MAPKKK5 (At5g66850, Q9C5H5) notes

Sources: UniProt Q9C5H5; Falcon deep research (MAPKKK5-deep-research-falcon.md, used as retrieval aid only);
cached papers PMID:27679653 (full text), PMID:35652263 (full text), PMID:29871986, PMID:29440595, PMID:21477822 (abstracts).

Activity

• MAP3K of the MEKK subfamily. Kinase domain directly phosphorylates MKK4/MKK5 activation loops
  PMID:27679653;
  PMID:27679653.
• Autophosphorylation weak PMID:27679653.

Upstream inputs (MAPKKK5 is the substrate)

• PBL27 (CERK1-dependent) PMID:27679653.
• RLCK VII kinases at Ser-599; MPK6 feedback at Ser-682/692 PMID:29871986.
• BSK1 at Ser-289 (PMID:29440595).

Genetics

• Redundant with MAPKKK3 downstream of >=4 PRRs PMID:29871986;
  PMID:35652263
• Yamada single mutants: reduced chitin MAPK activation and callose, larger A. brassicicola lesions, no ROS defect
  PMID:27679653. Yamada also saw enhanced flg22 MAPK activation
  PMID:27679653 - conflicts with Bi 2018 (positive role in double mutant).
• With YDA in embryogenesis/gamete transmission (PMID:35652263) - not in GOA; not proposed as NEW (redundant genetic necessity only).

Localization

• Cytosol and PM (N. benthamiana transient; Arabidopsis protoplast BiFC)
  PMID:27679653.
  Chloroplast ISM prediction contradicted -> REMOVE.

Curation decisions

• Core: GO:0004709 MAP3K activity; GO:0000165 MAPK cascade; GO:0002752 cell surface PRR signaling pathway. Agrees with modules/chitin_perception.yaml annoton (GO:0004709).
• Protein binding (5 rows) removed (consistent with MPK3 review).
• PRR signaling (GO:0002221) -> MODIFY to GO:0002752.
• Defense/callose/immune-regulation rows kept non-core (necessity via MAPK relay, not participation in effector steps).
• No NEW annotations.