AVR9 (Fulvia fulva / Cladosporium fulvum; UniProt P22287) - curation notes

2026-10-02 - initial review

Sources: UniProt P22287, GOA (5 rows, all PHI-base), AVR9-deep-research-falcon.md,
cached publications (all abstract-only except PMID:25902074, which is full text).

Identity, processing, structure

• 63-aa precursor: signal 1-23, propeptide 24-35, mature peptide 36-63 (UniProt).
• Processing: PMID:8208859;
  PMID:8208859
• Apoplastic: PMID:8555455
  had the same sequence as AVR9 from infected tomato. UniProt ref 3 (non-PubMed) purified it from
  apoplastic fluids of infected tomato.
• Knottin: PMID:9119054; fold homologous to
  carboxypeptidase inhibitor, but no inhibitory activity shown (deep research, citing van den Burg 2003 thesis).

Recognition

• HR in Cf-9 tomato: PMID:8208859.
• Indirect recognition: binding site independent of Cf-9
  PMID:12239406;
  PMID:9625714;
  PMID:25902074.
• Natural escape by gene loss: PMID:25902074.

Virulence function: unknown

• PMID:25902074.
• NRF1 mutants with strongly reduced Avr9 expression were fully virulent on susceptible tomato
  PMID:11277429
  -- not a clean test of AVR9 itself. No virulence function asserted in the review.

GO decisions

• GO:0080185 (EXP x2): ACCEPT. Definition explicitly includes recognition of the effector by plant R proteins;
  GO treats the recognised effector as participant (ligand-like). Same term used for AVR4 and other Avr effectors.
• GO:0140404 (EXP x1, TAS x2): MODIFY -> GO:0080185. Correct but uninformative parent; its subtree is mostly
  suppression terms, inviting an implied immunosuppressive role. PMID:26946045 (Ve1/Ave1 paper) abstract does not
  mention AVR9 -- likely the Cf-9/Avr9 control; not verifiable, so not removed.
• NEW GO:0140593 host apoplast (location; used for other apoplastic effectors such as Mg1LysM, AvrLm1).
• No MF: no biochemical activity shown; Cf-9 binding not shown. Did not propose a "recognised-by-host" MF.

Ontology observation (project gap: how GO represents "being recognised")

• QuickGO ancestry: GO:0080185 is_a GO:0034055 "effector-mediated activation of host programmed cell death by symbiont",
  defined as activating PCD "to suppress the host innate immune response", and GO:0034055 is_a GO:0140403
  effector-mediated suppression of host innate immune response. So every avirulence effector annotated to
  GO:0080185 inherits a suppression-of-immunity claim -- logically inverted for AVR9. Raised in suggested_questions.
• "Being recognised" exists only as a process (GO:0080185); there is no MF/relation for an indirectly perceived elicitor.