title: Inhibition of Arabidopsis growth by the allelopathic compound azetidine-2-carboxylate is due to the low amino acid specificity of cytosolic prolyl-tRNA synthetase.
abstract: The toxicity of azetidine-2-carboxylic acid (A2C), a structural analogue of L-proline, results from its incorporation into proteins due to misrecognition by prolyl-tRNA synthetase (ProRS). The growth of Arabidopsis thaliana seedling roots is more sensitive to inhibition by A2C than is cotyledon growth. Arabidopsis contains two ProRS isozymes. AtProRS-Org (At5g52520) is localized in chloroplasts/mitochondria, and AtProRS-Cyt (At3g62120) is cytosolic. AtProRS-Cyt mRNA is more highly expressed in roots than in cotyledons. Arabidopsis ProRS isoforms were expressed as His-tagged recombinant proteins in Escherichia coli. Both enzymes were functionally active in ATP-PPi exchange and aminoacylation assays, and showed similar Kmfor L-proline. A major difference was observed in the substrate specificity of the two enzymes. AtProRS-Cyt showed nearly identical substrate specificity for L-proline and A2C, but for AtProRS-Org the specificity constant was 77.6 times higher for L-proline than A2C, suggesting that A2C-sensitivity may result from lower amino acid specificity of AtProRS-Cyt. Molecular modelling and simulation results indicate that this specificity difference between the AtProRS isoforms may result from altered modes of substrate binding. Similar kinetic results were obtained with the ProRSs from Zea mays, suggesting that the difference in substrate specificity is a conserved feature of ProRS isoforms from plants that do not accumulate A2C and are sensitive to A2C toxicity. The discovery of the mode of action of A2C toxicity could lead to development of biorational weed management strategies.
authors.affiliation: Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ, 08901-8520, USA.
authors.forename: Jiyeon
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ, 08901-8520, USA.
authors.forename: Naveen
authors.initials: N
authors.lastname: Joshi
authors.affiliation: Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ, 08901-8520, USA.
authors.forename: Rita
authors.initials: R
authors.lastname: Pasini
authors.affiliation: Biomolecular Interaction Centre, School of Biological Sciences, University of Canterbury, Christchurch, 8140, New Zealand.|Department of Biochemistry and Molecular Biology, Bio21 Institute, Melbourne, VIC, 3010, Australia.|Maurice Wilkins Centre for Biodiscovery, Auckland, New Zealand.
authors.forename: Renwick C J
authors.initials: RC
authors.lastname: Dobson
authors.affiliation: Maurice Wilkins Centre for Biodiscovery, Auckland, New Zealand.|Centre for Theoretical Chemistry and Physics, Institute of Natural and Mathematical Sciences, Massey University Albany, Auckland, 0632, New Zealand.
authors.forename: Jane
authors.initials: J
authors.lastname: Allison
authors.affiliation: Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ, 08901-8520, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Leustek
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001383:Azetidinecarboxylic Acid / Q000494:pharmacology*; D018548:Cotyledon / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D013379:Substrate Specificity; D003313:Zea mays / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; C511747:PRORS1 protein, Arabidopsis; D001383:Azetidinecarboxylic Acid; D000604:Amino Acyl-tRNA Synthetases; C100134:prolyl T RNA synthetase
keywords: 
  Arabidopsis thaliana
  ; 
  Zea mays
  ; aminoacyl-tRNA synthetase; azetidine-2-carboxylic acid; prolyl-tRNA synthetase