GLN2 (At5g35630; GS2) encodes the only plastid-type glutamine synthetase of Arabidopsis, a nuclear-encoded, light-induced, leaf-expressed enzyme with an N-terminal chloroplast transit peptide. It catalyses the ATP-dependent amidation of L-glutamate with ammonium to form L-glutamine in the chloroplast stroma and, together with ferredoxin-dependent glutamate synthase (GLU1), forms the GS/GOGAT cycle that assimilates ammonium into glutamate. GS2 refixes the ammonia released by glycine decarboxylation during photorespiration and also assimilates primary ammonium from nitrate reduction. In contrast to barley and Lotus, Arabidopsis gln2 knockouts are viable in air but are smaller, slightly chlorotic and altered in nitrogen metabolism, consistent with partial compensation by cytosolic GS1 isoforms. GLN2 activity in shoots under high ammonium supply causes acidification and contributes to ammonium toxicity. A minor mitochondrial pool of GS2 has been reported from GFP fusion studies but is disputed. Its activity is stimulated in vitro by the ACT-domain protein ACR11.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003729 mRNA binding | IDA PMID:32344669 Discovering the RNA-Binding Proteome of Plant Leaves with an... | MARK AS OVER ANNOTATED | Summary: GLN2 was among 717 proteins captured by UV-crosslinking/oligo(dT) RNA interactome capture (ptRIC) from Arabidopsis leaves. Reason: Proteome-wide RNA interactome capture recovers many abundant metabolic and photosynthetic enzymes that lack RNA-binding domains. GS2 has no known RNA-binding domain and no study has shown that it binds specific mRNAs or that RNA binding affects its function. The capture is a real observation but does not establish mRNA binding as a function of GS2. Supporting Evidence: PMID:32344669 As has previously been reported for mammals, a large proportion of leaf RBPs lack known RNA-binding domains, suggesting unconventional modes of RNA binding. file:ARATH/GLN2/GLN2-uniprot.txt Belongs to the glutamine synthetase family. |
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapping from the glutamine synthetase/guanido kinase catalytic domain. Reason: Correct but uninformative; the specific activity is glutamine synthetase activity (GO:0004356), already carried by the gene. Proposed replacements: glutamine synthetase activity Supporting Evidence: file:ARATH/GLN2/GLN2-uniprot.txt Reaction=L-glutamate + NH4(+) + ATP = L-glutamine + ADP + phosphate + H(+) file:ARATH/GLN2/GLN2-uniprot.txt Belongs to the glutamine synthetase family. |
| GO:0004356 glutamine synthetase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference of glutamine synthetase activity for the eukaryotic GS (GSII-type) clade; GLN2 (AT5G35630) is among the descendants. Reason: GS2 is a canonical member of the glutamine synthetase family with conserved catalytic and ATP-binding motifs, and GS activity attributable to GLN2 has been measured. Core function. Supporting Evidence: file:ARATH/GLN2/GLN2-uniprot.txt Belongs to the glutamine synthetase family. file:ARATH/GLN2/GLN2-uniprot.txt Reaction=L-glutamate + NH4(+) + ATP = L-glutamine + ADP + phosphate + H(+) |
| GO:0004356 glutamine synthetase activity | IDA PMID:15273293 Arabidopsis thaliana GLN2-encoded glutamine synthetase is du... | ACCEPT | Summary: Taira et al. 2004 measured GS activity in purified leaf mitochondria and identified GLN2 as the only candidate gene encoding it; GLN2 is the plastid GS. Reason: Glutamine synthetase activity of GLN2 is not in doubt (UniProt cites this paper for the catalytic activity); the mitochondrial location of that activity is a separate, disputed question handled on the location rows. Supporting Evidence: PMID:15273293 we report glutamine synthetase (GS) activity in highly purified Arabidopsis thaliana mitochondria isolated from light-adapted leaf tissue. file:ARATH/GLN2/GLN2-uniprot.txt Reaction=L-glutamate + NH4(+) + ATP = L-glutamine + ADP + phosphate + H(+) PMID:28339983 Here we showed that the recombinant ACR11 protein increased GS2 activity in vitro by reducing the Km values of its substrate glutamine. |
| GO:0004356 glutamine synthetase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA (EC 6.3.1.2, RHEA:16169, InterPro GS domains). Reason: Agrees with family membership and experimental evidence; core activity. Supporting Evidence: file:ARATH/GLN2/GLN2-uniprot.txt Reaction=L-glutamate + NH4(+) + ATP = L-glutamine + ADP + phosphate + H(+) file:ARATH/GLN2/GLN2-uniprot.txt Belongs to the glutamine synthetase family. |
| GO:0004356 glutamine synthetase activity | TAS PMID:1684022 The glutamine synthetase gene family of Arabidopsis thaliana... | ACCEPT | Summary: Peterman and Goodman 1991 cloned the Arabidopsis GS gene family and identified the leaf-specific, light-inducible GS cDNA corresponding to GS2. Reason: Traceable author statement for the GS activity of the leaf (plastid) isoform; consistent with all other evidence. Abstract only, but the activity is not in question. Supporting Evidence: PMID:1684022 lambda Atgsl1, which represents the leaf-specific mRNA, is induced by light. PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | MODIFY | Summary: PAINT inference of cytoplasm for the GS clade; most members (GS1-type) are cytosolic, while GS2 is targeted to plastids. Reason: In GO the chloroplast is part of the cytoplasm, so the statement is technically true for GS2, but it is far less specific than the evidence. GS2 carries a transit peptide and acts in the chloroplast stroma; replace with chloroplast stroma (already carried by the gene). Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000465001 Β· PTN000465001 SUPPORTS SOURCE BUT NOT TARGET Node spans cytosolic GS1-type and animal/fungal GS (MGI, FlyBase sources); GS2 is plastid-targeted, so cytoplasm is true only through chloroplast part_of cytoplasm. Proposed replacements: chloroplast stroma Supporting Evidence: PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0005739 mitochondrion | IDA PMID:15273293 Arabidopsis thaliana GLN2-encoded glutamine synthetase is du... | KEEP AS NON CORE | Summary: GLN2::GFP showed punctate fluorescence colocalizing with mitochondria and was detected by immunoblot in mitochondrial and chloroplast fractions of 35S::GLN2::GFP plants. Reason: Taira et al. reported GLN2::GFP in mitochondria by microscopy and immunoblotting of fractions from overexpressing plants. This dual targeting is disputed: GS was depleted from FFE-purified mitochondria and has not been found in mitochondrial matrix proteomes, suggesting plastid contamination. A minor mitochondrial pool cannot be excluded, so the annotation is kept but not as core; the dominant and functionally established location is the chloroplast stroma. Supporting Evidence: PMID:15273293 In immunoblot experiments, a 41-kD chimeric GLN2::GFP protein was present in both leaf mitochondria and chloroplasts of these stably transgenic plants. PMID:19223513 However, GS is depleted from mitochondrial fractions highly purified by free-flow electrophoresis (FFE) relative to pre-FFE mitochondrial fractions, suggesting that it was primarily detected as a plastidic contaminant of incompletely purified mitochondrial fractions PMID:22303256 On the other hand, neither Fd-GOGAT nor GS have been identified in proteome analyses of the mitochondrial matrix |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt SubCell mapping of the curated Mitochondrion location, based on Taira et al. 2004. Reason: Taira et al. reported GLN2::GFP in mitochondria by microscopy and immunoblotting of fractions from overexpressing plants. This dual targeting is disputed: GS was depleted from FFE-purified mitochondria and has not been found in mitochondrial matrix proteomes, suggesting plastid contamination. A minor mitochondrial pool cannot be excluded, so the annotation is kept but not as core; the dominant and functionally established location is the chloroplast stroma. Supporting Evidence: PMID:15273293 In immunoblot experiments, a 41-kD chimeric GLN2::GFP protein was present in both leaf mitochondria and chloroplasts of these stably transgenic plants. PMID:19223513 However, GS is depleted from mitochondrial fractions highly purified by free-flow electrophoresis (FFE) relative to pre-FFE mitochondrial fractions, suggesting that it was primarily detected as a plastidic contaminant of incompletely purified mitochondrial fractions |
| GO:0009507 chloroplast | HDA PMID:18431481 Sorting signals, N-terminal modifications and abundance of t... | ACCEPT | Summary: Identified in a large-scale MS analysis of ten independent purified chloroplast preparations. Reason: GS2 is the only chloroplast-targeted GS in Arabidopsis; chloroplast localization is supported by its transit peptide, GFP/immunoblot work, and multiple independent chloroplast proteomes. Accepted at this level; the sub-organellar location (stroma) is also accepted. Supporting Evidence: PMID:18431481 Here we present a large scale analysis by nanoLC-Q-TOF and nanoLC-LTQ-Orbitrap mass spectrometry (MS) of ten independent chloroplast preparations from Arabidopsis thaliana which unambiguously identified 1325 proteins. PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast |
| GO:0009507 chloroplast | HDA PMID:25293756 A proteomic strategy for global analysis of plant protein co... | ACCEPT | Summary: Detected in subcellular-fraction size-exclusion/MS profiling of leaf protein complexes. Reason: GS2 is the only chloroplast-targeted GS in Arabidopsis; chloroplast localization is supported by its transit peptide, GFP/immunoblot work, and multiple independent chloroplast proteomes. Accepted at this level; the sub-organellar location (stroma) is also accepted. Supporting Evidence: PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast PMID:28339983 GS2, encoded by GLN2, is the only plastid-type GS in Arabidopsis thaliana. |
| GO:0009507 chloroplast | IDA PMID:15273293 Arabidopsis thaliana GLN2-encoded glutamine synthetase is du... | ACCEPT | Summary: GLN2::GFP fluorescence and immunoblots placed the fusion protein in chloroplasts (as well as mitochondria). Reason: GS2 is the only chloroplast-targeted GS in Arabidopsis; chloroplast localization is supported by its transit peptide, GFP/immunoblot work, and multiple independent chloroplast proteomes. Accepted at this level; the sub-organellar location (stroma) is also accepted. Supporting Evidence: PMID:15273293 In immunoblot experiments, a 41-kD chimeric GLN2::GFP protein was present in both leaf mitochondria and chloroplasts of these stably transgenic plants. PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast |
| GO:0009507 chloroplast | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt SubCell mapping of curated "Plastid, chloroplast". Reason: GS2 is the only chloroplast-targeted GS in Arabidopsis; chloroplast localization is supported by its transit peptide, GFP/immunoblot work, and multiple independent chloroplast proteomes. Accepted at this level; the sub-organellar location (stroma) is also accepted. Supporting Evidence: PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast |
| GO:0009507 chloroplast | ISM GO_REF:0000122 | ACCEPT | Summary: AtSubP prediction of chloroplast localization from the N-terminal transit peptide. Reason: GS2 is the only chloroplast-targeted GS in Arabidopsis; chloroplast localization is supported by its transit peptide, GFP/immunoblot work, and multiple independent chloroplast proteomes. Accepted at this level; the sub-organellar location (stroma) is also accepted. Supporting Evidence: PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast |
| GO:0009535 chloroplast thylakoid membrane | HDA PMID:15322131 New functions of the thylakoid membrane proteome of Arabidop... | MARK AS OVER ANNOTATED | Summary: Detected in a proteome of salt-stripped thylakoid membranes. Reason: GS2 is a soluble stromal octamer/decamer with no transmembrane segment and no evidence for thylakoid association; abundant stromal enzymes are common contaminants of thylakoid preparations. Not removed because the full dataset was not examined, but this is not a functional location. Supporting Evidence: PMID:15322131 we analyzed the salt-stripped thylakoid membrane of chloroplasts of Arabidopsis thaliana. PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0009536 plastid | HDA PMID:28887381 Global Analysis of Membrane-associated Protein Oligomerizati... | MODIFY | Summary: Detected in plastid membrane-associated fractions by size-exclusion/MS correlation profiling. Reason: Correct but general: in leaves the plastid is a chloroplast and GS2 resides in the stroma. Replace with chloroplast stroma, already carried by the gene. Proposed replacements: chloroplast stroma Supporting Evidence: PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0009570 chloroplast stroma | HDA PMID:16207701 The oligomeric stromal proteome of Arabidopsis thaliana chlo... | ACCEPT | Summary: Identified in the oligomeric stromal proteome of purified Arabidopsis chloroplasts. Reason: GS2 is a soluble chloroplast enzyme; detection in independent stromal proteomes is consistent with its transit peptide and function in the stromal GS/GOGAT cycle. Core location. Supporting Evidence: PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0009570 chloroplast stroma | HDA PMID:18633119 Quantitative proteomics of a chloroplast SRP54 sorting mutan... | ACCEPT | Summary: Quantified in chloroplast proteomes of wild type and the cpSRP54 mutant. Reason: GS2 is a soluble chloroplast enzyme; detection in independent stromal proteomes is consistent with its transit peptide and function in the stromal GS/GOGAT cycle. Core location. Supporting Evidence: PMID:18633119 a quantitative comparison of ffc2-1 was carried out for total leaf proteomes of young seedlings and for chloroplast proteomes of fully developed leaves PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0009570 chloroplast stroma | HDA PMID:20061580 AT_CHLORO, a comprehensive chloroplast proteome database wit... | ACCEPT | Summary: Assigned to the stroma in the AT_CHLORO subplastidial proteome database. Reason: GS2 is a soluble chloroplast enzyme; detection in independent stromal proteomes is consistent with its transit peptide and function in the stromal GS/GOGAT cycle. Core location. Supporting Evidence: PMID:20061580 We went a step further into the knowledge of the chloroplast proteome by focusing, in the same set of experiments, on the localization of proteins in the stroma, the thylakoids, and envelope membranes. |
| GO:0009579 thylakoid | HDA PMID:16648217 High light response of the thylakoid proteome in arabidopsis... | MARK AS OVER ANNOTATED | Summary: Detected in the soluble thylakoid-associated proteome in a high-light study. Reason: GS2 is a stromal enzyme; its detection in thylakoid-associated fractions most likely reflects stromal carry-over rather than a thylakoid location. Supporting Evidence: PMID:16648217 we analyzed the quantitative response of the thylakoid-associated proteome of Arabidopsis (Arabidopsis thaliana) wild type and the ascorbate-deficient mutant vtc2-2 PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0009941 chloroplast envelope | HDA PMID:12938931 Proteomic study of the Arabidopsis thaliana chloroplastic en... | MARK AS OVER ANNOTATED | Summary: Detected in a proteome of "mixed" chloroplast envelope membranes. Reason: GS2 is a soluble stromal protein without membrane-spanning segments; envelope preparations commonly contain abundant stromal proteins. Not a functional location. Supporting Evidence: PMID:12938931 "mixed" envelopes were subsequently isolated using sucrose step gradients PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0019676 ammonia assimilation cycle | TAS PMID:16338958 Gln49 and Ser174 residues play critical roles in determining... | ACCEPT | Summary: TAS from a site-directed mutagenesis study of cytosolic GS1 isoenzymes (GLN1;3, GLN1;4); the abstract does not mention GS2. Reason: The cited abstract concerns GS1 kinetics, so it is weak support for this specific annotation, but the claim is clearly correct for GS2: it catalyses the GS half of the GS/GOGAT ammonia assimilation cycle in chloroplasts, for both photorespiratory and primary ammonium. Core process. Supporting Evidence: PMID:22303256 Re-assimilation of NH 3 takes place in the chloroplast through the sequential action of two enzymes, glutamine synthetase (GS; EC 6.1.3.2) and ferredoxin-dependent glutamine:oxoglutarate aminotransferase PMID:34400629 Even under conditions that lower photorespiration, the GLN2-deficient mutants show growth impairment, suggesting an important role of GLN2 in primary nitrogen assimilation. file:ARATH/GLN2/GLN2-uniprot.txt The light-modulated chloroplast/mitochondrial enzyme, encoded by a nuclear gene and expressed primarily in leaves, is responsible for the reassimilation of the ammonia generated by photorespiration. |
| GO:0022626 cytosolic ribosome | HDA PMID:15821981 High heterogeneity within the ribosomal proteins of the Arab... | MARK AS OVER ANNOTATED | Summary: Detected among proteins co-migrating with cytosolic 80S ribosomes in a ribosome proteomics study. Reason: The authors note that non-ribosomal proteins co-migrate with 80S ribosomes on gradients. GS2 is a plastid stromal enzyme and cannot be a component of cytosolic ribosomes; this is a co-sedimentation artefact. Supporting Evidence: PMID:15821981 In addition, we have identified a number of non-ribosomal proteins that co-migrate with the plant 80S ribosomes during gradient centrifugation suggesting their possible association with the 80S ribosomes. PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast |
| GO:0043436 oxoacid metabolic process | IEA GO_REF:0000117 | MODIFY | Summary: ARBA-based assignment of oxoacid metabolic process. Reason: Correct but very general; the specific process is L-glutamine biosynthesis (GO:1901704), already carried by the gene. Proposed replacements: L-glutamine biosynthetic process Supporting Evidence: file:ARATH/GLN2/GLN2-uniprot.txt Reaction=L-glutamate + NH4(+) + ATP = L-glutamine + ADP + phosphate + H(+) |
| GO:0046686 response to cadmium ion | IEP PMID:20005002 Leaf proteome responses of Arabidopsis thaliana exposed to m... | KEEP AS NON CORE | Summary: Leaf proteome study of seedlings exposed to cadmium; GS2 presumably among the 21 Cd-responsive proteins (abstract does not name it). Reason: An expression-level response from a proteomics survey; it does not show a role for GS2 in cadmium responses. Kept as a non-core observation since the full text was not available to check. Supporting Evidence: PMID:20005002 Of the 730 reproducible proteins among all gels, 21 were statistically upregulated in response to Cd. |
| GO:0048046 apoplast | HDA PMID:18538804 Hydroponic isotope labelling of entire plants (HILEP) for qu... | MARK AS OVER ANNOTATED | Summary: Detected in an apoplast-oriented quantitative proteomics dataset (HILEP) of plants under oxidative stress. Reason: GS2 has a chloroplast transit peptide and no secretion signal; detection in apoplastic extracts most likely reflects cell-damage contamination by abundant stromal proteins. Supporting Evidence: PMID:18538804 it was possible to show differential protein expression in the apoplast of plants submitted to oxidative stress. PMID:22303256 Six Arabidopsis genes encode GS enzymes, but only GS2 (encoded by At5g35630) is targeted to the chloroplast |
| GO:1901149 salicylic acid binding | HDA PMID:25628632 Identification of multiple salicylic acid-binding proteins u... | REMOVE | Summary: GS2 was a candidate SA-binding protein in the 4AzSA immunoselection and protein microarray screens, but in follow-up assays with recombinant protein it failed to bind the SA analog 3AESA and did not meet the authors' criteria for an SA-binding protein. Reason: The source paper itself reports that GS2 failed validation (no SPR binding to 3AESA) and explicitly excludes it from the confirmed SA-binding proteins. Being a screen candidate is not evidence of binding, so the annotation is contradicted by its own reference (full text reviewed). Supporting Evidence: PMID:25628632 Analysis of protein phosphatase 2A (PP2A), GS2, and an Ξ±/Ξ² hydrolase superfamily member failed to meet the criteria for designation as SABPs (data not shown). PMID:25628632 However, while GS2 failed to exhibit binding to 3AESA in the SPR assay, GSR2 was found to be an SABP |
| GO:1901704 L-glutamine biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference of L-glutamine biosynthetic process for the GS clade. Reason: GS catalyses ATP-dependent amidation of glutamate to glutamine; GS2 supplies glutamine in chloroplasts for photorespiratory and primary nitrogen assimilation. Core process. Supporting Evidence: file:ARATH/GLN2/GLN2-uniprot.txt Reaction=L-glutamate + NH4(+) + ATP = L-glutamine + ADP + phosphate + H(+) PMID:34400629 Even under conditions that lower photorespiration, the GLN2-deficient mutants show growth impairment, suggesting an important role of GLN2 in primary nitrogen assimilation. |
| GO:1901704 L-glutamine biosynthetic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO mapping from GS N-terminal domain. Reason: GS catalyses ATP-dependent amidation of glutamate to glutamine; GS2 supplies glutamine in chloroplasts for photorespiratory and primary nitrogen assimilation. Core process. Supporting Evidence: file:ARATH/GLN2/GLN2-uniprot.txt Reaction=L-glutamate + NH4(+) + ATP = L-glutamine + ADP + phosphate + H(+) file:ARATH/GLN2/GLN2-uniprot.txt Belongs to the glutamine synthetase family. |
| GO:0009853 photorespiration | TAS PMID:22303256 Photorespiration. | NEW | Summary: GS2 catalyses the first step of chloroplast refixation of the NH3 released by mitochondrial glycine decarboxylation, regenerating glutamine for Fd-GOGAT and ultimately glutamate for peroxisomal glyoxylate transamination. Reason: Participation test: GS2 catalyses a step of the photorespiratory nitrogen cycle (ammonia refixation), so it does work in the process rather than merely being required for it. Comparator check: the partner enzyme in the same cycle, Fd-GOGAT GLU1, carries photorespiration (IMP); GS2 orthologs in other plants (rice, maize, barley, pea, alfalfa) carry only IEA/IBA glutamine biosynthesis in GOA, so the absence reflects missing curation rather than a GO convention. Caveat: unlike barley and Lotus GS2 mutants, Arabidopsis gln2 knockouts survive in air, probably because GS1 isoforms and GDH partly compensate; GS2 therefore contributes to, but is not indispensable for, Arabidopsis photorespiration. GLN2 also acts in primary nitrogen assimilation (ammonia assimilation cycle row). Supporting Evidence: PMID:22303256 Re-assimilation of NH 3 takes place in the chloroplast through the sequential action of two enzymes, glutamine synthetase (GS; EC 6.1.3.2) and ferredoxin-dependent glutamine:oxoglutarate aminotransferase PMID:15273293 Therefore, the GLN2 gene product, heretofore labeled plastidic GS-2, functions in both leaf mitochondria and chloroplasts to faciliate ammonium recovery during photorespiration. PMID:34400629 Thus, in A. thaliana, GLN2, GLN1s, and GDHs proteins could redundantly contribute to the re-assimilation of photorespiratory ammonia. PMID:31622939 It was shown that GS2 mutants although smaller, slightly chlorotic and with the nitrogen metabolism impaired, were able to grow and complete their life cycle under ordinary air conditions. PMID:35279841 there is no doubt that this enzyme has a central role in photorespiration. file:ARATH/GLN2/GLN2-uniprot.txt The light-modulated chloroplast/mitochondrial enzyme, encoded by a nuclear gene and expressed primarily in leaves, is responsible for the reassimilation of the ammonia generated by photorespiration. |
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Download this section (compressed HTML)Q: Is there a functionally relevant mitochondrial pool of GS2 in wild-type leaves, given conflicting GFP-fusion and free-flow-electrophoresis proteomic results?
Q: Which enzymes (GS1 isoforms, GDH) refix photorespiratory ammonia in Arabidopsis gln2 knockouts, and why is Arabidopsis less dependent on GS2 than barley or Lotus?
Q: Does ACR11-mediated activation of GS2 operate in vivo to coordinate GS2 and Fd-GOGAT with photorespiratory flux?
Experiment: 15NH4+ or 15N-glycine labelling of wild type, gln2 and gln2 gln1 multiple mutants under high and low CO2 to quantify the share of photorespiratory ammonia refixed by GS2 versus cytosolic GS1.
Experiment: Free-flow-electrophoresis-purified mitochondria from plants expressing GLN2 under its native promoter, probed with GS2-specific antibodies, to test the proposed mitochondrial pool.
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