| Aspect | Evidence/notes | Best supporting citations (pqac ids) | External URL(s)/publication date(s) |
|---|---|---|---|
| Family/domain | **Target identity verification:** direct literature for **Nicotiana attenuata DTX40_3 / UniProt A0A314KVN4 / ORF A4A49_09978** was not found in the retrieved corpus, so annotation should remain **family-based and inferential**. UniProt describes A0A314KVN4 as a **plant MATE/DTX transporter** with **MATE_euk / MATE_fam / MatE** domains. Broad plant MATE reviews describe this family as one of the largest transporter families in plants, involved in transport of secondary metabolites, organic acids, hormones, and xenobiotics. | (pqac-00000001, pqac-00000012) | UniProt entry for A0A314KVN4: https://www.uniprot.org/uniprotkb/A0A314KVN4 ; Takanashi et al. 2014, Plant Biotechnology, Dec 2014: https://doi.org/10.5511/plantbiotechnology.14.0904a |
| Topology/energy coupling | Plant MATE transporters are typically predicted to have **12 transmembrane domains** and commonly function as **secondary antiporters**, usually **H+ coupled** in plant examples. For Nicotiana alkaloid transporters, **NtMATE1 shows H+/nicotine antiport** activity in yeast; broader reviews state plant MATEs generally use **Na+ or H+ electrochemical gradients**, though proton coupling is the strongest inference for vacuolar alkaloid transporters. Thus, DTX40_3 is best annotated as a **probable 12-TM H+-coupled antiporter** unless direct data prove otherwise. | (pqac-00000015, pqac-00000018, pqac-00000012) | Shitan 2016, Biosci Biotechnol Biochem, Jul 2016: https://doi.org/10.1080/09168451.2016.1151344 ; Takanashi et al. 2014, Dec 2014: https://doi.org/10.5511/plantbiotechnology.14.0904a |
| Likely subcellular localization | Direct localization for DTX40_3 is unavailable. In **Nicotiana tabacum**, the closest functional precedents for alkaloid-associated MATEs (**Nt-JAT1, Nt-JAT2, NtMATE1/2**) localize primarily to the **tonoplast/vacuolar membrane** and mediate vacuolar sequestration. Nt-JAT2-GFP was localized to the **tonoplast** in BY-2 cells; yeast heterologous expression can show plasma-membrane signal, so plant-cell localization is more informative. Therefore DTX40_3 is **most plausibly tonoplast-localized**, though plasma membrane cannot be excluded without experiment. | (pqac-00000002, pqac-00000003, pqac-00000005, pqac-00000010, pqac-00000015) | Shitan et al. 2014, PLOS ONE, Sep 2014: https://doi.org/10.1371/journal.pone.0108789 ; Figure evidence for tonoplast localization in the same paper, Sep 2014 |
| Likely substrates | No direct substrate assay for DTX40_3 was found. The strongest Nicotiana precedent is **alkaloid transport**, especially **nicotine**, plus related alkaloids **anabasine** and **anatabine**; Nt-JAT2 also handled **berberine** and **scopolamine** in yeast assays, but not tested flavonoids such as **cyanidin 3-O-glucoside** or **rutin**. Because A0A314KVN4 is annotated as a detoxification/MATE protein from **Nicotiana attenuata**, a species well known for inducible defensive alkaloid metabolism, the most conservative substrate prediction is **specialized metabolite cation(s), likely pyridine alkaloids or other defense-related toxic metabolites**, not a broad flavonoid transporter. | (pqac-00000002, pqac-00000003, pqac-00000005, pqac-00000018) | Shitan et al. 2014, Sep 2014: https://doi.org/10.1371/journal.pone.0108789 ; Takanashi et al. 2014, Dec 2014: https://doi.org/10.5511/plantbiotechnology.14.0904a |
| Biological role/process | Best-supported inferred role is **detoxification by compartmentation**, i.e., moving specialized metabolites from the cytosol into the vacuole to reduce self-toxicity while enabling accumulation for defense. In Nicotiana homologs, this role is specifically **vacuolar sequestration of nicotine/alkaloids** after root-to-shoot transport. More generally, plant MATEs mediate xenobiotic efflux, alkaloid/flavonoid accumulation, citrate export, Fe homeostasis, and hormone transport; however, the Nicotiana homolog evidence points most strongly to **alkaloid sequestration/detoxification** rather than metal or hormone transport. | (pqac-00000000, pqac-00000001, pqac-00000005, pqac-00000015) | Takanashi et al. 2014, Dec 2014: https://doi.org/10.5511/plantbiotechnology.14.0904a ; Shitan 2016, Jul 2016: https://doi.org/10.1080/09168451.2016.1151344 |
| Signaling/pathway context | Nicotiana MATE alkaloid transporters are closely linked to **jasmonate (JA/MeJA)-responsive defense pathways**. **Nt-JAT2** is rapidly induced by **methyl jasmonate**, with strong leaf-preferential expression, supporting a role during herbivory-induced nicotine deployment. For DTX40_3 in **N. attenuata**, the most plausible pathway placement is therefore within **JA-regulated defensive specialized metabolism**, likely downstream of alkaloid biosynthesis and long-distance transport, where it would mediate final sequestration/storage. This remains an inference, not a gene-specific demonstration. | (pqac-00000002, pqac-00000004, pqac-00000006, pqac-00000019) | Shitan et al. 2014, Sep 2014: https://doi.org/10.1371/journal.pone.0108789 ; Shitan et al. 2015, Plant Signaling & Behavior, Jul 2015: https://doi.org/10.1080/15592324.2015.1035852 |
| Key quantitative data | Family- and homolog-level quantitative anchors useful for annotation: **Arabidopsis has >50 / 56 MATE genes**; **Nt-JAT2** is induced by **MeJA within ~2 h** and remains elevated for **24 h**; Nt-JAT2 is a **~507 aa** protein predicted to contain **12 TM helices**; recent plant-MATE work showed another alkaloid-pathway transporter, **CrMATE1**, transports **1 mM secologanin within 25 min**, and VIGS reduced transcript by **~73–80%**, causing **16–38-fold** secologanol accumulation and reduced downstream MIAs. These values do **not** measure DTX40_3 directly but illustrate realistic MATE family behavior and experimental expectations. | (pqac-00000012, pqac-00000015, pqac-00000004, pqac-00000008, pqac-00000009) | Takanashi et al. 2014, Dec 2014: https://doi.org/10.5511/plantbiotechnology.14.0904a ; Shitan et al. 2014, Sep 2014: https://doi.org/10.1371/journal.pone.0108789 ; Li et al. 2024, Communications Biology, Aug 2024: https://doi.org/10.1038/s42003-024-06624-5 |
| Confidence/limitations | **High confidence:** A0A314KVN4 is a **plant MATE/DTX family transporter**. **Moderate confidence:** it is a **12-TM, proton-coupled transporter**. **Moderate-to-low confidence:** it is **tonoplast-localized** and transports **nicotine/related alkaloids**, because these are inferred from Nicotiana homologs rather than shown directly for DTX40_3. **Low confidence for exact substrate specificity, tissue expression, and physiological phenotype** until gene-specific localization, transport assays, and expression profiling are performed in **N. attenuata**. | (pqac-00000001, pqac-00000003, pqac-00000015, pqac-00000018) | Evidence synthesis based on cited sources above; no direct publication located for A0A314KVN4 / DTX40_3 in retrieved literature corpus |


*Table: This table summarizes the most defensible functional annotation for Nicotiana attenuata DTX40_3 (UniProt A0A314KVN4) using direct identity information plus experimentally characterized plant and Nicotiana MATE homologs. It is useful for separating high-confidence family-level facts from lower-confidence gene-specific inferences.*