Journal
JOURNAL OF PLANT PHYSIOLOGY
Volume 165, Issue 3, Pages 262-277Publisher
ELSEVIER GMBH
DOI: 10.1016/j.jplph.2007.01.020
Keywords
electron paramagnetic resonance; Fusarium oxysporum; Lupinus luteus; oxidative stress; sucrose
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This study was designed to investigate whether and to what extent oxidative stress is induced in embryo axes of Lupinus luteus L. cv. Polo inoculated with a necrotrophic fungus, Fusarium oxysporum and cultured on Heller medium for 96 h. Four variants were compared: inoculated embryo axes cultured with 60 mM sucrose (+Si) or without it (-Si), and non-inoculated embryo axes cultured with 60 mM sucrose (+Sn) or without it (-Sn). After inoculation, an accumulation of stable free radicals and Mn2+ ions in +Si and -Si were detected by electron paramagnetic resonance. Concentrations of the radicals with g-values of 2.0052 +/- 0.0004 and 2.0029 +/- 0.0003 were generally higher in -Si than in +Si. Beginning at 24 h after inoculation, in both +Si and -Si the concentrations of these ions decreased, but more strongly in -Si than in +Si. After inoculation, the activities of superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6) were higher in -Si than in +Si. SOD and CAT zymograms showed that the synthesis of new isoforms was induced after inoculation. Simultaneously, superoxide anions were assayed in embryo axes by using their specific indicator dihydroethidium (DHE). The DHE-derived fluorescence was stronger and covered a much larger tissue area in +Si than in -Si. The respiration rate was generally much higher in +Si than in -Si. Electron micrographs revealed that, in contrast to -Si cells, +Si cells had numerous mitochondria with less reduced numbers of cristae and long sections of rough endoplasmic reticulum and Golgi bodies. These results indicate that different defensive strategies against F. oxysporum were induced depending on soluble sugar levels in yellow lupine embryo axes. (C) 2007 Elsevier GmbH. All rights reserved.
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