Iron deficiency differently affects peroxidase isoforms in sunflower

Abstract

The response of both specific (ascorbate peroxidase, APX) and unspecific (POD) peroxidases and H(2)O(2) content of sunflower plants (Helianthus annuus L. cv. Hor) grown hydroponically with (C) or without (-Fe) iron in the nutrient solution were analysed to verify whether iron deficiency led to cell oxidative status. In -Fe leaves a significant increase of H(2)O(2) content was detected, a result confirmed by electron microscopy analysis. As regards extracellular peroxidases, while APX activity significantly decreased, no change was observed in either soluble guaiacol or syringaldazine-dependent POD activity following iron starvation. Moreover, guaiacol-dependent POD activity was found to decrease in both ionically and covalently-cell-wall bound fractions, while syringaldazine-POD activity decreased only in the covalently-bound fraction. At the intracellular level both guaiacol-POD and APX activities underwent a significant decrease. The overall reduction of peroxidase activity was confirmed by the electrophoretic separation of POD isoforms and, at the extracellular level, by cytochemical localization of peroxidases by diaminobenzidine staining. The electrophoretic separation, besides quantitative differences, also revealed quantitative changes, particularly evident for ionically and covalently-bound fractions. Therefore, in sunflower plants, iron deficiency seems to affect the different peroxidase isoenzymes to different extents and to induce a secondary oxidative stress, as indicated by the increased levels of H(2)O(2). However, owing to the almost completely lack of catalytic iron capable of triggering the Fenton reaction, iron-deficient sunflower plants are probably still sufficiently protected against oxidative stress.

Oxidative stress, antioxidant activity and Fe(III)-chelate reductase activity of five Prunus rootstocks explants in response to Fe deficiency

“…It can be hypothesized that the difference in stress tolerance among plant species and genotypes within a species is intrinsically associated with the development of antioxidant systems under stress (Mittler 2002). On the other hand, it has been observed that Fe deficiency causes the accumulation of ROS in sunflower (Ranieri et al 2001) but not in pea (Iturbe-Ormaexte et al 1995). Although Fe deficiency-induced changes in activities of ROS-scavenging enzymes have been detected in several plants (Iturbe-Ormaexte et al 1995;Ranieri et al 2001;Lombardi et al 2003;Chouliaras et al 2004), no comparative analyses have examined the effect of Fe deficiency on isoform of antioxidant enzymes in genotypes with different tolerance to Fe deficiency.…”

“…On the other hand, it has been observed that Fe deficiency causes the accumulation of ROS in sunflower (Ranieri et al 2001) but not in pea (Iturbe-Ormaexte et al 1995). Although Fe deficiency-induced changes in activities of ROS-scavenging enzymes have been detected in several plants (Iturbe-Ormaexte et al 1995;Ranieri et al 2001;Lombardi et al 2003;Chouliaras et al 2004), no comparative analyses have examined the effect of Fe deficiency on isoform of antioxidant enzymes in genotypes with different tolerance to Fe deficiency. Recently, tolerance to long-term Fe deficiency in hydroponically grown Prunus rootstocks has been associated with the induction of antioxidant system (Molassiotis et al 2005a).…”

Thermal inactivation of polyphenoloxidase and peroxidase in Jubileu clingstone peach and yeast isolated from its spoiled puree

“…Furthermore, the enzyme action aims primarily to control the level of peroxides generated in almost all cellular compartments and, in the absence of a hydrogen donor, peroxidase converts hydrogen peroxide into H 2 O and O 2 . This catalatic reaction is at least a thousand times slower than peroxidation (Pinto, 2008;Ranieri et al, 2001).…”

Nitric oxide alleviates Fe deficiency-induced stress in Solanum nigrum

“…Ranieri et al (2001) reported that Fe deficiency enhanced H 2 O 2 accumulation in sunflower leaves. Iron deficiency reduces the activity of ascorbate peroxidase (APX; EC 1.11.1.11) and increases the contents of glutathione (GSH) and ascorbate (ASC), indicating that iron deficiency induces secondary oxidative stress in plants (Ranieri et al 2001, Zaharieva et al 2004, Sun et al 2007). Navarre et al (2000) reported that NO inhibits the activity of tobacco aconitase, an Fe-containing enzyme that regulates iron homeostasis, suggesting that NO plays a role in modulating iron accumulation in plants.…”

“…In response to iron deficiency, plants can increase iron solubility in soil by proton extrusion and enhance iron absorption through root hair proliferation (Curie andBriat 2003, Graziano andLamattina 2007). Ranieri et al (2001) reported that Fe deficiency enhanced H 2 O 2 accumulation in sunflower leaves. Iron deficiency reduces the activity of ascorbate peroxidase (APX; EC 1.11.1.11) and increases the contents of glutathione (GSH) and ascorbate (ASC), indicating that iron deficiency induces secondary oxidative stress in plants (Ranieri et al 2001, Zaharieva et al 2004, Sun et al 2007).…”