OST1 / SRK2E / SnRK2.6 (Arabidopsis thaliana, AT4G33950, UniProt Q940H6) — review notes

Identity and family

Core molecular function — ABA-activated Ser/Thr protein kinase

Biological processes

Regulators / interactors (mostly upstream regulation, not OST1 MF)

Subcellular location

Notes on specific annotation issues

Core function summary

  1. ABA-activated Ser/Thr protein kinase (protein serine/threonine kinase activity; EC 2.7.11.1; ATP binding) — autophosphorylates and phosphorylates downstream targets. Core.
  2. Positive regulator of the ABA-activated signaling pathway -> regulation of stomatal closure / response to water deprivation / drought tolerance. Core biological role.
  3. Activation of the guard-cell S-type anion channel SLAC1 (ion channel regulator activity) driving stomatal closure. Core.

Deep research synthesis (Falcon / Edison Scientific report, 2026-06-06)

Source: OST1-deep-research-falcon.md (provider: falcon). Used to corroborate and strengthen existing annotation decisions; no decisions were reversed. Key additional findings and provenance:

New/expanded biology in the report not yet annotatable as core OST1 GO terms (no verified GO ID; kept as context only, NOT added):
- Compartmentalized SnRK2 signaling: prolonged ABA drives N-glycosylation-dependent nucleus-to-peroxisome relocalization of SnRK2.2/2.3 (Lu 2024), but this is explicitly NOT yet assigned to OST1/SnRK2.6 — not annotated.
- Additional reported direct targets (review-synthesized, not primary-extracted): CNGC5/6/9/12, KAT1, QUAC1, PIP2;1, BRM, ICE1, PUB25/26, AtANN1. These remain candidate substrates; no new GO term added.
- PTM regulation of OST1: S-nitrosylation by NO negatively regulates OST1 (Yastreb 2024 review). Candidate suggested_question/experiment, not annotated.

No UNDECIDED actions were present; none required resolution. No NEW annotation added (no clearly missing function with a verifiable GO ID from existing GOA/UniProt). Status kept DRAFT.

PR #1417 review fix (catch-all PMID:22090030 evidence on protein-binding REMOVE entries)

The reviewer (ai4c-agent) flagged ~8 GO:0005515 (protein binding) REMOVE entries that
used PMID:22090030 as a single catch-all supported_by reference while each entry's
original_reference_id was a different paper. REMOVE actions are correct (bare protein
binding is uninformative per curation guidelines); only the evidence attribution was fixed.
For each of the 6 entries whose original paper is cached, the catch-all PMID:22090030
supporting_text was replaced with a verbatim quote from the actual original_reference_id:

Remaining PMID:22090030 occurrences in the file are legitimate (it is the actual
original_reference_id for GO:0046777 autophosphorylation, a properly attributed secondary
reference for GO:0009789, and a references-block entry) — not catch-all misattributions.
Validation: ✓ Valid (1 pre-existing unrelated plasma-membrane location warning).

2026-10-25 — ABA module member audit

Assessed all 80 existing annotation decisions and the evidence synthesis for the ABA module's kinase activation and output steps. The core kinase, ABA, stomatal and stress-response claims remain supported. The negated cytosol row is a NOT assertion, so its REMOVE does not contradict accepted positive localization. Broad kinase terms are refined to GO:0004674, matching the independently justified edits in open PR #5402. No CBL10 content was copied.

The previous description and core function conflated initiation with amplification. PMID:33911084 states "transphosphorylation by RAFs is required for the reactivation of SnRK2.2/2.3/2.6." PMID:31896774 establishes the MAP3K input after PP2C dephosphorylation and resulting SLAC1/transcriptional outputs. Both full texts were inspected. Autophosphorylation remains accepted, but as an observed reaction/amplification mechanism rather than sufficient autonomous reactivation. The two identical-protein-binding IPI rows are now UNDECIDED: neither accessible abstract resolves its self-association experiment, and lack of a stable dimer does not show that binding is over-annotated.

Research used existing provider reports/manual notes and cached primary literature. All rows retain explicit decisions; unresolved findings are UNDECIDED rather than inferred from missing text. Record-section backfill and targeted validation were run for this session.

The plasma-membrane localization is accepted as a core site of OST1-SLAC1 action: PMID:19955405 directly localizes the BiFC complex at that membrane. This corroborates the existing HDA localization and reconciles it with the channel-regulation core function.