MVP1 (MODIFIED VACUOLE PHENOTYPE 1; also ERMO3, GOLD36, NUC, GLL25; At1g54030) is a catalytically inactive member of the GDSL lipase/esterase (SGNH hydrolase) family, related to the myrosinase-associated proteins of Brassicaceae such as ESM1 and GLL23. Its block-I motif reads GDGL instead of GDSL and the recombinant protein shows no esterase or lipase activity. MVP1 is a soluble, N-glycosylated secretory protein with an N-terminal signal peptide; it is translated into the endoplasmic reticulum (ER), passes through the ER/Golgi and accumulates in the lumen of the vacuole. Loss-of-function alleles, isolated independently in four forward-genetic screens, cause the ER to collapse into large perinuclear aggregates and bulges that entangle Golgi stacks, vacuolar membranes and other organelles, with secondary defects in ER export and in delivery of secretory, vacuolar and plasma-membrane cargo, including the myrosinase TGG2, the GDSL protein GLL23 and the PEN3 ABC transporter. The aggregation is confined to ER-body-forming cells and depends on the ER-body transcription factor NAI1. MVP1 co-purifies with components of the PYK10 beta-glucosidase complex and binds the myrosinase TGG2. A version retained by ER/Golgi cycling (HDEL tag) is sufficient for function, so it acts early in the secretory pathway to keep ER morphology and organelle distribution normal. Mutants are salt-sensitive, release more nitriles during glucosinolate hydrolysis and are less resistant to fungal pathogens.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000325 plant-type vacuole | HDA PMID:15539469 The vegetative vacuole proteome of Arabidopsis thaliana reve... | ACCEPT | Summary: At1g54030 was identified by mass spectrometry in purified rosette-leaf vacuoles. Reason: Whole-organelle proteomics of purified vacuoles cannot resolve membrane from lumen, but the vacuolar location is independently confirmed by fluorescent-protein fusions showing MVP1 in the vacuolar lumen (PMID:23155454) and by GOLD36-mRFP (PMID:20626647). The vacuole is the protein's steady-state destination; the more specific lumen term is added as a NEW row. Supporting Evidence: PMID:15539469 Interestingly, we also identified five additional MAP gene products (At1g54000, At1g54010, At1g54020, At1g54030, and At1g14220) PMID:23155454 strongly support the vacuolar localization of ERMO3/MVP1/GOLD36 |
| GO:0005773 vacuole | IDA PMID:20626647 A missense mutation in the vacuolar protein GOLD36 causes or... | ACCEPT | Summary: GOLD36 fluorescent fusion localizes to the vacuole; the P80L mutant protein is retained in the ER. Reason: Abstract states the vacuolar localization directly, and it is reproduced with a different tag and a null background in PMID:23155454. The vacuole is the final destination of the protein. Plant-type vacuole and plant-type vacuole lumen rows carry the more specific claims. Supporting Evidence: PMID:20626647 Subcellular localization analyses indicated that GOLD36 is a vacuolar protein and that its mutated form is retained in the ER. |
| GO:0005773 vacuole | IDA PMID:23155454 ERMO3/MVP1/GOLD36 is involved in a cell type-specific mechan... | ACCEPT | Summary: ERMO3-tagRFP and ERMO3G59S-tagRFP label the vacuolar lumen; the signal persists after cycloheximide treatment while ER signal disappears. Reason: Full text read. The fusion complements the ermo3-2 null, and cycloheximide chase shows the ER pool is newly synthesized protein in transit while the vacuolar pool is the steady state. The lumen-level location is added as a NEW row. Supporting Evidence: PMID:23155454 This suggests that ERMO3-tagRFP was translated in the ER and transported to the vacuolar lumen, further supporting the conclusion of Marti et al. |
| GO:0005773 vacuole | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular location "Vacuole" mapped to GO. Reason: The UniProt location rests on the experimental papers (PMID:20626647, PMID:23155454) and is correct; same claim as the IDA vacuole rows. Supporting Evidence: PMID:23155454 We concluded that ERMO3/MVP1/GOLD36 was transported to the vacuole |
| GO:0005783 endoplasmic reticulum | IDA PMID:19880612 MODIFIED VACUOLE PHENOTYPE1 is an Arabidopsis myrosinase-ass... | ACCEPT | Summary: Transiently expressed MVP1-GFP shows an ER network pattern with ER bodies. Reason: MVP1 is a signal-peptide protein translated into the ER, and the ER is where its function is exerted: an ER/Golgi-cycling HDEL version fully complements the mutant (PMID:23155454), and NUC is required in the ER for GLL23 export (PMID:24330158). The ER pool is largely transit (cleared by cycloheximide), but the location is real and functionally relevant. The assay does not resolve lumen from membrane; the protein is soluble and lumenal by topology, but with no assay resolving the sub-compartment the organelle term is kept rather than adding ER lumen. Supporting Evidence: PMID:19880612 MVP1 showed an ER-like pattern with a characteristic network of GFP around the cell periphery PMID:23155454 its role in maintaining ER morphology was exerted between the ER and Golgi bodies |
| GO:0005783 endoplasmic reticulum | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular location "Endoplasmic reticulum" mapped to GO. Reason: Checked the source: the UniProt location reflects the experimental ER localization (PMID:19880612, PMID:23155454) and ER retention of mutant forms; the claim holds and matches the IDA row. Supporting Evidence: PMID:23155454 ERMO3-tagRFP labeled the vacuolar lumen and the ER, but not aggregates |
| GO:0006886 intracellular protein transport | IMP PMID:19880612 MODIFIED VACUOLE PHENOTYPE1 is an Arabidopsis myrosinase-ass... | KEEP AS NON CORE | Summary: In mvp1 mutants, TGG2-GFP, TGG1-GFP and other endomembrane markers are trapped in perinuclear aggregates instead of reaching their destinations. Reason: The mislocalization phenotype is solid and the acts_upstream_of_or_within qualifier fits, but the later full-text analysis (PMID:23155454) argues the transport defects are secondary to ER disorganization rather than MVP1 acting as a transport factor. Kept as a non-core consequence of the core ER-organization role. Supporting Evidence: PMID:19880612 These results reinforce our hypothesis that the mvp1 mutations cause global trafficking blocks early in the endomembrane trafficking system. PMID:23155454 Our results suggest that the defective protein transport observed in ermo3 cells was the secondary effect caused by abnormal organization of the ER. |
| GO:0006886 intracellular protein transport | IMP PMID:24330158 Trafficking of the myrosinase-associated protein GLL23 requi... | KEEP AS NON CORE | Summary: GLL23 accumulates in perinuclear ER aggregates in the nuc mutant. Reason: Abstract only. The abstract supports that NUC is required for ER export of GLL23 and that the two may travel together (both trapped in cyb compartments), which is compatible with a cargo-handling role, but the evidence remains mutant phenotype. Consistent with the other intracellular protein transport row, kept as non-core. Supporting Evidence: PMID:24330158 Without NUC, GLL23 accumulates in the ER this situation suggests that NUC is in fact active in the ER. |
| GO:0006888 endoplasmic reticulum to Golgi vesicle-mediated transport | IMP PMID:20626647 A missense mutation in the vacuolar protein GOLD36 causes or... | KEEP AS NON CORE | Summary: gold36 mutants partially retain the Golgi marker ST-GFP in the ER and fail to secrete a bulk-flow marker. Reason: Abstract only, but the ER-export defect was reproduced in ermo3-2 (PMID:23155454), where it occurred only in cells with ER aggregates; the authors conclude the transport defect is secondary to a disorganized ER-Golgi interface. The acts_upstream_of_or_within qualifier is appropriate; non-core. Supporting Evidence: PMID:20626647 GOLD36 showed defects in ER protein export as evidenced by our observations that, besides the partial retention of Golgi markers in the ER, the trafficking of a soluble bulk-flow marker to the cell surface was also compromised. PMID:23155454 our results suggest that ERMO3/MVP1/GOLD36 was involved in endomembrane organization itself, and the defective protein transport was due to disorganized ER-Golgi interface. |
| GO:0007029 endoplasmic reticulum organization | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT propagation of ER organization from a node seeded by MVP1 itself. Reason: MVP1 is the experimental seed (AT1G54030 in With/From), as expected for an IBA whose target has its own IMP evidence. The term is the core biological process of MVP1, established by four independent mutant screens. Supporting Evidence: PMID:23155454 We showed that ERMO3/MVP1/GOLD36 is required for maintaining ER morphology and organelle distribution |
| GO:0007029 endoplasmic reticulum organization | IMP PMID:20626647 A missense mutation in the vacuolar protein GOLD36 causes or... | ACCEPT | Summary: The gold36 P80L mutant and a knockout show ER bulges and skein-like ER structures entangling Golgi stacks. Reason: Core phenotype, reproduced with knockout alleles and independent screens (PMID:19880612, PMID:23155454, PMID:24330158). Supporting Evidence: PMID:20626647 GOLD36 showed partial distribution of ST-GFP into a modified endoplasmic reticulum (ER) network, which formed bulges and large skein-like structures entangling Golgi stacks. |
| GO:0007029 endoplasmic reticulum organization | IMP PMID:23155454 ERMO3/MVP1/GOLD36 is involved in a cell type-specific mechan... | ACCEPT | Summary: ermo3 alleles develop huge ER aggregates and ER-derived punctate structures in ER-body-forming cells; complemented by tagged MVP1. Reason: Full text read. Multiple alleles (ermo3-1, ermo3-2, mvp1-2) and complementation establish that MVP1 is required to maintain ER morphology. This is the core process. Supporting Evidence: PMID:23155454 Our results suggest that ERMO3/MVP1/GOLD36 is required for preventing ER and other organelles from abnormal aggregation and for maintaining proper ER morphology in a coordinated manner with NAI1. |
| GO:0009506 plasmodesma | HDA PMID:21533090 Arabidopsis plasmodesmal proteome. | MARK AS OVER ANNOTATED | Summary: High-throughput proteomics of a plasmodesma-enriched cell-wall fraction. Reason: At1g54030 is not named in the cached text, so the identification cannot be inspected (supplementary data). Plasmodesmal fractions co-purify ER (the desmotubule) and secretory cargo; MVP1 is an abundant soluble secretory/vacuolar lumen protein with no reported plasmodesmal function or targeting. The row probably reflects a co-purifying secretory protein rather than a plasmodesma-resident protein. Not removed because the dataset itself could not be checked. Supporting Evidence: PMID:23155454 This suggests that ERMO3-tagRFP was translated in the ER and transported to the vacuolar lumen |
| GO:0009507 chloroplast | ISM GO_REF:0000122 | REMOVE | Summary: AtSubP sequence-based prediction of chloroplast localization. Reason: Electronic prediction contradicted by sequence features and experiment. MVP1 has an N-terminal secretory signal peptide and N-glycosylation sites, and all experimental localizations place it in the ER, ER bodies and vacuole lumen. No study reports plastid localization. Supporting Evidence: file:ARATH/MVP1/MVP1-uniprot.txt SIGNAL 1..50 PMID:23155454 This suggests that ERMO3-tagRFP was translated in the ER and transported to the vacuolar lumen |
| GO:0009705 plant-type vacuole membrane | IDA PMID:19880612 MODIFIED VACUOLE PHENOTYPE1 is an Arabidopsis myrosinase-ass... | MARK AS OVER ANNOTATED | Summary: Transient MVP1-GFP fluorescence in transvacuolar strands was taken as tonoplast localization; earlier tonoplast proteomics also detected the protein. Reason: Full text read. The tonoplast call rests on GFP in transvacuolar strands, which also contain ER and cytoplasm, after transient overexpression. MVP1 is a soluble signal-peptide protein with no transmembrane segment, and the later, complemented stable fusions (PMID:23155454) place it in the vacuolar lumen, not the membrane. The vacuolar claim holds; the membrane sub-compartment is likely an over-interpretation and is better captured by plant-type vacuole lumen. Supporting Evidence: PMID:19880612 We also observed GFP fluorescence in transvacuolar strands ( Fig. 6C ), confirming that MVP1 was localized to the tonoplast. PMID:23155454 ERMO3-tagRFP labeled the vacuolar lumen and the ER, but not aggregates |
| GO:0010168 ER body | IDA PMID:19880612 MODIFIED VACUOLE PHENOTYPE1 is an Arabidopsis myrosinase-ass... | KEEP AS NON CORE | Summary: Transient MVP1-GFP labels spindle-shaped ER bodies. Reason: Full text read. ER bodies are ER-derived compartments, and an ER/Golgi-cycling ERMO3-Venus-HDEL also labels ER bodies (PMID:23155454); MVP1 binds PYK10-complex components that fill ER bodies. The location is plausible but reflects transient overexpression, and Nakano et al. found little contribution of MVP1 to ER body formation; peripheral to the core function. Supporting Evidence: PMID:19880612 Because there was strong localization of MVP1:GFP to the ER bodies PMID:23155454 In both lines, ERMO3-Venus-HDEL localized in the ER lumen and ER bodies. |
| GO:0016298 lipase activity | IBA NOT GO_REF:0000033 | ACCEPT | Summary: PAINT NOT annotation recording loss of lipase activity at the MVP1 node. Reason: The NOT is directly supported: MVP1 carries GDGL instead of the catalytic GDSL motif and recombinant MVP1 showed no esterase activity on p-nitrophenyl acetate and no lipase or esterase activity on tributyrin, Tween 20 or Tween 80 plates. The PAINT curator placed the loss at the node containing MVP1, which is consistent with the target's own experimental data. Supporting Evidence: PMID:19880612 Both the MVP1 and mvp1-1 constructs were negative for the formation of halos and precipitate, further demonstrating that MVP1 does not act as a lipase or esterase |
| GO:0016788 hydrolase activity, acting on ester bonds | IEA GO_REF:0000002 | REMOVE | Summary: InterPro2GO mapping from the GDSL lipase signature IPR001087. Reason: Demonstrably wrong for this gene. The family signature is present, but MVP1 is a pseudoenzyme: its block-I motif lacks the catalytic serine (GDGL), recombinant protein has no esterase or lipase activity, and a version with the serine restored (G59S) complements the mutant, showing that function does not need catalysis. The PAINT NOT lipase activity row already records the loss. Supporting Evidence: PMID:19880612 We concluded that MVP1 did not act as an esterase for this particular substrate in vitro, and the mvp1-1 mutation had no effect on this lack of activity. file:ARATH/MVP1/MVP1-uniprot.txt Lacks the conserved active site 'GDSL' motif and has no lipase activity. |
| GO:0000330 plant-type vacuole lumen | IDA PMID:23155454 ERMO3/MVP1/GOLD36 is involved in a cell type-specific mechan... | NEW | Summary: Complementing MVP1 fluorescent fusions accumulate in the vacuolar lumen. Reason: Two independent lines agree on the lumenal sub-compartment: complementing ERMO3-tagRFP and ERMO3G59S-tagRFP label the vacuolar lumen (persisting after cycloheximide), and the protein is a soluble secretory protein with an N-terminal signal peptide and no transmembrane segment. Added beside, not instead of, the vacuole rows. Supporting Evidence: PMID:23155454 Our results, that both ERMO3-tagRFP and ERMO3G59S-tagRFP labeled the vacuolar lumen (Figure S3), strongly support the vacuolar localization of ERMO3/MVP1/GOLD36. file:ARATH/MVP1/MVP1-uniprot.txt SIGNAL 1..50 |
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Download this section (compressed HTML)Q: Does MVP1 directly limit PYK10 complex assembly (for example by competing with PBP1/JALs or by escorting GLL23 out of the ER), and is that how it prevents ER aggregation in ER-body cells?
Q: Is the plasmodesma HDA identification of At1g54030 (PMID:21533090) a co-purifying secretory/ER cargo rather than a plasmodesma-resident protein?
Experiment: Reconstitute PYK10 complex assembly in vitro (PYK10, PBP1, GLL23) with and without recombinant MVP1 and measure complex size and PYK10 activity; in parallel test whether MVP1 binds GLL23 directly.
Type: biochemical reconstitution
Experiment: Immuno-electron microscopy of stably expressed, complementing MVP1 fusions at native levels to resolve vacuolar lumen versus tonoplast and ER-lumen localization.
Type: localization
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