B8BAB0

UniProt ID: B8BAB0
Organism: Oryza sativa subsp. indica
Review Status: DRAFT
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Gene Description

B8BAB0 (ORF OsI_29064) is a BURP domain-containing protein from rice (Oryza sativa subsp. indica). It belongs to the PG1beta-like subfamily of BURP proteins, classified by PANTHER (PTHR31458:SF2, Polygalacturonase 1 beta-like protein 2) and containing the InterPro PG-associated BURP domain (IPR051897). The protein is 623 amino acids long, with an N-terminal signal peptide (residues 1-21) directing it to the secretory pathway and a conserved C-terminal BURP domain (residues 384-595) containing the characteristic cysteine-histidine (CH) motif pattern. The intervening variable region contains repeated sequence units. PG1beta-like BURP proteins in rice, such as the well-characterized OsBURP16 and OsBURP14, function as non-catalytic beta-subunits of polygalacturonase isozyme 1, modulating cell wall pectin remodeling. OsBURP16 overexpression increases polygalacturonase activity, decreases pectin content, and reduces cell adhesion. These proteins are regulated by the ethylene signaling transcription factor OsEIL2 and are strongly induced by ABA, ethylene, salt stress, and drought. B8BAB0 has not been directly characterized experimentally (UniProt protein evidence level 4, Predicted), and its specific biological role remains to be determined.

Core Functions

Predicted non-catalytic regulatory subunit of polygalacturonase, inferred from PG1beta-like BURP subfamily membership (PTHR31458:SF2). Related rice proteins OsBURP16 and OsBURP14 modulate polygalacturonase enzymatic activity and cell wall pectin content. Contains an N-terminal signal peptide consistent with secretion to the extracellular matrix.

Molecular Function:
enzyme regulator activity
Directly Involved In:
cell wall organization
Cellular Locations:
plant-type cell wall apoplast
Supporting Evidence:
  • file:ORYSI/B8BAB0/B8BAB0-uniprot.txt
    PANTHER classification PTHR31458:SF2 POLYGALACTURONASE 1 BETA-LIKE PROTEIN 2 and InterPro IPR051897 PG-associated BURP domain.
  • file:ORYSI/B8BAB0/B8BAB0-deep-research-falcon.md
    OsBURP16 overexpression in rice results in increased polygalacturonase enzyme activity, decreased pectin content in cell walls, reduced cell adhesion and cell wall integrity.
  • file:interpro/panther/PTHR31458/PTHR31458-metadata.yaml
    This family of proteins includes non-catalytic subunits of polygalacturonase as well as proteins containing a BURP domain at the C-terminus.

References

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Suggested Questions for Experts

Q: Which BURP subfamily does B8BAB0 belong to based on phylogenetic analysis within the 17 rice BURP genes, and does it cluster with OsBURP12/OsBURP16 or with a different PG1beta-like clade?

Q: Is B8BAB0 expressed under specific stress conditions (drought, salt, ABA treatment) or developmental stages, similar to characterized PG1beta-like BURP proteins in rice?

Q: Does B8BAB0 physically interact with catalytic polygalacturonase subunits, and does it affect PG enzyme activity when co-expressed?

Suggested Experiments

Experiment: Generate transgenic rice lines overexpressing B8BAB0 and measure polygalacturonase activity, pectin content, and cell adhesion in leaf tissue. Compare phenotypes under normal and salt/drought stress conditions to determine if B8BAB0 modulates stress tolerance via cell wall remodeling.

Hypothesis: B8BAB0 functions as a non-catalytic beta-subunit of polygalacturonase and its overexpression increases PG activity and decreases cell wall pectin content, similar to OsBURP16.

Type: transgenic overexpression / functional assay

Experiment: Express B8BAB0 fused to a fluorescent reporter (e.g. GFP) in rice protoplasts or stable transformants and determine subcellular localization by confocal microscopy, with co-localization analysis using cell wall markers.

Hypothesis: B8BAB0 is secreted to the apoplast or cell wall via its signal peptide and colocalizes with polygalacturonase enzymes.

Type: subcellular localization

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

The secretory, PG-associated BURP architecture does not establish a pollen-maturation role.

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: The target has a signal peptide and a PG-associated BURP-domain assignment, but the focused BURP comparison places B8BAB0 in the PG1beta-like cell-wall clade rather than the cereal anther RAFTIN/BURP-VII clade that supplies the reproductive-development precedent. The inspected evidence therefore supports an extracellular PG1beta-like protein, with candidate cell-wall leads needing separate verification, not a pollen-maturation role. ProtNLM2 appears to have over-transferred a pollen label across nonisofunctional BURP paralog clades.
Supporting Evidence:

Deep Research

Falcon

(B8BAB0-deep-research-falcon.md)

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OpenScientist

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

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