Up-regulation and localization of asparagine synthetase in tomato [Lycopersicon esculentum] leaves infected by the bacterial pathogen Pseudomonas syringae

• Published in: Plant and cell physiology 2004-06, Vol.45 (6), p.770-780
• Main Authors: Olea, F. (Universidad de Malaga (Spain)), Perez-Garcia, A, Canton, F.R, Rivera, M.E, Canas, R, Avila, C, Cazorla, F.M, Canovas, F.M, de Vicente, A
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence - genetics; amino acid sequences; Ammonia - metabolism; ASPARAGINE; Asparagine - biosynthesis; asparagine synthase (glutamine-hydrolysing); asparagine synthetase; Aspartate-Ammonia Ligase - genetics; Aspartate-Ammonia Ligase - isolation & purification; Aspartate-Ammonia Ligase - metabolism; Bacteria; Base Sequence - genetics; bioaccumulation; biochemical pathways; chloroplastic glutamine synthetase; complementary DNA; cytosolic glutamine synthetase; DNA, Complementary - analysis; DNA, Complementary - genetics; gene expression regulation; Gene Expression Regulation, Plant - genetics; glutamate-ammonia ligase; Glutamate-Ammonia Ligase - metabolism; GS1; GS2; histology; host-pathogen relationships; Keywords: Asparagine synthetase (EC 6.3.5.4) — Bacterial pathogenesis — Glutamine synthetase — Nitrogen mobilization — Pseudomonas syringae — Tomato (Lycopersicon esculentum Mill.); leaves; LIGASES; LYCOPERSICON ESCULENTUM; Lycopersicon esculentum - cytology; Lycopersicon esculentum - enzymology; Lycopersicon esculentum - microbiology; messenger RNA; Molecular Sequence Data; NITROGEN METABOLISM; nucleotide sequences; PATHOGENS; plant anatomy; Plant Leaves - cytology; Plant Leaves - enzymology; Plant Leaves - microbiology; plant pathogenic bacteria; plant proteins; Plant Proteins - genetics; Plant Proteins - isolation & purification; Plant Proteins - metabolism; polypeptides; protein synthesis; Pseudomonas Infections - enzymology; PSEUDOMONAS SYRINGAE; Pseudomonas syringae pv. tomato; Solanum lycopersicum var. lycopersicum; tomatoes; Up-Regulation - genetics; vegetable crops
• ISSN: 0032-0781; 1471-9053
• DOI: 10.1093/pcp/pch092

Nitrogen metabolism is one aspect of basic metabolism, which is still quite unknown in the field of plant-pathogen interactions. Evidence derived from previous studies conducted in our laboratory strongly suggests that during microbial pathogenesis an important nitrogen mobilization process takes place in diseased tissues. Here we describe the expression pattern of asparagine synthetase (AS; EC 6.3.5.4) in tomato leaves infected by the bacterial pathogen Pseudomonas syringae pv. tomato. Using an homologous AS cDNA probe isolated by RT-PCR from infected leaves, we have observed a high level induction of AS expression during the course of infection. Concomitantly, a single AS polypeptide also accumulated in response to bacterial infection. Furthermore, immunohistochemical analysis of AS in infected leaves revealed a strong immunostaining in phloem cells of the main vascular bundles and in secondary veins of the leaf blade. These data correlate with those previously reported for expression of a cytosolic isoform of glutamine synthetase (GS1) also induced during development of the infectious process. Taken together, our results suggest the existence of a GS1/AS pathway representing a metabolic route for transferring ammonium released from protein catabolism into asparagine, an amino acid that may have a major role in nitrogen mobilization from diseased tissues.