ZTL (ZEITLUPE; also ADAGIO 1/ADO1, LKP1) is a blue-light photoreceptor F-box protein of the ZTL/FKF1/LKP2 family in Arabidopsis. It has a unique tripartite architecture, an N-terminal LOV (light, oxygen, voltage) domain (a specialized PAS domain that binds an FMN chromophore and senses blue light) fused to an F-box and a C-terminal Kelch-repeat beta-propeller. The F-box recruits SKP1 and CUL1 to assemble an SCF-ZTL E3 ubiquitin ligase in which ZTL serves as the substrate-recognition subunit, and the Kelch repeats bind substrates. ZTL targets the core circadian clock proteins TIMING OF CAB EXPRESSION 1 (TOC1/PRR1) and PSEUDO-RESPONSE REGULATOR 5 (PRR5) for ubiquitin-dependent proteasomal degradation, thereby setting the pace (period) of the circadian oscillator and contributing to photomorphogenesis and photoperiodic flowering. ZTL activity and stability are gated by blue light through its LOV/FMN photosensor and through direct, blue-light-enhanced interaction with GIGANTEA (GI), which stabilizes ZTL. ZTL is found predominantly in the cytoplasm/cytosol, where it heterodimerizes with GI and acts on nucleocytoplasmically shuttling clock proteins.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:11260718 An Arabidopsis circadian clock component interacts with both... | REMOVE | Summary: Yeast two-hybrid and in vitro interaction of ZTL (ADO1) with the photoreceptor CRY1. The functional role of this interaction has not been established. Reason: Bare protein binding is uninformative, and the abstract gives no activity or regulatory consequence that a more specific term could capture. Removal does not mean the reported interaction is false. Supporting Evidence: PMID:11260718 Both yeast two-hybrid and in vitro binding studies show that there is a physical interaction between ADO1 and the photoreceptors CRY1 and phyB |
| GO:0005515 protein binding | IPI PMID:12795696 Protein interaction analysis of SCF ubiquitin E3 ligase subu... | MODIFY | Summary: Interaction of ZTL with the SKP1-like protein ASK11 (SKP1K). ZTL binds ASK proteins through its F-box, the step that assembles ZTL into an SCF E3 ubiquitin ligase in which ZTL is the substrate-recognition subunit. Reason: Bare protein binding carries no functional information. The informative function of the F-box/ASK interaction is the substrate-adaptor activity of the F-box subunit within SCF-ZTL, so MODIFY to GO:1990756, as done for FKF1 and other F-box proteins in this repository. The interaction itself is not in doubt. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:12795696 selected members of the protein family interact generally while others interact more specifically with members of the F-box protein family PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0005515 protein binding | IPI PMID:12795696 Protein interaction analysis of SCF ubiquitin E3 ligase subu... | MODIFY | Summary: Interaction of ZTL with the SKP1-like protein ASK1 (SKP1A). ZTL binds ASK proteins through its F-box, the step that assembles ZTL into an SCF E3 ubiquitin ligase in which ZTL is the substrate-recognition subunit. Reason: Bare protein binding carries no functional information. The informative function of the F-box/ASK interaction is the substrate-adaptor activity of the F-box subunit within SCF-ZTL, so MODIFY to GO:1990756, as done for FKF1 and other F-box proteins in this repository. The interaction itself is not in doubt. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:12795696 selected members of the protein family interact generally while others interact more specifically with members of the F-box protein family PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0005515 protein binding | IPI PMID:12795696 Protein interaction analysis of SCF ubiquitin E3 ligase subu... | MODIFY | Summary: Interaction of ZTL with the SKP1-like protein ASK2 (SKP1B). ZTL binds ASK proteins through its F-box, the step that assembles ZTL into an SCF E3 ubiquitin ligase in which ZTL is the substrate-recognition subunit. Reason: Bare protein binding carries no functional information. The informative function of the F-box/ASK interaction is the substrate-adaptor activity of the F-box subunit within SCF-ZTL, so MODIFY to GO:1990756, as done for FKF1 and other F-box proteins in this repository. The interaction itself is not in doubt. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:12795696 selected members of the protein family interact generally while others interact more specifically with members of the F-box protein family PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0005515 protein binding | IPI PMID:14654842 Targeted degradation of TOC1 by ZTL modulates circadian func... | MODIFY | Summary: Interaction of ZTL with its proteolytic substrate TOC1 (APRR1/PRR1). ZTL binds TOC1 and targets it for proteasome-dependent degradation; the ztl-1 Kelch mutation abolishes the interaction and stabilizes TOC1. Reason: Bare protein binding is uninformative. Binding of the F-box subunit to its ubiquitination substrate is the substrate-recruiting half of ubiquitin-ligase substrate-adaptor activity, so MODIFY to GO:1990756. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:14654842 The physical interaction of TOC1 with ZTL is abolished by the ztl-1 mutation, resulting in constitutive levels of TOC1 protein expression PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway |
| GO:0005515 protein binding | IPI PMID:15310821 Identification of ASK and clock-associated proteins as molec... | MODIFY | Summary: Interaction of ZTL with the SKP1-like protein ASK11 (SKP1K). ZTL binds ASK proteins through its F-box, the step that assembles ZTL into an SCF E3 ubiquitin ligase in which ZTL is the substrate-recognition subunit. This paper is mainly about the paralog LKP2; the abstract notes that ZTL family members also bind ASK proteins, and the ZTL interaction data are in the full text (not cached). Reason: Bare protein binding carries no functional information. The informative function of the F-box/ASK interaction is the substrate-adaptor activity of the F-box subunit within SCF-ZTL, so MODIFY to GO:1990756, as done for FKF1 and other F-box proteins in this repository. The interaction itself is not in doubt. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:15310821 LKP2 interacted with some Arabidopsis Skp1-like proteins (ASK), as do other ADO/FKF/LKP/ZTL family proteins PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0005515 protein binding | IPI PMID:15310821 Identification of ASK and clock-associated proteins as molec... | MODIFY | Summary: Interaction of ZTL with the SKP1-like protein ASK2 (SKP1B). ZTL binds ASK proteins through its F-box, the step that assembles ZTL into an SCF E3 ubiquitin ligase in which ZTL is the substrate-recognition subunit. This paper is mainly about the paralog LKP2; the abstract notes that ZTL family members also bind ASK proteins, and the ZTL interaction data are in the full text (not cached). Reason: Bare protein binding carries no functional information. The informative function of the F-box/ASK interaction is the substrate-adaptor activity of the F-box subunit within SCF-ZTL, so MODIFY to GO:1990756, as done for FKF1 and other F-box proteins in this repository. The interaction itself is not in doubt. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:15310821 LKP2 interacted with some Arabidopsis Skp1-like proteins (ASK), as do other ADO/FKF/LKP/ZTL family proteins PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0005515 protein binding | IPI PMID:15310821 Identification of ASK and clock-associated proteins as molec... | MODIFY | Summary: Interaction of ZTL with its proteolytic substrate TOC1 (APRR1/PRR1). ZTL binds TOC1 and targets it for proteasome-dependent degradation; the ztl-1 Kelch mutation abolishes the interaction and stabilizes TOC1. This paper is mainly about LKP2; the ZTL-TOC1 data are in the full text, which is not cached. Reason: Bare protein binding is uninformative. Binding of the F-box subunit to its ubiquitination substrate is the substrate-recruiting half of ubiquitin-ligase substrate-adaptor activity, so MODIFY to GO:1990756. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:14654842 The physical interaction of TOC1 with ZTL is abolished by the ztl-1 mutation, resulting in constitutive levels of TOC1 protein expression PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway |
| GO:0005515 protein binding | IPI PMID:15447654 Formation of an SCF(ZTL) complex is required for proper regu... | MODIFY | Summary: Interaction of ZTL with the SKP1-like protein ASK1 (SKP1A). ZTL binds ASK proteins through its F-box, the step that assembles ZTL into an SCF E3 ubiquitin ligase in which ZTL is the substrate-recognition subunit. Reason: Bare protein binding carries no functional information. The informative function of the F-box/ASK interaction is the substrate-adaptor activity of the F-box subunit within SCF-ZTL, so MODIFY to GO:1990756, as done for FKF1 and other F-box proteins in this repository. The interaction itself is not in doubt. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:15447654 F-box proteins are well-established components of the Skp/Cullin/F-box (SCF) class of E3 ubiquitin ligases that link the target substrates to the core ubiquitinating activity of the ligase complex via direct association with the Skp protein PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0005515 protein binding | IPI PMID:17704763 ZEITLUPE is a circadian photoreceptor stabilized by GIGANTEA... | MODIFY | Summary: Interaction of ZTL with its proteolytic substrate TOC1 (APRR1/PRR1). ZTL binds TOC1 and targets it for proteasome-dependent degradation; the ztl-1 Kelch mutation abolishes the interaction and stabilizes TOC1. Reason: Bare protein binding is uninformative. Binding of the F-box subunit to its ubiquitination substrate is the substrate-recruiting half of ubiquitin-ligase substrate-adaptor activity, so MODIFY to GO:1990756. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:14654842 The physical interaction of TOC1 with ZTL is abolished by the ztl-1 mutation, resulting in constitutive levels of TOC1 protein expression PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway |
| GO:0005515 protein binding | IPI PMID:17704763 ZEITLUPE is a circadian photoreceptor stabilized by GIGANTEA... | REMOVE | Summary: Interaction of ZTL with GIGANTEA. GI binds the ZTL LOV domain in a blue-light-enhanced manner and stabilizes ZTL; GI is a stabilizing partner, not a proteolytic substrate. Reason: Bare protein binding is uninformative and no GO term captures "binds a stabilizing partner" better. The functional content of this paper, blue-light-dependent LOV signalling that enhances GI binding, is already captured by the IDA GO:0009882 blue light photoreceptor activity row from the same paper. Removal does not mean the ZTL-GI interaction is in doubt; it is well established. Supporting Evidence: PMID:17704763 the ZTL-GI interaction is strongly and specifically enhanced by blue light, through the amino-terminal flavin-binding LIGHT, OXYGEN OR VOLTAGE (LOV) domain of ZTL PMID:17704763 These data establish ZTL as a blue-light photoreceptor, which facilitates its own stability through a blue-light-enhanced GI interaction |
| GO:0005515 protein binding | IPI PMID:18055606 PRR3 Is a vascular regulator of TOC1 stability in the Arabid... | MODIFY | Summary: Interaction of ZTL with its proteolytic substrate TOC1 (APRR1/PRR1). ZTL binds TOC1 and targets it for proteasome-dependent degradation; the ztl-1 Kelch mutation abolishes the interaction and stabilizes TOC1. Reason: Bare protein binding is uninformative. Binding of the F-box subunit to its ubiquitination substrate is the substrate-recruiting half of ubiquitin-ligase substrate-adaptor activity, so MODIFY to GO:1990756. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:18055606 PRR3 was able to bind to TOC1 in yeast and in plants and to perturb TOC1 interaction with ZEITLUPE (ZTL), which targets TOC1 for proteasome-dependent degradation |
| GO:0005515 protein binding | IPI PMID:20407420 PRR5 regulates phosphorylation, nuclear import and subnuclea... | MODIFY | Summary: Interaction of ZTL with its proteolytic substrate TOC1 (APRR1/PRR1). ZTL binds TOC1 and targets it for proteasome-dependent degradation; the ztl-1 Kelch mutation abolishes the interaction and stabilizes TOC1. Reason: Bare protein binding is uninformative. Binding of the F-box subunit to its ubiquitination substrate is the substrate-recruiting half of ubiquitin-ligase substrate-adaptor activity, so MODIFY to GO:1990756. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:20407420 In Arabidopsis, the F-box protein ZEITLUPE (ZTL) controls circadian period through the targeted proteasome-dependent degradation of TOC1 and PRR5 |
| GO:0005515 protein binding | IPI PMID:21798944 Evidence for network evolution in an Arabidopsis interactome... | MODIFY | Summary: Interaction of ZTL with the SKP1-like protein ASK1 (SKP1A). ZTL binds ASK proteins through its F-box, the step that assembles ZTL into an SCF E3 ubiquitin ligase in which ZTL is the substrate-recognition subunit. Detected in the Arabidopsis Interactome-1 yeast two-hybrid map. Reason: Bare protein binding carries no functional information. The informative function of the F-box/ASK interaction is the substrate-adaptor activity of the F-box subunit within SCF-ZTL, so MODIFY to GO:1990756, as done for FKF1 and other F-box proteins in this repository. The interaction itself is not in doubt. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:15447654 F-box proteins are well-established components of the Skp/Cullin/F-box (SCF) class of E3 ubiquitin ligases that link the target substrates to the core ubiquitinating activity of the ligase complex via direct association with the Skp protein PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0005515 protein binding | IPI PMID:21798944 Evidence for network evolution in an Arabidopsis interactome... | MODIFY | Summary: Interaction of ZTL with the SKP1-like protein ASK2 (SKP1B). ZTL binds ASK proteins through its F-box, the step that assembles ZTL into an SCF E3 ubiquitin ligase in which ZTL is the substrate-recognition subunit. Detected in the Arabidopsis Interactome-1 yeast two-hybrid map. Reason: Bare protein binding carries no functional information. The informative function of the F-box/ASK interaction is the substrate-adaptor activity of the F-box subunit within SCF-ZTL, so MODIFY to GO:1990756, as done for FKF1 and other F-box proteins in this repository. The interaction itself is not in doubt. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:15447654 F-box proteins are well-established components of the Skp/Cullin/F-box (SCF) class of E3 ubiquitin ligases that link the target substrates to the core ubiquitinating activity of the ligase complex via direct association with the Skp protein PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0005515 protein binding | IPI PMID:21798944 Evidence for network evolution in an Arabidopsis interactome... | MODIFY | Summary: Interaction of ZTL with its proteolytic substrate TOC1 (APRR1/PRR1). ZTL binds TOC1 and targets it for proteasome-dependent degradation; the ztl-1 Kelch mutation abolishes the interaction and stabilizes TOC1. Detected in the Arabidopsis Interactome-1 yeast two-hybrid map. Reason: Bare protein binding is uninformative. Binding of the F-box subunit to its ubiquitination substrate is the substrate-recruiting half of ubiquitin-ligase substrate-adaptor activity, so MODIFY to GO:1990756. Proposed replacements: ubiquitin-like ligase-substrate adaptor activity Supporting Evidence: PMID:14654842 The physical interaction of TOC1 with ZTL is abolished by the ztl-1 mutation, resulting in constitutive levels of TOC1 protein expression PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway |
| GO:0005634 nucleus | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Phylogenetic (PAINT) inference that ZTL is active in the nucleus, from the ZTL/FKF1/LKP2 clade with ZTL itself among the descendant evidence. ZTL has a time-of-day-dependent nuclear pool, but its principal site of action with GI and TOC1 is the cytosol. Reason: Correct (a nuclear ZTL pool is reported experimentally), but cytosol is the principal site of ZTL action, so nucleus is non-core. Supporting Evidence: PMID:10998191 LKP1 is a new nucleo-cytoplasmic factor that influences file:ARATH/ZTL/ZTL-notes.md So ZTL has a time-of-day-dependent nuclear pool |
| GO:0005634 nucleus | IDA PMID:10998191 LKP1 (LOV kelch protein 1): a factor involved in the regulat... | KEEP AS NON CORE | Summary: GFP-LKP1 (ZTL) fluorescence observed in nuclei and cytosol of overexpressing plants. Supports a nuclear pool; the main site of ZTL action is the cytosol. Reason: Experimentally observed, but not the principal location of ZTL activity. Supporting Evidence: PMID:10998191 LKP1 is a new nucleo-cytoplasmic factor that influences |
| GO:0005634 nucleus | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: Electronic location call mapped from a UniProtKB SubCell statement. ZTL is predominantly cytosolic, where it binds and stabilizes GIGANTEA. Swiss-Prot curation of the canonical ZTL entry (Q94BT6) also records a time-of-day-dependent nuclear pool (nuclear in the afternoon of long days), and ZTL's substrates TOC1 and PRR5 are nuclear clock proteins. The nucleus location is therefore correct, but it is not the principal site of ZTL activity. Reason: A nuclear pool of ZTL is reported, so the annotation is not wrong. The core location is cytosol (supported by IDA and IBA rows and used in core_functions), so nucleus is kept as non-core. Supporting Evidence: PMID:24004949 the levels of ZTL, a cytosolic protein, help govern the abundance and distribution of GI in the cytosol and nucleus file:ARATH/ZTL/ZTL-notes.md So ZTL has a time-of-day-dependent nuclear pool |
| GO:0005634 nucleus | ISM GO_REF:0000122 | KEEP AS NON CORE | Summary: AtSubP sequence-based prediction of nuclear localization. A nuclear ZTL pool is reported experimentally, but ZTL acts mainly in the cytosol. Reason: Prediction agrees with the reported time-of-day nuclear pool; not the core location. Supporting Evidence: PMID:10998191 LKP1 is a new nucleo-cytoplasmic factor that influences file:ARATH/ZTL/ZTL-notes.md So ZTL has a time-of-day-dependent nuclear pool |
| GO:0005634 nucleus | TAS PMID:10998191 LKP1 (LOV kelch protein 1): a factor involved in the regulat... | KEEP AS NON CORE | Summary: Traceable author statement of nuclear localization from the LKP1 GFP study, which reports nucleo-cytoplasmic localization. Reason: Correct but not the principal site of ZTL activity. Supporting Evidence: PMID:10998191 LKP1 is a new nucleo-cytoplasmic factor that influences |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Electronic location from the UniProt SubCell statement "Cytoplasm". ZTL is mainly cytoplasmic/cytosolic, where it binds GI and its substrates. Reason: Correct and consistent with experimental localization; cytosol (GO:0005829, IDA) is the more specific core term. Supporting Evidence: PMID:10998191 LKP1 is a new nucleo-cytoplasmic factor that influences PMID:24004949 the levels of ZTL, a cytosolic protein, help govern the abundance and distribution of GI in the cytosol and nucleus |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference that ZTL is active in the cytosol; ZTL appears in its own WITH/FROM, reflecting its experimental cytosol annotation. Consistent with experimental data that ZTL is mainly cytosolic, where it binds GI and TOC1. Reason: Consistent with direct evidence (GFP-LKP1 in cytosol; cytosolic ZTL-GI and ZTL-TOC1 interactions). Core location. Supporting Evidence: PMID:24004949 the levels of ZTL, a cytosolic protein, help govern the abundance and distribution of GI in the cytosol and nucleus PMID:20407420 PRR3 achieves this as a competitive inhibitor of the cytosolic TOC1–ZTL interaction |
| GO:0005829 cytosol | IDA PMID:10998191 LKP1 (LOV kelch protein 1): a factor involved in the regulat... | ACCEPT | Summary: GFP-LKP1 (ZTL) fluorescence observed in the cytosol (and nuclei). Cytosol is the main site of ZTL action with GI and TOC1. Reason: Direct observation; core location. Supporting Evidence: PMID:10998191 LKP1 is a new nucleo-cytoplasmic factor that influences |
| GO:0006511 ubiquitin-dependent protein catabolic process | IEA GO_REF:0000117 | MODIFY | Summary: ZTL is the substrate-recognition subunit of an SCF-ZTL E3 ubiquitin ligase that targets the clock proteins TOC1 and PRR5 for proteasome-dependent degradation. This electronic annotation is well supported by experimental literature and represents a core function. Reason: Direct experimental evidence shows ZTL controls proteasome-dependent degradation of TOC1 and PRR5. ZTL is the F-box substrate adaptor of SCF(ZTL), so the more specific child term SCF-dependent proteasomal ubiquitin-dependent protein catabolic process (GO:0031146), which ZTL already carries by IC and uses as its core process, is the appropriate term, as in the TIR1 and COI1 reviews. Proposed replacements: SCF-dependent proteasomal ubiquitin-dependent protein catabolic process Supporting Evidence: PMID:17693530 ZTL targets PRR5 for degradation by 26S proteasomes in the circadian clock and in early photomorphogenesis. PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway. file:ARATH/ZTL/ZTL-deep-research-falcon.md in an SCF E3 ligase that controls proteasome-mediated turnover of circadian proteins |
| GO:0006511 ubiquitin-dependent protein catabolic process | TAS PMID:11019805 Protein degradation in signaling. | MODIFY | Summary: Author statement from a review of ubiquitin/proteasome proteolysis in plant signaling. The claim is borne out by later experimental work on SCF-ZTL degradation of TOC1 and PRR5. Reason: Correct in substance, with experimental grounding from PMID:14654842 and PMID:17693530, but over-general for an F-box substrate adaptor. The specific child GO:0031146 (SCF-dependent proteasomal ubiquitin-dependent protein catabolic process) is used, as TIR1 and COI1 do for the identical PMID:11019805 row. Proposed replacements: SCF-dependent proteasomal ubiquitin-dependent protein catabolic process Supporting Evidence: PMID:11019805 Recent studies have linked proteolysis by the ubiquitin/proteasome pathway to a variety of signaling pathways in higher plants PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway |
| GO:0007623 circadian rhythm | IEA GO_REF:0000117 | ACCEPT | Summary: ZTL is a core component of the Arabidopsis circadian clock; rhythmic ZTL activity controls the degradation of TOC1 and PRR5 and is necessary to sustain a normal circadian period. Well supported as a core function. Reason: Genetic and molecular evidence establish ZTL's role in setting circadian period via timed degradation of clock proteins; the term fits the ~24 h clock process. Supporting Evidence: PMID:17704763 is necessary to sustain a normal circadian period by controlling the proteasome-dependent degradation of a central clock protein file:ARATH/ZTL/ZTL-deep-research-falcon.md ZTL is a central post-translational regulator of the Arabidopsis circadian oscillator, acting primarily through **protein turnover of TOC1 and PRR5** |
| GO:0007623 circadian rhythm | IMP PMID:11260718 An Arabidopsis circadian clock component interacts with both... | ACCEPT | Summary: The ado1 (ztl) loss-of-function mutant has a long period under constant white or blue light and is arrhythmic in red light. Reason: Direct mutant evidence for a role in circadian rhythm. Supporting Evidence: PMID:11260718 Under constant white or blue light, the ado1 mutant exhibits a longer period than that of wild-type Arabidopsis seedlings |
| GO:0007623 circadian rhythm | TAS PMID:10847686 ZEITLUPE encodes a novel clock-associated PAS protein from A... | ACCEPT | Summary: Author statement that ZTL is a clock-associated protein; ztl mutants lengthen free-running period. Reason: Correct; supported by the mutant data in the same paper. Supporting Evidence: PMID:10847686 mutations at a locus, ZEITLUPE (ZTL), that lengthen the free-running period of clock-controlled gene transcription |
| GO:0007623 circadian rhythm | TAS PMID:11260718 An Arabidopsis circadian clock component interacts with both... | ACCEPT | Summary: Author statement that ADO1 (ZTL) is a component of the Arabidopsis circadian system. Reason: Correct; supported by mutant data in the same paper. Supporting Evidence: PMID:11260718 We propose that ADO1 is an important component of the Arabidopsis circadian system |
| GO:0009637 response to blue light | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of response to blue light for the LOV/F-box/Kelch clade. ZTL is a blue-light photoreceptor whose GI interaction and stability are enhanced by blue light. Reason: The LOV-domain photoreceptor function is conserved across ZTL/FKF1/LKP2 and experimentally shown for ZTL. Supporting Evidence: PMID:17704763 These data establish ZTL as a blue-light photoreceptor, which facilitates its own stability through a blue-light-enhanced GI interaction |
| GO:0009637 response to blue light | IEA GO_REF:0000117 | ACCEPT | Summary: ZTL is a bona fide blue-light photoreceptor; its N-terminal LOV/FMN domain senses blue light and its interaction with GIGANTEA is strongly and specifically enhanced by blue light. Core function. Reason: Experimentally established blue-light photoreception through the flavin-binding LOV domain; the response-to-blue-light term is directly supported. Supporting Evidence: PMID:17704763 the ZTL-GI interaction is strongly and specifically enhanced by blue light, through the amino-terminal flavin-binding LIGHT, OXYGEN OR VOLTAGE (LOV) domain of ZTL file:ARATH/ZTL/ZTL-deep-research-falcon.md ZTL contains an N-terminal LOV domain (flavin-binding) that functions as a blue-light-regulated switch |
| GO:0009785 blue light signaling pathway | IEA GO_REF:0000108 | ACCEPT | Summary: Inferred from the blue light photoreceptor activity annotation by an inter-ontology link. ZTL senses blue light through its LOV domain and transduces it into GI-dependent stabilization and SCF-ZTL proteolysis of clock proteins. Reason: A logical consequence of ZTL being a blue-light photoreceptor whose signalling output (light-enhanced GI binding, stabilization, TOC1 turnover) is experimentally shown. Supporting Evidence: PMID:17704763 These data establish ZTL as a blue-light photoreceptor, which facilitates its own stability through a blue-light-enhanced GI interaction |
| GO:0009882 blue light photoreceptor activity | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of blue light photoreceptor activity, with ZTL itself among the descendant evidence. The LOV domain binds FMN, and a C82A mutation of the photochemically active cysteine abolishes blue-light-enhanced GI binding. Reason: Core molecular function; consistent with direct experimental evidence (IDA, PMID:17704763) and the conserved LOV/FMN domain. Supporting Evidence: PMID:17704763 These data establish ZTL as a blue-light photoreceptor, which facilitates its own stability through a blue-light-enhanced GI interaction PMID:17704763 a C82A mutation in the LOV domain, implicated in the flavin-dependent photochemistry, eliminates blue-light-enhanced binding of GI to ZTL |
| GO:0009882 blue light photoreceptor activity | IDA PMID:17704763 ZEITLUPE is a circadian photoreceptor stabilized by GIGANTEA... | ACCEPT | Summary: Direct evidence that ZTL is a blue-light photoreceptor: the FMN-binding LOV domain mediates blue-light-enhanced GI binding, abolished by the C82A photochemistry mutation. Reason: Defining molecular function of ZTL, directly demonstrated. Supporting Evidence: PMID:17704763 These data establish ZTL as a blue-light photoreceptor, which facilitates its own stability through a blue-light-enhanced GI interaction PMID:17704763 a C82A mutation in the LOV domain, implicated in the flavin-dependent photochemistry, eliminates blue-light-enhanced binding of GI to ZTL |
| GO:0009908 flower development | IMP PMID:10998191 LKP1 (LOV kelch protein 1): a factor involved in the regulat... | KEEP AS NON CORE | Summary: 35S:LKP1 (ZTL) overexpression delays flowering under long days but not short days. ZTL affects flowering time indirectly through the clock and photoperiod pathway. Reason: The overexpression phenotype is real but reflects clock/photoperiod effects downstream of TOC1/PRR5 turnover rather than a direct role in building flowers; non-core. Supporting Evidence: PMID:10998191 Expression of 35S:LKP1 in transgenic Arabidopsis promotes late flowering in plants grown under long-day, but not under short-day conditions |
| GO:0010114 response to red light | IMP PMID:16428597 Forward genetic analysis of the circadian clock separates th... | KEEP AS NON CORE | Summary: ztl mutations alter circadian and developmental (hypocotyl) responses to red light, possibly via the ZTL-PHYB interaction. Reason: Supported mutant phenotype, but red-light effects are indirect (ZTL does not absorb red light); non-core. Supporting Evidence: PMID:16428597 ztl mutations affect both circadian and developmental responses to red light, possibly through ZTL interaction with PHYTOCHROME B (PHYB) |
| GO:0010498 proteasomal protein catabolic process | IMP PMID:14654842 Targeted degradation of TOC1 by ZTL modulates circadian func... | ACCEPT | Summary: Mutant evidence that ZTL acts upstream of or within proteasomal degradation: TOC1 dark-dependent degradation requires functional ZTL and is blocked by proteasome inhibition. Reason: Directly supported and precise for what the mutant experiment shows, which is that TOC1 degradation requires ZTL and is blocked by proteasome inhibition. The paper does not itself show SCF dependence, so TAIR coded the SCF-dependent child GO:0031146 from this paper as IC (curator inference) rather than IMP. The experimental row is therefore kept at GO:0010498, and the SCF-specific process rests on the IC row and on the SCF-ZTL co-immunoprecipitation in PMID:15447654. Supporting Evidence: PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway |
| GO:0016567 protein ubiquitination | IEA GO_REF:0000041 | ACCEPT | Summary: As the F-box substrate-recognition subunit of an SCF-ZTL E3 ubiquitin ligase, ZTL mediates ubiquitination of its substrates (TOC1, PRR5), marking them for proteasomal degradation. Core function. Reason: ZTL forms an SCF-ZTL complex that ubiquitinates clock proteins; the protein ubiquitination term reflects this E3 ligase substrate-adapter role. Supporting Evidence: file:ARATH/ZTL/ZTL-notes.md an SCF^ZTL Complex Regulates Clock Function and Photomorphogenesis in Arabidopsis thaliana |
| GO:0019005 SCF ubiquitin ligase complex | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference that ZTL is part of an SCF ubiquitin ligase complex; ZTL is among the descendant evidence. Co-immunoprecipitation shows ZTL assembles with ASK1, CUL1 and RBX1 in vivo. Reason: Directly supported by in vivo co-immunoprecipitation of SCF-ZTL. Core complex membership. Supporting Evidence: PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo |
| GO:0019005 SCF ubiquitin ligase complex | IPI PMID:15447654 Formation of an SCF(ZTL) complex is required for proper regu... | ACCEPT | Summary: Co-immunoprecipitation of ZTL with core SCF subunits (ASK1, CUL1, RBX1) shows ZTL assembles into an SCF complex in vivo. Reason: Direct experimental support for SCF-ZTL. Core complex. Supporting Evidence: PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo PMID:15447654 our data establish SCFZTL as an essential SCF class E3 ligase controlling circadian period in plants |
| GO:0019005 SCF ubiquitin ligase complex | IPI PMID:15447654 Formation of an SCF(ZTL) complex is required for proper regu... | ACCEPT | Summary: Co-immunoprecipitation of ZTL with core SCF subunits (ASK1, CUL1, RBX1) shows ZTL assembles into an SCF complex in vivo. Reason: Direct experimental support for SCF-ZTL. Core complex. Supporting Evidence: PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo PMID:15447654 our data establish SCFZTL as an essential SCF class E3 ligase controlling circadian period in plants |
| GO:0031146 SCF-dependent proteasomal ubiquitin-dependent protein catabolic process | IC PMID:14654842 Targeted degradation of TOC1 by ZTL modulates circadian func... | ACCEPT | Summary: Curator inference (from ubiquitin-protein transferase activity) that ZTL participates in SCF-dependent proteasomal degradation. ZTL is required for proteasome-dependent degradation of TOC1, and forms an SCF complex. Reason: The most precise process term for ZTL: SCF-ZTL targets TOC1 and PRR5 to the proteasome. Core process. Supporting Evidence: PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway PMID:15447654 Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo PMID:17693530 ZTL targets PRR5 for degradation by 26S proteasomes in the circadian clock and in early photomorphogenesis |
| GO:0042752 regulation of circadian rhythm | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of regulation of circadian rhythm for the ZTL/FKF1/LKP2 clade. ZTL sets clock period by degrading TOC1 and PRR5; ztl loss of function lengthens period. Reason: Strongly supported for ZTL by mutant period phenotypes and its molecular mechanism (TOC1/PRR5 degradation). Supporting Evidence: PMID:10847686 mutations at a locus, ZEITLUPE (ZTL), that lengthen the free-running period of clock-controlled gene transcription PMID:14654842 The dark-dependent degradation of TOC1 protein requires functional ZTL, and is prevented by inhibiting the proteosome pathway |
| GO:0042752 regulation of circadian rhythm | IMP PMID:16428597 Forward genetic analysis of the circadian clock separates th... | ACCEPT | Summary: Forward genetic screen recovering multiple ztl alleles that alter circadian period, separating the functions of the ZTL domains. Reason: Mutant evidence for ZTL control of clock period, consistent with its core role. Supporting Evidence: PMID:16428597 The proposed function of ZTL is to target the TOC1 protein for degradation |
| GO:0043153 entrainment of circadian clock by photoperiod | IMP PMID:10847686 ZEITLUPE encodes a novel clock-associated PAS protein from A... | KEEP AS NON CORE | Summary: ztl mutants have a fluence-rate-dependent long period and altered daylength-dependent flowering, implicating ZTL in light input to the clock. Reason: ZTL contributes light (fluence-rate) input to the clock, but the mutant phenotype is a period change rather than a defect in entrainment per se; kept as non-core rather than as the core clock role. Supporting Evidence: PMID:10847686 The striking fluence rate-dependent effect of the ztl mutations suggests that ZTL plays a primary role in the photocontrol of circadian period in higher plants |
Loading supporting content…
Download this section (compressed HTML)Q: How does blue-light activation of the ZTL LOV domain change ZTL substrate (TOC1/PRR5) binding and ubiquitination, as opposed to GIGANTEA binding and ZTL stability?
Q: Does the time-of-day-dependent nuclear pool of ZTL contribute to TOC1/PRR5 degradation, or does ZTL act only on the cytosolic substrate pool?
Experiment: In vitro reconstitution of SCF-ZTL ubiquitination of TOC1 and PRR5 in dark versus blue light, with wild-type ZTL and the LOV C82A photochemistry mutant, to test whether photoactivation directly modulates substrate ubiquitination.
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)