SnRK2.3 (SRK2I, At5g66880) is an ABA- and osmotic-stress-activated serine/threonine protein kinase of the plant-specific subclass III SnRK2 (SNF1-related protein kinase 2) family, closely related to SnRK2.2 (SRK2D) and SnRK2.6/OST1 (SRK2E). In the absence of ABA it is held inactive by clade A type 2C protein phosphatases (ABI1, ABI2, HAB1, AHG1) that bind it and dephosphorylate its activation loop; when ABA-bound PYR/PYL/RCAR receptors inhibit these phosphatases, upstream B2/B3 RAF kinases initiate activation-loop phosphorylation, after which active SnRK2 molecules can amplify signaling by intermolecular phosphorylation. Active SnRK2.3 phosphorylates RXXS/T motifs in transcription factors, including the ABRE-binding bZIP factors ABF1, ABF2/AREB1 and ABI5, bHLH AKS factors and the HD-ZIP factor HAT1, as well as the ESCRT component FREE1, thereby driving ABA-responsive gene expression. It is expressed at low levels in most organs, particularly root tips, and acts in the nucleus and cytoplasm. Acting redundantly with SnRK2.2, it mediates ABA inhibition of seed germination and seedling root growth, seed dormancy and ABA-induced proline accumulation, with only a minor role in stomatal control; together with SnRK2.2 and SnRK2.6 it is required for essentially all ABA-activated kinase activity, drought and osmotic-stress tolerance, seed development and normal growth. Its abundance is limited by SCF(AtPP2-B11)-mediated proteasomal degradation, and its activity is also restrained by TOPP1/AtI-2.
| 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 with ABF2, ABI5 and ABF1 fragments show that SnRK2.3 (with SnRK2.2) accounts for the ABA-induced 42-kD protein kinase activity in seedlings; the activity is reduced in snrk2.3 and almost lost in snrk2.2 snrk2.3. Reason: Direct experimental evidence of protein kinase activity toward bZIP transcription factor fragments. The term is correct but less specific than the evidence. SnRK2.3 phosphorylates Ser/Thr sites of ABF/AREB bZIPs, so the replacement is protein serine/threonine kinase activity (GO:0004674), which the gene already carries by IBA and IEA. Same action as the SnRK2.2 review. 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 |
| GO:0004672 protein kinase activity | IEA GO_REF:0000120 | MODIFY | Summary: Combined automated (InterPro Ser/Thr kinase active-site signature) assignment of protein kinase activity. SnRK2.3 has a canonical protein kinase domain (residues 22-278) and is an experimentally verified kinase. Reason: Correct but general. The InterPro signature cited is the Ser/Thr kinase active site, and the gene already carries protein serine/threonine kinase activity (GO:0004674), so that term replaces this one. This matches the IDA row here and the SnRK2.2 review. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: file:ARATH/SnRK2.3/SnRK2.3-uniprot.txt Belongs to the protein kinase superfamily. Ser/Thr protein 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:0004672 protein kinase activity | TAS PMID:10634783 Regulation of abscisic acid-induced stomatal closure and ani... | MODIFY | Summary: Traceable author statement citing Li et al. 2000, which cloned the Vicia faba guard-cell kinase AAPK, an OST1-type subclass III SnRK2. The paper does not study SnRK2.3 itself. Reason: The asserted claim (protein kinase activity) is correct for SnRK2.3 and is independently established by in-gel kinase assays (PMID:17307925). The cited reference concerns a Vicia faba ortholog of the subclass III SnRK2s, so an Arabidopsis SnRK2.3 reference would be a better citation. As for the other rows to this term, the specific replacement is protein serine/threonine kinase activity (GO:0004674). Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:10634783 encoding a guard cell-specific ABA-activated serine-threonine protein kinase (AAPK) 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 phylogenetic inference of protein serine/threonine kinase activity for the SnRK/AMPK-related kinase clade. SnRK2.3 lies well inside this clade, has the catalytic residues, and is experimentally an ABA-activated Ser/Thr kinase that phosphorylates ABFs, ABI5, AKS1 and HAT1. Reason: Core molecular function, supported by the phylogeny and by direct biochemistry on SnRK2.3; same action as in 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 PMID:29659577 both protein stability and binding activity of HAT1 was repressed by SnRK2.3 phosphorylation |
| 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. UniProt records both seryl- and threonyl-protein phosphorylation reactions for SnRK2.3. Reason: Correct and core; consistent with the IBA row and experimental data. Supporting Evidence: file:ARATH/SnRK2.3/SnRK2.3-uniprot.txt Reaction=L-seryl-[protein] + ATP = O-phospho-L-seryl-[protein] + ADP + 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:0005515 protein binding | IPI PMID:19805022 Type 2C protein phosphatases directly regulate abscisic acid... | MODIFY | Summary: Interaction with the clade A PP2C ABI2 (Umezawa et al. 2009). Clade A PP2Cs bind subclass III SnRK2s and dephosphorylate their activation loop, keeping them inactive without ABA. 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 SnRK2.3 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: Interaction with the clade A PP2C ABI1 (Umezawa et al. 2009); ABI1 binds and dephosphorylates SnRK2.3, inactivating it. 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 SnRK2.3 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: Interaction with the clade A PP2C AHG1 (Umezawa et al. 2009), one of the PP2C gatekeepers of SnRK2 activity. 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 SnRK2.3 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-SnRK2.3 interaction recovered in planta by YFP-ABI1 affinity purification and confirmed by co-immunoprecipitation (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 SnRK2.3 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 ABI1 interacts with the ABA-signalling kinases OST1, SnRK2.2 and SnRK2.3 in plants |
| GO:0005515 protein binding | IPI PMID:19924127 In vitro reconstitution of an abscisic acid signalling pathw... | MODIFY | Summary: Yeast two-hybrid interaction with ABI2 from the in vitro reconstitution study of 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 SnRK2.3 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 The three clade A PP2Cs (ABI1, ABI2 and HAB1) were each capable of interacting with the three SnRK2 kinases (SnRK2.2, SnRK2.3 and SnRK2.6) in yeast two-hybrid (Y2H) assays |
| GO:0005515 protein binding | IPI PMID:19924127 In vitro reconstitution of an abscisic acid signalling pathw... | MODIFY | Summary: Yeast two-hybrid and BiFC interaction with ABI1 (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 SnRK2.3 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 The three clade A PP2Cs (ABI1, ABI2 and HAB1) were each capable of interacting with the three SnRK2 kinases (SnRK2.2, SnRK2.3 and SnRK2.6) in yeast two-hybrid (Y2H) assays 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: Yeast two-hybrid interaction with HAB1 (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 SnRK2.3 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 The three clade A PP2Cs (ABI1, ABI2 and HAB1) were each capable of interacting with the three SnRK2 kinases (SnRK2.2, SnRK2.3 and SnRK2.6) in yeast two-hybrid (Y2H) assays |
| GO:0005515 protein binding | IPI PMID:23290725 Protein conformation ensembles monitored by HDX reveal a str... | MODIFY | Summary: Hydrogen-deuterium exchange analysis of SnRK2.3 in the presence and absence of the PP2C HAB1, mapping the phosphatase-binding surface of the kinase. 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 SnRK2.3 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:23290725 for SnRK2.3 in the presence and absence of HAB1 phosphatase |
| GO:0005515 protein binding | IPI PMID:28438792 Reconstitution of Abscisic Acid Signaling from the Receptor ... | REMOVE | Summary: Interaction with bHLH122 (Q9C690), an AKS-type bHLH transcription factor, from the AKS reconstitution study; AKS factors are SnRK2 substrates. Reason: Bare protein binding (GO:0005515) is uninformative and is removed per the protein-binding policy; removal does not dispute the interaction. The interaction is a kinase-substrate relationship already represented by protein serine/threonine kinase activity; same treatment as the protein binding rows in the OST1 review. Supporting Evidence: PMID:28438792 Three ABA-responsive SnRK2s (SnRK2.2/SRK2D, SnRK2.3/SRK2I, and SnRK2.6/SRK2E/OST1) phosphorylated AKS1 in vitro |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro protein kinase domain and ATP-binding site signatures. SnRK2.3 has the glycine-rich ATP-binding loop (28-36) and Lys51; a K51N mutant is used as the kinase-dead control. Reason: ATP binding is an intrinsic property of this active protein kinase and is consistent with the OST1 review; retained, although it is entailed by the kinase activity. Supporting Evidence: file:ARATH/SnRK2.3/SnRK2.3-uniprot.txt Belongs to the protein kinase superfamily. Ser/Thr protein |
| GO:0005634 nucleus | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of nuclear activity for the subclass III SnRK2 clade (SnRK2.2, SnRK2.3, SnRK2.6 and rice SAPK orthologs). SnRK2.3 is nuclear in planta and phosphorylates nuclear bZIP and bHLH transcription factors. Reason: Consistent with direct localization evidence and the nuclear substrates of the kinase; SnRK2.3 itself is among the experimental donors for this node, which is expected. 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-localize and interact with AREB1 in nuclei in planta (Fujita et al. 2009). Reason: Direct experimental localization; supported further by mainly nuclear localization in seeds (PMID:19541597) and BiFC with ABI1 in the nucleus (PMID:19924127). 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 prediction of nuclear localization, agreeing with experimental data. Reason: Correct; supported by experimental IDA localization of SnRK2.3 in nuclei. 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: SnRK2.3 fluorescent fusion protein was observed in the cytoplasm as well as the nucleus (Fujita et al. 2009; cached abstract mentions only the nuclear co-localization, the curator read the full text). Reason: Consistent with BiFC detection of SnRK2-ABI1 complexes in the cytosol (PMID:19924127); defer to the curator for the IDA. 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 sequence-based prediction of cytoplasmic localization for a soluble kinase lacking targeting signals. Reason: Agrees with experimental observation of the kinase and its PP2C complexes in the cytosol/cytoplasm; same action as in the OST1 review. Supporting Evidence: PMID:19924127 ABI1 interacts with the SnRK2s in the nucleus as well as the cytosol |
| GO:0005829 cytosol | RCA NOT PMID:21166475 Analysis of the Arabidopsis cytosolic proteome highlights su... | REMOVE | Summary: NOT located_in cytosol, from absence of SnRK2.3 in a cytosolic proteome of Arabidopsis cell suspensions (reviewed computational analysis). Reason: A negative call based on non-detection in one proteomic dataset (where a low-abundance kinase can easily be missed) is contradicted by BiFC detection of SnRK2-ABI1 complexes in the cytosol and by IDA cytoplasm localization (PMID:19880399). The same NOT row was removed in the OST1 review. Supporting Evidence: PMID:21166475 This generated a robust set of 1071 cytosolic proteins 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: SnRK2.3 is among the nine Arabidopsis SnRK2s activated by mannitol-induced hyperosmolarity in transient expression assays (Boudsocq et al. 2004). Reason: Direct demonstration that osmotic stress activates the kinase; SnRK2.2/2.3/2.6 integrate ABA-dependent and ABA-independent osmotic signalling (PMID:21220313). 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:21220313 SnRK2.2/3/6 is activated not only by ABA, but also by osmotic stress |
| GO:0006970 response to osmotic stress | IGI PMID:21220313 Arabidopsis decuple mutant reveals the importance of SnRK2 k... | ACCEPT | Summary: The SnRK2 decuple mutant (including snrk2.3) is defective in growth, gene regulation and ABA, proline and IP3 accumulation under hyperosmotic stress (Fujii et al. 2011). Reason: Genetic evidence that SnRK2s, including SnRK2.3, are required for osmotic stress responses; consistent with the IDA row and the OST1 review. Supporting Evidence: PMID:21220313 These results demonstrate critical functions of the SnRK2s in mediating osmotic stress signaling and tolerance PMID:21220313 SnRK2.2/3/6 is activated not only by ABA, but also by osmotic stress |
| GO:0009414 response to water deprivation | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA prediction of involvement in response to water deprivation. Reason: Supported by genetic data: the srk2d srk2e srk2i triple mutant has greatly reduced drought tolerance and loses water extremely fast (PMID:19880399, PMID:19420218). 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 srk2e srk2i triple mutants, but not single or double mutants, show greatly reduced drought tolerance and impaired water-stress-induced gene expression (Fujita et al. 2009). Reason: Direct genetic evidence, with SnRK2.2 and SnRK2.6 as the interacting genes; SnRK2.3 acts redundantly in ABA-dependent water-stress signalling. 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:0009536 plastid | HDA PMID:28887381 Global Analysis of Membrane-associated Protein Oligomerizati... | UNDECIDED | Summary: High-throughput fractionation assigns SnRK2.3 to plastids, but the gene-specific assignment was not resolved in the available article text. Reason: The HDA localization should not be dismissed solely because the accessible text does not discuss SnRK2.3 or because its best-characterized functions are nuclear/cytoplasmic. The gene-level fractionation evidence and targeting mechanism require inspection; the present sources do not establish or refute a plastid pool. Keep this uncertainty explicit and omit plastid from the core locations. Supporting Evidence: PMID:19880399 SRK2D/E/I and AREB1 co-localize and interact in nuclei in planta |
| GO:0009651 response to salt stress | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | KEEP AS NON CORE | Summary: SnRK2.3 is activated by NaCl in transient expression assays (Boudsocq et al. 2004). Reason: Supported, but salt activation reflects the shared hyperosmotic component of salinity across the SnRK2 family rather than a salt-specific role; same action 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 |
| GO:0009651 response to salt stress | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA prediction of involvement in response to salt stress. Reason: Consistent with NaCl activation of the kinase; peripheral to the core ABA signalling role, as for OST1. 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: SnRK2.3 is one of five SnRK2s activated by ABA in transient expression assays (Boudsocq et al. 2004). Reason: ABA activation of the kinase is a defining property of subclass III SnRK2s. 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 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:0009737 response to abscisic acid | IDA PMID:17307925 Identification of two protein kinases required for abscisic ... | ACCEPT | Summary: ABA induces SnRK2.3-dependent kinase activity in seedlings, and snrk2.2 snrk2.3 mutants are ABA-insensitive in germination, root growth, Pro accumulation and ABRE-driven gene expression (Fujii et al. 2007). Reason: Core role, directly demonstrated. 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 PMID:17307925 SnRK2.2 and SnRK2.3 are redundant but key protein kinases that mediate a major part of ABA signaling in Arabidopsis |
| GO:0009737 response to abscisic acid | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA prediction of response to abscisic acid. Reason: Correct and core; supported by experimental IDA rows of the same term. 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 SnRK2.2 and SnRK2.3 are redundant but key protein kinases that mediate a major part of ABA signaling in Arabidopsis |
| GO:0009738 abscisic acid-activated signaling pathway | TAS PMID:10634783 Regulation of abscisic acid-induced stomatal closure and ani... | ACCEPT | Summary: Traceable author statement citing Li et al. 2000 (Vicia faba AAPK). SnRK2.3 is one of the three subclass III SnRK2s that transduce the ABA signal downstream of PYR/PYL-PP2C de-repression. Reason: Core process for SnRK2.3, independently established by snrk2.2 snrk2.3 and snrk2.2/2.3/2.6 mutant analysis (PMID:17307925, PMID:19420218). The cited reference is about a Vicia faba ortholog; an SnRK2.3-specific reference would be better, but the claim is correct. Supporting Evidence: PMID:10634783 encoding a guard cell-specific ABA-activated serine-threonine protein kinase (AAPK) PMID:17307925 SnRK2.2 and SnRK2.3 are redundant but key protein kinases that mediate a major part of ABA signaling in Arabidopsis PMID:19420218 In-gel kinase assays showed that all ABA-activated protein kinase activities are eliminated in the triple mutant |
| GO:0009739 response to gibberellin | IGI PMID:18941053 The gibberellic acid signaling repressor RGL2 inhibits Arabi... | KEEP AS NON CORE | Summary: From Piskurewicz et al. 2008 (with SnRK2.2): the GA-DELLA (RGL2) repression of germination operates through ABA synthesis and SnRK2-dependent ABI5 phosphorylation. The cached text lacks the Results, so the exact genetic assay (presumably snrk2.2 snrk2.3 germination under reduced GA) could not be read. Reason: Plausible and curator-asserted: SnRK2.3 lies downstream of the RGL2-induced rise in ABA rather than in GA signalling itself, so the effect on GA responses is indirect. Kept as non-core, deferring to the curator who read the full text. Supporting Evidence: 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 and SnRK2.3 redundantly mediate ABA inhibition of seed germination; snrk2.2 snrk2.3 seeds germinate in the presence of ABA and low GA, consistent with SnRK2-dependent ABI5 phosphorylation repressing germination. Reason: The direction of the effect is well established: SnRK2.2/2.3 positively regulate ABA signalling that inhibits germination, so the specific child term negative regulation of seed germination (GO:0010187) is supported. Germination control is a defining physiological role of SnRK2.2/2.3 (in contrast to the guard-cell role of SnRK2.6). Proposed replacements: negative regulation of seed germination Supporting Evidence: 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 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:0016301 kinase activity | IDA PMID:15292193 Identification of nine sucrose nonfermenting 1-related prote... | MODIFY | Summary: Kinase activity of SnRK2.3 activated by hyperosmotic and saline stress (Boudsocq et al. 2004), measured with protein substrates. Reason: Correct but very general: the activity is protein serine/threonine phosphorylation, so the specific term protein serine/threonine kinase activity (GO:0004674), already accepted on the IBA and IEA rows, should replace it. 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: Correct; SnRK2.3 phosphorylates serine residues in RXXS/T motifs of ABFs, AKS1 and HAT1. Consistent with the OST1 review. Supporting Evidence: file:ARATH/SnRK2.3/SnRK2.3-uniprot.txt Reaction=L-seryl-[protein] + ATP = O-phospho-L-seryl-[protein] + ADP + PMID:29659577 both protein stability and binding activity of HAT1 was repressed by SnRK2.3 phosphorylation |
| GO:0046777 protein autophosphorylation | IDA PMID:22160701 Structural basis for basal activity and autoactivation of ab... | NEW | Summary: SnRK2.3 can autophosphorylate in vitro, but the observed reaction does not establish RAF-independent initiation after PP2C inactivation. Reason: SnRK2.3 itself performs the phosphotransfer in the biochemical experiment, so the catalytic participation claim is retained. PMID:33911084 subsequently showed that RAF3/RAF10 strongly enhance SnRK2.3 activity and that RAF transphosphorylation is required for reactivation of SnRK2.2/2.3/2.6. The earlier structural/biochemical finding is interpreted as phosphorylation capacity rather than evidence that PP2C release alone is sufficient. Supporting Evidence: PMID:22160701 This stabilization enables SnRK2s to gain full activity by activation loop autophosphorylation PMID:22160701 Autophosphorylation is more efficient in SnRK2.6, which has higher stability than SnRK2.3 file:ARATH/SnRK2.3/SnRK2.3-uniprot.txt Autophosphorylated in vitro. {ECO:0000269|PubMed:22160701} PMID:33911084 transphosphorylation by RAFs is required for the reactivation of SnRK2.2/2.3/2.6. |
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Download this section (compressed HTML)Q: Beyond expression differences, does SnRK2.3 differ from SnRK2.2 and SnRK2.6 in substrate preference in vivo (e.g. HAT1, FREE1), given that AtPP2-B11 selectively degrades SnRK2.3?
Q: Should SnRK2 substrate relationships (ABFs, ABI5, AKS1, HAT1, FREE1) be captured as has_input on the SnRK2.3 kinase activity in a GO-CAM rather than as interaction-based protein binding annotations?
Experiment: Quantitative in vivo phosphoproteomics comparing snrk2.2 snrk2.6 (SnRK2.3 only) with snrk2.2 snrk2.3 snrk2.6 seeds and roots, to define the substrates that SnRK2.3 alone can phosphorylate.
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