OsPIN2 is a canonical PIN-family auxin efflux carrier in rice. It localizes asymmetrically at the plasma membrane of root epidermal and cortical cells and contributes to auxin redistribution, root gravitropic responses and root growth angle. Native mutants and complementation establish its developmental transport role; overexpression also alters shoot-to-root auxin distribution and tiller architecture. Transport function and homodimeric organization are supported by conserved PIN biochemistry, with homodimerization inferred from Arabidopsis PIN1 rather than directly measured for rice PIN2.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | UNDECIDED | Summary: ER localization is unresolved for rice PIN2. Reason: PAINT places the ER IBD at the land-plant ancestor PTN001589272 using Arabidopsis PIN6 (AT1G77110), PIN8 (AT5G15100), and PIN5 (AT5G16530). This is an ancestral localization judgment, not a pairwise transfer. Native rice root immunostaining establishes plasma-membrane localization (PMID:29294052), but neither excludes an ER pool nor measures ER residence. No target-specific loss or an erroneous tree placement has been established. The root-organelle claim is therefore unresolved, not replaced with plasma membrane. Propagation Review Root cause: UNRESOLVED Sources checked: PANTHER:PTN001589272 UNRESOLVED ER IBD and source identities inspected in the committed PTHR31752 PAINT table; native target ER residence remains untested in the inspected sources. Supporting Evidence: PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
| GO:0005886 plasma membrane | IBA GO_REF:0000033 | ACCEPT | Summary: Native rice PIN2 is localized at the plasma membrane. Reason: PMID:29294052 uses anti-OsPIN2 immunostaining with loss of signal in lra1 mutant roots. Epidermis and cortex have opposite membrane-face enrichment. This independently grounds the PAINT localization; the target appearing among descendant evidence is legitimate. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001589272 SUPPORTS TRANSFER Independent native rice localization supports inheritance of the plasma-membrane claim. Supporting Evidence: PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
| GO:0009921 auxin efflux carrier complex | IDA PMID:21777365 Over-expression of OsPIN2 leads to increased tiller numbers,... | ACCEPT | Summary: PIN2 is a component of the auxin efflux carrier complex. Reason: Retain the curator-assigned complex-component claim, independently corroborated by the experimentally curated UniProt function and inferred PIN homodimer architecture. PMID:21777365 is abstract-only locally, so it is not presented as a direct rice complex-assembly or stoichiometry measurement. The evidence supports carrier membership, not a universal obligatory PIN–ABCB heterocomplex. Supporting Evidence: file:ORYSJ/PIN2/PIN2-uniprot.txt Acts as a component of the auxin efflux carrier. file:ORYSJ/PIN2/PIN2-uniprot.txt Homodimer. {ECO:0000250|UniProtKB:Q9C6B8}. |
| GO:0009926 auxin polar transport | IBA GO_REF:0000033 | ACCEPT | Summary: PIN2 participates in native rice polar auxin transport. Reason: Rice overexpression changes shoot-to-root auxin distribution (PMID:21777365), while native lra1 loss and complementation, polar membrane localization and Arabidopsis pin2 complementation (PMID:29294052) establish the carrier role. DR5 is an auxin-response reporter, not a direct measurement of molecular transport rate. PIN2 performs the transport step; this is not participation inferred from necessity alone. Supporting Evidence: PMID:29294052 These results suggest that OsPIN2 plays a similar role to Arabidopsis PIN2 as an auxin efflux carrier that regulates the root gravitropic response in rice. PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
| GO:0009926 auxin polar transport | IMP PMID:21777365 Over-expression of OsPIN2 leads to increased tiller numbers,... | ACCEPT | Summary: PIN2 participates in native rice polar auxin transport. Reason: Rice overexpression changes shoot-to-root auxin distribution (PMID:21777365), while native lra1 loss and complementation, polar membrane localization and Arabidopsis pin2 complementation (PMID:29294052) establish the carrier role. DR5 is an auxin-response reporter, not a direct measurement of molecular transport rate. PIN2 performs the transport step; this is not participation inferred from necessity alone. Supporting Evidence: PMID:29294052 These results suggest that OsPIN2 plays a similar role to Arabidopsis PIN2 as an auxin efflux carrier that regulates the root gravitropic response in rice. PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
| GO:0010315 auxin export across the plasma membrane | ISS GO_REF:0000024 | ACCEPT | Summary: PIN2 supports auxin efflux across the plasma membrane. Reason: Conserved PIN transporter function, locus-specific native rice phenotypes, polar PM localization and complementation of Arabidopsis pin2 support this functional inference (PMID:29294052). The original ISS source is Arabidopsis PIN1 Q9C6B8; these rice studies do not constitute a purified-protein or oocyte transport assay. The IBA represents ancestral acquisition and is compatible with the native evidence. Supporting Evidence: PMID:29294052 These results suggest that OsPIN2 plays a similar role to Arabidopsis PIN2 as an auxin efflux carrier that regulates the root gravitropic response in rice. PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
| GO:0010329 auxin efflux transmembrane transporter activity | IBA GO_REF:0000033 | ACCEPT | Summary: PIN2 supports auxin efflux across the plasma membrane. Reason: Conserved PIN transporter function, locus-specific native rice phenotypes, polar PM localization and complementation of Arabidopsis pin2 support this functional inference (PMID:29294052). The original ISS source is Arabidopsis PIN1 Q9C6B8; these rice studies do not constitute a purified-protein or oocyte transport assay. The IBA represents ancestral acquisition and is compatible with the native evidence. Supporting Evidence: PMID:29294052 These results suggest that OsPIN2 plays a similar role to Arabidopsis PIN2 as an auxin efflux carrier that regulates the root gravitropic response in rice. PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
| GO:0010329 auxin efflux transmembrane transporter activity | ISS GO_REF:0000024 | ACCEPT | Summary: PIN2 supports auxin efflux across the plasma membrane. Reason: Conserved PIN transporter function, locus-specific native rice phenotypes, polar PM localization and complementation of Arabidopsis pin2 support this functional inference (PMID:29294052). The original ISS source is Arabidopsis PIN1 Q9C6B8; these rice studies do not constitute a purified-protein or oocyte transport assay. The IBA represents ancestral acquisition and is compatible with the native evidence. Supporting Evidence: PMID:29294052 These results suggest that OsPIN2 plays a similar role to Arabidopsis PIN2 as an auxin efflux carrier that regulates the root gravitropic response in rice. PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
| GO:0016020 membrane | IEA GO_REF:0000120 | MODIFY | Summary: Membrane localization can be refined to plasma membrane. Reason: Native immunostaining establishes the specific membrane (PMID:29294052), already represented by GO:0005886 in this review. This refines the generic membrane annotation and does not replace or disprove the separate ER root-organelle assertion. Proposed replacements: plasma membrane Supporting Evidence: PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
| GO:0042802 identical protein binding | ISS GO_REF:0000024 | MODIFY | Summary: Refine identical-protein binding to the supported homodimerization activity. Reason: The curated UniProt SUBUNIT statement infers homodimerization from Arabidopsis PIN1 Q9C6B8, the original ISS source. That specific assembly property is already represented by GO:0042803 in this review, so refine the broader identical-protein-binding claim to it. This retains the biological interaction without asserting direct rice oligomerization assays or other untested self-associated assemblies. Proposed replacements: protein homodimerization activity Supporting Evidence: file:ORYSJ/PIN2/PIN2-uniprot.txt Homodimer. {ECO:0000250|UniProtKB:Q9C6B8}. |
| GO:0042803 protein homodimerization activity | ISS GO_REF:0000024 | ACCEPT | Summary: PIN2 self-association is supported as a conserved homodimer inference. Reason: The curated UniProt SUBUNIT statement explicitly infers homodimerization from Arabidopsis PIN1 Q9C6B8, the original ISS source. This supports both specific identical-protein binding and homodimerization without claiming direct rice oligomerization assays. These are assembly properties of the transporter, not bare uninformative protein binding. Supporting Evidence: file:ORYSJ/PIN2/PIN2-uniprot.txt Homodimer. {ECO:0000250|UniProtKB:Q9C6B8}. |
| GO:0055085 transmembrane transport | IEA GO_REF:0000002 | MODIFY | Summary: Transmembrane transport is specifically auxin export. Reason: The broad family-level transport term is correct but less informative than the supported auxin-export process already represented by GO:0010315. Refine to that term; no additional process proposal is needed. Proposed replacements: auxin export across the plasma membrane Supporting Evidence: PMID:29294052 These results suggest that OsPIN2 plays a similar role to Arabidopsis PIN2 as an auxin efflux carrier that regulates the root gravitropic response in rice. PMID:29294052 In WT plants, signals were observed on the plasma membranes of epidermal and cortex cells in the root tip, and polar localization could be seen on the upper side in epidermal cells and on the lower side in cortex cells (Fig. 4A). |
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