D6PK is a plant AGCVIII protein serine/threonine kinase that activates PIN-mediated auxin efflux by phosphorylating PIN cytoplasmic loops. It occupies the basal plasma membrane in many cells and cycles through intracellular trafficking compartments; during root-hair formation it can move into a planar polar membrane domain. Membrane recruitment involves polyacidic-phospholipid binding through a polybasic motif, S-acylated middle-domain cysteine motifs and PDK1-dependent regulation. D6PK and PID have overlapping but different PIN phosphosite preferences. D6PK activation of transport does not by itself establish a PIN polarity switch. Together with D6PK-like paralogs, it contributes to auxin transport, tropic growth and root-hair positioning.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004672 protein kinase activity | IDA PMID:19168677 The polarly localized D6 PROTEIN KINASE is required for effi... | MODIFY | Summary: D6PK protein kinase activity on PINs. Reason: Direct PIN phosphorylation establishes protein serine/threonine kinase activity, a more specific function than this broad kinase term and already retained in this review. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:19168677 D6PK phosphorylates PIN proteins in vitro and in vivo |
| GO:0004672 protein kinase activity | IEA GO_REF:0000120 | MODIFY | Summary: Protein kinase activity from ARBA/InterPro. Reason: Direct PIN phosphorylation establishes protein serine/threonine kinase activity, a more specific function than this broad kinase term and already retained in this review. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:19168677 D6PK phosphorylates PIN proteins in vitro and in vivo |
| GO:0004674 protein serine/threonine kinase activity | IBA GO_REF:0000033 | ACCEPT | Summary: AGCVIII serine/threonine kinase activity; consistent with direct D6PK phosphorylation of PINs. Reason: Core MF. Supporting Evidence: PMID:19168677 D6PK phosphorylates PIN proteins in vitro and in vivo |
| GO:0004674 protein serine/threonine kinase activity | IEA GO_REF:0000003 | ACCEPT | Summary: EC 2.7.11.1 mapping. Reason: Core MF. Supporting Evidence: PMID:19168677 D6PK phosphorylates PIN proteins in vitro and in vivo |
| GO:0005515 protein binding | IPI PMID:14749726 A protein kinase target of a PDK1 signalling pathway is invo... | REMOVE | Summary: Physical interaction of D6PK with PDK1. The cached abstract describes AGC2-1 (OXI1) as the PDK1 target studied; the D6PK (AGC1-1) interaction presumably comes from additional assays in the full text, which was not checked. GO:0005515 protein binding conveys no molecular function. Reason: The interaction assertion from PMID:14749726 is retained as mechanistic context (UniProtKB:Q9XF67), but bare protein binding does not specify the kinase reaction or a distinct functional binding role. REMOVE follows the uninformative-binding policy and does not deny the reported interaction. Supporting Evidence: PMID:14749726 AGC2-1 specifically interacts with AtPDK1 through a conserved C-terminal hydrophobic motif |
| GO:0005515 protein binding | IPI PMID:16973627 Structural and functional insights into the regulation of Ar... | REMOVE | Summary: Physical interaction of D6PK with PDK1 (AGCVIIIa kinases are PDK1 substrates). GO:0005515 protein binding conveys no molecular function. Reason: The interaction assertion from PMID:16973627 is retained as mechanistic context (UniProtKB:Q9XF67), but bare protein binding does not specify the kinase reaction or a distinct functional binding role. REMOVE follows the uninformative-binding policy and does not deny the reported interaction. Supporting Evidence: PMID:16973627 the majority of Arabidopsis AGCVIIIa kinases are substrates for the 3-phosphoinositide-dependent kinase 1 (PDK1) |
| GO:0005515 protein binding | IPI PMID:32612234 Extensive signal integration by the phytohormone protein net... | REMOVE | Summary: Physical interaction of D6PK with BREVIS RADIX (BRX) in a large-scale phytohormone Y2H interactome. GO:0005515 protein binding conveys no molecular function. Reason: The interaction assertion from PMID:32612234 is retained as mechanistic context (UniProtKB:Q17TI5), but bare protein binding does not specify the kinase reaction or a distinct functional binding role. REMOVE follows the uninformative-binding policy and does not deny the reported interaction. Supporting Evidence: PMID:32612234 we experimentally generated a systems-level map of the Arabidopsis phytohormone signalling network |
| GO:0005515 protein binding | IPI PMID:33705718 AGC kinases and MAB4/MEL proteins maintain PIN polarity by l... | REMOVE | Summary: Physical interaction of D6PK with MEL1/NPY5, an NPH3-family PIN polarity adaptor. GO:0005515 protein binding conveys no molecular function. Reason: The interaction assertion from PMID:33705718 is retained as mechanistic context (UniProtKB:Q0WL52), but bare protein binding does not specify the kinase reaction or a distinct functional binding role. REMOVE follows the uninformative-binding policy and does not deny the reported interaction. Supporting Evidence: PMID:33705718 Indeed, HIS-D6PK was clearly pulled down with GST-MEL1 |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: ATP binding of the kinase domain. Reason: ATP is the phosphate-donor substrate of the experimentally demonstrated kinase reaction. Binding is integral to the catalytic mechanism, not a peripheral activity merely because it is a binding annotation. Supporting Evidence: PMID:24948515 a kinase-dead variant of D6PK could not activate auxin efflux in this system |
| GO:0005546 phosphatidylinositol-4,5-bisphosphate binding | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | ACCEPT | Summary: D6PK bound PI(4,5)P2 in lipid-binding assays. D6PK binds polyacidic phospholipids rather broadly through a polybasic lysine-rich motif, which targets it to the plasma membrane. Reason: Direct lipid binding contributes to D6PK recruitment to its functional membrane compartment. The 2015 GST-D6PK overlay and the independent 2016 lipid-binding/motif studies support this chemistry; the membrane-recruitment role is integral to PIN phosphorylation, not peripheral solely because it is binding. Supporting Evidence: PMID:27836964 We further show that D6PK directly binds polyacidic phospholipids through a polybasic lysine-rich motif in the middle domain of the kinase. |
| GO:0005547 phosphatidylinositol-3,4,5-trisphosphate binding | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | KEEP AS NON CORE | Summary: D6PK binds this phospholipid in the defined in vitro overlay assay. Reason: The directly inspected 2015 Fig.5 GST-D6PK lipid overlay supports this binding capability. A physiological role for each individual ligand is not established by the overlay; in particular, the PtdIns(3,4,5)P3 signal should not be promoted to a native plant signaling pathway. Retain the measured biochemical interaction as non-core rather than denying it because of uncertain endogenous ligand availability. Supporting Evidence: file:publications/url_https___www.nature.com_articles_nplants2015162_figures_5.md Protein-lipid overlay assay of lipid strips with 0.5 µg ml–1 GST (b) or GST–D6PK (c) detected by anti-GST antibody. |
| GO:0005634 nucleus | IBA GO_REF:0000033 | UNDECIDED | Summary: Nuclear localization remains unresolved for D6PK. Reason: The ancestral PTN000682243 or AtSubP nuclear assignment is not resolved by the recovered target data. D6PK has strong plasma-membrane evidence, but principal membrane localization does not exclude a nuclear population. The cited AGCVIII comparison is heterologous and highlights WAG1/KIPK nuclear versus PID peripheral enrichment; it does not establish an exhaustive negative for this target. The current family source lacks a recovered authoritative IBD record for this node, so no loss/node-pruning assertion is made. Propagation Review Root cause: UNRESOLVED Sources checked: PANTHER:PTN000682243 UNRESOLVED This ancestral identifier and the WAG1/KIPK-associated seed list are recorded in the original payload. A target-resolved IBD/tree placement was not recovered for the current family; plasma-membrane imaging alone cannot establish nuclear exclusion. No inferred node placement or source failure is asserted. Supporting Evidence: PMID:19168677 D6PK localizes to the basal (lower) membrane of Arabidopsis root cells, where it colocalizes with PIN1, PIN2 and PIN4. |
| GO:0005634 nucleus | ISM GO_REF:0000122 | UNDECIDED | Summary: Nuclear localization remains unresolved for D6PK. Reason: The ancestral PTN000682243 or AtSubP nuclear assignment is not resolved by the recovered target data. D6PK has strong plasma-membrane evidence, but principal membrane localization does not exclude a nuclear population. The cited AGCVIII comparison is heterologous and highlights WAG1/KIPK nuclear versus PID peripheral enrichment; it does not establish an exhaustive negative for this target. The current family source lacks a recovered authoritative IBD record for this node, so no loss/node-pruning assertion is made. Supporting Evidence: PMID:19168677 D6PK localizes to the basal (lower) membrane of Arabidopsis root cells, where it colocalizes with PIN1, PIN2 and PIN4. |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: D6PK cycles between the plasma membrane and endosomal compartments (BFA-sensitive), so a cytoplasmic/endosomal pool exists. Reason: Non-core; the active pool is at the basal plasma membrane. Supporting Evidence: PMID:33705718 the related, basally localized AGC1 D6 protein kinase (D6PK), which also phosphorylates PINs |
| GO:0005886 plasma membrane | EXP PMID:19168677 The polarly localized D6 PROTEIN KINASE is required for effi... | ACCEPT | Summary: D6PK localizes to the basal plasma membrane of root cells. Reason: Core location. Supporting Evidence: PMID:19168677 D6PK localizes to the basal (lower) membrane of Arabidopsis root cells, where it colocalizes with PIN1, PIN2 and PIN4. |
| GO:0005886 plasma membrane | IBA GO_REF:0000033 | ACCEPT | Summary: Plasma membrane localization of the AGCVIII kinases. Reason: Core location. Supporting Evidence: PMID:19168677 D6PK localizes to the basal (lower) membrane of Arabidopsis root cells, where it colocalizes with PIN1, PIN2 and PIN4. |
| GO:0005886 plasma membrane | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | ACCEPT | Summary: D6PK at the plasma membrane of root epidermal cells. Reason: Core location. Supporting Evidence: PMID:27251533 D6PK undergoes phosphatidylinositol-4,5-bisphosphate- and sterol-dependent basal-to-planar polarity switching into the polar, lipid-enriched domain just before hair formation |
| GO:0005886 plasma membrane | IDA PMID:33705718 AGC kinases and MAB4/MEL proteins maintain PIN polarity by l... | ACCEPT | Summary: D6PK at the plasma membrane. Reason: Core location. Supporting Evidence: PMID:33705718 the related, basally localized AGC1 D6 protein kinase (D6PK), which also phosphorylates PINs |
| GO:0005886 plasma membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular location: plasma membrane. Reason: Core location. Supporting Evidence: PMID:19168677 D6PK localizes to the basal (lower) membrane of Arabidopsis root cells, where it colocalizes with PIN1, PIN2 and PIN4. |
| GO:0006468 protein phosphorylation | IDA PMID:19168677 The polarly localized D6 PROTEIN KINASE is required for effi... | ACCEPT | Summary: D6PK phosphorylates PIN proteins. Reason: Process accompanying the core kinase activity. Supporting Evidence: PMID:19168677 D6PK phosphorylates PIN proteins in vitro and in vivo |
| GO:0009630 gravitropism | IMP PMID:29490064 Roles of AGCVIII Kinases in the Hypocotyl Phototropism of Ar... | KEEP AS NON CORE | Summary: D6PK-family mutants are defective in gravitropism. Reason: Physiological outcome of reduced PIN activation/auxin transport; non-core. Supporting Evidence: PMID:29490064 the D6PK family and AGC1-12 are critical components for both hypocotyl phototropism and gravitropism PMID:19168677 d6pk mutants have defects in lateral root initiation, root gravitropism, and shoot differentiation in axillary shoots |
| GO:0009638 phototropism | IMP PMID:29490064 Roles of AGCVIII Kinases in the Hypocotyl Phototropism of Ar... | KEEP AS NON CORE | Summary: D6PK-family kinases are required for first and second positive hypocotyl phototropism. Reason: Physiological outcome of D6PK-dependent PIN3/4/7 activation; non-core. Supporting Evidence: PMID:29490064 the D6PK family and AGC1-12 are critical components for both hypocotyl phototropism and gravitropism PMID:23709629 phototropic hypocotyl bending is strongly dependent on the activity of D6PKs and the PIN proteins PIN3, PIN4, and PIN7 |
| GO:0009925 basal plasma membrane | IDA PMID:19168677 The polarly localized D6 PROTEIN KINASE is required for effi... | ACCEPT | Summary: D6PK at the basal (lower) plasma membrane of root cells. Reason: Core polar location. Supporting Evidence: PMID:19168677 D6PK localizes to the basal (lower) membrane of Arabidopsis root cells, where it colocalizes with PIN1, PIN2 and PIN4. |
| GO:0009925 basal plasma membrane | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | ACCEPT | Summary: Basal plasma-membrane localization of D6PK in root epidermis prior to planar switching. Reason: Core location. Supporting Evidence: PMID:27251533 D6PK undergoes phosphatidylinositol-4,5-bisphosphate- and sterol-dependent basal-to-planar polarity switching into the polar, lipid-enriched domain just before hair formation |
| GO:0009925 basal plasma membrane | IDA PMID:33705718 AGC kinases and MAB4/MEL proteins maintain PIN polarity by l... | ACCEPT | Summary: D6PK is basally localized, where it phosphorylates basal PINs. Reason: Core polar location. Supporting Evidence: PMID:33705718 the related, basally localized AGC1 D6 protein kinase (D6PK), which also phosphorylates PINs |
| GO:0010314 phosphatidylinositol-5-phosphate binding | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | KEEP AS NON CORE | Summary: D6PK binds this phospholipid in the defined in vitro overlay assay. Reason: The directly inspected 2015 Fig.5 GST-D6PK lipid overlay supports this binding capability. A physiological role for each individual ligand is not established by the overlay; in particular, the PtdIns(3,4,5)P3 signal should not be promoted to a native plant signaling pathway. Retain the measured biochemical interaction as non-core rather than denying it because of uncertain endogenous ligand availability. Supporting Evidence: file:publications/url_https___www.nature.com_articles_nplants2015162_figures_5.md Protein-lipid overlay assay of lipid strips with 0.5 µg ml–1 GST (b) or GST–D6PK (c) detected by anti-GST antibody. |
| GO:0016301 kinase activity | ISS PMID:13678909 Growth signalling pathways in Arabidopsis and the AGC protei... | MODIFY | Summary: Kinase activity by similarity (AGC kinase review). Reason: Direct PIN phosphorylation establishes protein serine/threonine kinase activity, a more specific function than this broad kinase term and already retained in this review. Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:13678909 The Arabidopsis AGC kinases contain sequence motives required for the docking of PDK1 and phosphorylation of their activation loop in the kinase catalytic domain. |
| GO:0032266 phosphatidylinositol-3-phosphate binding | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | KEEP AS NON CORE | Summary: D6PK binds this phospholipid in the defined in vitro overlay assay. Reason: The directly inspected 2015 Fig.5 GST-D6PK lipid overlay supports this binding capability. A physiological role for each individual ligand is not established by the overlay; in particular, the PtdIns(3,4,5)P3 signal should not be promoted to a native plant signaling pathway. Retain the measured biochemical interaction as non-core rather than denying it because of uncertain endogenous ligand availability. Supporting Evidence: file:publications/url_https___www.nature.com_articles_nplants2015162_figures_5.md Protein-lipid overlay assay of lipid strips with 0.5 µg ml–1 GST (b) or GST–D6PK (c) detected by anti-GST antibody. |
| GO:0045178 basal part of cell | IDA PMID:33705718 AGC kinases and MAB4/MEL proteins maintain PIN polarity by l... | MODIFY | Summary: Basal part of cell. Reason: D6PK is associated with the basal plasma membrane rather than an unspecified basal cell region. Proposed replacements: basal plasma membrane Supporting Evidence: PMID:33705718 the related, basally localized AGC1 D6 protein kinase (D6PK), which also phosphorylates PINs |
| GO:0048766 root hair initiation | IMP PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | KEEP AS NON CORE | Summary: D6PK modulates root-hair positioning (planar polarity) in root epidermal cells, switching into the lipid-enriched hair initiation domain. Reason: D6PK is a modulator rather than a core component of root hair initiation; non-core. Supporting Evidence: PMID:27251533 D6PK undergoes phosphatidylinositol-4,5-bisphosphate- and sterol-dependent basal-to-planar polarity switching into the polar, lipid-enriched domain just before hair formation |
| GO:0070273 phosphatidylinositol-4-phosphate binding | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | ACCEPT | Summary: D6PK bound PI4P in lipid-binding assays. D6PK binds polyacidic phospholipids rather broadly through a polybasic lysine-rich motif, which targets it to the plasma membrane. Reason: Direct lipid binding contributes to D6PK recruitment to its functional membrane compartment. The 2015 GST-D6PK overlay and the independent 2016 lipid-binding/motif studies support this chemistry; the membrane-recruitment role is integral to PIN phosphorylation, not peripheral solely because it is binding. Supporting Evidence: PMID:27836964 We further show that D6PK directly binds polyacidic phospholipids through a polybasic lysine-rich motif in the middle domain of the kinase. |
| GO:0070300 phosphatidic acid binding | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | ACCEPT | Summary: D6PK bound phosphatidic acid in lipid-binding assays. D6PK binds polyacidic phospholipids rather broadly through a polybasic lysine-rich motif, which targets it to the plasma membrane. Reason: Direct lipid binding contributes to D6PK recruitment to its functional membrane compartment. The 2015 GST-D6PK overlay and the independent 2016 lipid-binding/motif studies support this chemistry; the membrane-recruitment role is integral to PIN phosphorylation, not peripheral solely because it is binding. Supporting Evidence: PMID:27836964 We further show that D6PK directly binds polyacidic phospholipids through a polybasic lysine-rich motif in the middle domain of the kinase. |
| GO:0071944 cell periphery | IDA PMID:29490064 Roles of AGCVIII Kinases in the Hypocotyl Phototropism of Ar... | MODIFY | Summary: Cell periphery localization. Reason: The imaged cell-peripheral kinase pool is at the plasma membrane, supported independently by target localization and membrane-recruitment studies. Refine the broad cellular region. Proposed replacements: plasma membrane Supporting Evidence: PMID:19168677 D6PK localizes to the basal (lower) membrane of Arabidopsis root cells, where it colocalizes with PIN1, PIN2 and PIN4. |
| GO:0071944 cell periphery | IDA PMID:33705718 AGC kinases and MAB4/MEL proteins maintain PIN polarity by l... | MODIFY | Summary: Cell periphery. Reason: The imaged cell-peripheral kinase pool is at the plasma membrane, supported independently by target localization and membrane-recruitment studies. Refine the broad cellular region. Proposed replacements: plasma membrane Supporting Evidence: PMID:33705718 the related, basally localized AGC1 D6 protein kinase (D6PK), which also phosphorylates PINs |
| GO:0080025 phosphatidylinositol-3,5-bisphosphate binding | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | KEEP AS NON CORE | Summary: D6PK binds this phospholipid in the defined in vitro overlay assay. Reason: The directly inspected 2015 Fig.5 GST-D6PK lipid overlay supports this binding capability. A physiological role for each individual ligand is not established by the overlay; in particular, the PtdIns(3,4,5)P3 signal should not be promoted to a native plant signaling pathway. Retain the measured biochemical interaction as non-core rather than denying it because of uncertain endogenous ligand availability. Supporting Evidence: file:publications/url_https___www.nature.com_articles_nplants2015162_figures_5.md Protein-lipid overlay assay of lipid strips with 0.5 µg ml–1 GST (b) or GST–D6PK (c) detected by anti-GST antibody. |
| GO:0106310 protein serine kinase activity | EXP PMID:19168677 The polarly localized D6 PROTEIN KINASE is required for effi... | ACCEPT | Summary: D6PK phosphorylates serines of PIN proteins in vitro and in vivo. Reason: Core MF (substrate-level evidence). Supporting Evidence: PMID:19168677 D6PK phosphorylates PIN proteins in vitro and in vivo |
| GO:0106310 protein serine kinase activity | IEA GO_REF:0000116 | ACCEPT | Summary: Protein serine kinase activity (Rhea). D6PK phosphorylates serines in the PIN loop. Reason: Correct. Supporting Evidence: PMID:19168677 D6PK phosphorylates PIN proteins in vitro and in vivo |
| GO:1901981 phosphatidylinositol phosphate binding | IDA PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | ACCEPT | Summary: D6PK binds phosphoinositides; PI(4,5)P2 and the PIP5K1/PIP5K2 kinases are required for its plasma-membrane and polar association. Reason: Direct lipid binding contributes to D6PK recruitment to its functional membrane compartment. The 2015 GST-D6PK overlay and the independent 2016 lipid-binding/motif studies support this chemistry; the membrane-recruitment role is integral to PIN phosphorylation, not peripheral solely because it is binding. Supporting Evidence: PMID:27836964 We further show that D6PK directly binds polyacidic phospholipids through a polybasic lysine-rich motif in the middle domain of the kinase. PMID:27251533 D6PK undergoes phosphatidylinositol-4,5-bisphosphate- and sterol-dependent basal-to-planar polarity switching into the polar, lipid-enriched domain just before hair formation |
| GO:2000114 regulation of establishment of cell polarity | IMP PMID:27251533 Arabidopsis D6PK is a lipid domain-dependent mediator of roo... | KEEP AS NON CORE | Summary: D6PK modulates planar polarity of root-hair positioning. Reason: Secondary role; non-core. Supporting Evidence: PMID:27251533 the AGCVIII kinase D6 PROTEIN KINASE (D6PK) is a modulator of this process |
| GO:2000012 regulation of auxin polar transport | IDA PMID:24948515 Auxin efflux by PIN-FORMED proteins is activated by two diff... | NEW | Summary: NEW annotation. D6PK directly activates PIN1- and PIN3-mediated auxin efflux in Xenopus oocytes in a kinase-activity-dependent manner, and d6pk mutants have reduced basipetal auxin transport in stems and hypocotyls. Reason: D6PK performs the regulatory phosphorylation of the transporter. GOA carries only phenotype-level process terms (tropisms, root hair initiation) and no transport-regulation term. Supporting Evidence: PMID:24948515 PIN-mediated auxin transport is directly activated by D6 PROTEIN KINASE (D6PK) and PINOID (PID)/WAG kinases of the Arabidopsis AGCVIII kinase family PMID:24948515 a kinase-dead variant of D6PK could not activate auxin efflux in this system PMID:23709629 This is accompanied by a reduction of basipetal auxin transport in the hypocotyls of d6pk as well as in pin mutants. |
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Download this section (compressed HTML)Q: How is D6PK basal polarity maintained independently of PIN polarity, given its rapid BFA-sensitive endosomal cycling?
Suggested experts: Plant cell polarity researchers
Experiment: Reconstitute PIN1 or PIN3 with D6PK in proteoliposomes and compare transport kinetics of phosphomimic and phosphodead PIN variants at D6PK-preferred sites.
Hypothesis: D6PK-specific phosphosites on PINs increase transport turnover rather than PIN abundance at the membrane.
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