TIR1 is the Arabidopsis F-box/LRR auxin receptor and substrate-recognition subunit of the SCF(TIR1) E3 ubiquitin ligase complex. Auxin binds the TIR1 pocket and promotes recruitment of Aux/IAA transcriptional repressors, leading to their SCF-dependent degradation and auxin-regulated transcription. Lateral-root, stamen, phosphate-starvation, and other developmental phenotypes are downstream outputs of this auxin receptor and degradation mechanism.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0019005 SCF ubiquitin ligase complex | IDA PMID:10398681 Identification of an SCF ubiquitin-ligase complex required f... | ACCEPT | Summary: TIR1 is a component of SCF(TIR1) ubiquitin ligase complexes. Reason: The SCF complex context is central to TIR1's auxin receptor/substrate-recognition function. |
| GO:0000151 ubiquitin ligase complex | IDA PMID:10398681 Identification of an SCF ubiquitin-ligase complex required f... | MODIFY | Summary: TIR1 is in a ubiquitin ligase complex, but the SCF-specific term is more precise. Reason: SCF ubiquitin ligase complex better captures the TIR1-containing complex. Proposed replacements: SCF ubiquitin ligase complex |
| GO:0010011 auxin binding | IDA PMID:17410169 Mechanism of auxin perception by the TIR1 ubiquitin ligase. | ACCEPT | Summary: Structural work shows auxin bound in the TIR1 receptor pocket. Reason: Auxin binding is a direct molecular property of TIR1. |
| GO:0010011 auxin binding | IDA PMID:18391211 Small-molecule agonists and antagonists of F-box protein-sub... | ACCEPT | Summary: Auxin agonist/antagonist studies support ligand binding by TIR1. Reason: Auxin binding is a direct molecular property of TIR1. Supporting Evidence: PMID:18391211 their mode of action in binding to TIR1 is confirmed by x-ray crystallographic analysis |
| GO:0038198 auxin receptor activity | IDA PMID:15917797 The F-box protein TIR1 is an auxin receptor. | ACCEPT | Summary: TIR1 is an auxin receptor that mediates Aux/IAA degradation and auxin-regulated transcription. Reason: Auxin receptor activity is the core molecular function of TIR1. Supporting Evidence: file:ARATH/TIR1/TIR1-deep-research-falcon.md |
| GO:0000822 inositol hexakisphosphate binding | IDA PMID:17410169 Mechanism of auxin perception by the TIR1 ubiquitin ligase. | KEEP AS NON CORE | Summary: The TIR1 structure contains an inositol hexakisphosphate cofactor. Reason: This is a supported cofactor-binding feature of the TIR1 receptor pocket, but the core molecular roles are auxin receptor and substrate-adaptor activity. |
| GO:0004842 ubiquitin-protein transferase activity | IC PMID:10398681 Identification of an SCF ubiquitin-ligase complex required f... | MODIFY | Summary: TIR1 contributes to SCF E3 ligase function as an F-box substrate receptor, but it is not the catalytic RING subunit. Reason: The term overstates TIR1's independent catalytic role; TIR1 is better represented as the auxin-dependent substrate adaptor of SCF(TIR1). Proposed replacements: ubiquitin-like ligase-substrate adaptor activity |
| GO:0009734 auxin-activated signaling pathway | IMP PMID:18391211 Small-molecule agonists and antagonists of F-box protein-sub... | ACCEPT | Summary: TIR1 mediates auxin-activated signaling through auxin-dependent Aux/IAA recruitment and degradation. Reason: This is the central biological process controlled by TIR1. Supporting Evidence: PMID:18391211 Auxin binding enhances the interaction between TIR1 and its substrates, the Aux/IAA repressors |
| GO:0016036 cellular response to phosphate starvation | IEP PMID:19106375 Phosphate availability alters lateral root development in Ar... | KEEP AS NON CORE | Summary: TIR1-dependent auxin sensitivity affects root responses to phosphate availability. Reason: Phosphate starvation response is a physiological output of auxin signaling. |
| GO:0010311 lateral root formation | IMP PMID:9436980 The TIR1 protein of Arabidopsis functions in auxin response ... | KEEP AS NON CORE | Summary: tir1 mutants affect lateral root formation. Reason: Lateral root formation is a downstream developmental output of auxin signaling. |
| GO:0010152 pollen maturation | IGI PMID:18628351 Auxin regulates Arabidopsis anther dehiscence, pollen matura... | KEEP AS NON CORE | Summary: Auxin signaling through TIR1/AFB proteins contributes to pollen maturation. Reason: Pollen maturation is a downstream reproductive output. |
| GO:0009733 response to auxin | IMP PMID:26236497 Untethering the TIR1 auxin receptor from the SCF complex inc... | KEEP AS NON CORE | Summary: Altering TIR1 stability and SCF association changes auxin response. Reason: The response term is correct but less mechanistic than auxin receptor activity and auxin-activated signaling. |
| GO:0009733 response to auxin | IMP PMID:9436980 The TIR1 protein of Arabidopsis functions in auxin response ... | KEEP AS NON CORE | Summary: tir1 mutants are deficient in auxin response phenotypes. Reason: The response term is correct but less mechanistic than auxin receptor activity and auxin-activated signaling. |
| GO:0048443 stamen development | IGI PMID:18628351 Auxin regulates Arabidopsis anther dehiscence, pollen matura... | KEEP AS NON CORE | Summary: Auxin signaling through TIR1/AFB proteins contributes to stamen development. Reason: Stamen development is a downstream reproductive output. |
| GO:0006511 ubiquitin-dependent protein catabolic process | TAS PMID:11019805 Protein degradation in signaling. | MODIFY | Summary: TIR1 participates in ubiquitin-dependent degradation, but the SCF-dependent term is more precise. Reason: TIR1 functions in SCF-dependent Aux/IAA degradation rather than generic ubiquitin-dependent catabolism. Proposed replacements: SCF-dependent proteasomal ubiquitin-dependent protein catabolic process |
| GO:0031146 SCF-dependent proteasomal ubiquitin-dependent protein catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: TIR1 family context supports SCF-dependent proteasomal degradation of Aux/IAA repressors. Reason: This is the core mechanistic process downstream of auxin-bound TIR1. |
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Q: Which TIR1/AFB developmental phenotypes should be represented directly versus modeled as downstream auxin transcriptional outputs?
Experiment: Quantify native TIR1-dependent Aux/IAA degradation kinetics across auxin analogs and SCF assembly mutants.
Experiment: Compare TIR1 versus related AFB subfamily members for substrate specificity and developmental-output specificity.
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