an enzyme with a defined catalytic reaction; rather, it behaves as a chromosome-associated regulatory protein. **Inference/comparative context:** AM1 is homologous to Arabidopsis **SWI1/DYAD** and rice **OsAM1**, supporting a conserved plant reproductive role. (pqac-00000005, pqac-00000018, pqac-00000006) | Genetics, sequence/domain inference, review | Protein length reported as **780 aa** (~85.6 kDa) in maize. (pqac-00000018, pqac-00000024) | Pawlowski et al. 2009, PNAS, https://doi.org/10.1073/pnas.0810115106; Wang & Tseng 2014, Front Plant Sci, https://doi.org/10.3389/fpls.2014.00497 |
| Molecular function | **Direct maize evidence:** AM1 is a **nuclear/chromatin-associated regulator** needed to establish meiotic chromosome structure, recruit/install cohesion and axis components, and enable recombination machinery loading. It is required for AFD1/Rec8 and ASY1 localization and for RAD51 focus formation. **Inference from Arabidopsis/rice:** family members likely help maintain meiotic chromosome architecture/cohesion. (pqac-00000001, pqac-00000016, pqac-00000007, pqac-00000009) | Cytology, immunolocalization, genetics, review/inference | Wild-type RAD51 peaks at about **500 ± 47 foci/nucleus** at mid-zygotene (**n = 9**); **no RAD51 foci** detected in **am1-1** or **am1-praI**. (pqac-00000001) | Pawlowski et al. 2009, PNAS, https://doi.org/10.1073/pnas.0810115106; Wang et al. 2021, J Exp Bot, https://doi.org/10.1093/jxb/erab217 |
| Biological process | **Direct maize evidence:** AM1 functions in **meiotic entry/initiation**, telomere bouquet formation, homolog pairing, chromosome axis/cohesion establishment, DSB-associated early recombination steps, and the **leptotene–zygotene transition**. Strong alleles divert meiocytes into mitosis-like divisions; **am1-praI** enters meiosis but arrests early in prophase I. (pqac-00000005, pqac-00000001, pqac-00000004, pqac-00000021) | Genetics, cytology | Strong mutant meiocytes undergo **2 or 3 equational divisions** instead of normal meiosis. Tight telomere bouquet in **~8%** of **am1-praI** meiocytes; **37.5%** show loose/multiple telomere clusters. (pqac-00000005, pqac-00000001) | Pawlowski et al. 2009, PNAS, https://doi.org/10.1073/pnas.0810115106 |
| Localization | **Direct maize evidence:** AM1 first shows **diffuse nuclear localization** in premeiotic interphase, then localizes as **punctate/elongated chromatin foci** in leptotene/early zygotene, then largely disappears from bulk chromatin by late zygotene while persisting at **pericentromeric regions** into pachytene. In **am1-praI**, protein is present but remains diffuse/nucleolar and fails to localize properly to chromosomes. (pqac-00000000, pqac-00000013, pqac-00000019) | Immunolocalization, Western blot | Pericentromeric persistence reported on **5–6 of 10 maize chromosomes**; faint chromosomal staining seen in **8/54** cells in one assay. (pqac-00000000, pqac-00000004) | Pawlowski et al. 2009, PNAS, https://doi.org/10.1073/pnas.0810115106 |
| Expression | **Direct maize evidence:** AM1 protein is detected in **anthers/meiocytes** but not in vegetative tissues such as root, shoot, or leaf; expression/accumulation begins in **premeiotic interphase**. Transcriptomic work shows AM1 modulates a subset of meiotic genes in stage-specific fashion rather than globally turning on all meiotic transcription. (pqac-00000000, pqac-00000002, pqac-00000023) | Western blot, immunolocalization, transcriptomics | In shared misregulated transcripts from two mutants, **~60%** are PMC-enriched and only **~1%** tapetum-enriched. At 1.5 mm anthers, **4,418 genes** are differentially expressed in either mutant; shared misregulated set **N = 530**. (pqac-00000002) | Pawlowski et al. 2009, PNAS, https://doi.org/10.1073/pnas.0810115106; Nan et al. 2011, BMC Plant Biol, https://doi.org/10.1186/1471-2229-11-120 |
| Mutant phenotypes | **Direct maize evidence:** Strong/null-like alleles (**am1-1, am1-2, am1-485, am1-489**) typically fail to initiate normal meiosis and instead show **mitosis-like** chromosome and cytoskeletal behavior. **am1-praI** is a separation-of-function allele: meiocytes enter prophase I but arrest near the **L/Z transition**. Female meiotic phenotypes can vary by allele, including interphase arrest or mitosis-like behavior. (pqac-00000005, pqac-00000004, pqac-00000006) | Genetics, cytology | **R358W** substitution in **am1-praI**; allele order reported as **am1-489 most recessive**, **am1-praI most dominant**, **am1-2/am1-485 codominant**. (pqac-00000002, pqac-00000001) | Pawlowski et al. 2009, PNAS, https://doi.org/10.1073/pnas.0810115106; Nan et al. 2011, BMC Plant Biol, https://doi.org/10.1186/1471-2229-11-120; Wang & Tseng 2014, Front Plant Sci, https://doi.org/10.3389/fpls.2014.00497 |
| Downstream effects | **Direct maize evidence:** AM1 loss disrupts telomere clustering, homolog pairing, AFD1/ASY1 loading, DSB formation in strong alleles, RAD51 installation, and meiosis-specific cytoskeleton organization. In **am1-1**, **dmc1** transcript abundance is specifically reduced, whereas some other recombination genes are not strongly changed, suggesting selective transcriptional control. (pqac-00000001, pqac-00000003, pqac-00000016, pqac-00000023) | Cytology, transcriptomics, genetics | **dmc1** signal: wild type **1,230 ± 88**, **am1-1 485 ± 86**, **am1-praI 1,346 ± 150**. Strong allele lacks TUNEL-detected DSBs; **am1-praI** retains DSBs but lacks RAD51 foci. (pqac-00000001, pqac-00000003) | Pawlowski et al. 2009, PNAS, https://doi.org/10.1073/pnas.0810115106 |
| Mechanistic model | **Direct maize model:** AM1 acts in the nucleus at the **mitosis→meiosis switch** and again at a distinct **leptotene–zygotene progression checkpoint**. The **am1-praI** phenotype indicates that chromosomal localization of AM1 is required specifically for prophase progression. **Inference from Arabidopsis SWI1/DYAD:** this family may help preserve cohesin/chromosome architecture, possibly by antagonizing WAPL-like cohesin release pathways. (pqac-00000004, pqac-00000015, pqac-00000009, pqac-00000010) | Genetics, immunolocalization, comparative review/inference | Conserved region implicated in localization/function spans about **aa 324–436** and includes **Arg358**. (pqac-00000004) | Pawlowski et al. 2009, PNAS, https://doi.org/10.1073/pnas.0810115106; Wang et al. 2021, J Exp Bot, https://doi.org/10.1093/jxb/erab217; Cook et al. 2023, Front Plant Sci, https://doi.org/10.3389/fpls.2023.1204813 |
| Applications | **Direct application evidence is limited for maize AM1 itself**, but **review-based translational relevance** is strong. AM1/SWI1/DYAD-like pathways are discussed as candidate levers for **synthetic apomixis**, **male sterility/fertility control**, and especially **in vitro meiosis induction** to accelerate breeding. Manipulating timing of the mitosis–meiosis transition could help hybrid seed production. (pqac-00000008, pqac-00000011, pqac-00000012) | Review/inference, crop breeding context | Reviews note that even a **2–3 day** delay in male sporogenesis/meiotic initiation could aid hybrid crossing systems. (pqac-00000012) | Cook et al. 2023, Front Plant Sci, https://doi.org/10.3389/fpls.2023.1204813; Mahlandt et al. 2023, TAG, https://doi.org/10.1007/s00122-023-04357-3; Wang et al. 2021, J Exp Bot, https://doi.org/10.1093/jxb/erab217 |


*Table: This table summarizes functional annotation for maize AM1/AMEIOTIC1 (UniProt C0RWW9), separating direct maize experimental evidence from comparative inference. It compiles function, localization, phenotypes, mechanistic models, quantitative findings, and application relevance with source-linked citations.*