Gene Ontology annotation through association of InterPro records with GO terms
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
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UniProt subcellular location "Secreted, extracellular space, apoplast" and "Secreted, cell wall" maps to the apoplast cellular-component term; confirmed experimentally.
Electronic Gene Ontology annotations created by ARBA machine learning models
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ARBA rules propagate family-level (GH28) process terms (cell wall modification involved in abscission, anther dehiscence, fruit dehiscence) that reflect distinct polygalacturonase paralogs, not the tomato fruit-ripening PG2.
Combined Automated Annotation using Multiple IEA Methods
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Combined IEA methods (ARBA, InterPro IPR000743, EC 3.2.1.15) assign polygalacturonase activity, the core and experimentally validated molecular function.
Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
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SwissProt keyword-derived (SPKW) annotation present in the Sept 2025 goa_uniprot_gcrp snapshot but removed from the current GOA release after GOA retired the keyword2GO pipeline for cellular organisms.
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For PG2 the keyword "Fruit ripening" mapped to the whole developmental process GO:0009835, conflating the enzyme's function with the process it serves; its removal was justified.
Changes in polygalacturonase isoenzymes during the 'ripening' of normal and mutant tomato fruit.
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PG activity is undetectable in mature-green fruit and appears as fruit begin to change colour, increasing through ripening; two isoenzymes (PG1, PG2) appear sequentially.
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The ripening increase in PG activity is due to net synthesis of protein; rin and Nr ripening mutants produce little or only PG1.
Analysis of tomato polygalacturonase expression in transgenic tobacco.
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Tomato PG is a cell-wall enzyme secreted in large amounts during fruit ripening, synthesized as a glycoprotein precursor processed to PG1, PG2A and PG2B isozymes.
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PG is properly processed and localized to the cell wall and is enzymatically active; supports apoplast/cell-wall localization.
Reduction of tomato polygalacturonase beta subunit expression affects pectin solubilization and degradation during fruit ripening.
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PG2 is the single catalytic PG polypeptide; PG1 is PG2 associated with a non-catalytic beta subunit.
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PG2 is responsible for pectin solubilization and depolymerization in vivo during fruit ripening; the beta subunit modulates the extent of pectin metabolism.
Insertional inactivation of the tomato polygalacturonase gene.
Polygalacturonase-mediated solubilization and depolymerization of pectic polymers in tomato fruit cell walls. Regulation by pH and ionic conditions.
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PG isozyme 2 (PG2) hydrolyzes polygalacturonic acid and cell-wall pectins in vitro; reaction characterized under apoplast-approximating pH/ionic conditions.
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Pectin depolymerization by PG2 is extensive at pH 4.0-5.0 and enhanced by high K+; establishes the catalytic activity (EC 3.2.1.15) and apoplastic operating conditions.
Deep-research report (falcon / Edison Scientific Literature) - functional annotation of tomato PG2 (P05117).
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PG2 is an extracellular/apoplastic, ripening-associated endo-polygalacturonase (EC 3.2.1.15) that hydrolyzes homogalacturonan and is strongly implicated in depolymerization of pectic polymers during fruit softening.
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Antisense suppression of PG (foundation of the Flavr Savr tomato) reduces pectin depolymerization without altering ethylene production or lycopene accumulation, showing PG2 acts downstream of ripening as a cell-wall disassembly effector.
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PG2A/PG2B are catalytic glyco-isoforms that can bind a wall-associated converter (beta) subunit to form PG1-like complexes under apoplast-like pH (4-5.5).