PMT2 is a root-expressed putrescine N-methyltransferase paralog from Nicotiana attenuata that converts putrescine to N-methylputrescine for the pyrrolidine branch of nicotine biosynthesis. Like PMT1, it is embedded in the inducible nicotine defense program and shows jasmonate-, wound-, and herbivory-responsive transcript accumulation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: This annotation is correct only at a very generic level and should not be treated as an informative curation outcome for PMT2. Reason: GO:0030750 putrescine N-methyltransferase activity already captures the actual chemistry performed by PMT2. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine. |
| GO:0004766 spermidine synthase activity | IEA GO_REF:0000118 | REMOVE | Summary: This TreeGrafter assignment is a family-level miscall and should not be kept as the catalytic function of PMT2. Reason: PMT2 belongs to a lineage derived from spermidine synthase but now performs specialized methyltransferase chemistry in nicotine biosynthesis. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md TreeGrafter assignment to spermidine synthase reflects PMT's evolutionary origin from spermidine synthase rather than its present catalytic activity. |
| GO:0005829 cytosol | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: Cytosolic localization is plausible for PMT2 but is not a major focus of the current literature-backed curation pass. Reason: Retain the localization as a reasonable non-core inference while prioritizing the better-supported catalytic and pathway assignments. |
| GO:0008295 spermidine biosynthetic process | IEA GO_REF:0000118 | REMOVE | Summary: This process annotation does not fit PMT2 biology. PMT2 contributes to nicotine alkaloid production, not spermidine biosynthesis. Reason: The same family-level overtransfer that caused the spermidine synthase activity annotation also incorrectly projects PMT2 into the spermidine process. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine. file:NICAT/NaPMT1.2/NaPMT1.2-notes.md TreeGrafter assignment to spermidine synthase reflects PMT's evolutionary origin from spermidine synthase rather than its present catalytic activity. |
| GO:0009753 response to jasmonic acid | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: Jasmonate responsiveness is supported for PMT2, but it is better treated as regulatory context than as a core function. Reason: MeJA induction is part of the defense program that controls PMT2 expression, yet the core role of the gene is catalytic entry into nicotine biosynthesis. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md In N. attenuata, Winz and Baldwin cloned PMT1 and PMT2 and found that both root PMT transcripts rose after MeJA, wounding, and Manduca sexta herbivory, while ethylene suppressed this induction. |
| GO:0030750 putrescine N-methyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: This is the core molecular function of PMT2 and accurately captures the enzyme's specialized chemistry. Reason: PMT2 catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine. |
| GO:0042179 nicotine biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: This is an appropriate core pathway assignment for PMT2. Reason: PMT2 generates the first dedicated pyrrolidine-branch intermediate and is part of the duplicated root nicotine pathway in N. attenuata. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine. file:NICAT/NaPMT1.2/NaPMT1.2-notes.md UniProt curates Q93XQ4 as Putrescine N-methyltransferase 2 and places it in nicotine biosynthesis with predominant root expression. |
| GO:0009611 response to wounding | IEP PMID:11299398 Molecular interactions between the specialist herbivore Mand... | KEEP AS NON CORE | Summary: Wound-responsive expression is supported for PMT2 but is ancillary to the gene's catalytic pathway role. Reason: Retain the annotation as valid defense-response context without elevating it above the core enzymatic curation. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md In N. attenuata, Winz and Baldwin cloned PMT1 and PMT2 and found that both root PMT transcripts rose after MeJA, wounding, and Manduca sexta herbivory, while ethylene suppressed this induction. |
| GO:0009625 response to insect | IEP PMID:11299398 Molecular interactions between the specialist herbivore Mand... | KEEP AS NON CORE | Summary: PMT2 participates in insect-triggered defense induction, but that inducibility is not its central curated function. Reason: Manduca sexta feeding induces PMT transcripts as part of nicotine defense, so the annotation should be preserved as a non-core context term. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md In N. attenuata, Winz and Baldwin cloned PMT1 and PMT2 and found that both root PMT transcripts rose after MeJA, wounding, and Manduca sexta herbivory, while ethylene suppressed this induction. |
| GO:0009753 response to jasmonic acid | IEP PMID:11299398 Molecular interactions between the specialist herbivore Mand... | KEEP AS NON CORE | Summary: The experimental annotation is supported, but the response term should remain explicitly non-core in this review. Reason: MeJA induction helps explain defense regulation of PMT2 without changing the gene's primary biochemical interpretation. Supporting Evidence: file:NICAT/NaPMT1.2/NaPMT1.2-notes.md In N. attenuata, Winz and Baldwin cloned PMT1 and PMT2 and found that both root PMT transcripts rose after MeJA, wounding, and Manduca sexta herbivory, while ethylene suppressed this induction. |
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Download this section (compressed HTML)Q: Are PMT1 and PMT2 dosage balanced in roots, or does one paralog dominate inducible nicotine flux under natural herbivory?
Q: How should PMT3 be classified relative to PMT1 and PMT2 once the core duplicated pathway members are fully reviewed?
Experiment: Measure nicotine-pathway metabolites and transcript compensation in PMT2 single-loss and PMT1 PMT2 double-loss lines before and after methyl jasmonate or Manduca sexta challenge.
Hypothesis: PMT2 contributes nonredundant but overlapping catalytic flux within the inducible root nicotine pathway.
Type: genetic perturbation plus metabolite profiling
Experiment: Reconstitute PMT2 biochemistry in vitro and compare catalytic efficiency and substrate preference directly against PMT1 using the same assay conditions.
Hypothesis: PMT2 retains core PMT chemistry but may differ quantitatively from PMT1 in kinetics or stability.
Type: biochemical enzyme assay
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