Hydrogen peroxide, nitric oxide and cytosolic ascorbate peroxidase at the crossroad between defence and cell death. Plant J

Department of Plant Biology and Pathology, University of Bari, Via Orabona 4, I-70125, Bari, Italy.
The Plant Journal (Impact Factor: 5.97). 01/2007; 48(5):784-95. DOI: 10.1111/j.1365-313X.2006.02919.x
Source: PubMed


An increase in the production of reactive oxygen species (ROS) is a typical event occurring during different stress conditions and activating conflicting responses in plants. In order to investigate the relevance of different timing and amounts of ROS production, tobacco (Nicotiana tabacum) Bright Yellow-2 (TBY-2) cells were incubated with different amounts of glucose plus glucose oxidase, for generating H(2)O(2) during time, or directly with known amounts of H(2)O(2). Data presented here indicate that, in TBY-2 cells, a difference in H(2)O(2) level is a critical point for shifting metabolic responses towards strengthening of antioxidant defences, or their depletion with consequent cell death. Timing of ROS production is also critical because it can determine programmed cell death (PCD) or necrosis. Depending on the different kinds of activated cell death, ascorbate (ASC) and glutathione (GSH) pools are altered differently. Moreover, an H(2)O(2)-dependent activation of nitric oxide synthesis is triggered only in the conditions inducing PCD. Ascorbate peroxidase (APX) has been analysed under different conditions of H(2)O(2) generation. Under a threshold value of H(2)O(2) overproduction, a transient increase in APX occurs, whereas under conditions inducing cell necrosis, the activity of APX decreases in proportion to cell death without any evident alteration in APX gene expression. Under conditions triggering PCD, the suppression of APX involves both gene expression and alteration of the kinetic characteristics of the enzyme. The changes in ASC, GSH and APX are involved in the signalling pathway leading to PCD, probably contributing to guaranteeing the cellular redox conditions required for successful PCD.

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    • "However, the balance between production and scavenging of H 2 O 2 may be disrupted by various abiotic and biotic stresses, leading to a rapid and transient increase in intracellular H 2 O 2 levels [25]. Overall, a low concentration of H 2 O 2 may function as a signaling molecule, whereas high concentrations of H 2 O 2 cause programmed cell death [26] [27]. "
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    ABSTRACT: Biological significance: In plants, H2O2 plays a dual role as the toxic by-product of normal cell physiological metabolism and as a regulatory molecule in stress perception and signal transduction. However, how plants maintain normal life activity under H2O2-triggered oxidative stress through mobilization of the intercellular metabolic mechanism and antioxidative system is largely unknown. Our integrated proteomic analysis combined with comparative view of ultrastructures of roots and leaves provides novel insights into the mechanisms underlying the plant response to, and defense against, oxidative stress in different organs.
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    • "DNA fragmentation appears as a smear on agarose gels (McCabe et al., 1997) and seems to occur later than complete DNA degradation. Production of H 2 O 2 is considered to be a key event during the action of different stress factors; production increases early in this process of PCD (Locato et al., 2008) and different concentrations of exogenous H 2 O 2 induce cell death (Houot et al., 2001; de Pinto et al., 2006). In this process, the control of H 2 O 2 by the defence system, including the enzymes ascorbate peroxidase (APX) and catalase, has been demonstrated to play a key role (Murgia et al., 2004; Locato et al., 2008, 2009; de Pinto et al., 2013). "
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    ABSTRACT: Reactive oxygen species (ROS), especially hydrogen peroxide, play a critical role in the regulation of plant development and in the induction of plant defence responses during stress adaptation, as well as in plant cell death. The antioxidant system is responsible for controlling ROS levels in these processes but redox homeostasis is also a key factor in plant cell metabolism under normal and stress situations. Thioredoxins (Trxs) are ubiquitous small proteins found in different cell compartments, including mitochondria and nuclei (Trxo1), and are involved in the regulation of target proteins through reduction of disulphide bonds, although their role under oxidative stress has been less well studied. This study describes over-expression of a Trxo1 for the first time, using a cell-culture model subjected to an oxidative treatment provoked by H2O2. Control and over-expressing PsTrxo1 tobacco (Nicotiana tabacum) BY-2 cells were treated with 35 mm H2O2 and the effects were analysed by studying the growth dynamics of the cultures together with oxidative stress parameters, as well as several components of the antioxidant systems involved in the metabolism of H2O2. Analysis of different hallmarks of programmed cell death was also carried out. Over-expression of PsTrxo1 caused significant differences in the response of TBY-2 cells to high concentrations of H2O2, namely higher and maintained viability in over-expressing cells, whilst the control line presented a severe decrease in viability and marked indications of oxidative stress, with generalized cell death after 3 d of treatment. In over-expressing cells, an increase in catalase activity, decreases in H2O2 and nitric oxide contents and maintenance of the glutathione redox state were observed. A decreased content of endogenous H2O2 may be responsible in part for the delayed cell death found in over-expressing cells, in which changes in oxidative parameters and antioxidants were less extended after the oxidative treatment. It is concluded that PsTrxo1 transformation protects TBY-2 cells from exogenous H2O2, thus increasing their viability via a process in which not only antioxidants but also Trxo1 seem to be involved. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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    • "During the incompatible interaction, pathogen infection can induce PCD at the site of infection through the hypersensitive response. The PCD mediated by H 2 O 2 involves the transcription and activity of a large number of genes encoding protein kinases MAPK [56] [57] which, in turn, transmit the signal activating transcription factors that regulate gene expression by activating the cell death process dependent H 2 O 2 [58]. "
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