title: Senescence-specific regulation of catalases in Arabidopsis thaliana (L.) Heynh.
abstract: Oxygen free radicals are thought to play an essential role in senescence, especially those derived from peroxisomes. Therefore, the activities of different isoforms of the peroxisomal hydrogen peroxide (H2O2)-scavenging enzyme catalase (CAT) were analysed during senescence of Arabidopsis. CAT2 activity decreased with bolting time parallel with cytosolic ascorbate peroxidase 1 (APX1) activity before loss of chlorophyll could be measured. At the same time point, the H2O2 content increased. Subsequently, the stress-inducible CAT3 isoform was activated and APX1 activity was recovered, accompanied by a decline of the H2O2 content. In very late stages, low activities of the seed-specific CAT1 became detectable in leaves, but H2O2 increased again. Further analyses of CAT expression by promoter: beta-glucuronidase (GUS) fusions in transgenic plants revealed a vasculature-specific CAT3 expression, whereas CAT2 expression turned out to be specific for photosynthetic active tissues. CAT2 expression is down-regulated during leaf senescence, while CAT3 expression is induced with age and corresponds to an accumulation of H2O2 in the vascular bundles. CAT2 down-regulation on the transcriptional level appears as the initial step in creating the H2O2 peak during bolting time, while the decrease in APX1 activity might only be a secondary and amplifying effect.
authors.affiliation: ZMBP (Centre of Molecular Biology of Plants), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Zimmermann
authors.forename: Christina
authors.initials: C
authors.lastname: Heinlein
authors.forename: Gabriele
authors.initials: G
authors.lastname: Orendi
authors.forename: Ulrike
authors.initials: U
authors.lastname: Zentgraf
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D060387:Ascorbate Peroxidases; D002374:Catalase / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D016922:Cellular Senescence / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000032:analysis; D006540:Herbicides / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018384:Oxidative Stress / Q000235:genetics; D010269:Paraquat / Q000494:pharmacology; D010544:Peroxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020675:Peroxisomes / Q000201:enzymology; D018515:Plant Leaves / Q000201:enzymology; D030821:Plants, Genetically Modified / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000032:analysis
chemical_list: D029681:Arabidopsis Proteins; D006540:Herbicides; D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D006861:Hydrogen Peroxide; C490323:CAT3 protein, Arabidopsis; D010544:Peroxidases; D060387:Ascorbate Peroxidases; C490276:CAT2 protein, Arabidopsis; D002374:Catalase; D005966:Glucuronidase; D010269:Paraquat