| Claim/Fact | Evidence summary | Organism/context | Source (with DOI URL) | Publication date/year | Citation ID(s) |
|---|---|---|---|---|---|
| Target identity from provided UniProt context | User-provided UniProt annotation identifies F6LAX4 as a **Triticum aestivum** protein phosphatase 2A structural/scaffold subunit family member, with gene name **LOC123103357**, linked to **TraesCS5A02G168400.5** and synonym **LOC123120841 / TraesCS5D02G172700.4**; domains reported include ARM-like/HEAT. However, retrieved literature did **not** directly map or experimentally characterize F6LAX4/LOC123103357/TraesCS5A02G168400 specifically, so annotation must be treated as family-based rather than gene-specific literature-backed. | Wheat; UniProt-derived target context plus literature gap | No direct paper retrieved for this exact wheat gene; family interpretation supported by PP2A-A structural reviews: https://doi.org/10.2174/1389202920666190517110605 ; https://doi.org/10.3390/kinasesphosphatases3010005 | UniProt context provided by user; supporting reviews 2019, 2025 | (pqac-00000000, pqac-00000001) |
| Canonical PP2A A-subunit structure | PP2A A is the **scaffolding/structural** subunit, approximately **~65 kDa**, built from **15 tandem HEAT repeats**; these repeats form a **horseshoe-shaped α-helical scaffold** characteristic of PR65/PP2AA proteins. | Eukaryotic PP2A; applicable to plant PP2AA family inference | Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 ; Cortelezzi et al. 2025, https://doi.org/10.3390/kinasesphosphatases3010005 | 2019; 2025 | (pqac-00000000, pqac-00000001, pqac-00000007) |
| Core biochemical role | The A subunit binds the **catalytic C subunit** to form the **PP2A core enzyme (A–C dimer)** and provides the platform for **regulatory B-subunit recruitment**. This is the principal function of a PP2AA protein; it is a scaffold, not the catalytic phosphatase itself. | General PP2A holoenzyme biology; used for functional annotation of wheat PP2AA-like proteins | Cortelezzi et al. 2025, https://doi.org/10.3390/kinasesphosphatases3010005 ; Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 | 2025; 2019 | (pqac-00000000, pqac-00000001, pqac-00000006, pqac-00000008) |
| Substrate specificity and localization logic | The **B subunit** is the major determinant of **substrate specificity**, **subcellular localization**, and modulation of enzymatic activity; thus a PP2AA scaffold influences substrate choice indirectly by enabling assembly of particular holoenzymes rather than recognizing phosphosubstrates directly. | General plant/eukaryotic PP2A principle | Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 ; Cortelezzi et al. 2025, https://doi.org/10.3390/kinasesphosphatases3010005 | 2019; 2025 | (pqac-00000000, pqac-00000006) |
| Assembly mechanism details | Conserved loops in A-subunit HEAT repeats contact both C and B subunits; C-subunit C-terminal **TPDYFL** motif and terminal Leu methylation promote B-subunit association with the A–C dimer, facilitating holoenzyme assembly. | Canonical PP2A assembly mechanism; inferred for plant PP2AA proteins | Cortelezzi et al. 2025, https://doi.org/10.3390/kinasesphosphatases3010005 ; Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 | 2025; 2019 | (pqac-00000001, pqac-00000002) |
| Localization evidence relevant to annotation | Reviews indicate plant A and B subunits show **diverse predicted/observed subcellular localizations**, whereas catalytic C subunits are more predominantly cytosolic. No direct localization experiment for wheat F6LAX4 was retrieved. | Plant PP2A family; not gene-specific for F6LAX4 | Cortelezzi et al. 2025, https://doi.org/10.3390/kinasesphosphatases3010005 | 2025 | (pqac-00000001) |
| Plant functional role: auxin/root development | PP2AA family members participate in **auxin distribution and root developmental control**. In Arabidopsis, **RCN1/PP2AA1** helps maintain normal auxin distribution and root stem cell function; genetic redundancy is evident because single **pp2aa2** or **pp2aa3** mutants are near-normal, whereas **rcn1 pp2aa2** and **rcn1 pp2aa3** double mutants show developmental defects. | Arabidopsis PP2AA family evidence informing plant functional annotation | Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 | 2019 | (pqac-00000005) |
| Plant functional role: low-phosphate adaptation | In maize, **ZmPP2AA1** is induced in roots by **low phosphate**; overexpression promotes **lateral and axial root formation**, alters free IAA/auxin sensitivity, and improves performance under Pi deficiency, showing a practical growth-regulatory role for PP2AA scaffolds in cereals. | Maize; closest cereal functional evidence for PP2AA application | Wang et al. 2017, https://doi.org/10.1371/journal.pone.0176538 ; summarized in Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 | 2017; 2019 | (pqac-00000005) |
| Broad plant roles | Plant PP2A complexes are described as key regulators of **abiotic stress**, **biotic stress**, and **developmental programs**; because A subunits are essential scaffolds for holoenzyme assembly, these roles are mechanistically relevant to PP2AA family members even when direct wheat-gene evidence is sparse. | Plant PP2A family overview | Cortelezzi et al. 2025, https://doi.org/10.3390/kinasesphosphatases3010005 ; Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 | 2025; 2019 | (pqac-00000006, pqac-00000000) |
| Quantitative stats: structural and family counts | Key quantitative values reported include **15 HEAT repeats**, A subunit **~65 kDa**, catalytic C subunit **~36 kDa**, and in **Arabidopsis**: **3 A**, **5 C**, and **17 B** subunits, allowing a theoretical **255** heterotrimeric PP2A combinations. | General/Arabidopsis PP2A family statistics | Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 ; Cortelezzi et al. 2025, https://doi.org/10.3390/kinasesphosphatases3010005 | 2019; 2025 | (pqac-00000000, pqac-00000001) |
| Quantitative stat relevant to wheat | A review excerpt reports **67 PP2A entries/genes in wheat** in genome-wide comparative data, but this number is for the broader PP2A family and does **not** specifically validate F6LAX4 as one experimentally studied PP2AA scaffold gene. | Wheat genome-wide PP2A family overview | Bheri & Pandey 2019, https://doi.org/10.2174/1389202920666190517110605 | 2019 | (pqac-00000002) |


*Table: This table consolidates the verified identity context and the strongest literature-supported facts relevant to annotating wheat UniProt F6LAX4 as a PP2A A/scaffold subunit. It is useful because direct wheat gene-specific papers were not found, so the best-supported annotation relies on canonical PP2AA structure-function evidence and cereal/plant family studies.*