PMK1 (Pathogenicity MAP Kinase 1) encodes a Fus3/Kss1-type mitogen-activated protein kinase of the rice blast fungus Magnaporthe oryzae (Pyricularia oryzae), a CMGC-family serine/threonine kinase with a TEY activation-loop motif. It is the terminal kinase of the Mst11 (MAPKKK) - Mst7 (MAPKK) - Pmk1 cascade, which relays plant-surface cues (hydrophobicity, cutin monomers, leaf waxes) perceived through the Msb2/Sho1 sensors and the Mst50 adaptor, acting cooperatively with, and downstream of, cAMP signalling. Activated Pmk1 phosphorylates fungal substrates including the homeobox transcription factor Hox7, the Ste12-like transcription factor Mst12 and the actin-bundling protein fimbrin (MoFim1), driving a hierarchical transcriptional program for appressorium differentiation, septin-dependent cytoskeletal reorganisation, polarised exocytosis and effector gene expression. Pmk1 is essential for appressorium formation and invasive growth, and later controls the hyphal constriction that allows invasive hyphae to move from one rice cell to the next through plasmodesmata-rich pit fields. It is dispensable for vegetative growth and reproduction in culture, and it complements the mating defect of a yeast fus3 kss1 double mutant.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000165 MAPK cascade | IDA PMID:8946911 MAP kinase and cAMP signaling regulate infection structure f... | ACCEPT | Summary: Pmk1 is the terminal MAP kinase of the Mst11-Mst7-Pmk1 cascade. Xu and Hamer showed in vitro kinase activity and functional equivalence to yeast Fus3/Kss1; Zhao et al. 2005 established Mst7/Mst11 as the upstream MAPKK/MAPKKK that activate Pmk1 by TEY phosphorylation. Reason: Pmk1 performs the final kinase step of the cascade and is the core of its biological role. Well supported by the cited paper and by the cascade reconstruction in PMID:15749760. Supporting Evidence: PMID:8946911 These results demonstrate that PMK1 is part of a highly conserved MAP kinase signal transduction pathway that acts cooperatively with a cAMP signaling pathway for fungal pathogenesis. PMID:15749760 These data indicate that MST11 , MST7 , and PMK1 function as a MAP kinase cascade regulating infection-related morphogenesis in M. grisea . |
| GO:0000921 septin ring assembly | IMP PMID:29567712 A single fungal MAP kinase controls plant cell-to-cell invas... | KEEP AS NON CORE | Summary: Sakulkoo et al. 2018 showed that Pmk1 controls the septin-dependent hyphal constriction of invasive hyphae crossing pit fields; OsΓ©s-Ruiz et al. 2021 placed septin-dependent cytoskeletal reorganisation downstream of Pmk1-dependent Mst12 phosphorylation. Reason: Pmk1 is a signalling kinase upstream of septin reorganisation (via Mst12 and transcription), not a structural component that assembles septin rings; a regulatory term would be more precise. However, the curator's IMP is based on full text that is not cached (abstract only), so the annotation is retained as a non-core, downstream process rather than overruled. Supporting Evidence: PMID:29567712 Pmk1 controls the hyphal constriction required for fungal growth from one rice cell to the neighboring cell PMID:34707224 Pmk1-dependent phosphorylation of Mst12 then regulates gene functions involved in septin-dependent cytoskeletal re-organization, polarized exocytosis and effector gene expression |
| GO:0004672 protein kinase activity | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro-based assignment of generic protein kinase activity, consistent with the experimentally demonstrated kinase activity of Pmk1. Reason: Correct, though less specific than the MAP kinase activity (GO:0004707) also annotated; accepted as a valid general parent assignment. Supporting Evidence: PMID:8946911 a GST-Pmk1 fusion protein has kinase activity in vitro |
| GO:0004707 MAP kinase activity | IDA PMID:8946911 MAP kinase and cAMP signaling regulate infection structure f... | ACCEPT | Summary: GST-Pmk1 has kinase activity in vitro (autophosphorylation and myelin basic protein phosphorylation per the deep research); Pmk1 is a Fus3/Kss1 homolog that rescues the yeast fus3 kss1 mating defect. Reason: Core molecular function. Pmk1 is activated by the MAPKK Mst7 and phosphorylates native substrates (Hox7, Mst12, MoFim1). Supporting Evidence: PMID:8946911 The PMK1 gene of M. grisea is homologous to the Saccharomyces cerevisiae MAP kinases FUS3/KSS1, and a GST-Pmk1 fusion protein has kinase activity in vitro. PMID:38252344 The results showed that Pmk1 could autophosphorylate (Fig. 3A, lane 1). In the presence of Pmk1, MoFim1 was phosphorylated. |
| GO:0004707 MAP kinase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Automated assignment (ARBA, InterPro MAP kinase signature, EC 2.7.11.24) concordant with the experimental data. Reason: Consistent with the IDA annotation and the TEY-containing MAPK signature. Supporting Evidence: PMID:8946911 The PMK1 gene of M. grisea is homologous to the Saccharomyces cerevisiae MAP kinases FUS3/KSS1 |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro-based ATP binding assignment from the protein kinase ATP-binding signature (UniProt BINDING 30..38, 53). Reason: Correct (ATP is the phosphate donor of the kinase reaction) but uninformative beyond the kinase activity term. Supporting Evidence: file:PYRO7/PMK1/PMK1-deep-research-falcon.md Its catalytic reaction is transfer of a phosphate group from ATP to a hydroxyl group on a protein serine or threonine, producing ADP and a phosphoprotein. |
| GO:0030448 hyphal growth | IMP PMID:29567712 A single fungal MAP kinase controls plant cell-to-cell invas... | KEEP AS NON CORE | Summary: Pmk1 is dispensable for vegetative growth in culture, but its inhibition alters invasive hyphal morphology in planta, and Pmk1 phosphorylation of fimbrin (MoFim1 Ser94) promotes hyphal-tip actin bundling; phosphomimetic MoFim1-S94D restores hyphal growth of a pmk1 deletion mutant. Reason: Supported, with a direct mechanism (fimbrin phosphorylation), but the effect on hyphal growth is modest compared to the essential roles in appressorium formation and invasive cell-to-cell growth; non-core. Supporting Evidence: PMID:38252344 S94D expression could restore the hyphal growth of Ξpmk1 PMID:8946911 PMK1 is nonessential for vegetative growth and sexual and asexual reproduction in culture. |
| GO:0075018 positive regulation of appressorium formation | IDA PMID:29567712 A single fungal MAP kinase controls plant cell-to-cell invas... | ACCEPT | Summary: Pmk1 is the central regulator of appressorium development; this row derives from the 2018 chemical-genetic study (analog-sensitive Pmk1 inhibition). Reason: Core process: Pmk1 performs the signalling step (phosphorylation of Hox7 and Mst12) that drives appressorium differentiation. Full text not cached, but the function is well established and consistent with the IMP from PMID:8946911. Supporting Evidence: PMID:34707224 this tiered regulatory mechanism involves Pmk1-dependent phosphorylation of the Hox7 homeobox transcription factor, which regulates genes associated with induction of major physiological changes required for appressorium development |
| GO:0075018 positive regulation of appressorium formation | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA-based assignment concordant with the experimental evidence. Reason: Consistent with experimental IMP/IDA annotations for this gene. Supporting Evidence: PMID:8946911 pmk1 mutants of M. grisea fail to form appressoria and fail to grow invasively in rice plants. |
| GO:0075018 positive regulation of appressorium formation | IMP PMID:8946911 MAP kinase and cAMP signaling regulate infection structure f... | ACCEPT | Summary: pmk1 deletion mutants fail to form appressoria; they still respond to cAMP for early stages, placing Pmk1 downstream of cAMP signalling. Reason: Founding experimental evidence for the core process; Pmk1 performs the signalling step rather than merely being required. Supporting Evidence: PMID:8946911 pmk1 mutants of M. grisea fail to form appressoria and fail to grow invasively in rice plants. PMID:8946911 suggests Pmk1 acts downstream of a cAMP signal for infection structure formation |
| GO:0106310 protein serine kinase activity | EXP PMID:8946911 MAP kinase and cAMP signaling regulate infection structure f... | ACCEPT | Summary: In vitro kinase activity of GST-Pmk1 (UniProt catalytic activity, RHEA:17989, evidence PMID:8946911); native serine substrates later identified (MoFim1 Ser94, Hox7 Ser158, Mst12 Ser133). Reason: Correct and experimentally supported; MAP kinase activity is the more informative term but this serine-specific term is accurate. Supporting Evidence: PMID:8946911 a GST-Pmk1 fusion protein has kinase activity in vitro PMID:38252344 S94A but not S117A lost phosphorylation |
| GO:0106310 protein serine kinase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Automated assignment (ARBA, RHEA:17989) concordant with experimental data. Reason: Consistent with the EXP annotation and identified serine phosphosites. Supporting Evidence: PMID:38252344 These results indicated that Pmk1 could regulate the phosphorylation of MoFim1 at serine 94. |
| GO:0140649 symbiont-mediated cell-to-cell migration by invasive hypha | IMP PMID:29567712 A single fungal MAP kinase controls plant cell-to-cell invas... | ACCEPT | Summary: Chemical-genetic inhibition of an analog-sensitive Pmk1 after host entry traps the fungus in the first invaded rice cell; Pmk1 controls the hyphal constriction at pit fields and the expression of effectors needed to move into adjacent cells. Reason: Although a host-interaction term, this is not a loss-of-virulence inference: the inhibition was applied after penetration, separating this step from the appressorium defect, and the process is a fungal morphogenetic one (invasive hyphal constriction) controlled by Pmk1 signalling. Effector-mediated suppression of host immunity is a further downstream output and is correctly not annotated to Pmk1. Supporting Evidence: PMID:29567712 chemical genetic inhibition of a single fungal mitogen-activated protein (MAP) kinase, Pmk1, prevents M. oryzae from infecting adjacent plant cells, leaving the fungus trapped within a single plant cell. PMID:29567712 Pmk1 controls the hyphal constriction required for fungal growth from one rice cell to the neighboring cell, enabling host tissue colonization and blast disease. |
Loading supporting contentβ¦
Download this section (compressed HTML)Q: Should the septin ring assembly (GO:0000921) IMP be recast as a regulatory term, given that Pmk1 acts upstream of septin reorganisation through Mst12-dependent transcription rather than assembling septins itself?
Q: Where does Pmk1 act in the cell (nucleus in appressoria versus hyphal tip with MoFim1), and should cellular component annotations be added from GFP-Pmk1 localisation data?
Experiment: Phosphoproteomics with analog-sensitive Pmk1 during invasive growth (rather than appressorium development) to identify the substrates that mediate hyphal constriction at pit fields.
Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)