SnRK2.2 (SRK2D; SNF1-related protein kinase 2.2, At3g50500) is a subclass III SnRK2 serine/threonine protein kinase of Arabidopsis thaliana and one of the three core positive transducers of abscisic acid (ABA) signaling, acting redundantly with SnRK2.3/SRK2I and SnRK2.6/OST1. The 362-residue protein consists of an N-terminal protein kinase domain and a short acidic C-terminal regulatory region. In the absence of ABA, clade A type 2C protein phosphatases (ABI1, ABI2, HAB1, PP2CA/AHG3, AHG1, HAI1) bind SnRK2.2 and dephosphorylate its activation loop, keeping it inactive. ABA-bound PYR/PYL/RCAR receptors inhibit these phosphatases, permitting upstream B2/B3 RAF kinases to initiate activation-loop phosphorylation. Activated SnRK2 molecules can then amplify the response by intermolecular phosphorylation. The type one protein phosphatase TOPP1 and its regulatory protein AtI-2 also bind SnRK2.2 and negatively regulate SnRK2-driven ABA-responsive transcription. SnRK2.2 is also activated by hyperosmotic and saline stress. Active SnRK2.2 phosphorylates the ABRE-binding bZIP transcription factors ABF1, ABF2/AREB1 and ABI5, the bHLH factor AKS1 and the ESCRT component FREE1, driving ABA-responsive gene expression in the nucleus and cytoplasm. SnRK2.2 is expressed in all tissues. With SnRK2.3 it is the main kinase mediating ABA control of seed dormancy, germination, seedling and root growth, proline accumulation and ABRE-dependent gene induction, whereas its contribution to stomatal closure is minor compared with OST1. Together with SnRK2.3 and OST1 it is required for drought and osmotic stress tolerance, seed development, and growth and fertility. In roots, SnRK2.2 acting in elongation-zone cortical cells is required for hydrotropism.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004672 protein kinase activity | IDA PMID:17307925 Identification of two protein kinases required for abscisic ... | MODIFY | Summary: In-gel kinase assays show that SnRK2.2 accounts for most of an ABA-induced 42-kD kinase activity that phosphorylates ABF2, ABI5 and ABF1 peptide fragments (Fujii et al. 2007). Reason: Protein kinase activity is correct but less specific than the evidence supports: SnRK2.2 is an EC 2.7.11.1 Ser/Thr kinase phosphorylating Ser/Thr sites of ABF/AREB bZIPs. Replace with protein serine/threonine kinase activity (GO:0004674), which the gene already carries by IBA and IEA. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:17307925 these data demonstrate that SnRK2.2 and SnRK2.3 have ABA-inducible kinase activity and together are likely to play a major role in phosphorylating and activating ABF2, ABI5, ABF1, and possibly other ABFs. PMID:17307925 The stronger band of kinase activity was at 42 kD, and this activity was reduced in all three of the mutants. snrk2.2 had a greater reduction in the 42-kD activity than did snrk2.3 |
| GO:0004672 protein kinase activity | IEA GO_REF:0000120 | MODIFY | Summary: Electronic protein kinase activity from the InterPro Ser/Thr kinase active-site signature (IPR008271) and ARBA. Reason: Correct but general; the same InterPro active-site signature specifically indicates Ser/Thr kinase activity, and experimental data support GO:0004674. Refine to protein serine/threonine kinase activity, consistent with the IDA row for this term. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: file:ARATH/SnRK2.2/SnRK2.2-uniprot.txt Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. PMID:17307925 these data demonstrate that SnRK2.2 and SnRK2.3 have ABA-inducible kinase activity and together are likely to play a major role in phosphorylating and activating ABF2, ABI5, ABF1, and possibly other ABFs. |
| GO:0004674 protein serine/threonine kinase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA placing protein serine/threonine kinase activity on the ancestral node of the SNF1/AMPK-related CAMK-like kinase clade that contains the SnRK2s. Reason: SnRK2.2 retains an intact kinase domain (active-site Asp-142, ATP-binding Lys-52) and is an ABA- and osmotic stress-activated Ser/Thr kinase that phosphorylates ABF/AREB/ABI5 bZIPs and AKS1. This is the core molecular function and the right level of specificity. Supporting Evidence: PMID:17307925 these data demonstrate that SnRK2.2 and SnRK2.3 have ABA-inducible kinase activity and together are likely to play a major role in phosphorylating and activating ABF2, ABI5, ABF1, and possibly other ABFs. PMID:28438792 Three ABA-responsive SnRK2s (SnRK2.2/SRK2D, SnRK2.3/SRK2I, and SnRK2.6/SRK2E/OST1) phosphorylated AKS1 in vitro file:ARATH/SnRK2.2/SnRK2.2-uniprot.txt Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. |
| GO:0004674 protein serine/threonine kinase activity | IEA GO_REF:0000003 | ACCEPT | Summary: EC 2.7.11.1 mapping to protein serine/threonine kinase activity. Reason: Consistent with experimental phosphorylation of Ser/Thr residues in ABF and AKS1 substrates; core MF. Supporting Evidence: PMID:17307925 these data demonstrate that SnRK2.2 and SnRK2.3 have ABA-inducible kinase activity and together are likely to play a major role in phosphorylating and activating ABF2, ABI5, ABF1, and possibly other ABFs. PMID:28438792 Three ABA-responsive SnRK2s (SnRK2.2/SRK2D, SnRK2.3/SRK2I, and SnRK2.6/SRK2E/OST1) phosphorylated AKS1 in vitro |
| GO:0005515 protein binding | IPI PMID:19407142 Abscisic acid inhibits type 2C protein phosphatases via the ... | MODIFY | Summary: Y2H interaction of SnRK2.2 with PP2CA/AHG3 and AHG1 (Park et al. 2009). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, ABI1, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. The WITH/FROM partner here is ABI1 (P49597), but the cached main text of this paper reports SnRK2.2 Y2H interaction with PP2CA/AHG3 (P49598) and AHG1 (Q9FLI3); the ABI1 entry may be a one-digit accession slip or may come from the supplementary figure, which is not cached (see source_defects). Either way the partner is a clade A PP2C and the replacement term holds. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19407142 we observe interaction of SnRK2.2 with PP2CA/AHG3 and AHG1 using the Y2H assay |
| GO:0005515 protein binding | IPI PMID:19407142 Abscisic acid inhibits type 2C protein phosphatases via the ... | MODIFY | Summary: Y2H interaction of SnRK2.2 with PP2CA/AHG3 and AHG1 (Park et al. 2009). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, AHG1, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19407142 we observe interaction of SnRK2.2 with PP2CA/AHG3 and AHG1 using the Y2H assay |
| GO:0005515 protein binding | IPI PMID:19805022 Type 2C protein phosphatases directly regulate abscisic acid... | MODIFY | Summary: Physical interaction of group A PP2Cs (here ABI2) with subclass III SnRK2s (Umezawa et al. 2009; abstract only in cache). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, ABI2, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19805022 Group A PP2Cs interacted physically with SnRK2s in various combinations, and efficiently inactivated ABA-activated SnRK2s via dephosphorylation of multiple Ser/Thr residues in the activation loop. |
| GO:0005515 protein binding | IPI PMID:19805022 Type 2C protein phosphatases directly regulate abscisic acid... | MODIFY | Summary: Physical interaction of group A PP2Cs (here ABI1) with subclass III SnRK2s (Umezawa et al. 2009; abstract only in cache). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, ABI1, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19805022 Group A PP2Cs interacted physically with SnRK2s in various combinations, and efficiently inactivated ABA-activated SnRK2s via dephosphorylation of multiple Ser/Thr residues in the activation loop. |
| GO:0005515 protein binding | IPI PMID:19805022 Type 2C protein phosphatases directly regulate abscisic acid... | MODIFY | Summary: Physical interaction of group A PP2Cs (here HAB1) with subclass III SnRK2s (Umezawa et al. 2009; abstract only in cache). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, HAB1, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19805022 Group A PP2Cs interacted physically with SnRK2s in various combinations, and efficiently inactivated ABA-activated SnRK2s via dephosphorylation of multiple Ser/Thr residues in the activation loop. |
| GO:0005515 protein binding | IPI PMID:19805022 Type 2C protein phosphatases directly regulate abscisic acid... | MODIFY | Summary: Physical interaction of group A PP2Cs (here AHG1) with subclass III SnRK2s (Umezawa et al. 2009; abstract only in cache). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, AHG1, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19805022 Group A PP2Cs interacted physically with SnRK2s in various combinations, and efficiently inactivated ABA-activated SnRK2s via dephosphorylation of multiple Ser/Thr residues in the activation loop. |
| GO:0005515 protein binding | IPI PMID:19874541 PYR/PYL/RCAR family members are major in-vivo ABI1 protein p... | MODIFY | Summary: ABI1 co-purifies and co-immunoprecipitates with SnRK2.2 in planta (Nishimura et al. 2010). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, ABI1, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19874541 YFP–ABI1 constitutively interacted with HA–SnRK2.2, HA–SnRK2.3 and HA–OST1/SnRK2.6 both in the absence and presence of exogenously applied ABA |
| GO:0005515 protein binding | IPI PMID:19924127 In vitro reconstitution of an abscisic acid signalling pathw... | MODIFY | Summary: Y2H/BiFC interaction of clade A PP2C ABI2 with SnRK2.2 (Fujii et al. 2009). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, ABI2, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19924127 ABI1 interacts with the SnRK2s in the nucleus as well as the cytosol |
| GO:0005515 protein binding | IPI PMID:19924127 In vitro reconstitution of an abscisic acid signalling pathw... | MODIFY | Summary: Y2H/BiFC interaction of clade A PP2C ABI1 with SnRK2.2 (Fujii et al. 2009). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, ABI1, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19924127 ABI1 interacts with the SnRK2s in the nucleus as well as the cytosol |
| GO:0005515 protein binding | IPI PMID:19924127 In vitro reconstitution of an abscisic acid signalling pathw... | MODIFY | Summary: Y2H/BiFC interaction of clade A PP2C HAB1 with SnRK2.2 (Fujii et al. 2009). Reason: Bare protein binding is uninformative, so the row is refined rather than kept. The partner, HAB1, is a clade A type 2C protein phosphatase that binds SnRK2.2 and dephosphorylates its activation loop, keeping the kinase inactive in the absence of ABA. Protein phosphatase binding (GO:0019903) captures this regulatory interaction. The refinement describes the partner-specific regulatory interaction; it does not depend on whether another annotation already states the function. Proposed replacements: protein phosphatase binding Supporting Evidence: PMID:19924127 ABI1 interacts with the SnRK2s in the nucleus as well as the cytosol |
| GO:0005515 protein binding | IPI PMID:28438792 Reconstitution of Abscisic Acid Signaling from the Receptor ... | REMOVE | Summary: Interaction with the bHLH transcription factor AKS1, a SnRK2 substrate (Takahashi et al. 2017). Reason: Bare protein binding is uninformative. This is a kinase-substrate interaction with the AKS1 transcription factor, whose phosphorylation by SnRK2.2 is established in the same study. Removing the generic binding term does not dispute the interaction; kinase activity and ABA signaling capture its functional role. The previous rationale incorrectly described this row as a PP2C interaction. Supporting Evidence: PMID:28438792 Three ABA-responsive SnRK2s (SnRK2.2/SRK2D, SnRK2.3/SRK2I, and SnRK2.6/SRK2E/OST1) phosphorylated AKS1 in vitro |
| GO:0005515 protein binding | IPI PMID:41417897 MAP4K1 and MAP4K2 regulate ABA-induced and Ca(2+)-mediated s... | REMOVE | Summary: IP-MS interaction with MAP4K1 (At1g53165) in guard-cell ABA signaling (2025 study). Reason: Bare protein binding is uninformative and is removed under the project's protein-binding policy. The interaction itself is real; its biological meaning (clade A PP2C phosphatases binding and dephosphorylating the SnRK2.2 activation loop, i.e. SnRK2.2 acting as the regulated kinase/phosphatase substrate) is captured by the kinase activity and ABA-signaling annotations rather than by a binding MF on SnRK2.2. Supporting Evidence: PMID:41417897 MAP4K1 preferentially interacts with subclass III SnRK2s (SRK2D/E/I) |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: ATP binding inferred from the protein kinase domain and ATP-binding-site signatures (IPR000719, IPR017441). Reason: SnRK2.2 has the canonical glycine-rich loop and Lys-52 ATP-binding residues and is catalytically active, so ATP binding is correct (kept consistent with the OST1 review). Supporting Evidence: file:ARATH/SnRK2.2/SnRK2.2-uniprot.txt Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. PMID:17307925 these data demonstrate that SnRK2.2 and SnRK2.3 have ABA-inducible kinase activity and together are likely to play a major role in phosphorylating and activating ABF2, ABI5, ABF1, and possibly other ABFs. |
| GO:0005634 nucleus | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for nucleus on the subclass III SnRK2 node (SnRK2.2, SnRK2.3, SnRK2.6 and rice SAPK orthologs). Reason: Nuclear localisation is experimentally shown for SnRK2.2 and is where it phosphorylates AREB/ABF transcription factors; the IBA agrees with direct evidence. Supporting Evidence: PMID:19880399 SRK2D/E/I and AREB1 co-localize and interact in nuclei in planta PMID:19541597 These SnRK2 proteins were mainly expressed in the nucleus during seed development and germination. |
| GO:0005634 nucleus | IDA PMID:19880399 Three SnRK2 protein kinases are the main positive regulators... | ACCEPT | Summary: SRK2D/E/I co-localise and interact with AREB1 in nuclei in planta (Fujita et al. 2009). Reason: Direct localisation evidence; nucleus is a functional location where SnRK2.2 phosphorylates ABF/AREB bZIPs. Abstract-only in cache but explicit. Supporting Evidence: PMID:19880399 SRK2D/E/I and AREB1 co-localize and interact in nuclei in planta PMID:19541597 These SnRK2 proteins were mainly expressed in the nucleus during seed development and germination. |
| GO:0005634 nucleus | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA-predicted nuclear localisation. Reason: Prediction agrees with experimental nuclear localisation (IDA row). 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: Cytoplasmic localisation of SRK2D fusion protein (Fujita et al. 2009; full text not cached). Reason: SnRK2.2 is nucleocytoplasmic; BiFC with ABI1 shows interaction in both nucleus and cytosol. Accept as a functional location, consistent with the OST1 review. Supporting Evidence: PMID:19924127 ABI1 interacts with the SnRK2s in the nucleus as well as the cytosol |
| GO:0005737 cytoplasm | ISM GO_REF:0000122 | ACCEPT | Summary: AtSubP-predicted cytoplasmic localisation. Reason: Consistent with experimental cytoplasmic/cytosolic localisation. Supporting Evidence: PMID:19924127 ABI1 interacts with the SnRK2s in the nucleus as well as the cytosol |
| GO:0005829 cytosol | HDA PMID:28887381 Global Analysis of Membrane-associated Protein Oligomerizati... | ACCEPT | Summary: Detected in the cytosolic (S200) fraction in a leaf fractionation/size-exclusion proteomics survey. Reason: High-throughput but consistent with BiFC evidence for SnRK2-PP2C complexes in the cytosol; SnRK2.2 lacks membrane anchors. Supporting Evidence: PMID:28887381 Over 150 proteins had a complicated localization pattern, and were clearly partitioned between cytosolic and membrane-associated pools. PMID:19924127 ABI1 interacts with the SnRK2s in the nucleus as well as the cytosol |
| GO:0006970 response to osmotic stress | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | ACCEPT | Summary: SnRK2s, including SnRK2.2, are activated by hyperosmolarity (mannitol) in Arabidopsis cells (Boudsocq et al. 2004). Reason: Activation by osmotic stress is a defining property of SnRK2.2; consistent with OST1 review. Abstract-only in cache, defer to curator for the SnRK2.2-specific assay. 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/SnRK2.2/SnRK2.2-uniprot.txt By abscisic acid (ABA), salt, and osmotic stress (at protein level). |
| GO:0006970 response to osmotic stress | IGI PMID:21220313 Arabidopsis decuple mutant reveals the importance of SnRK2 k... | ACCEPT | Summary: SnRK2 decuple and snrk2.2/3/6 triple mutants are defective in osmotic stress responses (Fujii et al. 2011). Reason: Genetic evidence that SnRK2.2 (with its paralogs) mediates osmotic stress signaling and tolerance. Supporting Evidence: PMID:21220313 SnRK2s are a merging point of ABA-dependent and -independent pathways for osmotic stress responses PMID:21220313 The decuple mutant snrk2.1/2/3/4/5/6/7/8/9/10 grew poorly under hyperosmotic stress conditions but was similar to the wild type in culture media in the absence of osmotic stress. |
| GO:0009414 response to water deprivation | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA-predicted response to water deprivation. Reason: Supported by the drought-hypersensitive srk2d/e/i triple mutant; consistent with the IGI row. 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:0009414 response to water deprivation | IGI PMID:19880399 Three SnRK2 protein kinases are the main positive regulators... | ACCEPT | Summary: srk2d/e/i triple mutants show greatly reduced drought tolerance and globally impaired water-stress gene expression (Fujita et al. 2009). Reason: Clear genetic evidence; SnRK2.2 acts redundantly with SnRK2.3 and OST1 in water-stress ABA signaling. 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:0009651 response to salt stress | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | KEEP AS NON CORE | Summary: SnRK2.2 is activated by NaCl in transient expression assays (Boudsocq et al. 2004). Reason: Salt activation is a facet of the osmotic component of salinity; real but peripheral to the core ABA-signaling role. Kept non-core, as in the OST1 review. 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/SnRK2.2/SnRK2.2-uniprot.txt By abscisic acid (ABA), salt, and osmotic stress (at protein level). |
| GO:0009651 response to salt stress | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA-predicted response to salt stress. Reason: Consistent with the IDA row (salt activation); non-core. 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 | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | ACCEPT | Summary: SnRK2.2 is one of the ABA-activated SnRK2s (Boudsocq et al. 2004). Reason: ABA activation of SnRK2.2 is well established and central to its function. GO:0009737 is kept alongside the more specific GO:0009738 because the mutant phenotypes are whole-organism ABA responses (germination, root growth, gene expression), not only the signaling step itself. Supporting Evidence: PMID:15292193 abscisic acid only activated five of the nine SnRK2 PMID:17307925 Of the Arabidopsis SnRK2s, SnRK2.2, SnRK2.3, SnRK2.6, SnRK2.7, and SnRK2.8 could be activated by ABA when expressed in Arabidopsis protoplasts |
| GO:0009737 response to abscisic acid | IDA PMID:17307925 Identification of two protein kinases required for abscisic ... | ACCEPT | Summary: snrk2.2 mutants have reduced ABA-induced 42-kD ABF-kinase activity; snrk2.2 snrk2.3 is ABA-insensitive in germination and seedling growth (Fujii et al. 2007). Reason: Direct evidence for ABA-induced SnRK2.2 kinase activity and ABA responses. GO:0009737 is kept alongside the more specific GO:0009738 because the mutant phenotypes are whole-organism ABA responses (germination, root growth, gene expression), not only the signaling step itself. Supporting Evidence: PMID:17307925 The stronger band of kinase activity was at 42 kD, and this activity was reduced in all three of the mutants. snrk2.2 had a greater reduction in the 42-kD activity than did snrk2.3 PMID:17307925 snrk2.2 snrk2.3 plants are insensitive to ABA in seed germination, indicating that SnRK2.2 and SnRK2.3 are the protein kinases that positively regulate ABA signaling in seed germination. |
| GO:0009737 response to abscisic acid | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA-predicted response to abscisic acid. Reason: Consistent with experimental evidence (IDA rows). GO:0009737 is kept alongside the more specific GO:0009738 because the mutant phenotypes are whole-organism ABA responses (germination, root growth, gene expression), not only the signaling step itself. Supporting Evidence: PMID:17307925 these data demonstrate that SnRK2.2 and SnRK2.3 have ABA-inducible kinase activity and together are likely to play a major role in phosphorylating and activating ABF2, ABI5, ABF1, and possibly other ABFs. |
| GO:0009739 response to gibberellin | IGI PMID:18941053 The gibberellic acid signaling repressor RGL2 inhibits Arabi... | KEEP AS NON CORE | Summary: Genetic interaction with SnRK2.3 in GA-ABA control of germination via ABI5 phosphorylation (Piskurewicz et al. 2008). Reason: The paper shows that low GA raises ABA and ABI5, whose activity needs SnRK2-mediated phosphorylation. The effect of snrk2.2 snrk2.3 on the germination response to reduced GA is therefore indirect, through ABA signaling. The cached text lacks the Results section, so the exact assay was not read. Deferring to the curator, this is kept as a non-core, upstream annotation. Supporting Evidence: PMID:18941053 a recent report showed that two SnRK2-type kinases (SnRK2.2 and SnRK2.3) phosphorylate ABI5 peptides and redundantly mediate ABA-dependent responses during seed germination in Arabidopsis PMID:18941053 The endogenous ABI5 phosphorylation and inhibition of germination could be recapitulated by the addition of a SnRK2 protein kinase to the ABI5 overexpression line. |
| GO:0010029 regulation of seed germination | IGI PMID:18941053 The gibberellic acid signaling repressor RGL2 inhibits Arabi... | MODIFY | Summary: snrk2.2 snrk2.3 affects ABA/ABI5-dependent repression of germination (Piskurewicz et al. 2008); double mutant is ABA-insensitive in germination (Fujii et al. 2007). Reason: Control of seed germination and dormancy is the principal physiological output of SnRK2.2/2.3 ABA signaling, well supported by the snrk2.2 snrk2.3 phenotype. The direction is known (the double mutant germinates on ABA, so SnRK2.2/2.3 mediate ABA inhibition of germination), so the specific child term negative regulation of seed germination (GO:0010187) fits better. Same action as the SnRK2.3 review for this row. Proposed replacements: negative regulation of seed germination Supporting Evidence: PMID:18941053 a recent report showed that two SnRK2-type kinases (SnRK2.2 and SnRK2.3) phosphorylate ABI5 peptides and redundantly mediate ABA-dependent responses during seed germination in Arabidopsis PMID:17307925 snrk2.2 snrk2.3 plants are insensitive to ABA in seed germination, indicating that SnRK2.2 and SnRK2.3 are the protein kinases that positively regulate ABA signaling in seed germination. |
| GO:0016301 kinase activity | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | MODIFY | Summary: SnRK2 kinase activity detected by in-gel assays after osmotic/ABA activation (Boudsocq et al. 2004). Reason: Kinase activity is correct but far too general; SnRK2.2 is a protein Ser/Thr kinase. Replace with GO:0004674, which the gene already carries. Proposed replacements: protein serine/threonine kinase activity 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. PMID:17307925 these data demonstrate that SnRK2.2 and SnRK2.3 have ABA-inducible kinase activity and together are likely to play a major role in phosphorylating and activating ABF2, ABI5, ABF1, and possibly other ABFs. |
| GO:0106310 protein serine kinase activity | IEA GO_REF:0000116 | ACCEPT | Summary: Rhea-based mapping (RHEA:17989, L-seryl-[protein] phosphorylation) to protein serine kinase activity. Reason: SnRK2.2 phosphorylates serine residues of substrates (ABF and AKS1); accurate and consistent with the OST1 review. Supporting Evidence: PMID:17307925 these data demonstrate that SnRK2.2 and SnRK2.3 have ABA-inducible kinase activity and together are likely to play a major role in phosphorylating and activating ABF2, ABI5, ABF1, and possibly other ABFs. PMID:28438792 Three ABA-responsive SnRK2s (SnRK2.2/SRK2D, SnRK2.3/SRK2I, and SnRK2.6/SRK2E/OST1) phosphorylated AKS1 in vitro |
| GO:0009738 abscisic acid-activated signaling pathway | IGI PMID:19420218 Arabidopsis mutant deficient in 3 abscisic acid-activated pr... | NEW | Summary: SnRK2.2 is one of the three subclass III SnRK2 kinases that transduce the ABA signal; the snrk2.2/2.3/2.6 triple mutant loses all ABA-activated kinase activity and ABA-induced gene expression, and in vitro/protoplast reconstitution places the SnRK2s between PP2Cs and ABFs. Reason: Participation test: SnRK2.2 itself performs a signal-transduction step of the pathway (once released from PP2C inhibition it phosphorylates ABF/AREB/ABI5 and AKS1 transcription factors). Comparator check: its paralogs in the same role, OST1/SnRK2.6 (Q940H6) and SnRK2.3 (Q39193), both carry GO:0009738 in GOA, so the absence on SnRK2.2 is a gap rather than a convention. The term is not an ancestor or descendant of any other term on the gene. The existing process rows (response to abscisic acid, regulation of seed germination) do not capture membership of the core pathway. Supporting Evidence: PMID:19420218 In-gel kinase assays showed that all ABA-activated protein kinase activities are eliminated in the triple mutant. PMID:19420218 These SnRK2s, SnRK2.2, SnRK2.3, and SnRK2.6 (also known as OST1), are activated by ABA and can phosphorylate the ABA-responsive element binding factor family of b-ZIP transcription factors PMID:19924127 our study reveals a surprising simplicity of the pathway and demonstrates that the PYR/PYLs, clade-A PP2Cs, SnRK2s, and ABFs are the only core components to complete the ABA regulation of gene expression. file:ARATH/SnRK2.2/SnRK2.2-uniprot.txt Together with SRK2I, key component and activator of the abscisic acid (ABA) signaling pathway |
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Download this section (compressed HTML)Q: What explains the functional specialisation of SnRK2.2/2.3 (seeds, seedlings, roots) versus OST1 (guard cells): expression pattern alone, as Fujii et al. 2007 proposed, or differences in substrate preference or in PP2C/receptor pairing?
Q: Does SnRK2.2 directly phosphorylate RaptorB and FREE1 in vivo, given that the RaptorB phosphorylation was shown only for SnRK2.6 and the FREE1 work used the SnRK2 family? Which substrates are specific to SnRK2.2?
Q: Root hydrotropism requires SnRK2.2 acting in elongation-zone cortical cells (PMID:28481327). Which cortical substrates mediate this, and should SnRK2.2 carry a hydrotropism (GO:0010274) annotation once the full text is reviewed?
Experiment: Cortex- or seed-specific phosphoproteomics comparing wild type, snrk2.2 and snrk2.2 snrk2.3 after ABA treatment, to define the SnRK2.2-dependent substrate set outside guard cells.
Hypothesis: SnRK2.2 phosphorylates a substrate set in seeds and root cortex that differs from the guard-cell substrates of OST1.
Type: phosphoproteomics
Experiment: Promoter-swap complementation (SnRK2.2 coding sequence expressed from the OST1 promoter in ost1, and the reverse) to test whether expression domain or protein-intrinsic properties underlie the SnRK2.2 versus OST1 specialisation.
Hypothesis: Expression domain, rather than intrinsic kinase properties, determines the SnRK2.2 versus OST1 specialisation.
Type: genetic complementation
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