Nicotine Biosynthesis Project

Completing the nicotine biosynthesis pathway in Nicotiana attenuata

Chris Mungall | AI-Assisted Gene Review

2026-06-22

Why now: the pathway is finally complete

  • A 2026 Cell paper ("Complete biosynthesis of nicotine", Chang et al.) closes the last gaps in the N. attenuata pathway.
  • A parallel 2025 bioRxiv preprint (Schwabe et al.) shows nicotine biosynthesis is finished by a cryptic activating glucosylation.
  • New steps upgraded from side chemistry to pathway core: a glycosylation step and a deglycosylation step.
  • Provides a minimal heterologous reconstruction path (yeast / N. benthamiana).
  • Makes a transporter, NaMATE1, a core metabolon component rather than a peripheral annotation.

Why Nicotiana attenuata

  • The new Cell mechanistic closure is in N. attenuata itself — no cross-species translation noise at project start.
  • Strong prior pathway/evolution work already centered on N. attenuata (not just cultivated N. tabacum).
  • Rich root-expression and ecology literature helps separate true biosynthetic genes from housekeeping paralogs and regulators.
  • Deliberately not seeded in N. tabacum: forcing tobacco→attenuata orthology up front would add avoidable paralog noise.

Species code: NICAT.

The pathway: two branches that couple

  • Pyridine branch (from aspartate): supplies nicotinic acid.
    • NaAO2 (aspartate oxidase) → NaQPT2 (quinolinate phosphoribosyltransferase) → NaNAMNH (NAMN hydrolase → nicotinic acid).
  • Pyrrolidine branch (from polyamines): supplies the N-methyl-Δ1-pyrrolinium cation.
    • NaODC1/NaODC2 → NaPMT1.1/NaPMT1.2 (N-methylputrescine) → NaMPO1 (oxidation).
  • Coupling + late steps: the two branches join and are finished by the glycosylation/condensation/deglycosylation module.

The late module: glycosylate → couple → deglycosylate

From the bioRxiv mechanistic reconstitution (tobacco enzymes; N. benthamiana in planta):

Enzyme Assigned role
UGT1 (NaGT) nicotinic acid N-glucosyltransferase
A622 (NaGR) nicotinic acid N-glucoside reductase
BBLa (NicGS) (S)-nicotine glucoside synthase (sets stereoselectivity)
beta-GD1 (NicGH) nicotine glucoside hydrolase → (S)-nicotine

A four-enzyme cascade (UGT1 + A622 + BBLa + beta-GD1) reconstitutes (S)-nicotine in vitro.

The approach: AI gene review framework

  • Review each core gene's existing GO annotations against literature + bioinformatics evidence, then synthesize core functions.
  • Project owns three things:
    1. The canonical single-species nicotine pathway gene list.
    2. The review-job table that fetches/creates review stubs.
    3. The accession-resolution backlog for Cell-era names not yet normalized in public resources.
  • Two-layer naming: a canonical symbol layer (biology) and a launch-job layer (current fetchable accessions).

The seed gene set (1/2): upstream supply

Gene Role State
NaAO2 Pyridine branch entry from aspartate Provisional accession
NaNAMNH NAMN hydrolase → nicotinic acid (new Cell step) Pending accession
NaQPT2 Quinolinate phosphoribosyltransferase Provisional accession
NaODC1, NaODC2 Pyrrolidine precursor supply Provisional accession
NaPMT1.1, NaPMT1.2 N-methylputrescine formation Launch-ready
NaMPO1 Oxidation to pyrrolinium intermediate Candidate mapping

The seed gene set (2/2): coupling, late steps, transport

Gene Role State
NaUGT1 Glycosylation step producing NG (new Cell step) Candidate mapping
NaA622 Ring-condensation branch point Launch-ready
NaBBL1, NaBBL2 Late oxidation after condensation Provisional accession
NaBGL1, NaBGL2 Deglycosylation NG → nicotine (new Cell step) BGLU18 candidates ready
NaMATE1 Vacuolar metabolon transporter / export Candidate mapping

Minimal heterologous set (Cell): NaODC, NaPMT1, NaMPO, NaUGT1, NaA622, NaBBL2, NaBGL1, NaMATE1.

Accession mapping dive (2026-04-05)

Sequence-backed cross-release candidates (tobacco loci → NIATv7 → UniProt NICAT):

Canonical Candidate accession
NaMPO1 AMO_3 / A0A314KPU1
NaMATE1 DTX40_3 / A0A314KVN4
NaUGT1 UGT85A2_0 / A0A2H4GSI3
NaBGL1 BGLU18_6 / A0A1J6KFZ7
NaBGL2 BGLU18_1 / A0A314KWB2

BGLU18 candidates now anchor the beta-GD deglycosylases; BGLU42 demoted to a historical comparator.

Challenges

  • Non-model plant: public annotation still trails the Cell paper's Na... nomenclature for several genes.
  • Paralogs everywhere: ODC, PMT, BBL, BGL families each expose duplicated copies — pick the real pathway member, not a housekeeping paralog.
  • Cross-species evidence: mechanistic/structural work is on tobacco enzymes + N. benthamiana reconstitution, strong for role assignment but weak for exact NICAT accession resolution.
  • Transport / compartmentation: NaMATE1 (and follow-up NaNUP) tie biosynthesis to vacuolar export.
  • Open gap: NaNAMNH has a clear function but no stable public NICAT accession yet.

Status and what's left

Project maturity: MATURE.

  • All 22 current launch_ready aliases fetched into genes/NICAT/ and advanced to DRAFT review state.
  • NaUGT1, NaMPO1, NaBGL2, NaMATE1 converted from backlog into sequence-backed candidate jobs.
  • PMT paralog pair curated beyond seeded stubs.

Remaining worklist:

  • [ ] Resolve a stable public accession for NaNAMNH.
  • [ ] Revisit whether NaNUP belongs in the core transport batch after the minimal metabolon is reviewed.

Excluded from seed (tracked as follow-up)

  • NaNUP — transport-associated, but not part of the minimal Cell metabolon.
  • NaERF1-like, NaMYC2 — important regulators; settle the enzyme/transport core first.
  • NaAO1, NaQPT1, NaQS — housekeeping / parallel-pathway comparators.

Rationale: keep the seed conservative — enzymes and transport first, control logic later.

Key sources

  1. Chang L, et al. 2026. Complete biosynthesis of nicotine. Cell.
  2. Schwabe BTW, et al. 2025. Nicotine biosynthesis completed by cryptic activating glucosylation. bioRxiv (DOI 10.64898/2025.12.04.692101).
  3. Xu S, et al. 2017. Wild tobacco genomes reveal the evolution of nicotine biosynthesis. PNAS (PMC5468653).
  4. Zhang et al. 2025. DNA methylation valleys in root-specific nicotine genes in N. attenuata. Front. Plant Sci. (PMC12361153).

Proteome/accession resources: Sol Genomics Network (Nitab v4.5, NIATv7) + UniProtKB NICAT stream.