Metabolism of hydrogen peroxide during reserve mobilization and programmed cell death of barley (Hordeum vulgare L.) aleurone layer cells.
During germination, aleurone layer cells of barley (Hordeum vulgare) grains synthesize and secrete hydrolytic enzymes (principally alpha-amylase) in response to gibberellic acid (GA); shortly thereafter, the aleurone layer cells undergo programmed death. Gluconeogenesis of lipid reserves within aleurone cells, which supports this hydrolytic enzyme synthesis, results in the generation of H(2)O(2), which is catabolized by glyoxysomal catalase. Lowered amounts of catalase may contribute to aleurone cell death because of a compromised capacity to cope with reactive oxygen species generated by glyoxysomes and mitochondria. In the presence of GA, cells of intact aleurone layers underwent programmed death between 18 and 48 h; in the presence of ABA, no cell death was evident over 60 h. The capacity of GA-treated layers to metabolize exogenous H(2)O(2) increased steadily over the first 24 h, during the stage of lipid mobilization and the major synthesis and secretion of alpha-amylase; thereafter, this capacity declined markedly. In contrast, cells of ABA-treated aleurone layers exhibited little change in their capacity for H(2)O(2)-metabolism. Glyoxysomal catalase increased in activity over the first 12-24 h of GA treatment, which was accompanied by an increase in catalase-1 transcripts between 12 and 18 h. Catalase protein and activity declined after 24 h in GA-treated layers, prior to the onset of rapid programmed death at 30 h. These data suggest that a decline in glyoxysomal catalase precedes death of aleurone cells and may indeed contribute to an increase in cellular oxidative stress.
Palma
Kristoffer
K
Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada.
Kermode
Allison R
AR
D000040:Abscisic Acid / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002374:Catalase / Q000378:metabolism / Q000494:pharmacology; D005875:Gibberellins / Q000494:pharmacology; D005943:Gluconeogenesis; D020676:Glyoxysomes / Q000201:enzymology; D001467:Hordeum / Q000166:cytology / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology; D050356:Lipid Metabolism; D016877:Oxidants / Q000378:metabolism* / Q000494:pharmacology; D018384:Oxidative Stress; D010937:Plant Growth Regulators / Q000494:pharmacology; D000516:alpha-Amylases / Q000378:metabolism
D005875:Gibberellins; D016877:Oxidants; D010937:Plant Growth Regulators; D000040:Abscisic Acid; D006861:Hydrogen Peroxide; C007842:gibberellic acid; D002374:Catalase; D000516:alpha-Amylases