PMT1 is a root-expressed putrescine N-methyltransferase from Nicotiana attenuata that commits polyamine flux into the pyrrolidine branch of nicotine biosynthesis by converting putrescine to N-methylputrescine. It is part of an inducible anti-herbivore defense pathway whose transcript abundance rises after jasmonate treatment, wounding, and Manduca sexta feeding, while ethylene suppresses that induction.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0003824
catalytic activity
|
IEA
GO_REF:0000002 |
MARK AS OVER ANNOTATED |
Summary: This annotation is true but uninformative for PMT1. A specific catalytic term is already present for this enzyme.
Reason: GO:0030750 putrescine N-methyltransferase activity captures the actual chemistry; the generic catalytic parent term adds no useful biological resolution.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-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 annotation is not the current catalytic activity of PMT1. It reflects homology to the ancestral spermidine synthase family rather than the specialized methyltransferase activity of this nicotine-pathway enzyme.
Reason: PMT proteins evolved from spermidine synthase but catalyze S-adenosylmethionine-dependent methylation of putrescine, not spermidine synthesis.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-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 this soluble pathway enzyme, but it is peripheral to the main curated claims for PMT1.
Reason: The available evidence reviewed here strongly supports catalytic role, pathway placement, and root induction. The cytosol term is reasonable but not central enough to elevate as a core conclusion in this pass.
|
|
GO:0008295
spermidine biosynthetic process
|
IEA
GO_REF:0000118 |
REMOVE |
Summary: This process annotation is incorrect for PMT1. The enzyme directs putrescine into nicotine alkaloid biosynthesis rather than into spermidine biosynthesis.
Reason: PMT1 generates N-methylputrescine as a dedicated nicotine-pathway intermediate; the spermidine-process assignment is an ancestral family overcall.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine.
file:NICAT/NaPMT1.1/NaPMT1.1-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 PMT1, but it is regulatory context rather than the core biochemical role of the enzyme.
Reason: PMT1 transcripts rise after methyl jasmonate treatment in the herbivory defense program, which justifies retaining the annotation without treating it as a core function.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-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 PMT1 and the best available GO term for its catalytic role.
Reason: PMT1 catalyzes S-adenosylmethionine-dependent methylation of putrescine to form N-methylputrescine.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-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 biological-process annotation for PMT1. N-methylputrescine formation is an early committed step in nicotine biosynthesis.
Reason: PMT1 channels putrescine into the nicotine pathway by generating the first dedicated pyrrolidine-branch intermediate.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine.
file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
UniProt curates Q93XQ5 as Putrescine N-methyltransferase 1 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: PMT1 is part of a wound-inducible defense program, but this is context-level biology rather than its defining enzymatic function.
Reason: The 2001 N. attenuata study supports wound-responsive transcript induction, so the annotation should be preserved as non-core.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-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: This annotation is supported by herbivory-induced PMT transcript accumulation, but it is not part of the catalytic core function.
Reason: PMT1 participates in a defense response to Manduca sexta herbivory through inducible expression linked to nicotine production.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-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 evidence supports jasmonate-responsive expression of PMT1, but this should remain a contextual non-core annotation.
Reason: The same study that cloned PMT1 showed strong MeJA-induced transcript accumulation, supporting the response annotation without changing the core pathway-centric interpretation of the gene.
Supporting Evidence:
file:NICAT/NaPMT1.1/NaPMT1.1-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.
|
Q: Are PMT1 and PMT2 biochemically interchangeable in vivo, or do they make distinct quantitative contributions to nicotine production under herbivory?
Q: Does the more weakly characterized PMT3 paralog contribute measurable catalytic flux to the nicotine pathway, or is it a noncore duplicate?
Experiment: Generate clean PMT1, PMT2, and double-loss lines in Nicotiana attenuata and quantify N-methylputrescine and nicotine after methyl jasmonate treatment and Manduca sexta feeding.
Hypothesis: PMT1 and PMT2 jointly provide the dominant committed methyltransferase activity for inducible nicotine biosynthesis.
Type: genetic perturbation plus metabolite profiling
Experiment: Compare recombinant PMT1 and PMT2 kinetic parameters with putrescine and related diamines to test whether the paralogs are catalytically redundant or subtly specialized.
Hypothesis: The two root PMT paralogs retain the same core activity but may differ in catalytic efficiency or inducible pathway contribution.
Type: biochemical enzyme assay
Putrescine N-methyltransferase 1 (PMT1), encoded by the gene NaPMT1.1 in Nicotiana attenuata (coyote tobacco), is a pivotal enzyme in the biosynthesis of nicotine and related alkaloids. This enzyme catalyzes the methylation of putrescine, a polyamine, to form N-methylputrescine, marking the first committed step in the nicotine biosynthetic pathway.
Enzymatic Function and Substrate Specificity
PMT1 functions as a methyltransferase, transferring a methyl group from S-adenosyl-L-methionine (SAM) to putrescine, resulting in the production of N-methylputrescine and S-adenosyl-L-homocysteine. This reaction is crucial as it diverts putrescine from polyamine metabolism towards alkaloid biosynthesis. The enzyme's specificity for putrescine over other polyamines underscores its specialized role in this pathway.
Biological Processes and Localization
The expression of NaPMT1.1 is predominantly localized in the roots of N. attenuata, aligning with the root-specific synthesis of nicotine in this species. Transcriptome analyses have demonstrated that NaPMT1.1, along with other nicotine biosynthetic genes, is highly expressed in root tissues, while its expression in leaves is minimal. This root-specific expression pattern is consistent with findings in other Nicotiana species, where PMT genes are similarly upregulated in roots in response to jasmonate signaling, a plant hormone associated with stress responses and secondary metabolite production. (frontiersin.org)
Regulation and Pathway Involvement
The activity of NaPMT1.1 is tightly regulated within the nicotine biosynthetic pathway. In N. attenuata, a DNA methylation valley—a region of reduced DNA methylation—has been identified in the promoter regions of nicotine-related genes, including NaPMT1.1. This hypomethylation is associated with the root-specific expression of these genes, suggesting an epigenetic mechanism controlling their transcription. (frontiersin.org)
Furthermore, the expression of PMT genes in Nicotiana species is inducible by jasmonate treatment, indicating that NaPMT1.1 is part of a jasmonate-responsive regulatory network that modulates nicotine biosynthesis in response to environmental cues. (pubmed.ncbi.nlm.nih.gov)
Structural Insights and Evolutionary Context
Structurally, PMT1 belongs to the class I-like S-adenosylmethionine-dependent methyltransferase family, characterized by specific domains such as the PABS domain (IPR030374) and the SAM-dependent methyltransferase superfamily domain (IPR029063). These domains are integral to the enzyme's function in methyl group transfer. Evolutionary analyses suggest that PMT1 evolved from spermidine synthase, reflecting a functional divergence that enabled the specialized role of PMT1 in alkaloid biosynthesis. (en.wikipedia.org)
Conclusion
NaPMT1.1 encodes putrescine N-methyltransferase 1, a root-localized enzyme essential for the initiation of nicotine biosynthesis in Nicotiana attenuata. Its activity is regulated by both epigenetic modifications and jasmonate signaling, highlighting its role in the plant's adaptive responses. Understanding the function and regulation of NaPMT1.1 provides valuable insights into the metabolic pathways that contribute to the production of bioactive alkaloids in Nicotiana species.
id: Q93XQ5
gene_symbol: PMT1
product_type: PROTEIN
status: DRAFT
aliases:
- NaPMT1.1
- NaPMT1
- Putrescine N-methyltransferase 1
taxon:
id: NCBITaxon:49451
label: Nicotiana attenuata
description: >-
PMT1 is a root-expressed putrescine N-methyltransferase from Nicotiana
attenuata that commits polyamine flux into the pyrrolidine branch of nicotine
biosynthesis by converting putrescine to N-methylputrescine. It is part of an
inducible anti-herbivore defense pathway whose transcript abundance rises after
jasmonate treatment, wounding, and Manduca sexta feeding, while ethylene
suppresses that induction.
existing_annotations:
- term:
id: GO:0003824
label: catalytic activity
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: >-
This annotation is true but uninformative for PMT1. A specific catalytic
term is already present for this enzyme.
action: MARK_AS_OVER_ANNOTATED
reason: >-
GO:0030750 putrescine N-methyltransferase activity captures the actual
chemistry; the generic catalytic parent term adds no useful biological
resolution.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0004766
label: spermidine synthase activity
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: >-
This TreeGrafter annotation is not the current catalytic activity of PMT1.
It reflects homology to the ancestral spermidine synthase family rather than
the specialized methyltransferase activity of this nicotine-pathway enzyme.
action: REMOVE
reason: >-
PMT proteins evolved from spermidine synthase but catalyze
S-adenosylmethionine-dependent methylation of putrescine, not spermidine
synthesis.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: TreeGrafter assignment to spermidine synthase reflects PMT's evolutionary origin from spermidine synthase rather than its present catalytic activity.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0005829
label: cytosol
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: >-
Cytosolic localization is plausible for this soluble pathway enzyme, but it
is peripheral to the main curated claims for PMT1.
action: KEEP_AS_NON_CORE
reason: >-
The available evidence reviewed here strongly supports catalytic role,
pathway placement, and root induction. The cytosol term is reasonable but
not central enough to elevate as a core conclusion in this pass.
- term:
id: GO:0008295
label: spermidine biosynthetic process
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: >-
This process annotation is incorrect for PMT1. The enzyme directs
putrescine into nicotine alkaloid biosynthesis rather than into spermidine
biosynthesis.
action: REMOVE
reason: >-
PMT1 generates N-methylputrescine as a dedicated nicotine-pathway
intermediate; the spermidine-process assignment is an ancestral family
overcall.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine.
reference_section_type: LITERATURE_REVIEW
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: TreeGrafter assignment to spermidine synthase reflects PMT's evolutionary origin from spermidine synthase rather than its present catalytic activity.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0009753
label: response to jasmonic acid
evidence_type: IEA
original_reference_id: GO_REF:0000117
review:
summary: >-
Jasmonate responsiveness is supported for PMT1, but it is regulatory context
rather than the core biochemical role of the enzyme.
action: KEEP_AS_NON_CORE
reason: >-
PMT1 transcripts rise after methyl jasmonate treatment in the herbivory
defense program, which justifies retaining the annotation without treating
it as a core function.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: 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.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0030750
label: putrescine N-methyltransferase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: >-
This is the core molecular function of PMT1 and the best available GO term
for its catalytic role.
action: ACCEPT
reason: >-
PMT1 catalyzes S-adenosylmethionine-dependent methylation of putrescine to
form N-methylputrescine.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0042179
label: nicotine biosynthetic process
evidence_type: IEA
original_reference_id: GO_REF:0000041
review:
summary: >-
This is an appropriate core biological-process annotation for PMT1.
N-methylputrescine formation is an early committed step in nicotine
biosynthesis.
action: ACCEPT
reason: >-
PMT1 channels putrescine into the nicotine pathway by generating the first
dedicated pyrrolidine-branch intermediate.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine.
reference_section_type: LITERATURE_REVIEW
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: UniProt curates Q93XQ5 as Putrescine N-methyltransferase 1 and places it in nicotine biosynthesis with predominant root expression.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0009611
label: response to wounding
evidence_type: IEP
original_reference_id: PMID:11299398
review:
summary: >-
PMT1 is part of a wound-inducible defense program, but this is context-level
biology rather than its defining enzymatic function.
action: KEEP_AS_NON_CORE
reason: >-
The 2001 N. attenuata study supports wound-responsive transcript induction,
so the annotation should be preserved as non-core.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: 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.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0009625
label: response to insect
evidence_type: IEP
original_reference_id: PMID:11299398
review:
summary: >-
This annotation is supported by herbivory-induced PMT transcript
accumulation, but it is not part of the catalytic core function.
action: KEEP_AS_NON_CORE
reason: >-
PMT1 participates in a defense response to Manduca sexta herbivory through
inducible expression linked to nicotine production.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: 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.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0009753
label: response to jasmonic acid
evidence_type: IEP
original_reference_id: PMID:11299398
review:
summary: >-
The experimental evidence supports jasmonate-responsive expression of PMT1,
but this should remain a contextual non-core annotation.
action: KEEP_AS_NON_CORE
reason: >-
The same study that cloned PMT1 showed strong MeJA-induced transcript
accumulation, supporting the response annotation without changing the core
pathway-centric interpretation of the gene.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: 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.
reference_section_type: LITERATURE_REVIEW
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO terms
findings: []
- id: GO_REF:0000041
title: Gene Ontology annotation based on UniPathway vocabulary mapping
findings: []
- id: GO_REF:0000117
title: Electronic Gene Ontology annotations created by ARBA machine learning models
findings: []
- id: GO_REF:0000118
title: TreeGrafter-generated GO annotations
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: file:NICAT/NaPMT1.1/NaPMT1.1-uniprot.txt
title: UniProt entry Q93XQ5 for Nicotiana attenuata PMT1
findings:
- statement: UniProt identifies Q93XQ5 as Putrescine N-methyltransferase 1
supporting_text: 'DE RecName: Full=Putrescine N-methyltransferase 1'
reference_section_type: DATABASE_ENTRY
- statement: UniProt assigns PMT1 to nicotine biosynthesis
supporting_text: 'CC -!- PATHWAY: Alkaloid biosynthesis; nicotine biosynthesis.'
reference_section_type: DATABASE_ENTRY
- statement: UniProt reports predominant root expression for PMT1
supporting_text: 'CC -!- TISSUE SPECIFICITY: Mainly expressed in roots.'
reference_section_type: DATABASE_ENTRY
- id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
title: NaPMT1.1 literature review notes
findings:
- statement: PMT1 is the reviewed Nicotiana attenuata PMT1 pathway enzyme
supporting_text: UniProt curates Q93XQ5 as Putrescine N-methyltransferase 1 and places it in nicotine biosynthesis with predominant root expression.
reference_section_type: LITERATURE_REVIEW
- statement: PMT catalyzes the first dedicated pyrrolidine-branch step toward nicotine
supporting_text: PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine.
reference_section_type: LITERATURE_REVIEW
- statement: Spermidine synthase annotations on PMT1 are evolutionary-family overcalls
supporting_text: TreeGrafter assignment to spermidine synthase reflects PMT's evolutionary origin from spermidine synthase rather than its present catalytic activity.
reference_section_type: LITERATURE_REVIEW
- statement: PMT1 is part of jasmonate-, wound-, and herbivory-inducible nicotine defense
supporting_text: 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.
reference_section_type: LITERATURE_REVIEW
- statement: PMT1 fits the duplicated root nicotine pathway described in the Nicotiana genome study
supporting_text: The 2017 Nicotiana genome paper places root nicotine biosynthesis in N. attenuata as a duplicated specialization of polyamine and NAD metabolism, consistent with PMT as a root defense-pathway enzyme.
reference_section_type: LITERATURE_REVIEW
- id: PMID:11299398
title: Molecular interactions between the specialist herbivore Manduca sexta (Lepidoptera, Sphingidae) and its natural host Nicotiana attenuata. IV. Insect-Induced ethylene reduces jasmonate-induced nicotine accumulation by regulating putrescine N-methyltransferase transcripts.
findings:
- statement: PMT1 and PMT2 were cloned from Nicotiana attenuata as likely rate-limiting nicotine-pathway genes
supporting_text: we cloned the putrescine methyltransferase genes (NaPMT1 and NaPMT2) of N. attenuata, which are thought to represent the rate limiting step in nicotine biosynthesis
reference_section_type: ABSTRACT
- statement: Root PMT transcripts increase after methyl jasmonate treatment
supporting_text: Transcripts of both root putrescine N-methyltransferase (PMT) genes and nicotine accumulation increased dramatically within 10 h of shoot MeJA treatment
reference_section_type: ABSTRACT
- statement: Wounding and Manduca sexta herbivory elevate PMT transcript accumulation
supporting_text: 1-MCP pretreatment dramatically amplified the transcript accumulation resulting from both wounding and M. sexta herbivory
reference_section_type: ABSTRACT
- id: PMID:19651420
title: Putrescine N-methyltransferase--the start for alkaloids.
findings:
- statement: PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine
supporting_text: Putrescine N-methyltransferase (PMT) catalyses S-adenosylmethionine (SAM) dependent methylation of the diamine putrescine.
reference_section_type: ABSTRACT
- statement: N-methylputrescine is the first specific metabolite on the route to nicotine
supporting_text: The product N-methylputrescine is the first specific metabolite on the route to nicotine, tropane, and nortropane alkaloids.
reference_section_type: ABSTRACT
- statement: PMT evolved from plant spermidine synthase
supporting_text: PMT is likely to have evolved from the ubiquitous enzyme spermidine synthase.
reference_section_type: ABSTRACT
- id: PMID:28536194
title: Wild tobacco genomes reveal the evolution of nicotine biosynthesis.
findings:
- statement: Root nicotine biosynthesis in Nicotiana evolved from duplicated polyamine and NAD pathways
supporting_text: 'The biosynthetic machinery that allows for nicotine synthesis in the roots evolved from the stepwise duplications of two ancient primary metabolic pathways: the polyamine and nicotinamide adenine dinucleotide (NAD) pathways.'
reference_section_type: ABSTRACT
core_functions:
- molecular_function:
id: GO:0030750
label: putrescine N-methyltransferase activity
directly_involved_in:
- id: GO:0042179
label: nicotine biosynthetic process
description: >-
PMT1 catalyzes the S-adenosylmethionine-dependent methylation of putrescine
to N-methylputrescine, which commits polyamine-derived flux into the
pyrrolidine branch of nicotine biosynthesis in Nicotiana attenuata roots.
supported_by:
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: PMT catalyzes S-adenosylmethionine-dependent methylation of putrescine to N-methylputrescine, the first specific metabolite on the route to nicotine.
reference_section_type: LITERATURE_REVIEW
- reference_id: file:NICAT/NaPMT1.1/NaPMT1.1-notes.md
supporting_text: The 2017 Nicotiana genome paper places root nicotine biosynthesis in N. attenuata as a duplicated specialization of polyamine and NAD metabolism, consistent with PMT as a root defense-pathway enzyme.
reference_section_type: LITERATURE_REVIEW
proposed_new_terms: []
suggested_questions:
- question: Are PMT1 and PMT2 biochemically interchangeable in vivo, or do they make distinct quantitative contributions to nicotine production under herbivory?
- question: Does the more weakly characterized PMT3 paralog contribute measurable catalytic flux to the nicotine pathway, or is it a noncore duplicate?
suggested_experiments:
- description: Generate clean PMT1, PMT2, and double-loss lines in Nicotiana attenuata and quantify N-methylputrescine and nicotine after methyl jasmonate treatment and Manduca sexta feeding.
experiment_type: genetic perturbation plus metabolite profiling
hypothesis: PMT1 and PMT2 jointly provide the dominant committed methyltransferase activity for inducible nicotine biosynthesis.
- description: Compare recombinant PMT1 and PMT2 kinetic parameters with putrescine and related diamines to test whether the paralogs are catalytically redundant or subtly specialized.
experiment_type: biochemical enzyme assay
hypothesis: The two root PMT paralogs retain the same core activity but may differ in catalytic efficiency or inducible pathway contribution.