OST1 (SRK2E/SnRK2.6) is an ABA-activated serine/threonine protein kinase of the plant-specific subclass III SnRK2 family (SNF1-related kinase 2) in Arabidopsis thaliana. It is a central positive regulator of abscisic acid (ABA) signaling, most prominently in stomatal guard cells, where it triggers stomatal closure in response to drought, low atmospheric humidity, darkness, elevated CO2, reactive oxygen species, and pathogen-associated molecular patterns. In the resting state OST1 is held inactive by group A type-2C protein phosphatases (ABI1, ABI2, PP2CA/AHG3, HAB1); upon ABA perception, PYR/PYL/RCAR receptors inhibit these phosphatases, permitting RAF-like kinases to initiate OST1 activation-loop phosphorylation. Activated OST1 can then phosphorylate other SnRK2 molecules, amplifying the response; release from PP2C inhibition alone does not establish self-reactivation of a dephosphorylated kinase. Activated OST1 phosphorylates and activates the guard-cell slow-type anion channel SLAC1, phosphorylates the K+ channel KAT1 and the NADPH oxidase RBOHF (driving ROS production), and phosphorylates downstream transcription factors of the AREB/ABF bZIP and AKS bHLH families to reprogram ABA-responsive gene expression. OST1 is expressed in guard cells and vascular tissue but is broadly present, and acts in the cytoplasm/cytosol, at the plasma membrane (where SLAC1 resides), and in the nucleus (where it interacts with AREB1 and MAPKKK18). Beyond stomatal control, OST1 confers drought and osmotic-stress tolerance and influences primary metabolism, including sucrose synthesis, fatty-acid desaturation and seed oil accumulation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004672 protein kinase activity | IEA GO_REF:0000120 | MODIFY | Summary: OST1 is a bona fide protein kinase (EC 2.7.11.1). This IEA term is correct, though more general than the experimentally established serine/threonine kinase activity. Reason: The catalytic claim is correct but general. Direct substrate phosphorylation establishes protein serine/threonine kinase activity (GO:0004674), already present in this review, as the supported specific replacement. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:12468729 In-gel assays indicated that OST1 is an ABA-activated protein kinase related to the Vicia faba ABA-activated protein kinase (AAPK). |
| GO:0004674 protein serine/threonine kinase activity | IEA GO_REF:0000003 | ACCEPT | Summary: OST1/SnRK2.6 is a serine/threonine protein kinase that autophosphorylates and phosphorylates Ser/Thr residues of substrates such as SLAC1, RBOHF and AREB/ABF transcription factors. This is the core molecular function. Reason: Strongly supported by enzymatic assays and catalytic-activity curation (EC 2.7.11.1); also the IBA term assigned at GO_Central for this family. Supporting Evidence: PMID:19955427 the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. PMID:12514244 the p44 is encoded by a SnRK2-type protein kinase gene, SRK2E. file:ARATH/OST1/OST1-deep-research-falcon.md OST1/SRK2E/SnRK2.6 is an ABA-activated Ser/Thr protein kinase that transfers phosphate from ATP to serine/threonine residues on downstream effectors in ABA, osmotic-stress, and guard-cell signaling pathways; PP2C phosphatases antagonize this by dephosphorylation |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: As an active protein kinase, OST1 binds ATP; UniProt annotates a glycine-rich ATP-binding loop (residues 27-35) and an invariant Lys-50, with mutagenesis (K50N) abolishing kinase activity. Reason: Standard, well-supported molecular function for an ATP-dependent kinase; ATP-binding residues are defined structurally and by mutagenesis. Supporting Evidence: PMID:19955427 the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. file:ARATH/OST1/OST1-deep-research-falcon.md OST1/SRK2E/SnRK2.6 is an ABA-activated Ser/Thr protein kinase that transfers phosphate from ATP to serine/threonine residues on downstream effectors in ABA, osmotic-stress, and guard-cell signaling pathways; PP2C phosphatases antagonize this by dephosphorylation |
| GO:0005634 nucleus | IEA GO_REF:0000120 | ACCEPT | Summary: OST1 localizes to the nucleus, where it co-localizes/interacts with the AREB1 transcription factor and associates with MAPKKK18. Nuclear localization is supported by direct experimental evidence. Reason: Consistent with experimental IDA nucleus annotations (PMID:19880399, PMID:26852793) and UniProt subcellular location. Supporting Evidence: PMID:19880399 SRK2D/E/I and AREB1 co-localize and interact in nuclei in planta. file:ARATH/OST1/OST1-deep-research-falcon.md OST1 is also implicated in nuclear-proximal functions through phosphorylation of transcriptional regulators and chromatin-associated proteins |
| GO:0009414 response to water deprivation | IEA GO_REF:0000117 | ACCEPT | Summary: OST1 is required for drought/water-stress tolerance; srk2e mutants are wilty and the srk2d/e/i triple mutant is strongly drought-hypersensitive. Reason: A core biological role of OST1, supported by multiple experimental IMP/IGI annotations of the same term. Supporting Evidence: PMID:19880399 srk2d srk2e srk2i (srk2d/e/i) triple mutants exhibit greatly reduced tolerance to drought stress and highly enhanced insensitivity to ABA. file:ARATH/OST1/OST1-deep-research-falcon.md OST1 is a core positive regulator of ABA-induced stomatal closure, drought and osmotic-stress responses, ROS production in guard cells, and broader stress signaling |
| GO:0009651 response to salt stress | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: SnRK2.6 is among the SnRK2 kinases activated by saline/hyperosmotic stress; salt also induces it. Reflects involvement in salt/osmotic stress responses. Reason: Supported but represents the broader osmotic/saline stress response shared across the SnRK2 family rather than the OST1-specific guard-cell ABA function. Supporting Evidence: PMID:15292193 Nine of the 10 SnRK2 were activated by hyperosmolarity induced by mannitol, as well as NaCl, indicating an important role of the SnRK2 family in osmotic signaling. |
| GO:0009737 response to abscisic acid | IEA GO_REF:0000117 | ACCEPT | Summary: OST1 is an ABA-activated kinase and central positive regulator of ABA responses. This is a core process. Reason: Extensively supported (also by experimental IDA/IMP annotations of the same term); ABA activation is a defining feature of OST1. Supporting Evidence: PMID:12468729 OST1 is an ABA-activated protein kinase related to the Vicia faba ABA-activated protein kinase (AAPK). |
| GO:0106310 protein serine kinase activity | IEA GO_REF:0000116 | ACCEPT | Summary: OST1 phosphorylates serine residues of its substrates (e.g. AtrbohF Ser13/Ser174, SLAC1). This Rhea-mapped MF is correct and matches experimental EXP annotations. Reason: Supported by catalytic-activity curation (Rhea RHEA:17989) and direct enzymatic assays; duplicate of experimentally supported GO:0106310 entries. Supporting Evidence: PMID:19716822 OST1 phosphorylates Ser13 and Ser174 on AtrbohF. |
| GO:0005515 protein binding | IPI PMID:16365038 The regulatory domain of SRK2E/OST1/SnRK2.6 interacts with A... | REMOVE | Summary: This IPI records the interaction of OST1 with the PP2C phosphatase ABI1 via its C-terminal Domain II. The interaction is real and important (ABI1 negatively regulates OST1), but the bare 'protein binding' term is uninformative. Reason: Bare protein binding (GO:0005515) is uninformative as a molecular function. The functionally meaningful aspect (PP2C/phosphatase binding) is captured by GO:0019903 protein phosphatase binding; the regulatory relationship is upstream control of OST1 rather than an OST1 molecular function. Supporting Evidence: PMID:16365038 the direct interaction between SRK2E/OST1 and ABI1 through Domain II plays a critical role in the control of stomatal closure. |
| GO:0005515 protein binding | IPI PMID:19716822 Phosphorylation of the Arabidopsis AtrbohF NADPH oxidase by ... | REMOVE | Summary: OST1 physically interacts with and phosphorylates the NADPH oxidase AtrbohF (RBOHF). The interaction is genuine, but 'protein binding' is uninformative; the meaningful function is OST1's kinase activity toward RBOHF. Reason: Bare protein binding is uninformative. The RBOHF interaction reflects a kinase-substrate relationship better represented by protein serine/threonine kinase activity (already annotated). Supporting Evidence: PMID:19716822 We also show that OST1 physically interacts with AtrbohF. |
| GO:0005515 protein binding | IPI PMID:19805022 Type 2C protein phosphatases directly regulate abscisic acid... | REMOVE | Summary: Interaction with group A PP2C phosphatases (e.g. ABI1/PP2CA), which directly dephosphorylate and inactivate OST1. Bare 'protein binding' is uninformative. Reason: Uninformative MF; the relevant specific function (protein phosphatase binding, GO:0019903) is annotated separately and represents upstream regulation of OST1. The original paper (Umezawa et al.) directly demonstrates the SnRK2-PP2C physical interaction, supporting replacement of bare protein binding by the specific protein phosphatase binding term. Supporting Evidence: PMID:19805022 Group A PP2Cs interacted physically with SnRK2s in various combinations, and efficiently inactivated ABA-activated SnRK2s via |
| GO:0005515 protein binding | IPI PMID:19874541 PYR/PYL/RCAR family members are major in-vivo ABI1 protein p... | REMOVE | Summary: Records OST1 interaction with ABI1 in the context of PYR/PYL/RCAR-PP2C proteomics. Bare 'protein binding' is uninformative. Reason: Uninformative MF term; captured more specifically by protein phosphatase binding (GO:0019903) and reflecting upstream regulation. The original paper (Nishimura et al.) demonstrates the specific ABI1-OST1 in planta interaction, justifying the more informative protein phosphatase binding term. Supporting Evidence: PMID:19874541 ABI1 interacts with the ABA-signalling kinases OST1, SnRK2.2 and SnRK2.3 in plants. |
| GO:0005515 protein binding | IPI PMID:19898420 A gate-latch-lock mechanism for hormone signalling by abscis... | REMOVE | Summary: This paper (Melcher et al., gate-latch-lock structural study) reports the PYL2-HAB1 structure and uses a SnRK2.6 activation-loop phosphopeptide as a HAB1 substrate; it establishes that SnRK2.6 is a PP2C substrate rather than directly demonstrating an OST1-HAB1 protein-protein binding event. Bare 'protein binding' is uninformative. Reason: Bare protein binding (GO:0005515) is uninformative per curation guidelines. The original reference was reviewed; it demonstrates the SnRK2.6/PP2C substrate relationship (the kinase activation loop is a natural HAB1 substrate) rather than an OST1-HAB1 binding assay per se. The meaningful kinase-phosphatase relationship is better captured by protein phosphatase binding (GO:0019903) and the kinase activity terms. Supporting Evidence: PMID:19898420 SnRK2.6 is a natural substrate of PP2C and phosphorylation at S175 is required for SnRK2.6 kinase activation and its role in ABA signaling |
| GO:0005515 protein binding | IPI PMID:19924127 In vitro reconstitution of an abscisic acid signalling pathw... | REMOVE | Summary: From in-vitro reconstitution of the ABA pathway, recording OST1 interactions with receptor/PP2C components (e.g. ABI1, HAB1, ABF2). Bare 'protein binding' is uninformative. Reason: Uninformative MF; the specific interactions are better captured by protein phosphatase binding (GO:0019903) and the kinase activity toward ABF transcription factors. The original paper (Fujii et al.) reconstitutes the pathway and shows the SnRK2-PP2C physical interaction directly. Supporting Evidence: PMID:19924127 the SnRK2 kinases are kept inactive by the PP2Cs through physical interaction and dephosphorylation. |
| GO:0005515 protein binding | IPI PMID:19955405 Activity of guard cell anion channel SLAC1 is controlled by ... | REMOVE | Summary: Split-YFP interactions of OST1 with the SLAC1 anion channel and ABI1. Bare 'protein binding' is uninformative; the SLAC1 relationship reflects OST1 kinase/channel-regulator activity. Reason: Uninformative MF. The SLAC1 interaction is functionally captured by ion channel regulator activity (GO:0099106) and kinase activity; the ABI1 interaction by protein phosphatase binding (GO:0019903). Supporting Evidence: PMID:19955405 we identified OST1 as an interaction partner of SLAC1 and ABI1. |
| GO:0005515 protein binding | IPI PMID:19955427 A protein kinase-phosphatase pair interacts with an ion chan... | REMOVE | Summary: OST1 interacts with SLAC1 and PP2CA among others. Bare 'protein binding' is uninformative; specific functions are captured elsewhere. Reason: Uninformative MF; SLAC1 interaction is captured by ion channel regulator activity (GO:0099106) and PP2CA by protein phosphatase binding (GO:0019903), both from this same paper. Supporting Evidence: PMID:19955427 the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. |
| GO:0005515 protein binding | IPI PMID:20385816 Guard cell anion channel SLAC1 is regulated by CDPK protein ... | REMOVE | Summary: Interaction with SLAC1 in the context of CDPK regulation of the anion channel. Bare 'protein binding' is uninformative. Reason: Uninformative MF; SLAC1 regulation is captured by ion channel regulator activity (GO:0099106) and kinase activity. Supporting Evidence: PMID:19955427 the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. |
| GO:0005515 protein binding | IPI PMID:20729862 Identification and mechanism of ABA receptor antagonism. | REMOVE | Summary: PP2C/ABA-receptor antagonism structural study (Melcher et al., pyrabactin complexes). The paper itself describes the PP2C-SnRK2 physical interaction. Bare 'protein binding' is uninformative. Reason: Bare protein binding (GO:0005515) is uninformative per curation guidelines. The original reference was reviewed; it focuses on PYL-PP2C complexes but explicitly states the PP2C-SnRK2 binding/inactivation relationship, which is captured more specifically by protein phosphatase binding (GO:0019903) and represents upstream regulation. Supporting Evidence: PMID:20729862 these PP2Cs bind and inactivate subfamily 2 members of SNF1-related kinases (SnRK2 kinases) by dephosphorylating serine and threonine residues in their activation loop |
| GO:0005515 protein binding | IPI PMID:23290725 Protein conformation ensembles monitored by HDX reveal a str... | REMOVE | Summary: HDX-monitored interaction of the SnRK2.6/SnRK2.3 kinases with the PP2C HAB1. Bare 'protein binding' is uninformative. Reason: Uninformative MF; the PP2C interaction is captured by protein phosphatase binding (GO:0019903) and reflects upstream regulation of OST1. The original paper (Belda-Palazon/HDX study) directly probes the SnRK2.6-HAB1 complex and maps the kinase region responsible for phosphatase binding. Supporting Evidence: PMID:23290725 the function of the Ξ±G helix is primarily phosphatase binding |
| GO:0005515 protein binding | IPI PMID:25599916 A molecular pathway for COβ response in Arabidopsis guard ce... | REMOVE | Summary: Interaction with the CO2-signaling kinase HT1 and with SLAC1 within the guard-cell CO2 response pathway. Bare 'protein binding' is uninformative. Reason: Uninformative MF; the SLAC1 relationship is captured by ion channel regulator activity (GO:0099106) and the broader CO2 response by cellular response to carbon dioxide (GO:0071244). Supporting Evidence: PMID:30361234 OST1 is then thought to activate SLAC1 via phosphorylation to initiate stomatal closure. |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: High-throughput phytohormone protein-network interaction (with EDL2). Bare 'protein binding' is uninformative and the interaction is not functionally characterized for OST1. Reason: Uninformative MF from a large-scale interactome screen; does not define an OST1 molecular function. Supporting Evidence: PMID:32612234 Extensive signal integration by the phytohormone protein network. |
| GO:0005515 protein binding | IPI PMID:41417897 MAP4K1 and MAP4K2 regulate ABA-induced and Ca(2+)-mediated s... | REMOVE | Summary: Interaction with the upstream MAP4K kinases that regulate ABA/Ca2+-mediated stomatal closure. Bare 'protein binding' is uninformative. Reason: Uninformative MF; reflects an upstream kinase-cascade interaction rather than an OST1 molecular function. Supporting Evidence: PMID:41417897 MAP4K1 and MAP4K2 regulate ABA-induced and Ca(2+)-mediated stomatal closure in Arabidopsis. |
| GO:0005829 cytosol | IDA PMID:41417897 MAP4K1 and MAP4K2 regulate ABA-induced and Ca(2+)-mediated s... | ACCEPT | Summary: OST1 is localized to the cytosol, consistent with its action on cytoplasmic substrates and at the plasma-membrane-associated SLAC1 channel. Directly observed. Reason: Direct experimental localization; consistent with other IDA cytoplasm annotations (PMID:19880399). Contradicts the older RCA NOT-cytosol prediction. Supporting Evidence: PMID:41417897 MAP4K1 and MAP4K2 regulate ABA-induced and Ca(2+)-mediated stomatal closure in Arabidopsis. |
| GO:0099106 ion channel regulator activity | IDA PMID:19955427 A protein kinase-phosphatase pair interacts with an ion chan... | ACCEPT | Summary: OST1 activates the guard-cell slow anion channel SLAC1 by phosphorylation, directly regulating channel activity. This is an informative molecular function central to stomatal closure. Reason: Directly demonstrated activation of SLAC1 anion-channel currents upon OST1 coexpression; an informative MF that captures OST1's regulation of an ion channel. Supporting Evidence: PMID:19955427 the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. file:ARATH/OST1/OST1-deep-research-falcon.md OST1 interacts with SLAC1 and activates it via phosphorylation, linking ABA signaling to anion efflux and stomatal closure |
| GO:0042802 identical protein binding | IPI PMID:19955427 A protein kinase-phosphatase pair interacts with an ion chan... | UNDECIDED | Summary: Curator-reported OST1 self-interaction remains unverified in the accessible text of the cited experiment. Reason: The cached abstract does not resolve the self-interaction assay, and a stable homodimer is not required by the definition of identical protein binding. Lack of an established stable dimer therefore does not justify the earlier over-annotation verdict. New evidence for intermolecular SnRK2 phosphorylation is compatible with transient encounters but does not independently validate this specific binding assay. Supporting Evidence: |
| GO:0042802 identical protein binding | IPI PMID:22908257 FERONIA receptor kinase pathway suppresses abscisic acid sig... | UNDECIDED | Summary: Curator-reported OST1 self-interaction remains unverified in the accessible text of the cited experiment. Reason: The cached abstract does not resolve the self-interaction assay, and a stable homodimer is not required by the definition of identical protein binding. Lack of an established stable dimer therefore does not justify the earlier over-annotation verdict. New evidence for intermolecular SnRK2 phosphorylation is compatible with transient encounters but does not independently validate this specific binding assay. Supporting Evidence: |
| GO:0106310 protein serine kinase activity | EXP PMID:12468729 Arabidopsis OST1 protein kinase mediates the regulation of s... | ACCEPT | Summary: In-gel kinase assays demonstrate OST1 ABA-activated protein kinase activity. Core molecular function. Reason: Direct experimental evidence of kinase activity; serine-directed phosphorylation established across the literature. Supporting Evidence: PMID:12468729 In-gel assays indicated that OST1 is an ABA-activated protein kinase related to the Vicia faba ABA-activated protein kinase (AAPK). |
| GO:0106310 protein serine kinase activity | EXP PMID:12514244 ABA-activated SnRK2 protein kinase is required for dehydrati... | ACCEPT | Summary: SRK2E/p44 is an ABA- and humidity-activated SnRK2 protein kinase. Core molecular function. Reason: Direct experimental identification of SRK2E as an ABA-activated protein kinase. Supporting Evidence: PMID:12514244 the p44 is encoded by a SnRK2-type protein kinase gene, SRK2E. |
| GO:0106310 protein serine kinase activity | EXP PMID:19955427 A protein kinase-phosphatase pair interacts with an ion chan... | ACCEPT | Summary: OST1 phosphorylates SLAC1 to activate it; serine kinase activity directly demonstrated. Core molecular function. Reason: Direct experimental phosphorylation of a substrate (SLAC1). Supporting Evidence: PMID:19955427 the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. |
| GO:0106310 protein serine kinase activity | EXP PMID:26943172 Type One Protein Phosphatase 1 and Its Regulatory Protein In... | ACCEPT | Summary: OST1 kinase activity and its regulation by TOPP1/PP1 were assayed. Core molecular function. Reason: Direct experimental measurement of OST1 catalytic activity. Supporting Evidence: PMID:26943172 Type One Protein Phosphatase 1 and Its Regulatory Protein Inhibitor 2 Negatively Regulate ABA Signaling. |
| GO:0106310 protein serine kinase activity | EXP PMID:30361234 The Receptor-like Pseudokinase GHR1 Is Required for Stomatal... | ACCEPT | Summary: OST1 catalytic activity and autophosphorylation assayed in the GHR1/stomatal-closure study. Core molecular function. Reason: Direct experimental evidence of kinase/autophosphorylation activity. Supporting Evidence: PMID:30361234 OST1 is then thought to activate SLAC1 via phosphorylation to initiate stomatal closure. |
| GO:0005515 protein binding | IPI PMID:37514328 Arabidopsis Protein Phosphatase PIA1 Impairs Plant Drought T... | REMOVE | Summary: Interaction with the PP2C-like phosphatase PIA1, a negative regulator of ABA signaling. Bare 'protein binding' is uninformative. Reason: Uninformative MF; phosphatase interaction better captured by protein phosphatase binding (GO:0019903) and reflecting upstream regulation. Supporting Evidence: PMID:37514328 Arabidopsis Protein Phosphatase PIA1 Impairs Plant Drought Tolerance by Serving as a Common Negative Regulator in ABA Signaling Pathway. |
| GO:0005515 protein binding | IPI PMID:37226855 Cell type-specific proteomics uncovers a RAF15-SnRK2.6/OST1 ... | REMOVE | Summary: Interaction with the upstream Raf-like kinase RAF15 in a guard-cell RAF15-SnRK2.6/OST1 cascade. Bare 'protein binding' is uninformative. Reason: Uninformative MF; reflects an upstream kinase-cascade interaction rather than an OST1 molecular function. Supporting Evidence: PMID:37226855 a RAF15-SnRK2.6/OST1 kinase cascade in guard cells. |
| GO:0005515 protein binding | IPI PMID:27227462 Inhibition of the Arabidopsis bHLH transcription factor by m... | REMOVE | Summary: OST1 interacts with and phosphorylates the bHLH transcription factor AKS1, causing its monomerization. Bare 'protein binding' is uninformative; this is a kinase-substrate relationship. Reason: Uninformative MF; the AKS1 relationship is a substrate of OST1 kinase activity (already annotated as protein serine/threonine kinase activity). Supporting Evidence: PMID:27227462 Inhibition of the Arabidopsis bHLH transcription factor by monomerization through abscisic acid-induced phosphorylation. |
| GO:0005515 protein binding | IPI PMID:28438792 Reconstitution of Abscisic Acid Signaling from the Receptor ... | REMOVE | Summary: OST1 interacts with/phosphorylates AKS1 bHLH transcription factors in a reconstituted ABA-to-DNA signaling pathway. Bare 'protein binding' is uninformative. Reason: Uninformative MF; reflects a kinase-substrate relationship captured by protein serine/threonine kinase activity. Supporting Evidence: PMID:28438792 Reconstitution of Abscisic Acid Signaling from the Receptor to DNA via bHLH Transcription Factors. |
| GO:0005515 protein binding | IPI PMID:31699848 Two SnRK2-Interacting Calcium Sensor Isoforms Negatively Reg... | REMOVE | Summary: Interaction with SnRK2-interacting calcium sensor (SCS) isoforms that negatively regulate OST1/SnRK2 activity. Bare 'protein binding' is uninformative. Reason: Uninformative MF; reflects upstream/regulatory interaction rather than an OST1 molecular function. Supporting Evidence: PMID:31699848 Two SnRK2-Interacting Calcium Sensor Isoforms Negatively Regulate SnRK2 Activity by Different Mechanisms. |
| GO:0005886 plasma membrane | HDA PMID:28887381 Global Analysis of Membrane-associated Protein Oligomerizati... | ACCEPT | Summary: OST1 acts at the plasma membrane when complexed with its channel substrate SLAC1. Reason: The high-throughput localization is corroborated by the independent OST1-SLAC1 BiFC experiment in PMID:19955405, which places the interacting kinase-channel complex exclusively at the plasma membrane. This transient site of kinase action is relevant to the core SLAC1 activation function even though OST1 also has soluble cytoplasmic and nuclear pools. Supporting Evidence: PMID:19955405 YFP-fluorescence complementation was observed at the level of the plasma membrane exclusively |
| GO:0009737 response to abscisic acid | IMP PMID:30361234 The Receptor-like Pseudokinase GHR1 Is Required for Stomatal... | ACCEPT | Summary: ost1 mutants show reduced ABA-triggered stomatal closure, confirming involvement in the ABA response. Core process. Reason: Mutant phenotype directly demonstrates OST1's requirement for the ABA response. Supporting Evidence: PMID:30361234 ABA binding-induced conformational changes in the PYR/RCAR receptors lead to the inhibition of PP2Cs, which allows the activation of the protein kinase OST1 |
| GO:0071244 cellular response to carbon dioxide | IMP PMID:30361234 The Receptor-like Pseudokinase GHR1 Is Required for Stomatal... | ACCEPT | Summary: ost1 mutants show delayed CO2-mediated stomatal closure, implicating OST1 in the guard-cell CO2 response (as a convergent downstream kinase activating SLAC1). Reason: Direct mutant evidence for involvement in CO2-induced stomatal closure. Supporting Evidence: PMID:30361234 OST1 is then thought to activate SLAC1 via phosphorylation to initiate stomatal closure |
| GO:0071485 cellular response to absence of light | IMP PMID:30361234 The Receptor-like Pseudokinase GHR1 Is Required for Stomatal... | ACCEPT | Summary: ost1 mutants show delayed darkness-induced stomatal closure, implicating OST1 in the response to darkness/absence of light in guard cells. Reason: Direct mutant evidence for involvement in darkness-induced stomatal closure. Supporting Evidence: PMID:30361234 GHR1 is required for stomatal responses to apoplastic reactive oxygen species, abscisic acid, high CO 2 concentrations, and diurnal light/dark transitions. |
| GO:0090333 regulation of stomatal closure | IMP PMID:30361234 The Receptor-like Pseudokinase GHR1 Is Required for Stomatal... | ACCEPT | Summary: OST1 is a central positive regulator of stomatal closure across multiple stimuli (ABA, CO2, darkness, ROS). This is the core biological process. Reason: Strong mutant evidence; OST1/SLAC1 define the core pathway for rapid stomatal closure. Supporting Evidence: PMID:30361234 Genetic studies have established that SLAC1 and OST1 define the core pathway regulating rapid stomatal responses to most closure-inducing cues. file:ARATH/OST1/OST1-deep-research-falcon.md OST1 is a core positive regulator of ABA-induced stomatal closure, drought and osmotic-stress responses, ROS production in guard cells, and broader stress signaling |
| GO:0005515 protein binding | IPI PMID:22730405 A plasma membrane receptor kinase, GHR1, mediates abscisic a... | REMOVE | Summary: Interaction with the PP2C ABI2 (in the GHR1 study). Bare 'protein binding' is uninformative. Reason: Uninformative MF; phosphatase interaction captured by protein phosphatase binding (GO:0019903) and reflecting upstream negative regulation. Supporting Evidence: PMID:22730405 A plasma membrane receptor kinase, GHR1, mediates abscisic acid- and hydrogen peroxide-regulated stomatal movement in Arabidopsis. |
| GO:0005737 cytoplasm | ISM GO_REF:0000122 | ACCEPT | Summary: Predicted (AtSubP) cytoplasmic localization, consistent with experimental IDA cytoplasm/cytosol evidence. Reason: Sequence-based prediction concordant with experimental IDA cytoplasm (PMID:19880399) and cytosol (PMID:41417897) annotations. Supporting Evidence: PMID:19880399 SRK2D/E/I and AREB1 co-localize and interact in nuclei in planta. |
| GO:0005515 protein binding | IPI PMID:26175513 Identification of Open Stomata1-Interacting Proteins Reveals... | REMOVE | Summary: OST1 interactome study identifying interactions with other SnRK2s and type 2A protein phosphatases (PP2A subunits). Bare 'protein binding' is uninformative. Reason: Uninformative MF from an interactome screen; the phosphatase interactions are better captured by protein phosphatase binding (GO:0019903). Supporting Evidence: PMID:26175513 Identification of Open Stomata1-Interacting Proteins Reveals Interactions with Sucrose Non-fermenting1-Related Protein Kinases2 and with Type 2A Protein Phosphatases That Function in Abscisic Acid Responses. |
| GO:0005515 protein binding | IPI PMID:26852793 Regulation of Arabidopsis MAPKKK18 by ABI1 and SnRK2, compon... | REMOVE | Summary: OST1 associates with MAPKKK18 in the nucleus and contributes to its regulation. Bare 'protein binding' is uninformative; this reflects a kinase-substrate/regulatory relationship. Reason: Uninformative MF; the MAPKKK18 relationship is captured by OST1 kinase activity and the process positive regulation of the ABA signaling pathway. Supporting Evidence: PMID:26852793 MAPKKK18, an ABA-activated kinase, is regulated by the protein phosphatase type 2C (PP2C) ABI1 and the kinase SnRK2.6. |
| GO:0005634 nucleus | IDA PMID:26852793 Regulation of Arabidopsis MAPKKK18 by ABI1 and SnRK2, compon... | ACCEPT | Summary: OST1 associates with MAPKKK18 within the nucleus; direct observation of nuclear localization. Reason: Direct experimental nuclear localization; concordant with PMID:19880399 and UniProt subcellular location. Supporting Evidence: PMID:26852793 SnRK2.6 kinase also seems to be important for the regulation of MAPKKK18 function. |
| GO:0009789 positive regulation of abscisic acid-activated signaling pathway | IMP PMID:26443375 Arabidopsis ABA-Activated Kinase MAPKKK18 is Regulated by Pr... | ACCEPT | Summary: OST1 is a positive regulator of ABA signaling; it promotes MAPKKK18 activity upon ABA treatment, and ost1 disruption impairs ABA-induced MAPKKK18 activation. Core regulatory role. Reason: Mutant evidence (impaired MKKK18 induction in ost1) supports a positive-regulatory role in the ABA signaling pathway, the defining function of subclass III SnRK2s. Supporting Evidence: PMID:26443375 Arabidopsis ABA-Activated Kinase MAPKKK18 is Regulated by Protein Phosphatase 2C ABI1 and the Ubiquitin-Proteasome Pathway. PMID:22090030 Subclass III SnRK2s (SnRK2.6/2.3/2.2) are the key positive regulators of abscisic acid (ABA) signal transduction in Arabidopsis thaliana. |
| GO:1902456 regulation of stomatal opening | IMP PMID:23766366 Calcium-dependent and -independent stomatal signaling networ... | KEEP AS NON CORE | Summary: OST1 contributes to the guard-cell signaling network controlling stomatal aperture; ABA acting through OST1 inhibits light-induced stomatal opening. Reason: Supported as part of the stomatal-aperture regulatory network, but OST1's core, best-characterized role is promotion of stomatal CLOSURE; its effect on opening is via ABA inhibition of opening and is secondary. Supporting Evidence: PMID:12468729 These recessive ost1 mutations disrupted ABA induction of stomatal closure as well as ABA inhibition of light-induced stomatal opening. |
| GO:0046777 protein autophosphorylation | IDA PMID:22090030 Molecular mechanism for inhibition of a critical component i... | ACCEPT | Summary: OST1 autophosphorylation is observed, and activated OST1 can phosphorylate other OST1 molecules to amplify signaling. Reason: Retain the experimentally observed autophosphorylation. PMID:33911084 distinguishes this intermolecular amplification from initial activation: fully PP2C-inactivated SnRK2s require upstream RAF-mediated transphosphorylation. The older experiment does not establish that release from phosphatase inhibition alone reactivates an unphosphorylated kinase. Supporting Evidence: PMID:22090030 Activation of SnRK2s requires autophosphorylation. PMID:33911084 transphosphorylation by RAFs is required for the reactivation of SnRK2.2/2.3/2.6. |
| GO:0005829 cytosol | RCA NOT PMID:21166475 Analysis of the Arabidopsis cytosolic proteome highlights su... | REMOVE | Summary: A reviewed-computational-analysis (RCA) NOT-cytosol assignment derived from a cytosolic-proteome dataset (OST1 not recovered in the cytosolic fraction). This is contradicted by direct experimental IDA cytosol/cytoplasm localization. Reason: The negated cytosol call is an inference from absence in one proteomic dataset and is refuted by experimental IDA evidence that OST1 is cytosolic/cytoplasmic (PMID:41417897 IDA cytosol; PMID:19880399 IDA cytoplasm). The NOT annotation is misleading and should be removed. Supporting Evidence: PMID:41417897 MAP4K1 and MAP4K2 regulate ABA-induced and Ca(2+)-mediated stomatal closure in Arabidopsis. |
| GO:2000377 regulation of reactive oxygen species metabolic process | IMP PMID:15064385 Cytoplasmic alkalization precedes reactive oxygen species pr... | ACCEPT | Summary: OST1 acts upstream of ABA-induced ROS (H2O2) production in guard cells; ABA fails to elevate H2O2 in ost1-2, and OST1 phosphorylates the RBOHF NADPH oxidase. Supports a role in regulating ROS production. Reason: Mutant evidence places OST1 upstream of guard-cell ROS production, consistent with its phosphorylation of RBOHF (PMID:19716822). Supporting Evidence: PMID:15064385 ABA elevates H(2)O(2) production in wild-type and jar1-1 guard cells but not in ost1-2. PMID:12468729 OST1 acts in the interval between ABA perception and ROS production. file:ARATH/OST1/OST1-deep-research-falcon.md These phosphorylation events are linked to ROS production in guard cells and stomatal closure. |
| GO:0006970 response to osmotic stress | IGI PMID:21220313 Arabidopsis decuple mutant reveals the importance of SnRK2 k... | ACCEPT | Summary: OST1, with the broader SnRK2 family, is important for in-vivo osmotic-stress responses, demonstrated using a SnRK2 decuple mutant. OST1 is itself directly activated by osmotic stress. Reason: Supported by genetic and biochemical evidence; OST1 is directly activated by osmotic stress (consistent with the IDA annotation of the same term). Supporting Evidence: PMID:21220313 These results demonstrate critical functions of the SnRK2s in mediating osmotic stress signaling and tolerance. |
| GO:0019903 protein phosphatase binding | IPI PMID:19955427 A protein kinase-phosphatase pair interacts with an ion chan... | ACCEPT | Summary: OST1 physically interacts with the type 2C protein phosphatase PP2CA, which inhibits the kinase independently of phosphatase activity. An informative MF capturing the key regulatory PP2C binding. Reason: Direct interaction with a PP2C phosphatase is well documented (PP2CA, ABI1, ABI2, HAB1); this specific MF correctly replaces the generic protein-binding annotations for the phosphatase partners. Supporting Evidence: PMID:19955427 physical interaction with OSTI leading to inhibition of the kinase independently of phosphatase activity. file:ARATH/OST1/OST1-deep-research-falcon.md PP2CA inhibits SLAC1 and also physically interacts with OST1 to inhibit the kinase, indicating PP2C regulation can act at multiple nodes (OST1 and channel). |
| GO:0005985 sucrose metabolic process | IMP PMID:20200070 The protein kinase SnRK2.6 mediates the regulation of sucros... | KEEP AS NON CORE | Summary: SnRK2.6 overexpression increases sucrose synthesis in leaves, implicating it in regulation of sucrose/primary metabolism. A pleiotropic metabolic effect of a broadly expressed kinase. Reason: Supported by overexpression/knockout phenotypes but peripheral to OST1's core guard-cell ABA-signaling function. Supporting Evidence: PMID:20200070 its overexpression increased Suc synthesis and fatty acid desaturation in the leaves. |
| GO:0006636 unsaturated fatty acid biosynthetic process | IMP PMID:20200070 The protein kinase SnRK2.6 mediates the regulation of sucros... | KEEP AS NON CORE | Summary: SnRK2.6 overexpression increases fatty-acid desaturation in leaves, implicating it in unsaturated fatty acid biosynthesis. Pleiotropic metabolic effect. Reason: Supported but peripheral to OST1's core ABA/stomatal function. Supporting Evidence: PMID:20200070 its overexpression increased Suc synthesis and fatty acid desaturation in the leaves. |
| GO:0009737 response to abscisic acid | IMP PMID:20200070 The protein kinase SnRK2.6 mediates the regulation of sucros... | ACCEPT | Summary: SnRK2.6 confers ABA hypersensitivity during seedling growth, consistent with its positive role in ABA responses. Core process (duplicate term). Reason: Supports the ABA response role; duplicate of the well-supported response to abscisic acid annotation. Supporting Evidence: PMID:20200070 this kinase confers ABA hypersensitivity during seedling growth. |
| GO:0019432 triglyceride biosynthetic process | IMP PMID:20200070 The protein kinase SnRK2.6 mediates the regulation of sucros... | KEEP AS NON CORE | Summary: snrk2.6 inactivation reduces seed oil (triacylglycerol) synthesis, implicating it in triglyceride biosynthesis. Pleiotropic metabolic effect. Reason: Supported by knockout phenotype (reduced seed oil) but peripheral to OST1's core guard-cell ABA function. Supporting Evidence: PMID:20200070 Inactivation of this gene reduced oil synthesis in Arabidopsis (Arabidopsis thaliana) seeds. |
| GO:0048366 leaf development | IMP PMID:20200070 The protein kinase SnRK2.6 mediates the regulation of sucros... | MARK AS OVER ANNOTATED | Summary: SnRK2.6 overexpression affects plant growth/seed production via altered metabolism; the leaf development link is indirect. Reason: A loose, indirect growth/metabolism phenotype from overexpression; not a specific developmental function of OST1 and likely an over-annotation. Supporting Evidence: PMID:20200070 the metabolic alterations in the SnRK2.6 overexpressors were accompanied by amelioration of those physiological processes that require high levels of carbon and energy input, such as plant growth and seed production. |
| GO:0005634 nucleus | IDA PMID:19880399 Three SnRK2 protein kinases are the main positive regulators... | ACCEPT | Summary: SRK2E co-localizes and interacts with AREB1 in nuclei in planta; direct evidence of nuclear localization. Reason: Direct experimental nuclear localization; OST1 phosphorylates AREB/ABF transcription factors in the nucleus. Supporting Evidence: PMID:19880399 SRK2D/E/I and AREB1 co-localize and interact in nuclei in planta. |
| GO:0005737 cytoplasm | IDA PMID:19880399 Three SnRK2 protein kinases are the main positive regulators... | ACCEPT | Summary: OST1/SRK2E shows cytoplasmic as well as nuclear localization; directly observed. Reason: Direct experimental cytoplasmic localization, concordant with cytosol IDA (PMID:41417897) and predicted cytoplasm. Supporting Evidence: PMID:19880399 SRK2D/E/I and AREB1 co-localize and interact in nuclei in planta. |
| GO:0009414 response to water deprivation | IGI PMID:19880399 Three SnRK2 protein kinases are the main positive regulators... | ACCEPT | Summary: Genetic interaction among SRK2D/E/I; the triple mutant has greatly reduced drought tolerance, establishing OST1's role in the water-deprivation response. Reason: Strong genetic evidence (triple-mutant drought hypersensitivity) for a core role in drought/water-stress tolerance. Supporting Evidence: PMID:19880399 srk2d srk2e srk2i (srk2d/e/i) triple mutants exhibit greatly reduced tolerance to drought stress and highly enhanced insensitivity to ABA. |
| GO:0010118 stomatal movement | IMP PMID:16959575 Plant stomata function in innate immunity against bacterial ... | ACCEPT | Summary: Guard-cell OST1 is required for PAMP-triggered stomatal closure during innate immunity; ost1 mutants are impaired in this stomatal response. Reason: Mutant evidence for OST1's involvement in stomatal movement; consistent with its central guard-cell role. Supporting Evidence: PMID:16959575 Stomatal guard cells of Arabidopsis perceive bacterial surface molecules, which requires the FLS2 receptor, production of nitric oxide, and the guard-cell-specific OST1 kinase. |
| GO:0042742 defense response to bacterium | IMP PMID:16959575 Plant stomata function in innate immunity against bacterial ... | KEEP AS NON CORE | Summary: OST1 is required for stomatal closure as a PAMP-triggered innate-immune response that restricts bacterial entry into the leaf. A genuine but specialized role downstream of OST1's stomatal-closure function. Reason: Supported by mutant evidence, but this defense role is a context-specific application of OST1's core stomatal-closure activity rather than a separate core function. Supporting Evidence: PMID:16959575 stomatal closure is part of a plant innate immune response to restrict bacterial invasion. |
| GO:0004672 protein kinase activity | IDA PMID:12468729 Arabidopsis OST1 protein kinase mediates the regulation of s... | MODIFY | Summary: In-gel kinase assays directly demonstrate OST1 protein kinase activity. Correct, though more general than serine/threonine kinase activity. Reason: The catalytic claim is correct but general. Direct substrate phosphorylation establishes protein serine/threonine kinase activity (GO:0004674), already present in this review, as the supported specific replacement. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:12468729 In-gel assays indicated that OST1 is an ABA-activated protein kinase related to the Vicia faba ABA-activated protein kinase (AAPK). |
| GO:0009414 response to water deprivation | IMP PMID:12047634 Use of infrared thermal imaging to isolate Arabidopsis mutan... | ACCEPT | Summary: ost1 mutants isolated by infrared thermography are defective in limiting transpiration/water loss under drought. Core role in the water-deprivation response. Reason: Mutant phenotype directly establishes OST1's requirement for drought-induced reduction of water loss. Supporting Evidence: PMID:12468729 we isolated two allelic Arabidopsis mutants (ost1-1 and ost1-2) impaired in the ability to limit their transpiration upon drought. |
| GO:0009414 response to water deprivation | IMP PMID:12514244 ABA-activated SnRK2 protein kinase is required for dehydrati... | ACCEPT | Summary: The srk2e mutant has a wilty phenotype due to loss of stomatal closure upon rapid humidity decrease, confirming a role in the water-stress response. Reason: Mutant phenotype (wilty, water loss) supports the core water-deprivation role. Supporting Evidence: PMID:12514244 The srk2e mutation resulted in a wilty phenotype mainly due to loss of stomatal closure in response to a rapid humidity decrease. |
| GO:0009414 response to water deprivation | IMP PMID:16682349 The identification of genes involved in the stomatal respons... | ACCEPT | Summary: The ost1-4 allele (G178Q) fails to close stomata when relative humidity decreases, supporting OST1's role in responses limiting water loss. Reason: Mutant evidence for OST1 in the stomatal response to reduced humidity/water stress. Supporting Evidence: PMID:16682349 The identification of genes involved in the stomatal response to reduced atmospheric relative humidity. |
| GO:0009737 response to abscisic acid | IMP PMID:12047634 Use of infrared thermal imaging to isolate Arabidopsis mutan... | ACCEPT | Summary: ost1 mutants are ABA-insensitive for stomatal regulation, establishing OST1's requirement for the ABA response. Core process (duplicate term). Reason: Mutant ABA-insensitivity supports the core ABA-response role. Supporting Evidence: PMID:12468729 These recessive ost1 mutations disrupted ABA induction of stomatal closure as well as ABA inhibition of light-induced stomatal opening. |
| GO:0009737 response to abscisic acid | IMP PMID:12514244 ABA-activated SnRK2 protein kinase is required for dehydrati... | ACCEPT | Summary: SRK2E is ABA-activated and required for ABA-inducible gene expression (rd22, rd29B); srk2e impairs the ABA response. Core process (duplicate). Reason: Mutant evidence (loss of ABA-inducible gene expression) supports the core ABA-response role. Supporting Evidence: PMID:12514244 ABA-inducible gene expression of rd22 and rd29B was suppressed in srk2e. |
| GO:0009737 response to abscisic acid | IMP PMID:15064385 Cytoplasmic alkalization precedes reactive oxygen species pr... | ACCEPT | Summary: ost1-2 guard cells fail to produce ABA-induced H2O2, confirming OST1's requirement in the ABA response. Core process (duplicate). Reason: Mutant evidence supports the core ABA-response role. Supporting Evidence: PMID:15064385 ABA elevates H(2)O(2) production in wild-type and jar1-1 guard cells but not in ost1-2. |
| GO:0009931 calcium-dependent protein serine/threonine kinase activity | ISS PMID:12468729 Arabidopsis OST1 protein kinase mediates the regulation of s... | REMOVE | Summary: OST1/SnRK2.6 is a calcium-INDEPENDENT kinase, not a calcium-dependent (CDPK-type) kinase. SnRK2s were explicitly characterized as calcium-independent. This ISS to a calcium-dependent kinase class is incorrect. Reason: Misannotation. SnRK2 kinases including SRK2E/OST1 are calcium-independent; assigning a calcium-dependent kinase activity conflates them with the distinct CDPK family. The cited paper does not establish calcium-dependence. Supporting Evidence: PMID:15292193 Several calcium-independent protein kinases were activated by hyperosmotic and saline stresses in Arabidopsis cell suspension. |
| GO:0010119 regulation of stomatal movement | IMP PMID:12047634 Use of infrared thermal imaging to isolate Arabidopsis mutan... | ACCEPT | Summary: ost1 mutants are defective in ABA regulation of stomatal aperture. Core process (general parent of regulation of stomatal closure). Reason: Mutant evidence for OST1 regulation of stomatal movement; a well-supported core role. Supporting Evidence: PMID:12468729 These recessive ost1 mutations disrupted ABA induction of stomatal closure as well as ABA inhibition of light-induced stomatal opening. |
| GO:0010119 regulation of stomatal movement | IMP PMID:12514244 ABA-activated SnRK2 protein kinase is required for dehydrati... | ACCEPT | Summary: srk2e impairs stomatal closure in response to humidity decrease, supporting regulation of stomatal movement. Core process (duplicate). Reason: Mutant evidence supports the core stomatal-regulation role. Supporting Evidence: PMID:12514244 The srk2e mutation resulted in a wilty phenotype mainly due to loss of stomatal closure in response to a rapid humidity decrease. |
| GO:0010119 regulation of stomatal movement | IMP PMID:15064385 Cytoplasmic alkalization precedes reactive oxygen species pr... | ACCEPT | Summary: ost1-2 is impaired in ABA-induced stomatal closure (H2O2-dependent), supporting regulation of stomatal movement. Core process (duplicate). Reason: Mutant evidence supports the core stomatal-regulation role. Supporting Evidence: PMID:15064385 the stomata of ost1-2 are insensitive to ABA but are able to close in response to MJ. |
| GO:0006970 response to osmotic stress | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | ACCEPT | Summary: SRK2E/SnRK2.6 is directly activated by hyperosmotic (mannitol) and saline stress in cells/seedlings, demonstrating involvement in the osmotic-stress response. Reason: Direct biochemical activation by osmotic stress; OST1 is activated by osmotic stress independently of ABA (Domain I). Supporting Evidence: PMID:15292193 Nine of the 10 SnRK2 were activated by hyperosmolarity induced by mannitol, as well as NaCl, indicating an important role of the SnRK2 family in osmotic signaling. file:ARATH/OST1/OST1-deep-research-falcon.md Yoshida et al. showed SRK2E/OST1 is activated in vivo by both ABA and osmotic stress |
| GO:0009651 response to salt stress | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | KEEP AS NON CORE | Summary: SRK2E is activated by NaCl (saline) stress, supporting involvement in the salt-stress response. Reason: Supported, but reflects the family-wide osmotic/saline activation rather than the OST1-specific guard-cell ABA function. Supporting Evidence: PMID:15292193 Nine of the 10 SnRK2 were activated by hyperosmolarity induced by mannitol, as well as NaCl. |
| GO:0009737 response to abscisic acid | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | ACCEPT | Summary: SRK2E is one of the SnRK2s directly activated by ABA, confirming involvement in the ABA response. Core process (duplicate). Reason: Direct biochemical ABA activation supports the core ABA-response role. Supporting Evidence: PMID:15292193 abscisic acid only activated five of the nine SnRK2. |
| GO:0016301 kinase activity | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | MODIFY | Summary: OST1 has kinase activity (activated by osmotic stress/ABA). This is the broadest kinase MF term, superseded by the specific protein serine/threonine kinase activity. Reason: The catalytic claim is correct but general. Direct substrate phosphorylation establishes protein serine/threonine kinase activity (GO:0004674), already present in this review, as the supported specific replacement. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:15292193 these non-MAPK protein kinases activated by hyperosmolarity in cell suspension were SnRK2 proteins. |
| GO:0004672 protein kinase activity | TAS PMID:12514244 ABA-activated SnRK2 protein kinase is required for dehydrati... | MODIFY | Summary: Traceable statement that SRK2E is an ABA-activated protein kinase. Correct but more general than the specific Ser/Thr kinase activity. Reason: The catalytic claim is correct but general. Direct substrate phosphorylation establishes protein serine/threonine kinase activity (GO:0004674), already present in this review, as the supported specific replacement. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:12514244 the p44 is encoded by a SnRK2-type protein kinase gene, SRK2E. |
| GO:0009738 abscisic acid-activated signaling pathway | TAS PMID:12514244 ABA-activated SnRK2 protein kinase is required for dehydrati... | ACCEPT | Summary: OST1/SRK2E is a core component of the ABA-activated signaling pathway, acting downstream of PYR/PYL-PP2C de-repression to phosphorylate effectors. Core process. Reason: Well-established central role in the ABA signaling pathway; defining function of subclass III SnRK2s. Supporting Evidence: PMID:12514244 SRK2E plays an important role in ABA signaling in response to water stress. PMID:22090030 Subclass III SnRK2s (SnRK2.6/2.3/2.2) are the key positive regulators of abscisic acid (ABA) signal transduction in Arabidopsis thaliana. file:ARATH/OST1/OST1-deep-research-falcon.md In the absence of ABA, PP2Cs inhibit SnRK2s; ABA perception relieves this inhibition, enabling kinase activation and phosphorylation of downstream targets. |
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Q: What is the full in-vivo guard-cell substrate repertoire of OST1, and which phosphorylation events are rate-limiting for rapid stomatal closure across different stimuli (ABA vs CO2 vs darkness vs ROS)?
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