id1 (INDETERMINATE1) — manual literature synthesis

No deep-research provider was available for this session; this summary was assembled by
hand from cached publications (publications/PMID_*.md) and PubMed metadata. Every
assertion carries its source.

Identity

• UniProt O65215 (TrEMBL, unreviewed), Zea mays, 436 aa, GeneID 541693,
  Gramene Zm00001eb047750. PE 2 (transcript level).
• Domain architecture: the plant-specific ID domain (IDD) with C2H2 (Z1), C2H2 (Z3),
  C2HC (Z2) and C2HC (Z4) zinc fingers (InterPro IPR031140 IDD1-16; Pfam PF22995,
  PF22992, PF22996, PF12874).
• Founding member of the IDD family PMID:16784536
• Grass orthologs: rice OsId1/Ehd2/RID1 (UniProt B1B534) and a sorghum ortholog form a
  group separate from other IDD genes; no clear Arabidopsis ortholog PMID:16784536.

Molecular function

• Sequence-specific DNA binding via the ID domain, in vitro (SAAB selection + EMSA,
  GST fusions) PMID:15020707. Consensus 5'-TTTGTCG/CT/CT/aT/aT-3'. Z2 and Z3 required; Z1 and Z4 (incl.
  the canonical C2H2 Z1) dispensable; binding zinc-dependent (EDTA/phenanthroline
  abolish it; data not shown).
• Other IDD proteins (VEG7, VEG9) recognise the same motif, so target specificity of ID1
  likely does not come from the DNA-binding domain itself PMID:15020707.
• Transcriptional activation has not been tested for maize ID1 in the cached literature;
  the rice ortholog activates transcription in yeast PMID:18774969.

Location

• Nuclear: immunolocalization with anti-ID1 antibody PMID:17307745 (abstract only cached).
• Expression confined to immature, non-photosynthetic leaf tissue; absent from mature
  blades and the shoot apical meristem PMID:17307745.

Biological role

• Loss of function causes extreme late flowering (more than twice the normal leaf
  number), aberrant flowers and frequently no ears PMID:21730358.
• Acts non-cell-autonomously from the leaf, regulating a transmissible floral signal
  PMID:9604934.
• Acts in the autonomous (photoperiod-independent) pathway: expression and protein level
  are unaffected by light/dark or circadian cues PMID:17307745.
• Acts upstream of the florigen gene ZCN8; ZCN8 transcript is >15-fold reduced in id1
  leaves. Because id1 and ZCN8 expression domains do not overlap (immature vs mature
  leaf), ZCN8 is unlikely to be a direct target PMID:21730358.
• id1 function associated with H3 hyperacetylation at ZCN7/ZCN8 PMID:26084920 (abstract).
• Expression profiling of id1 vs WT immature leaves identifies 55 differentially expressed
  genes including the dhurrinase-like Zmdhr1-3 PMID:17928372 (abstract), and carbohydrate
  partitioning differences in source leaves PMID:22791826.
• In rice, OsId1 is required for flowering under both SD and LD PMID:18774969.
• A 2026 preprint (PMID:42818387, bioRxiv, not cached) reports scATAC/snRNA-seq of id1
  leaves and candidate direct targets; not used as evidence here.

Open questions

• Direct in vivo targets of ID1; whether it activates or represses them.
• Whether ID1 has a role in photoperiod-dependent tropical maize/teosinte (unknown per
  PMID:21730358).