title: Effect of manganese toxicity on the proteome of the leaf apoplast in cowpea.
abstract: Excess manganese (Mn) supply causes formation of visible brown depositions in the cell walls of leaves of cowpea (Vigna unguiculata), which consist of oxidized Mn and oxidized phenols. Because oxidation of Mn and phenolic compounds in the leaf apoplast was proposed to be catalyzed by apoplastic peroxidases (PODs), induction of these enzymes by Mn excess was investigated. POD activity increased upon prolonged Mn treatment in the leaf tissue. Simultaneously, a significant increase in the concentration of soluble apoplastic proteins in "apoplastic washing fluid" was observed. The identity of the released proteins was systematically characterized by analysis of the apoplast proteome using two-dimensional gel electrophoresis and liquid chromatography-tandem mass spectrometry. Some of the identified proteins exhibit sequence identity to acidic PODs from other plants. Several other proteins show homologies to pathogenesis-related proteins, e.g. glucanase, chitinase, and thaumatin-like proteins. Because pathogenesis-related-like proteins are known to be induced by various other abiotic and biotic stresses, a specific physiological role of these proteins in response to excess Mn supply remains to be established. The specific role of apoplastic PODs in the response of plants to Mn stress is discussed.
authors: Institute of Plant Nutrition, University of Hannover, Herrenhäuser Strasse 2, 30419 Hannover, Germany.
authors: Marion M
authors: MM
authors: Fecht-Christoffers
authors: Hans-Peter
authors: HP
authors: Braun
authors: Christelle
authors: C
authors: Lemaitre-Guillier
authors: Alain
authors: A
authors: VanDorsselaer
authors: Walter J
authors: WJ
authors: Horst
mesh_terms: D000595:Amino Acid Sequence; D002473:Cell Wall / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D015180:Electrophoresis, Gel, Two-Dimensional; D007887:Fabaceae / Q000187:drug effects*; D007525:Isoelectric Focusing; D007700:Kinetics; D020149:Manganese Poisoning; D010446:Peptide Fragments / Q000737:chemistry; D018515:Plant Leaves / Q000187:drug effects*; D010940:Plant Proteins / Q000737:chemistry / Q000187:drug effects / Q000302:isolation & purification; D020543:Proteome
chemical_list: D010446:Peptide Fragments; D010940:Plant Proteins; D020543:Proteome