OsCERK1 (ORYSJ CERK1, A0A0P0XII1) curation notes

Identity

• Rice LysM receptor-like kinase OsLysM-RLK9 / OsCERK1, Os08g0538300; 624 aa, signal peptide,
  extracellular region with a single recognisable LysM, one TM helix, cytoplasmic Ser/Thr kinase
  (UniProt). Not to be conflated with Arabidopsis CERK1 (A8R7E6; genes/ARATH/CERK1), whose
  three-LysM ectodomain binds chitin directly.

Chitin immunity (with OsCEBiP)

• Knockdown abolishes most chitin responses: PMID:21070404.
• Chitin-induced receptor complex with CEBiP: PMID:21070404.
• Ligand binding is done by CEBiP, not OsCERK1: PMID:21070404;
  PMID:21070404.
  Shinya et al. 2012 compared At/OsCERK1 ectodomains; only AtCERK1 is "sufficient for chitin perception by itself" PMID:22891159. Deep research: "in the tested colloidal-chitin assay, the rice OsCERK1 ectodomain did not bind" [file:ORYSJ/CERK1/CERK1-deep-research-falcon.md].
  => IEA (ARBA) and TAS chitin binding rows are transfers from AtCERK1 biology; REMOVE.
• Kinase substrates: OsRLCK185 PMID:23498959;
  OsRacGEF1 S549 PMID:23601108;
  OsCIE1 (E3 ligase brake) PMID:38750355.
• PGN signalling via LYP4/LYP6 PMID:25335639;
  knockout PMID:24964058.
• Plasma membrane: PMID:23498959 (abstract: "at the plasma membrane"), PMID:23601108, PMID:24964058 (GFP-OsCERK1 around infection hyphae).

AM symbiosis (with OsMYR1/OsLYK2)

• KO impaired in AM symbiosis while Oscebip KO is not: PMID:25231970.
• PMID:25399831.
• Receptor heteromer: PMID:31706032; kinase-dead T484A fails to rescue colonisation (deep research).
• Receptor competition between OsMYR1 and OsCEBiP for OsCERK1 PMID:33853950.

Curation decisions

• No existing annotation captures the symbiotic role; all BP rows are immune. Proposed NEW
  GO:0036377 arbuscular mycorrhizal association. Participation: OsCERK1 is the catalytically
  active kinase of the OsMYR1-OsCERK1 Myc-factor receptor heteromer (phosphorylates OsMYR1;
  kinase-dead does not rescue), so it does part of the work of symbiotic signalling.
  Comparator check (QuickGO, 2026-10-02): other symbiosis-signalling components carry
  GO:0036377 by IMP: rice D14L (Q10J20), rice CYCLOPS (A9XMT5), Medicago CNGC15a/b, CYCLOPS,
  and rice CCaMK has it in genes/ORYSJ/CCAMK. Passes.
• GO:0038187 pattern recognition receptor activity (EXP, PHI-base): OsCERK1 does not bind the
  PAMP itself in rice; MODIFY to transmembrane receptor protein kinase activity GO:0019199
  (co-receptor kinase).
• GO:0002768 -> MODIFY to the more specific GO:0002752 (is_a child, already IBA).
• Project question 4 (symbiosis vs defense): immunity terms remain on immune-specific rows;
  symbiosis captured separately by GO:0036377; the kinase MF is shared. No row conflates them.
• Project question 2 (LysM effector/receptor leakage): chitin binding on OsCERK1 is an
  ARBA/AtCERK1-derived leak; removed.