RCO1

id: A0A0D1E6L2
gene_symbol: RCO1
product_type: PROTEIN
status: IN_PROGRESS
taxon:
  id: NCBITaxon:5270
  label: Mycosarcoma maydis
description: >-
  RCO1 encodes Rco1 (Resveratrol cleavage oxygenase 1) of Ustilago maydis (Mycosarcoma maydis), a
  fungal member of the carotenoid cleavage oxygenase (CCO) superfamily and a close functional analog of
  Neurospora CAO-1. It is a non-heme iron dioxygenase that oxidatively cleaves the interphenyl
  Calpha-Cbeta double bond of the stilbene phytoalexin resveratrol (and its derivative piceatannol) to
  yield 3,5-dihydroxybenzaldehyde and 4-hydroxybenzaldehyde. Rco1 is highly substrate-specific and does
  not act on carotenoids. U. maydis encodes two CCO-family paralogs: Cco1, a genuine beta-carotene
  cleavage enzyme, and Rco1, the resveratrol/stilbene cleaver reviewed here - the same carotenoid- vs
  stilbene-cleaver paralog split seen in Neurospora (CAO-2 vs cao-1).
existing_annotations:
- term:
    id: GO:0010436
    label: carotenoid dioxygenase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: >-
      Phylogenetic (IBA) carotenoid dioxygenase activity. Experimentally refuted: purified Rco1 cleaves
      resveratrol and piceatannol but has no activity on carotenoids (PMID:21073977). A CCO-family
      over-propagation identical to the cao-1 case.
    action: REMOVE
    reason: >-
      Contradicted by direct enzyme assays showing Rco1 is a resveratrol/stilbene cleaver, not a
      carotenoid enzyme. The correct specific term is GO:7770086 (resveratrol dioxygenase activity,
      RHEA:73735; go-ontology PR #32332, merged 2026-07-17, live in QuickGO); the general activity is
      already covered by GO:0016702.
    propagation_review:
      root_cause: PROPAGATION_BAD
      failure_modes:
        - FUNCTIONAL_DIVERGENCE
    supported_by:
      - reference_id: PMID:21073977
        supporting_text: >-
          Um Rco1 exhibits a high degree of substrate specificity, as suggested by the lack of activity
          on carotenoids and the other resveratrol-related compounds tested
- term:
    id: GO:0016121
    label: carotene catabolic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      Phylogenetic (IBA) carotene catabolic process. Wrong substrate class; Rco1 acts in stilbene
      catabolism (resveratrol/piceatannol cleavage).
    action: MODIFY
    reason: >-
      Replace with GO:0046272 (stilbene catabolic process), matching the demonstrated activity. Same
      CCO-family over-propagation as the carotenoid MF term.
    proposed_replacement_terms:
      - id: GO:0046272
        label: stilbene catabolic process
    propagation_review:
      root_cause: PROPAGATION_BAD
      failure_modes:
        - FUNCTIONAL_DIVERGENCE
    supported_by:
      - reference_id: PMID:21073977
        supporting_text: >-
          the phytoalexin resveratrol and its derivative piceatannol
- term:
    id: GO:0016702
    label: oxidoreductase activity, acting on single donors with incorporation of
      molecular oxygen, incorporation of two atoms of oxygen
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      InterPro-based (IEA) dioxygenase MF term. Correct and consistent with the demonstrated stilbene
      dioxygenase activity of Rco1.
    action: ACCEPT
    reason: >-
      Accurate general dioxygenase MF; the specific resveratrol-cleavage activity sits under this term.
core_functions:
- description: >-
    Non-heme iron stilbene cleavage dioxygenase that oxidatively cleaves the interphenyl Calpha-Cbeta
    double bond of resveratrol and piceatannol into aromatic aldehydes; highly specific and inactive on
    carotenoids. GO:0016702 is the most specific MF term in the ontology snapshot this repo validates
    against; the specific term is GO:7770086 (resveratrol dioxygenase activity, RHEA:73735;
    go-ontology PR #32332, merged 2026-07-17).
  molecular_function:
    id: GO:0016702
    label: oxidoreductase activity, acting on single donors with incorporation of
      molecular oxygen, incorporation of two atoms of oxygen
  directly_involved_in:
    - id: GO:0046272
      label: stilbene catabolic process
  supported_by:
    - reference_id: PMID:21073977
      supporting_text: >-
        the phytoalexin resveratrol and its derivative piceatannol
suggested_questions:
- question: >-
    U. maydis has the same carotenoid/stilbene paralog split as Neurospora (Cco1/beta-carotene vs
    Rco1/resveratrol); is the biological role of fungal resveratrol cleavage (detoxification vs
    competition) shared between the two fungi?
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO
    terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
  reference_review:
    relevance: LOW
    correctness: MISCITED
    review_notes: >-
      IBA propagated carotenoid dioxygenase activity and carotene catabolic process to Rco1, a
      resveratrol cleaver experimentally shown to lack carotenoid activity - the same substrate-class
      over-annotation as cao-1.
- id: PMID:21073977
  title: 'Cleavage of resveratrol in fungi: characterization of the enzyme Rco1 from Ustilago maydis.'
  findings:
  - statement: >-
      Purified Um Rco1 cleaves the interphenyl double bond of resveratrol and piceatannol and is
      inactive on carotenoids; U. maydis Cco1 is the separate beta-carotene cleaver.
    supporting_text: >-
      Um Rco1 exhibits a high degree of substrate specificity, as suggested by the lack of activity
      on carotenoids and the other resveratrol-related compounds tested
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Primary characterization of Rco1 as a resveratrol/stilbene cleavage oxygenase lacking carotenoid
      activity; establishes the Cco1(carotenoid)/Rco1(stilbene) paralog split in U. maydis.