B8BAB0

UniProt ID: B8BAB0
Organism: Oryza sativa Indica Group
Review Status: DRAFT
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Gene Description

B8BAB0 (ORF OsI_29064, chromosome 8) is the indica rice gene model of OsBURP12, a PG1beta-like BURP-domain protein whose japonica allele is Q6ZA27 (Os08g0380100). It belongs to the plant-specific polygalacturonase-associated BURP family (PANTHER PTHR31458, subfamily SF2, shared with the tomato polygalacturonase 1 non-catalytic beta subunit, Arabidopsis PGL2 and rice OsBURP16). The predicted 623-residue protein has an N-terminal signal peptide (1-21), a repeat-rich variable region built from FxxY/FTNYG-type units typical of PG1beta proteins, and a C-terminal BURP domain (384-595). Compared with its japonica allele, the indica gene model lacks about 31 residues of the N-terminal propeptide region and ends in a divergent 42-residue tail, so it lacks the fourth CH motif of the BURP domain; this is probably a gene-model difference. In the PANTHER tree its nearest paralog is OsBURP16, from a grass-specific duplication. The tomato PG1beta subunit is a cell wall protein that binds and apparently regulates the catalytic polygalacturonase, and OsBURP16 overexpression increases polygalacturonase activity and lowers pectin content. By family membership B8BAB0 is a secreted, probably cell-wall protein. No activity, location or process has been shown experimentally for B8BAB0 or for OsBURP12.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0005576 extracellular region
ISM
file:ORYSI/B8BAB0/B8BAB0-uniprot.txt 		NEW
Summary: B8BAB0 has no GOA annotations. A SignalP signal peptide (1-21), no predicted transmembrane segment or retention signal, and membership of the secreted PG1beta-like BURP family support export to the extracellular region. The same term is carried by Arabidopsis PGL2 (same PANTHER subfamily) by ISM.
Reason: Location is the one property supported by the target's own sequence features. The more specific plant-type cell wall is not proposed: no grass PG1beta-like protein has been localized, and the PAINT cell-wall IBD (PTN004827911) was placed on the Brassicaceae SF10 node only, which does not include this clade.
Supporting Evidence:
file:ORYSI/B8BAB0/B8BAB0-uniprot.txt
FT SIGNAL 1..21
PMID:1392611
a cell wall protein that associates with, and apparently regulates, the catalytic PG2 polypeptides

Core Functions

Secreted PG1beta-like BURP-domain protein of unknown molecular activity. A signal peptide and PG1beta-like family membership indicate export through the secretory pathway to the extracellular space. A non-catalytic polygalacturonase-associated role, as described for the tomato PG1 beta subunit and inferred for the paralog OsBURP16, is a hypothesis only, and the B8BAB0 gene model lacks the fourth BURP CH motif.

Cellular Locations:
extracellular region
Supporting Evidence:
  • file:ORYSI/B8BAB0/B8BAB0-uniprot.txt
    FT SIGNAL 1..21
  • file:ORYSI/B8BAB0/B8BAB0-uniprot.txt
    DR PANTHER; PTHR31458:SF2; POLYGALACTURONASE 1 BETA-LIKE PROTEIN 2; 1.
  • PMID:1392611
    a cell wall protein that associates with, and apparently regulates, the catalytic PG2 polypeptides
  • file:ORYSI/B8BAB0/B8BAB0-bioinformatics/RESULTS-rereview.md
    B8BAB0 belongs to the PG1beta-like (PTHR31458) BURP family by HMM membership, the repeat-rich variable region and the BURP domain

References

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Suggested Questions for Experts

Q: Is the divergent B8BAB0 C-terminus (lacking the fourth BURP CH motif) supported by indica transcript evidence, or is it a gene-model error relative to japonica Os08g0380100?

Q: Does OsBURP12, like the tomato PG1 beta subunit, bind a catalytic polygalacturonase and reside in the cell wall? PAINT propagated cell wall terms only within Brassicaceae, so this is open for grass PG1beta-like proteins.

Q: Is OsBURP12 a member of the PG1beta-like group in the Ding et al. (2009) rice BURP classification, given that Liu et al. (2014) list only OsBURP02, OsBURP14 and OsBURP16 while PANTHER places OsBURP12 with OsBURP16?

Suggested Experiments

Experiment: Express a full-length OsBURP12 (japonica model) fluorescent fusion in rice and determine localization with plasmolysis and cell-wall markers; test association with rice PG catalytic subunits by co-immunoprecipitation from cell wall extracts.

Hypothesis: OsBURP12 is secreted to the cell wall and associates with polygalacturonase.

Type: subcellular localization / protein interaction

Experiment: Generate CRISPR knockouts of OsBURP12, alone and with OsBURP16, and measure PG activity, uronic acid content and cell adhesion in leaves.

Hypothesis: Loss of OsBURP12 changes polygalacturonase activity and pectin content.

Type: loss-of-function / biochemical phenotyping

External Prediction Reviews

These computational predictions are reviewed separately from the GOA annotation set used for this review. The assessments below are from this project and do not constitute official GO annotations or endorsement by GO/UniProt. They are not included in the existing annotation review above.

ProtNLM2 External predictions

View prediction review YAML · B8BAB0-protnlm-predictions-review.yaml · Review status: COMPLETE

B8BAB0 is the indica gene model of OsBURP12, a secreted PG1beta-like (PANTHER PTHR31458:SF2) BURP-domain protein. Its sequence, family placement and the japonica-allele loss-of-function data (burp12 mutants with lower polygalacturonase activity and higher pectin during low-temperature seed germination) point to a cell-wall/pectin role. The one ProtNLM2 prediction, pollen maturation, matches the function of the separate cereal anther-specific RAFTIN/BURP-VII clade, not the PG1beta-like clade that contains B8BAB0.

Source documents: genes/ORYSI/B8BAB0/B8BAB0-uniprot.txt · genes/ORYSI/B8BAB0/B8BAB0-goa.tsv · genes/ORYSI/B8BAB0/B8BAB0-hypotheses/prediction-pollen-maturation/openscientist.md

Review score: 2 = concordant with evidence; 1 = uncertain; 0 = discordant with evidence. This is an assessment score, not a model probability.

GO:0010152 pollen maturation GO_BP
PLI — Paralog incorrect Review score: 0/2
Prediction method: ProtNLM2 · Version: UniProt 2024_06 pilot
PARALOG OVERANNOTATION
Review rationale: B8BAB0 has no GOA annotations, so the term would be novel, but it is not supported. B8BAB0 is 95.6% identical to japonica OsBURP12 (Q6ZA27) and sits in the PG1beta-like subfamily PTHR31458:SF2 with a signal peptide, the PG1beta FxxY/FTNYG repeat region and a C-terminal BURP domain; its closest PANTHER paralog is OsBURP16. The reproductive-development precedent in the BURP superfamily comes from RAFTIN, an anther-specific, cereal-restricted BURP clade (rice RAFTIN RNAi collapses pollen), and from the monocot BURP VII subfamily whose members are flower-predominant. The OpenScientist analysis places B8BAB0 outside that clade by full-length alignment (46.5% identity to tomato PG1beta versus 28.2% to wheat RAFTIN1A). The only gene-specific experiment, on the japonica allele, links OsBURP12 to polygalacturonase activity, pectin content and low-temperature seed germination, not pollen. The gene review accepts only extracellular region. The pollen label is therefore best explained as a transfer across nonisofunctional BURP paralog clades. No study has tested OsBURP12 for a pollen phenotype, so the refutation rests on clade placement rather than a negative experiment.
Supporting Evidence:
  • file:ORYSI/B8BAB0/B8BAB0-uniprot.txt: "ID B8BAB0_ORYSI Unreviewed; 623 AA. ... DR InterPro; IPR004873; BURP_dom. ... DR InterPro; IPR051897; PG-associated_BURP. ... DR PANTHER; PTHR31458:SF2; POLYGALACTURONASE 1 BETA-LIKE PROTEIN 2; 1. ... FT SIGNAL 1..21 ... FT DOMAIN 384..595 ... FT /note="BURP""
  • file:ORYSI/B8BAB0/B8BAB0-bioinformatics/RESULTS-rereview.md: "Closest paralog: OsBURP16 (Q7XES5), last common ancestor at the grass duplication PTN000779097."
  • file:ORYSI/B8BAB0/B8BAB0-hypotheses/prediction-pollen-maturation/openscientist.md: "is **not** a member of the cereal anther-specific **RAFTIN / BURP-VII** clade"
  • PMID:14612572: "the occurrence RAFTIN per se is limited to cereals; neither the Arabidopsis genome nor the vast collection of ESTs suggests any obvious dicot homologs"
  • PMID:19363683: "Interestingly, all the genes of the BURP VII subfamily were predominantly expressed in flower organs."
  • PMID:40320839: "the nal11 and burp12 mutants had higher endogenous ABA levels and exhibited lower PG (polygalacturonase) activity and higher pectin content during low-temperature germination."

Deep Research

Falcon

(B8BAB0-deep-research-falcon.md)

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OpenScientist

(B8BAB0-hypotheses/prediction-pollen-maturation/openscientist.md)

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📚 Additional Documentation

Notes

(B8BAB0-notes.md)

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📄 View Raw YAML

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