Role of extracellular peroxidase in the superoxide production by wheat root cells

Abstract

Extracellular peroxidase has been shown to contribute to superoxide production in wounded wheat (Triticum aestivum L. cv. Ljuba) root cells. The superoxide-synthesizing system of root cells was considerably inhibited by KCN and NaN3 and activated by MnCl2 and H2O2. Treatment of roots with salicylic acid and a range of di- and tri-carbonic acids (malic, citric, malonic, fumaric, and succinic acids) stimulated superoxide production in both root cells and extracellular solution. The H2O2-stimulated superoxide production in the extracellular solution was much higher when roots were preincubated with salicylic or succinic acid. Exogenous acids enhanced peroxidase activity in the extracellular solution. Pretreatment of root cells with the detergents trypsin and sodium dodecyl sulfate had similar effects on the peroxidase activity. Significant inhibition of both superoxide production and peroxidase activity by diphenylene iodonium suggests that the specificity of the latter as an inhibitor of NADPH oxidase is doubtful. Results obtained indicate that extra-cellular peroxidase is involved in the superoxide production in wheat root cells. The mobile form of peroxidase can be readily secreted to the apoplastic solution and serve as an emergency enzyme involved in plant wound response.

In Vivo Cell Wall Loosening by Hydroxyl Radicals during Cress Seed Germination and Elongation Growth

“…O 2 ׯproduction, which is required for the peroxidase-mediated mechanism of × OH production (Schopfer, 2001) and potentially contributes to the Fenton-mediated mechanism (since O 2 ׯis rapidly dismutated to H 2 O 2 and O 2 ), was more sensitive to inhibition by cyanide (KCN) in the endosperm cap than in the radicle, while diphenyleneiodonium chloride (DPI) led to inhibition in both seed parts. KCN is known to inhibit peroxidases, which can produce O 2 ׯ ( Minibayeva et al, 2000), as well as ascorbate oxidase, which is hypothesized to play a role in ROS generation (Green and Fry, 2005) and other heme-containing enzymes, while DPI is an inhibitor of membrane-located NADPH oxidases and other flavoenzymes (Doussiere and Vignais, 1992). Our inhibitor results are in agreement with the hypothesis that NADPH oxidases, as well as apoplastic peroxidases or ascorbate oxidases, play a role in O 2 ×p roduction in germinating cress seeds.…”

Role of reactive oxygen species-generating enzymes and hydrogen peroxide during cadmium, mercury and osmotic stresses in barley root tip

“…In barley and wheat, the Mn-SOD activity of OxO-like protein (OLP) has recently been described with an important role in resistance response to infection (Christensen et al 2004). The role of extracellular peroxidases (PRXs) has been described in O 2 Á- (Minibayeva et al 2001), in OHÁ (Chen and Schopfer 1999), and also in H 2 O 2 production (Kawano 2003). Stress-induced ROS accumulation may also originate from the elevated activity of oxalate oxidase (OxO).…”

nduction of plant cells heat resistance by hydrogen sulfide donor is mediated by H(2)O(2) generation with participation of NADPH oxidase and superoxide dismutase

“…The basal parts of the coleoptiles were separated from the seedlings, they were incubated on distilled water for 2 h to remove the "wound stress" effect, and then transferred to Petri dishes with the main incubation medium -a sterilized 2% sucrose solution with penicillin (Na salt, 100,000 Unit/l). Medium of the respective variants in addition to sucrose and penicillin contained 100 μM hydrogen sulfide donor NaHS or inhibitors of NADPH oxidase -imidazole (1 μM) [17], peroxidase -sodium azide (NaN 3 -500 μM) [18], Cu/ZnSOD -sodium diethyldithiocarbamate (DDC -1 mM) [19,20] or a combination of each inhibitor with NaHS. The time of incubation of coleoptiles on a medium containing the hydrogen sulfide donor was 24 h. In variants with combined treatment, enzyme inhibitors were added to the coleoptiles incubation medium 2 h before NaHS was added thereto.…”