Senescence-specific regulation of catalases in Arabidopsis thaliana (L.) Heynh.
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.
Zimmermann
Petra
P
ZMBP (Centre of Molecular Biology of Plants), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
Heinlein
Christina
C
Orendi
Gabriele
G
Zentgraf
Ulrike
U
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
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