| Evidence type | Finding (domain/function/target/phenotype) | System/tissue/stage | Key experimental readout | Interpretation for VP1 function | Primary source (with year, journal, URL if available) | Citation ID |
|---|---|---|---|---|---|---|
| Molecular | VP1/ABI3 proteins contain four conserved domains (A1, B1, B2, B3); B3 is the DNA-binding domain | Comparative VP1/ABI3 protein analysis; maize VP1 discussed in seed context | Sequence/domain analysis summarized in functional study | Confirms that maize VP1 is a B3-domain transcription factor, matching UniProt P26307 annotation | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000008) |
| Molecular | VP1 co-activates seed-specific ABA-regulated genes, strongly ABA-dependent and mediated mainly via G-box-related cis-elements | Maize seed gene regulation; embryo/endosperm context | Functional analyses cited in review/introduction | Supports annotation of VP1 as an ABA-responsive transcriptional regulator rather than an enzyme or transporter | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000000, pqac-00000008) |
| Molecular | Direct activation of maize **C1** requires B3-mediated binding to the Sph element | Maize promoter regulation | Promoter-binding/activation evidence summarized in paper | Establishes direct DNA-binding target specificity for at least one VP1-regulated promoter | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000008) |
| Molecular | VP1 represses germination-specific gene expression in aleurone; repression/co-activation functions do not require B3 and likely involve protein–protein interactions | Maize aleurone/endosperm | Domain-function dissection summarized in study | Indicates VP1 has separable activator and repressor functions, including indirect transcriptional regulation via partner proteins | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000004, pqac-00000008, pqac-00000009) |
| Genetic | **vp1** mutants are ABA-insensitive, undergo precocious germination (vivipary), lose desiccation tolerance, and produce green embryos during maturation | Maize developing seeds/embryos | Mutant phenotype analysis | Strong genetic evidence that VP1 is essential for seed maturation, dormancy, and ABA responsiveness | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000000, pqac-00000008) |
| Genetic | Suppression of germination in maize kernels absolutely requires functional **Vp1**; GA reduction suppresses vivipary in ABA-deficient mutants but not in **vp1** | Maize embryos during maturation/germination transition | Hormone/genetic interaction studies summarized in thesis | Places VP1 downstream of, or epistatic to, ABA/GA balance as an essential executor of maturation/dormancy | White, 1995, thesis/review source | (pqac-00000020, pqac-00000021, pqac-00000018) |
| Molecular | Multiple maturation-associated seed transcripts are strongly reduced in **vp1** embryos; several are decreased ~4- to 10-fold, and one family ~10-fold specifically in **vp1** | Maize maturing embryos (~30 DAP) | Northern/slot-blot analyses of cDNA families | VP1 is required for normal expression of a broad maturation gene program, including storage/LEA-like genes | White, 1995, thesis/review source | (pqac-00000025) |
| Molecular | **rab28** mRNA is undetectable in young **vp1** embryos and remains low in mature **vp1** embryos despite near-normal ABA levels | Maize embryos during embryogenesis | Northern blots in viviparous mutants | VP1 is required for normal developmental ABA responsiveness of the LEA-like gene **rab28** | Pla et al., 1991, *Molecular and General Genetics*, https://doi.org/10.1007/bf00280296 | (pqac-00000011, pqac-00000013) |
| Molecular | Exogenous ABA (10 μM, 24 h) can induce **rab28** precociously in young **vp1** embryos, but induction is reduced in older mutant embryos | Excised young vs older maize **vp1** embryos | ABA treatment followed by Northern analysis | VP1 is not absolutely required for all ABA-induced **rab28** expression, but is needed for full developmental competence and sustained endogenous regulation | Pla et al., 1991, *Molecular and General Genetics*, https://doi.org/10.1007/bf00280296 | (pqac-00000011, pqac-00000013) |
| Molecular | The **rab28** promoter contains an ABA-related motif (CACGTGG at -146) that confers ABA-dependent expression and binds nuclear protein | Maize promoter assays | Promoter/motif analysis and nuclear protein binding | Supports a cis-regulatory basis for VP1-linked ABA control of **rab28**, likely via ABRE/G-box-centered transcription complexes | Pla et al., 1991, *Molecular and General Genetics*, https://doi.org/10.1007/bf00280296 | (pqac-00000011) |
| Transgenic | 35S-driven maize **VP1** partially complements Arabidopsis **abi3-6**; one copy restores green seed/desiccation-intolerant phenotypes and multiple lines fully restore ABA sensitivity of germination | Arabidopsis transgenic seeds expressing maize VP1 | Complementation of abi3 mutant phenotypes | Demonstrates functional conservation between maize VP1 and ABI3 and validates VP1 as a master seed maturation regulator | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000002, pqac-00000000) |
| Transgenic | 35S-VP1 restores repression of **cab3-GUS** and partially restores **C1-GUS** (~20% of wild type at seed maturity) in **abi3-6** | Arabidopsis developing seeds | Reporter gene assays | Shows VP1 can mediate both repression and activation functions in planta, but activation is incomplete in a heterologous seed context | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000001, pqac-00000002, pqac-00000009) |
| Transgenic | 35S-VP1 enhances ABA inhibition of root growth, induces seed-specific **CRC** in leaves under ABA, and mediates ABA–auxin interaction in roots; ABA suppresses auxin-induced lateral roots in VP1-expressing plants | Arabidopsis vegetative tissues/roots | Root growth, reporter expression, and hormone treatment assays | Indicates VP1 can act outside seeds when ectopically expressed and integrates ABA with auxin-responsive developmental programs | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000000, pqac-00000001, pqac-00000004) |
| Molecular | Distinct VP1 domains are required for different outputs: Em/C1 activation vs α-amylase repression | Domain-function analysis summarized from maize work | Functional dissection summarized in discussion | Supports fine-grained annotation of VP1 as a modular transcriptional regulator with separable activation and repression activities | Suzuki et al., 2001, *The Plant Journal*, https://doi.org/10.1046/j.1365-313x.2001.01165.x | (pqac-00000004, pqac-00000009) |
| Molecular/regulatory network | **ZmABI19** directly binds the **Vp1** promoter; ABA enhances this transactivation, and **Vp1** expression begins at 3–5 DAP and peaks around 10 DAP, overlapping with scutellum expression | Maize early seed development; embryo/scutellum | ChIP-seq, dual-luciferase, expression profiling | Places VP1 in an upstream ABA-responsive grain-filling/embryogenesis transcription network rather than as an isolated regulator | Yang et al., 2021, *The Plant Cell*, https://doi.org/10.1093/plcell/koaa008 | (pqac-00000003, pqac-00000007) |
| Molecular/regulatory network | ZmABI19 recognizes G-box4 in the **Vp1** promoter, whereas it binds RY motifs in many other targets | Maize promoter regulation | ChIP-seq and promoter-element analysis | Consistent with B3/seed-factor regulatory logic and with VP1 participation in ABA-coupled LAFL-like seed developmental circuits | Yang et al., 2021, *The Plant Cell*, https://doi.org/10.1093/plcell/koaa008 | (pqac-00000007) |
| Genetic/omics | In maize vivipary datasets, **vp1** is classified as a plant-specific transcription factor acting in ABA signaling; vivipary mutants show downregulation of **NCED4**, upregulation of **GA3ox**, and perturbation of the PYL-ABI1-SnRK2-ABI3 core module | Maize vivipary mutants, seed transcriptomes/metabolomes | Multi-omics comparison across seven vivipary mutants | Reinforces current systems-level view that VP1 functions within the ABA–GA antagonism network controlling dormancy vs germination | Wang et al., 2021, *Plants*, https://doi.org/10.3390/plants10112437 | (pqac-00000006) |


*Table: This table summarizes functional annotation evidence for maize viviparous-1 (VP1; UniProt P26307), covering domains, molecular functions, target genes, regulatory interactions, and mutant/transgenic phenotypes. It is restricted to findings directly supported by the cited context IDs from the preceding evidence collection.*