Chloroplastic ATP sulfurylase (sulfate adenylyltransferase, EC 2.7.7.4) in field pennycress (Thlaspi arvense), orthologous to Arabidopsis thaliana APS1/ATPS1 (AT3G22890). TAV2_LOCUS7508 contains an N-terminal plastid transit region followed by an ATP-sulfurylase PUA-like domain and a C-terminal sulfate adenylyltransferase catalytic domain. It catalyzes the first committed step of plastidic sulfate assimilation, converting inorganic sulfate and ATP into adenosine 5'-phosphosulfate (APS) and diphosphate, supplying activated sulfate for both reductive cysteine biosynthesis and 3'-phosphoadenosine 5'-phosphosulfate (PAPS)-dependent glucosinolate (sinigrin) sulfation. Its transcript contains a conserved miR395 target site at CDS positions 973-993 that mediates post-transcriptional regulation in response to sulfur status.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000103 sulfate assimilation | IEA GO_REF:0000120 | ACCEPT | Reason: Core biological process. Plastidic ATP sulfurylase catalyzes the first committed step of plant sulfate assimilation by activating inorganic sulfate to APS, providing activated sulfur for both reductive assimilation and glucosinolate biosynthesis. Supporting Evidence: PMID:24027241 In sulfate assimilation, sulfate has to be first activated by ATP sulfurylase to adenosine 5′-phosphosulfate ( APS ), which is reduced in two steps, by adenosine 5′-phosphosulfate reductase ( APR ) to sulfite and subsequently by sulfite reductase to sulfide. uniprot:A0AAU9RRK7 DR InterPro; IPR002650; Sulphate_adenylyltransferase. |
| GO:0004020 adenylylsulfate kinase activity | IEA GO_REF:0000118 | REMOVE | Reason: Classic TreeGrafter domain-fusion false positive from PANTHER family PTHR11055 (BIFUNCTIONAL 3'-PHOSPHOADENOSINE 5'-PHOSPHOSULFATE SYNTHASE), which includes metazoan bifunctional PAPSS1/PAPSS2 enzymes that fuse an ATP sulfurylase domain with an adenylylsulfate (APS) kinase domain. In plants, ATP sulfurylase (APS1-APS4) and APS kinase (APK1-APK4) are encoded by separate genes; TAV2_LOCUS7508 contains only the PUA-like (AA 265-428) and sulfate adenylyltransferase catalytic (AA 438-659) domains and has no APS kinase domain or activity. Supporting Evidence: uniprot:A0AAU9RRK7 FT /note="Sulphate adenylyltransferase catalytic" PMID:24027241 In sulfate assimilation, sulfate has to be first activated by ATP sulfurylase to adenosine 5′-phosphosulfate ( APS ), which is reduced in two steps, by adenosine 5′-phosphosulfate reductase ( APR ) to sulfite and subsequently by sulfite reductase to sulfide. |
| GO:0004781 sulfate adenylyltransferase (ATP) activity | IEA GO_REF:0000120 | ACCEPT | Reason: Core molecular function. TAV2_LOCUS7508 possesses a conserved sulfate adenylyltransferase catalytic domain (IPR024951/IPR002650, PF01747) and is orthologous to Arabidopsis APS1 (EC 2.7.7.4), which catalyzes the ATP-dependent activation of sulfate to adenosine 5'-phosphosulfate (APS) and diphosphate. Supporting Evidence: uniprot:A0AAU9RRK7 DR InterPro; IPR024951; Sulfurylase_cat_dom. PMID:8058839 ATP sulfurylase, the first enzyme in the sulfate assimilation pathway of plants, catalyzes the formation of adenosine phosphosulfate from ATP and sulfate. |
| GO:0009507 chloroplast | IEA GO_REF:0000044 | ACCEPT | Reason: Core cellular component. TAV2_LOCUS7508 belongs to the chloroplastic ATP sulfurylase clade (PTHR11055:SF39) and is orthologous to Arabidopsis APS1, which contains an N-terminal chloroplast transit peptide and is imported into intact chloroplasts. Supporting Evidence: uniprot:A0AAU9RRK7 DR PANTHER; PTHR11055:SF39; ATP SULFURYLASE 4, CHLOROPLASTIC; 1. PMID:8058839 Two lines of evidence indicate that APS1 encodes a chloroplast form of ATP sulfurylase. Its predicted amino-terminal sequence resembles a chloroplast transit peptide; and the APS1 polypeptide, synthesized in vitro, is capable of entering isolated intact chloroplasts. |
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Download this section (compressed HTML)Q: To what extent does seed-specific expression of tar-miR395 or partial loss of TAV2_LOCUS7508 reduce seed sinigrin (allylglucosinolate) accumulation in pennycress without impairing vegetative sulfur nutrition?
Experiment: Quantify TAV2_LOCUS7508 mRNA cleavage by 5' RLM-RACE at CDS positions 973-993 and measure seed sinigrin and total sulfur levels in pennycress lines with altered tar-miR395 expression or TAV2_LOCUS7508 knockdown.
Hypothesis: tar-miR395 cleaves TAV2_LOCUS7508 transcripts at CDS 973-993 and limits plastidic APS production, reducing PAPS flux into seed sinigrin biosynthesis.
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