title: ABA modulates the degradation of phosphoenolpyruvate carboxylase kinase in sorghum leaves.
abstract: Salt stresses strongly enhance the phosphoenolpyruvate carboxylase kinase (PEPC-k) activity of sorghum leaves. This work shows that (1) abscisic acid (ABA) increased the rise in kinase activity in illuminated leaf disks of the non-stressed plant, (2) ABA decreased the disappearance of PEPC-k activity in the dark, (3) two PEPC-k genes expressed in sorghum leaves, PPCK1 and PPCK2, were not up-regulated by the phytohormone and, (4) ABA effects were mimicked by MG132, a powerful inhibitor of the ubiquitin-proteasome pathway. Collectively these data support a role for the ubiquitin-proteasome pathway in the rapid turnover of PEPC-k. The negative control by ABA on this pathway might account for the increase of kinase activity observed in salt-treated plants.
authors.affiliation: Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Avenida Reina Mercedes no. 6, 41012 Seville, Spain.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Monreal
authors.forename: Ana Belén
authors.initials: AB
authors.lastname: Feria
authors.forename: José María
authors.initials: JM
authors.lastname: Vinardell
authors.forename: Jean
authors.initials: J
authors.lastname: Vidal
authors.forename: Cristina
authors.initials: C
authors.lastname: Echevarría
authors.forename: Sofía
authors.initials: S
authors.lastname: García-Mauriño
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D010766:Phosphorylation; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D045868:Sorghum / Q000187:drug effects* / Q000201:enzymology*; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D007527:Isoenzymes; D007976:Leupeptins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D000040:Abscisic Acid; C069767:phosphoenolpyruvate carboxylase kinase; D017346:Protein Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde