MPK6 (Q39026, At2g43790) — curation notes

Identity and core molecular function

Upstream activators (MAPKKs) — these are the IPI "protein binding" partners

Substrates (also annotated as bare protein binding -> REMOVE)

Negative regulators (phosphatases) — phosphatase binding GO:0019902 kept (informative)

Localization

Pleiotropy / biological processes (mostly KEEP_AS_NON_CORE)

Curation decisions summary

Proposed

Deep research synthesis (Falcon / Edison Scientific, file:ARATH/MPK6/MPK6-deep-research-falcon.md)

The Falcon deep-research report corroborates and does not contradict the existing review. Key points used to strengthen supported_by evidence:
- Core MF: MPK6 is a "Proline-directed CMGC MAP kinase; terminal kinase in MAPK cascades activated by dual Thr/Tyr phosphorylation in the TxY motif" that "phosphorylates downstream substrates including transcription factors, enzymes, RNA-metabolism proteins, and developmental regulators, often redundantly with MPK3." Added to MAP kinase activity, protein serine kinase activity and core_functions.
- MAPK cascade architecture: "MAPKs are terminal kinases in a conserved signaling architecture in which upstream kinases sequentially activate MAP2Ks and then MAPKs." Added to GO:0000165.
- Immunity (defense response to bacterium): "the MEKK1–MKK4/5–MPK3/MPK6 PTI module downstream of FLS2 that contributes to pathogen resistance"; "MPK6 is a core component of immune MAPK cascades activated by pattern recognition receptors."
- Ethylene: "MPK6 phosphorylates ACC synthase isoforms (e.g., ACS6) to affect stability and ethylene output" — supports response to ethylene.
- Development (stomatal): "MPK3/MPK6 phosphorylate SPEECHLESS (SPCH) downstream of the YODA–MKK4/5 module, modulating stomatal initiation and lineage progression" — supports nucleus localization and developmental core function.
- Freezing/ICE1: compiled substrates "include MYB41, MYB15, HsfA2, ICE1, DCP1 ... with outcomes such as enhanced DNA binding, altered protein stability, and nuclear accumulation" — supports response to freezing (ICE1).
- Localization: substrates span nucleus and cytoplasm — "This implies a functional distribution spanning nucleus and cytoplasm"; "classic reports note stress-triggered nuclear translocation of MAPKs."
- New 2023-2024 findings NOT added as GOA annotations (no verifiable GO IDs in current GOA/UniProt): MPK6 in stress granules / P-bodies via DCP1 phosphorylation (He et al. 2024 preprint); MYB36 phosphosites in endodermal SGN3/CIF signaling (Ma et al. 2024, Nature Plants); cat2-1 / glutathione modulation of flg22-induced MPK3/6 kinetics (Yang et al. 2024 preprint). These are recorded here for future review but are largely preprints and would need verifiable curated GO terms before annotation.
- No action: UNDECIDED entries existed; none required resolution (all 43 cited publications were accessible).

PR #1417 review fix (2026-06-06): title-as-evidence supporting_text

PR review follow-up: title-as-supporting_text on non-REMOVE annotations (2026-06-07)

Reviewer (ai4c-agent) flagged ~19 annotations whose supporting_text was merely the cited paper's title. Focused on the NON-REMOVE subset (ACCEPT / KEEP_AS_NON_CORE). Replaced bare titles with verbatim excerpts:
- GO:0106310 protein serine kinase activity (ACCEPT, PMID:15500467) -> "transient activation of 43 and 45 kDa MAPKs. These were identified as AtMPK3 and AtMPK6".
- GO:0009738 ABA-activated signaling (KEEP, PMID:27913741) -> "The activity of MPK6 was increased by ABA ... the AIK1-MKK5-MPK6 cascade functions in the ABA regulation of primary root growth and stomatal response".
- GO:1902065 response to L-glutamate (KEEP, PMID:29344832) -> "In-gel phosphorylation assays revealed a rapid and dose-dependent induction of MPK6 and MPK3 activities ... in response to L-Glu".
- GO:0006468 protein phosphorylation (ACCEPT, PMID:29056553) -> "mitogen-activated protein kinase 3 (MPK3) and MPK6 interact with and phosphorylate ICE1, which reduces its stability and transcriptional activity".
- GO:0050826 response to freezing (KEEP, PMID:29056553) -> "the mpk3 and mpk6 single mutants and the mpk3 mpk6 double mutants show enhanced freezing tolerance, whereas MPK3/MPK6 activation attenuates freezing tolerance".
- GO:0009555 pollen development (KEEP, PMID:24830428) -> "epitope-tagged WRKY34 is temporally phosphorylated by MPK3 and MPK6 ... at early stages in pollen development".
- GO:0009620 response to fungus (KEEP, PMID:21947882) -> "It was observed that the expression of both MAP2K9 and MAPK6 simultaneously increased up to middle stage of disease progression".
- GO:0010224 response to UV-B (KEEP, PMID:21790814) -> "The MKP1-interacting proteins MPK3 and MPK6 are activated by UV-B stress ... mutants mpk3 and mpk6 exhibit elevated UV-B tolerance".
- GO:0080136 priming of cellular response to stress (KEEP, PMID:19318610) -> "priming is associated with accumulation of mRNA and inactive proteins of ... MPK3 and MPK6. Upon challenge exposure ... more strongly activated in primed plants".
- GO:0048481 plant ovule development (KEEP, PMID:18364464) -> "two closely related mitogen-activated protein kinases ... MPK3 and MPK6, share a novel function in ovule development ...".
- GO:0042542 response to hydrogen peroxide (KEEP, PMID:17933903) -> "MPK6 and MPK7 were both activated by H(2)O(2), but only MPK7 activation was enhanced by MKK3".

Set to UNDECIDED (no quotable evidence in cached source):
- GO:0005829 cytosol (was ACCEPT, HDA, PMID:28887381): cached publication text (a global membrane-protein oligomerization proteomics study) does not mention MPK6/MAPK6 or its localization; the assignment lives only in supplementary dataset tables not present in the cached markdown, so no verbatim excerpt can substantiate it. Action -> UNDECIDED.

REMOVE annotations with bare-title supporting_text left as-is (out of scope; REMOVE stands on the protein-binding curation guideline).