Peroxynitrite (ONOO(-)) is a potent oxidant and nitrating species, generated by the reaction of nitric oxide and superoxide in one of the most rapid reactions known in biology. It is widely accepted that an enhanced ONOO(-) formation contributes to oxidative and nitrosative stress in various biological systems. However, an increasing number of studies have reported that ONOO(-) cannot only be considered as a mediator of cellular dysfunction, but also behaves as a potent modulator of the redox regulation in various cell signal transduction pathways. Although the formation of ONOO(-) has been demonstrated in vivo in plant cells, the relevance of this molecule during plant physiological responses is still far from being clarified. Admittedly, the detection of protein tyrosine nitration phenomena provides some justification to the speculations that ONOO() is generated during various plant stress responses associated with pathophysiological mechanisms. On the other hand, it was found that ONOO(-) itself is not as toxic for plant cells as it is for animal ones. Based on the concepts of the role played by ONOO(-) in biological systems, this review is focused mainly on the search for potential functions of ONOO(-) in plants. Moreover, it is also an attempt to stimulate a discussion on the significance of protein nitration as a paradigm in signal modulation, since the newest reports identified proteins associated with signal transduction cascades within the plant nitroproteome.
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