LOC123103357

Review rationale: F6LAX4 carries the PP2A regulatory subunit A family signatures (IPR051023, PANTHER PTHR10648:SF4) and descends from the eukaryote PP2A scaffold PAINT nodes, so the conserved scaffold-catalytic subunit association transfers to it as a family inference. Structural work on the PP2A holoenzyme shows that the scaffolding A subunit and the catalytic C subunit form a heterodimeric core enzyme to which a regulatory B subunit then binds (PMID:17174897), which is binding to a nonidentical protein to form a heterodimer. The term is not in the gene's GOA set and is not an ancestor or descendant of the existing protein phosphatase regulator activity IBA or of the protein complex scaffold activity the gene review proposes, so it is novel. It is a less informative description of the A subunit than complex scaffolding, but it is correct. The OpenScientist analysis judged the term NPI because the scaffold nucleates an A-B-C heterotrimer, but the A-C core enzyme it forms is itself a heterodimer, so the term is correct though less informative than a scaffold term.

TAXON CONSTRAINT VIOLATION

Review rationale: The target is a Triticum aestivum protein. Neuronal cell body denotes the soma of a neuron, a cell type absent from plants, so this compartment cannot apply to the wheat PP2A scaffold. The term is absent from the gene's annotations and nothing in the gene review or the PTHR10648 family review supports it for a plant member. The prediction alone does not establish which training example or model mechanism produced the error.

Review rationale: In Arabidopsis, the PP2A regulatory subunits B'alpha and B'beta are required to maintain centromeric sister chromatid cohesion in meiosis, and the A1 structural subunit, a co-ortholog of F6LAX4, localizes with them to meiotic centromeres (PMID:30061120). This places the wheat scaffold plausibly in a PP2A-B' holoenzyme acting on chromosomes. The demonstrated function, however, is protection of centromeric cohesion, which GO represents as a sister chromatid cohesion process outside chromosome segregation; segregation defects in the mutants are a downstream consequence, and the genetic evidence is on the B' subunits, not on an A subunit. PAINT placed its meiotic centromeric cohesion IBD on an animal/fungal subclade that does not include F6LAX4. Support for the exact segregation term is therefore insufficient. The OpenScientist analysis judged the term NPI because the Shugoshin-PP2A cohesion role is mediated by the B56 regulatory subunit; the call here is UNC rather than NPI because the A1 co-ortholog sits in that B' holoenzyme at meiotic centromeres, so a holoenzyme contribution is plausible but not shown for segregation itself.

Review rationale: GFP-tagged Arabidopsis PP2AA1, the structural A subunit and a co-ortholog of F6LAX4 (grasses have a single A-subunit lineage co-orthologous to all three Arabidopsis A subunits), colocalizes with centromeric histone CENH3 in male meiocytes from pachytene to metaphase II, together with the B'alpha regulatory subunit (PMID:30061120). Centromere targeting depends on the regulatory subunit rather than on the scaffold itself, but the A subunit is a member of the holoenzyme residing there, which suffices for a cellular component annotation. Transfer to the wheat ortholog is an inference, restricted in the source to meiotic stages. The term is absent from the gene's GOA set and is novel. The OpenScientist analysis judged the term NPI because centromere targeting is B56-mediated, but the colocalization of the A1 co-ortholog with CENH3 shows the scaffold is present there as a holoenzyme member, which a cellular component term requires.

TAXON CONSTRAINT VIOLATION

Review rationale: The target organism is Triticum aestivum. Neuron projections are neuronal structures, and plants have no neurons, so this localization is incompatible with the target taxon. It is absent from the gene's annotations and is not supported by the gene review or the PTHR10648 family review for a plant member. No inference about model frequency bias is needed to establish the incompatibility.

TAXON CONSTRAINT VIOLATION

Review rationale: The wheat product is a PP2A A-subunit scaffold. The human PP2A A-small t structure establishes that the viral small t antigen binds the scaffold as a PP2A inhibitor (PMID:17608567); the viral protein's name does not make that interaction immunological antigen recognition, which is what protein antigen binding describes. Plants lack the antibody and antigen-receptor systems that carry this activity, and the term is absent from the wheat annotations.