Some Enzymes of Hydrogen Peroxide Metabolism in Leaves and Root Nodules of Medicago sativa

Abstract

Leaves and nodules (bacteroids and cytosol) ofalfalfa (Medicago sativa L. cv Aragon) plants inoculated with Rhizobium meliloti strain 102F51 have been analyzed for the presence of the enzymes superoxide dismutase (SOD, EC 1.15.1.1), catalase (EC 1.11.1.6), and peroxidase (EC 1.11.1.7). All three fractions investigated (leaves, bacteroids, and nodular cytosol) show Cu,Zn-SOD activity. Besides, the bacteroids and cytosol of nodules possess CN-insensitive SOD activities. Studies of SOD inactivation with H202 indicate that, very likely, a Mn-SOD is present in the bacteroids, and suggest that the cytosol contain both Mn-SOD and Fe-SOD. Bacteroids show high catalase activity but lack peroxidase. By contrast, the nodule cytosol exhibits an elevated peroxidase activity as compared with the foliar tissue; this activity was completely inhibited by 50 to 100 micromolar KCN. The significantly lower contents of H202 and malondialdehyde (a product of lipid peroxidation) in nodules with respect to those in leaves reveal that the above-mentioned bacteroid and cytosol enzymes act in an efficient and combined manner to preserve integrity of nodule cell membranes and to keep leghemoglobin active.

Reactive oxygen species and plant resistance to fungal pathogens

“…The FOX method was used on cultured suspension cells (Boubakri et al, 2013;O'Brien et al, 2012b) or on incubation medium of leaf explants (Bellincampi et al, 2000). Other methods to determine H 2 O 2 spectrophotometrically in plant samples include the use of resorcinol/titanium oxalate (Becana et al, 1986) or ABTS (2,2 0 -Azino-bis-(3-ethylbenthiazoline-6-sulfonate)) (formation of blue colour) (Messner and Boll, 1994). The cytochemical staining using cerium (III) chloride (CeCl 3 ) is used for a subcellular localisation of H 2 O 2 .…”

Effects of soil warming and nitrogen fertilization on leaf physiology of Pinus tabulaeformis seedlings

“…The homogenates were centrifuged at 10,0009g for 30 min at 4°C, and the supernatant was used for the following assays. Superoxide dismutase (SOD) activity was determined according to the method of Becana et al (1986). One unit of SOD activity was defined as the amount of enzyme required to cause 50 % inhibition of nitro blue tetrazolium (NBT) reduction, measured with a scanning spectrophotometer (Unicam UV-330, Thermo Spectronic, England, UK) at 560 nm.…”

Short-term effects of experimental warming and enhanced ultraviolet-B radiation on photosynthesis and antioxidant defense of Picea asperata seedlings

“…(1) SOD (EC 1.15.1.1) activity was determined by the inhibition of the photochemical reduction of nitroblue tetrazolium (NBT), as described by Becana et al (1986). The reaction mixture in test tubes consisted of 50 ll of enzyme extract and 3.0 ml O 2 -generating mixture solution containing 50 mM potassium-phosphate (pH 7.8), 0.1 mM Na 2 EDTA, 13 mM methionine, 75 lM NBT, and 16.7 lM riboflavin.…”