SLAC1 (SLOW ANION CHANNEL-ASSOCIATED 1, At1g12480) is the guard-cell slow (S-type) anion channel of Arabidopsis thaliana, a 556-residue plasma-membrane protein with ten transmembrane helices and long cytosolic N- and C-terminal tails. It is a distant homologue of bacterial TehA and fungal Mae1/Ssu1 transporters and founds the plant SLAC/SLAH family. SLAC1 assembles as a homotrimer in which each protomer forms its own five-helix anion pore, gated by a conserved phenylalanine (Phe450). The channel is selective for anions, preferring nitrate and chloride over malate, sulfate and bicarbonate, and is weakly voltage dependent. It is electrically silent until phosphorylated on its cytosolic N-terminus by protein kinases, chiefly the ABA-activated SnRK2 kinase OST1 (Ser120), calcium-dependent protein kinases (CPK6, CPK21, CPK23) and the receptor kinase SIF2 (Ser65); phosphorylation releases a cytosolic plug from the transmembrane domain and opens the pore, whereas clade A PP2C phosphatases (ABI1, ABI2, PP2CA) keep it inactive. SLAC1 is expressed predominantly in guard cells, where anion efflux through it depolarises the plasma membrane, drives K+ efflux and loss of turgor, and so closes the stomatal pore. It is therefore the terminal effector of stomatal closure triggered by abscisic acid, elevated CO2, ozone, low humidity, darkness, calcium, reactive oxygen species and nitric oxide, and loss-of-function mutants have constitutively open stomata, excess guard-cell anion content, high water loss and ozone sensitivity. In a single study SLAC1 also bound and inhibited the inward-rectifying K+ channel KAT1 in Xenopus oocytes, which would couple closure to suppression of stomatal opening; slac1 guard cells, however, show reduced rather than increased inward K+ currents, an effect attributed to raised cytosolic Ca2+.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:19955405 Activity of guard cell anion channel SLAC1 is controlled by ... | MODIFY | Summary: Split-YFP (BiFC) interaction of SLAC1 with the SnRK2 kinase OST1 in Xenopus oocytes and Arabidopsis protoplasts; OST1 binds the SLAC1 N-terminus and phosphorylates it to activate the channel. Reason: Bare protein binding is uninformative. The partner is a protein kinase that docks on and phosphorylates SLAC1, so protein kinase binding (GO:0019901), which SLAC1 already carries from the same type of evidence, is the more informative MF for this interaction. Removal of the generic term does not question the interaction itself. Proposed replacements: protein kinase binding Supporting Evidence: PMID:19955405 Using split YFP assays, we identified OST1 as an interaction partner of SLAC1 and ABI1. PMID:19955405 YFP complementation could only be monitored between the SLAC1 N terminus and the protein kinase |
| GO:0005515 protein binding | IPI PMID:19955427 A protein kinase-phosphatase pair interacts with an ion chan... | MODIFY | Summary: Independent demonstration that OST1 interacts with SLAC1 and activates it by phosphorylation. Reason: Bare protein binding is uninformative; the partner is the activating kinase OST1, so the interaction is better captured by protein kinase binding (GO:0019901), matching the existing IPI row from this paper. Proposed replacements: protein kinase binding Supporting Evidence: PMID:19955427 Here we show that 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 ... | MODIFY | Summary: OST1-SLAC1 interaction used as reference in the CPK study, which also shows that the OST1 and CPK branches converge on SLAC1. Reason: Bare protein binding is uninformative; the partner is the protein kinase OST1, so protein kinase binding (GO:0019901) is the informative replacement. Proposed replacements: protein kinase binding Supporting Evidence: PMID:20385816 Thus the CPK and OST1 branch of ABA signal transduction in guard cells seem to converge on the level of SLAC1 under the control of the ABI1/ABA-receptor complex. |
| GO:0005515 protein binding | IPI PMID:20385816 Guard cell anion channel SLAC1 is regulated by CDPK protein ... | MODIFY | Summary: Split-YFP interaction of SLAC1 with the calcium-dependent protein kinase CPK23, which activates SLAC1 in oocytes. Reason: Bare protein binding is uninformative; CPK23 is a protein kinase that phosphorylates and activates SLAC1, so protein kinase binding (GO:0019901) is the informative replacement (and is already annotated for this pair). Proposed replacements: protein kinase binding Supporting Evidence: PMID:20385816 Split YFP-based protein-protein interaction assays, using SLAC1 as the bait, identified guard cell expressed CPK21 and 23 as major interacting partners. |
| GO:0005515 protein binding | IPI PMID:20385816 Guard cell anion channel SLAC1 is regulated by CDPK protein ... | MODIFY | Summary: Split-YFP interaction of SLAC1 with the calcium-dependent protein kinase CPK21, which confers Ca2+-sensitive activation of SLAC1. Reason: Bare protein binding is uninformative; CPK21 is an activating protein kinase, so protein kinase binding (GO:0019901) is the informative replacement. Proposed replacements: protein kinase binding Supporting Evidence: PMID:20385816 Split YFP-based protein-protein interaction assays, using SLAC1 as the bait, identified guard cell expressed CPK21 and 23 as major interacting partners. |
| GO:0005515 protein binding | IPI PMID:22730405 A plasma membrane receptor kinase, GHR1, mediates abscisic a... | REMOVE | Summary: Interaction of SLAC1 with the receptor-like kinase GHR1, which activates SLAC1 currents in oocytes. Reason: Bare protein binding is uninformative. A kinase-binding refinement is not appropriate here because GHR1 was later shown to be a catalytically inactive pseudokinase whose ATP-binding residues are dispensable for SLAC1 activation, so its role toward SLAC1 is likely scaffolding rather than phosphorylation. Removal concerns the uninformative term only; the GHR1-SLAC1 interaction is not disputed. Supporting Evidence: PMID:22730405 Interestingly, like OST1, GHR1 can directly phosphorylate and activate SLAC1. PMID:30361234 Furthermore, we show that the amino acid residues of GHR1 involved in ATP binding are not required for stomatal closure in Arabidopsis or the activation of SLAC1 anion currents in Xenopus laevis oocytes and present supporting in silico and in vitro evidence suggesting that GHR1 is an inactive pseudokinase. |
| GO:0005515 protein binding | IPI PMID:25599916 A molecular pathway for CO₂ response in Arabidopsis guard ce... | MODIFY | Summary: OST1-SLAC1 interaction in the reconstituted CO2 signalling relay (RHC1 - HT1 - OST1 - SLAC1). Reason: Bare protein binding is uninformative; the partner is the activating kinase OST1, so protein kinase binding (GO:0019901) is the informative replacement. Proposed replacements: protein kinase binding Supporting Evidence: PMID:25599916 We also show that HT1 phosphorylates and inactivates OST1, a kinase which is essential for the activation of the SLAC1 anion channel and stomatal closing. |
| GO:0005515 protein binding | IPI PMID:27002025 S-type Anion Channels SLAC1 and SLAH3 Function as Essential ... | REMOVE | Summary: Interaction of SLAC1 with the silent K+ channel regulatory subunit KC1 (KAT3/AtKC1). Reason: Bare protein binding is uninformative and no more specific MF is supported for this pair. KC1 is itself an inhibitory regulator of inward K+ channels and the abstract reports that SLAC1 and KC1 inhibit KAT1 by partly different mechanisms; it does not show that SLAC1 regulates KC1. Removal does not dispute the interaction. Supporting Evidence: PMID:27002025 Additionally, the inhibition of KAT1 by SLAC1 and KC1 only partially overlapped, suggesting that SLAC1 and KC1 inhibited K+in channels using different molecular mechanisms. |
| GO:0005515 protein binding | IPI PMID:27002025 S-type Anion Channels SLAC1 and SLAH3 Function as Essential ... | REMOVE | Summary: Interaction of SLAC1 with the inward-rectifying K+ channel KAT2. Reason: Bare protein binding is uninformative. Unlike KAT1, KAT2 currents were not inhibited by SLAC1, so no channel-regulator MF can be inferred for this pair. Removal does not dispute the interaction. Supporting Evidence: PMID:27002025 Voltage-clamp results demonstrated that SLAC1 inhibited KAT1 dramatically, but did not inhibit KAT2. |
| GO:0005515 protein binding | IPI PMID:27002025 S-type Anion Channels SLAC1 and SLAH3 Function as Essential ... | MODIFY | Summary: Interaction of SLAC1 with the weakly rectifying K+ channel AKT2; UniProt curators record from the same paper that SLAC1 binds and inhibits AKT2. Reason: Bare protein binding is uninformative. The functional content of the interaction is inhibition of the K+ channel, which is captured by potassium channel inhibitor activity (GO:0019870). Evidence is from a single study and the cached text is abstract-only, so this is non-core. PMID:23126621 instead finds reduced inward potassium currents in slac1 loss-of-function guard cells, rescued by lowering cytosolic calcium. These results support feedback regulation and leave the physiological contribution of the direct inhibitory interaction unresolved; it is not promoted to a core function. AKT2 has inward-rectifying and nonrectifying gating modes (PMID:16316977); the available SLAC1 evidence does not resolve the inhibited gating mode, so the broader potassium-channel inhibitor term is retained for this target. Proposed replacements: potassium channel inhibitor activity Supporting Evidence: file:ARATH/SLAC1/SLAC1-hypotheses/slac1-kat1-inhibition/openscientist.md single study, single lab, heterologous oocyte system, gain-of-function UniProtKB:Q9LD83 Binds to the highly selective inward-rectifying potassium channels KAT1 and AKT2, and inhibits their activities. PMID:23126621 reducing [Ca(2+)](cyt) to < 10 nM rapidly restored the activity of K(+)(in) channels in slac1 closer to wild-type levels. PMID:16316977 when nonphosphorylated AKT2 behaves as an inward-rectifying potassium channel |
| GO:0005515 protein binding | IPI PMID:27002025 S-type Anion Channels SLAC1 and SLAH3 Function as Essential ... | MODIFY | Summary: SLAC1 binds the inward-rectifying K+ channel KAT1 and strongly inhibits its current, suppressing stomatal opening. Reason: Bare protein binding is uninformative. The study shows that SLAC1 inhibits KAT1 through direct protein-protein interaction (both cytosolic termini contribute), which is inward rectifier potassium channel inhibitor activity (GO:0070320). This is a secondary activity of SLAC1 reported by one laboratory; non-core. PMID:23126621 instead finds reduced inward potassium currents in slac1 loss-of-function guard cells, rescued by lowering cytosolic calcium. These results support feedback regulation and leave the physiological contribution of the direct inhibitory interaction unresolved; it is not promoted to a core function. Proposed replacements: inward rectifier potassium channel inhibitor activity Supporting Evidence: file:ARATH/SLAC1/SLAC1-hypotheses/slac1-kat1-inhibition/openscientist.md single study, single lab, heterologous oocyte system, gain-of-function PMID:27002025 Here we show that S-type anion channels SLAC1 and SLAH3 mainly inhibit inward K+ (K+in) channel KAT1 by protein-protein interaction, and consequently prevent stomatal opening in Arabidopsis. PMID:23126621 reducing [Ca(2+)](cyt) to < 10 nM rapidly restored the activity of K(+)(in) channels in slac1 closer to wild-type levels. |
| GO:0005515 protein binding | IPI PMID:32327536 STRESS INDUCED FACTOR 2 Regulates Arabidopsis Stomatal Immun... | MODIFY | Summary: The malectin-like receptor kinase SIF2 interacts with and phosphorylates SLAC1 (Ser65), activating it during stomatal immunity. Reason: Bare protein binding is uninformative; SIF2 is a catalytically active kinase that phosphorylates SLAC1, so protein kinase binding (GO:0019901) is the informative replacement. Proposed replacements: protein kinase binding Supporting Evidence: PMID:32327536 SIF2 physically associates with the FLS2-BAK1 PRR complex and interacts with and phosphorylates the guard cell SLOW ANION CHANNEL1 (SLAC1) |
| GO:0005634 nucleus | ISM GO_REF:0000122 | REMOVE | Summary: AtSubP sequence-based prediction of nuclear localization. Reason: SLAC1 is a ten-transmembrane-helix plasma-membrane channel; GFP fusions and BiFC consistently localize it to the plasma membrane, and no study reports nuclear SLAC1. The prediction is contradicted by experimental localization. Supporting Evidence: PMID:18305484 The plasma membrane protein SLAC1 is essential for stomatal closure PMID:18305482 is localized specifically to the plasma membrane of guard cells |
| GO:0005886 plasma membrane | IDA PMID:18305482 CO2 regulator SLAC1 and its homologues are essential for ani... | ACCEPT | Summary: SLAC1 localizes to the guard-cell plasma membrane. Reason: Plasma membrane localization is shown independently in two 2008 papers and by plasma-membrane-restricted BiFC with OST1; it is where SLAC1 mediates anion efflux. Supporting Evidence: PMID:18305482 The SLAC1 protein is a distant homologue of bacterial and fungal C4-dicarboxylate transporters, and is localized specifically to the plasma membrane of guard cells. PMID:19955405 YFP-fluorescence complementation was observed at the level of the plasma membrane exclusively |
| GO:0005886 plasma membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (cell membrane) to plasma membrane. Reason: Consistent with the experimental IDA row; UniProt's cell-membrane location is backed by four experimental papers. Supporting Evidence: PMID:18305484 The plasma membrane protein SLAC1 is essential for stomatal closure |
| GO:0006820 monoatomic anion transport | IMP PMID:18305484 SLAC1 is required for plant guard cell S-type anion channel ... | MODIFY | Summary: slac1 guard cells lack S-type anion currents, showing SLAC1 is required for anion efflux across the guard-cell plasma membrane. Reason: Correct but general. SLAC1 itself is the pore that conducts anions across the plasma membrane, so monoatomic anion transmembrane transport (GO:0098656), which the gene already carries, is the appropriate is_a descendant. Proposed replacements: monoatomic anion transmembrane transport Supporting Evidence: PMID:18305484 Mutations in SLAC1 impair slow (S-type) anion channel currents that are activated by cytosolic Ca2+ and abscisic acid, but do not affect rapid (R-type) anion channel currents or Ca2+ channel function. |
| GO:0006873 intracellular monoatomic ion homeostasis | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro (SLAC/SLAH family) mapping to intracellular ion homeostasis. Reason: Supported by the SLAC1 mutant over-accumulation of guard-cell anions and by complementation with SLAH family members, which led the authors to propose a conserved role in anion homeostasis. This is a consequence of channel-mediated anion efflux rather than the primary physiological role (stomatal closure), so it is retained as non-core. Supporting Evidence: PMID:18305482 These results suggest that SLAC1-family proteins have an evolutionarily conserved function that is required for the maintenance of organic/inorganic anion homeostasis on the cellular level. |
| GO:0006873 intracellular monoatomic ion homeostasis | IMP PMID:18305482 CO2 regulator SLAC1 and its homologues are essential for ani... | KEEP AS NON CORE | Summary: slac1 guard-cell protoplasts over-accumulate osmoregulatory anions, which is relieved by SLAC1 or SLAH expression. Reason: Phenotype directly supports a role in guard-cell anion homeostasis; kept as non-core because it is the cellular consequence of the core anion-efflux activity. Consistent with the IEA row for the same term. Supporting Evidence: PMID:18305482 The loss-of-function mutation in SLAC1 was accompanied by an over-accumulation of the osmoregulatory anions in guard cell protoplasts. |
| GO:0008308 voltage-gated monoatomic anion channel activity | IDA PMID:20385816 Guard cell anion channel SLAC1 is regulated by CDPK protein ... | ACCEPT | Summary: SLAC1 coexpressed with CPK21 or CPK23 in Xenopus oocytes produces S-type anion currents. Reason: Core activity. SLAC1 forms the anion-selective, weakly voltage-dependent S-type channel pore; it is silent alone and becomes active when phosphorylated by OST1 or CPKs. Pore identity is confirmed by the structural and mutagenesis work (Phe450 gate) and by cryo-EM of AtSLAC1. Supporting Evidence: PMID:20385816 Upon coexpression of SLAC1 with CPK21 and 23, anion currents document SLAC1 stimulation by these guard cell protein kinases. PMID:19955405 Our studies demonstrate that SLAC1 represents the slow, deactivating, weak voltage-dependent anion channel of guard cells controlled by phosphorylation/dephosphorylation. |
| GO:0008308 voltage-gated monoatomic anion channel activity | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro SLAC/SLAH family mapping to voltage-gated anion channel activity. Reason: Consistent with the experimental electrophysiology on SLAC1 itself; the SLAC/SLAH family are S-type anion channels. Supporting Evidence: PMID:19955405 Upon coexpression of SLAC1 with OST1 in Xenopus oocytes, SLAC1-related anion currents appeared similar to those observed in guard cells. |
| GO:0008509 monoatomic anion transmembrane transporter activity | IDA DOI:10.1038/nature09487 | MODIFY | Summary: Structure-guided mutagenesis of AtSLAC1 in Xenopus oocytes defines the channel pore and the Phe450 gate (paper is PMID:20981093). Reason: Correct but general. The experiments characterize SLAC1 as a gated anion channel, so voltage-gated monoatomic anion channel activity (GO:0008308), an is_a descendant already annotated to SLAC1, is the precise term. Proposed replacements: voltage-gated monoatomic anion channel activity Supporting Evidence: PMID:20981093 In keeping with structural evidence that Phe262 blocks the HiTehA pore, removal of the phenyl group in HiTehA F262A or in the homologous AtSLAC1 F450A resulted in very large Cl− currents relative to wild-type levels PMID:20981093 The crystal structures of TehA and its mutant variants when taken together with the functional studies in Xenopus oocytes point to a crucial role for Phe450 in gating of the SLAC1 anion channel. |
| GO:0008509 monoatomic anion transmembrane transporter activity | IDA PMID:18305484 SLAC1 is required for plant guard cell S-type anion channel ... | MODIFY | Summary: Patch clamp of slac1 guard cells shows loss of S-type anion currents. Reason: Correct but general; SLAC1 is the S-type anion channel, so voltage-gated monoatomic anion channel activity (GO:0008308, an is_a descendant already on the gene) is the appropriate refinement. Note that this paper itself is genetic (loss of currents in mutants) and concluded only that SLAC1 is an essential subunit; direct channel activity was shown in later oocyte work. Proposed replacements: voltage-gated monoatomic anion channel activity Supporting Evidence: PMID:18305484 The data presented demonstrate that SLAC1 encodes an essential subunit for S-type anion channel function or regulation. PMID:19955405 Our studies demonstrate that SLAC1 represents the slow, deactivating, weak voltage-dependent anion channel of guard cells controlled by phosphorylation/dephosphorylation. |
| GO:0009270 response to humidity | IMP PMID:18305484 SLAC1 is required for plant guard cell S-type anion channel ... | KEEP AS NON CORE | Summary: slac1 plants respond much more slowly than wild type to lowered air humidity. Reason: Genuine phenotype, but it reflects SLAC1's role as the effector of stomatal closure common to many stimuli rather than a humidity-specific function. Supporting Evidence: PMID:18305484 slac1 exhibited a much slower response than the wild type to a decrease in the relative air humidity |
| GO:0009416 response to light stimulus | IMP PMID:29463779 Coordinating the overall stomatal response of plants: Rapid ... | KEEP AS NON CORE | Summary: SLAC1 is required for local and systemic stomatal closure in response to excess light. Reason: Supported phenotype; SLAC1 acts as the stomatal-closure effector downstream of the ROS wave, so the light response is non-core context for its channel function. Supporting Evidence: PMID:29463779 Furthermore, this response depended on the function of genes encoding the ROS-generating NADPH oxidase RBOHD and various stomatal regulators, such as the anion channel SLAC1 |
| GO:0009737 response to abscisic acid | IMP PMID:18305484 SLAC1 is required for plant guard cell S-type anion channel ... | KEEP AS NON CORE | Summary: slac1 stomata are strongly insensitive to ABA, and ABA-activated S-type currents are lost. Reason: Well supported; SLAC1 is the terminal ion-channel effector of ABA-induced stomatal closure, but the specific process it executes is stomatal closure (core), so the broad response term is non-core. Supporting Evidence: PMID:18305484 Stomata of slac1 mutants showed a strong insensitivity to ABA |
| GO:0010037 response to carbon dioxide | IMP PMID:18305484 SLAC1 is required for plant guard cell S-type anion channel ... | KEEP AS NON CORE | Summary: slac1 stomata do not close in response to elevated CO2. Reason: Strong phenotype (complete CO2 insensitivity); SLAC1 is the channel output of the CO2 relay (HT1-OST1-SLAC1). Kept as non-core context of the core stomatal closure role. Supporting Evidence: PMID:18305484 All slac1 alleles are recessive and show a complete lack of high CO 2 -induced stomatal closure |
| GO:0010118 stomatal movement | IMP PMID:18305484 SLAC1 is required for plant guard cell S-type anion channel ... | MODIFY | Summary: slac1 mutants are impaired in stomatal closure to many stimuli. Reason: Correct but general; the experimental phenotype is specifically loss of stomatal closure, so the is_a descendant stomatal closure (GO:0090332), already annotated by IBA and IMP, is the appropriate term. Proposed replacements: stomatal closure Supporting Evidence: PMID:18305484 The plasma membrane protein SLAC1 is essential for stomatal closure in response to CO2, abscisic acid, ozone, light/dark transitions, humidity change, calcium ions, hydrogen peroxide and nitric oxide. |
| GO:0010193 response to ozone | IMP PMID:18305484 SLAC1 is required for plant guard cell S-type anion channel ... | KEEP AS NON CORE | Summary: slac1 was isolated as an ozone-sensitive mutant whose stomata do not close in response to ozone. Reason: Supported; the ozone damage results from failure of ozone-induced stomatal closure, a context of SLAC1's core closure function. Supporting Evidence: PMID:18305484 Here we report the mapping and characterization of an ozone-sensitive Arabidopsis thaliana mutant, slac1. PMID:20128877 This revealed that the SLAC1 protein, essential for guard cell plasma membrane S-type anion channel function, and the protein kinase OST1 were required for the ROS-induced fast stomatal closure. |
| GO:0015698 inorganic anion transport | IDA DOI:10.1038/nature09487 | MODIFY | Summary: SLAC1 conducts chloride and other inorganic anions in oocytes (paper is PMID:20981093). Reason: Correct but general. SLAC1 is a plasma-membrane channel selective for nitrate and chloride, so the transmembrane-transport descendants chloride transmembrane transport (GO:1902476) and nitrate transmembrane transport (GO:0015706) are the specific supported terms (both is_a inorganic anion transport). Proposed replacements: chloride transmembrane transport nitrate transmembrane transport Supporting Evidence: PMID:20981093 removal of the phenyl group in HiTehA F262A or in the homologous AtSLAC1 F450A resulted in very large Cl− currents relative to wild-type levels PMID:19955405 In comparison the anions nitrate and thiocyanate similarly shifted V rev |
| GO:0016020 membrane | IDA DOI:10.1038/nature09487 | MODIFY | Summary: SLAC1 is an integral membrane protein (paper is PMID:20981093). Reason: Correct but general; SLAC1 is experimentally localized to the plasma membrane (GO:0005886), which it already carries. Proposed replacements: plasma membrane Supporting Evidence: PMID:18305482 is localized specifically to the plasma membrane of guard cells |
| GO:0016020 membrane | IEA GO_REF:0000002 | MODIFY | Summary: InterPro mapping to membrane. Reason: Correct but general; experimentally SLAC1 is in the plasma membrane (GO:0005886). Proposed replacements: plasma membrane Supporting Evidence: PMID:18305484 The plasma membrane protein SLAC1 is essential for stomatal closure |
| GO:0019901 protein kinase binding | IPI PMID:19955427 A protein kinase-phosphatase pair interacts with an ion chan... | KEEP AS NON CORE | Summary: SLAC1 binds the SnRK2 kinase OST1, which phosphorylates and activates it. Reason: Accurate description of a well-replicated interaction (several labs, BiFC and in vitro). Binding of the activating kinase is part of SLAC1's regulation rather than its core channel activity, so non-core. Supporting Evidence: PMID:19955427 Here we show that the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. |
| GO:0019901 protein kinase binding | IPI PMID:20385816 Guard cell anion channel SLAC1 is regulated by CDPK protein ... | KEEP AS NON CORE | Summary: Interaction of SLAC1 with CPK6 reported in the CPK study (abstract names CPK21 and CPK23 as the major partners). Reason: The curated UniProt record lists CPK6 among SLAC1 interactors from this paper; the cached abstract does not mention CPK6, so we defer to the curator who read the full text. Kinase binding is regulatory, non-core. Supporting Evidence: UniProtKB:Q9LD83 Interacts with SRK2E, CPK6, CPK21, CPK23 and PP2CA. |
| GO:0019901 protein kinase binding | IPI PMID:20385816 Guard cell anion channel SLAC1 is regulated by CDPK protein ... | KEEP AS NON CORE | Summary: SLAC1 binds CPK23, which activates it largely independently of Ca2+. Reason: Supported interaction with an activating kinase; regulatory, non-core. Supporting Evidence: PMID:20385816 Split YFP-based protein-protein interaction assays, using SLAC1 as the bait, identified guard cell expressed CPK21 and 23 as major interacting partners. |
| GO:0019901 protein kinase binding | IPI PMID:20385816 Guard cell anion channel SLAC1 is regulated by CDPK protein ... | KEEP AS NON CORE | Summary: SLAC1 binds CPK21, which confers Ca2+-dependent activation. Reason: Supported interaction with an activating kinase; regulatory, non-core. Supporting Evidence: PMID:20385816 Ca(2+)-sensitive activation of SLAC1, however, could be assigned to the CPK21 pathway only because CPK23 turned out to be rather Ca(2+)-insensitive. |
| GO:0019903 protein phosphatase binding | IPI PMID:19955427 A protein kinase-phosphatase pair interacts with an ion chan... | KEEP AS NON CORE | Summary: The clade A PP2C PP2CA binds SLAC1 directly and inhibits it. Reason: Supported interaction that mediates negative regulation of the channel; regulatory, non-core. Supporting Evidence: PMID:19955427 PP2CA, one of the PP2C phosphatase family members acts in an opposing manner and inhibits the activity of SLAC1 by two mechanisms: (1) direct interaction with SLAC1 itself |
| GO:0050891 multicellular organismal-level water homeostasis | IMP PMID:18305484 SLAC1 is required for plant guard cell S-type anion channel ... | KEEP AS NON CORE | Summary: Excised slac1 leaves lose water much faster than wild type. Reason: Supported organismal consequence of defective stomatal closure; non-core. Supporting Evidence: PMID:18305484 Water loss from excised slac1 leaves resulted in 70–80% fresh weight loss after 90 min, whereas in the wild type, fresh weight loss was only 30% after 90 min |
| GO:0055085 transmembrane transport | IDA DOI:10.1038/nature09487 | MODIFY | Summary: Anion conductance by SLAC1 in oocytes (paper is PMID:20981093). Reason: Correct but very general; the transported species are anions, so monoatomic anion transmembrane transport (GO:0098656), already on the gene, is the supported is_a descendant. Proposed replacements: monoatomic anion transmembrane transport Supporting Evidence: PMID:20981093 removal of the phenyl group in HiTehA F262A or in the homologous AtSLAC1 F450A resulted in very large Cl− currents relative to wild-type levels |
| GO:0055085 transmembrane transport | IEA GO_REF:0000002 | MODIFY | Summary: InterPro TehA/SLAC1 family mapping to transmembrane transport. Reason: Correct but general; monoatomic anion transmembrane transport (GO:0098656) is the specific supported term. Proposed replacements: monoatomic anion transmembrane transport Supporting Evidence: PMID:19955405 Upon coexpression of SLAC1 with OST1 in Xenopus oocytes, SLAC1-related anion currents appeared similar to those observed in guard cells. |
| GO:0090332 stomatal closure | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference of stomatal closure for the SLAC1 clade; SLAC1's own experimental data seed the node. Reason: Core process. SLAC1 executes the anion-efflux step that depolarizes guard cells and drives turgor loss; its presence among the IBA sources reflects its own experimental grounding. Supporting Evidence: PMID:18305484 The plasma membrane protein SLAC1 is essential for stomatal closure in response to CO2, abscisic acid, ozone, light/dark transitions, humidity change, calcium ions, hydrogen peroxide and nitric oxide. |
| GO:0090332 stomatal closure | IMP PMID:23396828 Nitrated cyclic GMP modulates guard cell signaling in Arabid... | ACCEPT | Summary: 8-nitro-cGMP-induced stomatal closure requires SLAC1. Reason: Consistent with SLAC1's core role in stomatal closure; SLAC1 acts downstream of the NO/8-nitro-cGMP messenger. Supporting Evidence: PMID:23396828 Moreover, inhibitor and genetic studies showed that calcium, cyclic adenosine-5'-diphosphate-ribose, and SLOW ANION CHANNEL1 act downstream of 8-nitro-cGMP. |
| GO:0090333 regulation of stomatal closure | IMP PMID:29463779 Coordinating the overall stomatal response of plants: Rapid ... | MODIFY | Summary: slac1 mutants lack local and systemic light-stress-induced stomatal closure. Reason: SLAC1 does not regulate stomatal closure; it is the channel that carries out the anion efflux that constitutes the closing movement. The phenotype supports stomatal closure (GO:0090332), the term used for SLAC1 elsewhere. Proposed replacements: stomatal closure Supporting Evidence: PMID:29463779 Furthermore, this response depended on the function of genes encoding the ROS-generating NADPH oxidase RBOHD and various stomatal regulators, such as the anion channel SLAC1 |
| GO:0098656 monoatomic anion transmembrane transport | IEA GO_REF:0000120 | ACCEPT | Summary: Process inferred from the anion channel MF annotations. Reason: SLAC1 conducts anions (chiefly NO3- and Cl-, weakly malate) across the plasma membrane; this is the direct process of its channel activity. Supporting Evidence: PMID:19955405 Upon coexpression of SLAC1 with OST1 in Xenopus oocytes, SLAC1-related anion currents appeared similar to those observed in guard cells. |
| GO:1902456 regulation of stomatal opening | IMP PMID:23766366 Calcium-dependent and -independent stomatal signaling networ... | KEEP AS NON CORE | Summary: slac1 mutants show altered stomatal opening, attributed to compensatory feedback on guard-cell signalling. Reason: The cached record is a one-sentence abstract, so the precise phenotype cannot be checked; we defer to the curator. A role in stomatal opening is independently supported by SLAC1's inhibition of KAT1, which suppresses opening. Direction of effect differs between studies (indirect feedback vs direct inhibition), so the neutral regulation term is kept, as non-core. Supporting Evidence: PMID:23766366 Guard cells use compensatory feedback controls to adapt to conditions that produce excessively open stomata. PMID:27002025 the over-expression of wild type and truncated SLAC1 dramatically impaired K+in currents of guard cells and light-induced stomatal opening |
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Download this section (compressed HTML)Q: Is potassium channel inhibitor activity (KAT1, AKT2) a physiologically significant SLAC1 function, given that it rests on a single study, and should TAIR annotate GO:0070320 (KAT1) and GO:0019870 (AKT2) to SLAC1?
Q: How does SLAC1 integrate phosphorylation by multiple kinases (OST1, CPK6/21/23, SIF2, and the GHR1 pseudokinase scaffold) at distinct N-terminal sites to set channel open probability?
Experiment: Test whether endogenous SLAC1 and KAT1 co-immunoprecipitate from guard-cell-enriched tissue and whether SLAC1 N-terminal peptides inhibit KAT1 currents in guard-cell patch clamp, to confirm the K+-channel inhibitor activity in planta.
Type: co-immunoprecipitation and electrophysiology
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