Nitric oxide, antioxidants and prooxidants in plant defence responses

Abstract

In plant cells the free radical nitric oxide (NO) interacts both with anti- as well as prooxidants. This review provides a short survey of the central roles of ascorbate and glutathione—the latter alone or in conjunction with S-nitrosoglutathione reductase—in controlling NO bioavailability. Other major topics include the regulation of antioxidant enzymes by NO and the interplay between NO and reactive oxygen species (ROS). Under stress conditions NO regulates antioxidant enzymes at the level of activity and gene expression, which can cause either enhancement or reduction of the cellular redox status. For instance chronic NO production during salt stress induced the antioxidant system thereby increasing salt tolerance in various plants. In contrast, rapid NO accumulation in response to strong stress stimuli was occasionally linked to inhibition of antioxidant enzymes and a subsequent rise in hydrogen peroxide levels. Moreover, during incompatible Arabidopsis thaliana-Pseudomonas syringae interactions ROS burst and cell death progression were shown to be terminated by S-nitrosylation-triggered inhibition of NADPH oxidases, further highlighting the multiple roles of NO during redox-signaling. In chemical reactions between NO and ROS reactive nitrogen species (RNS) arise with characteristics different from their precursors. Recently, peroxynitrite formed by the reaction of NO with superoxide has attracted much attention. We will describe putative functions of this molecule and other NO derivatives in plant cells. Non-symbiotic hemoglobins (nsHb) were proposed to act in NO degradation. Additionally, like other oxidases nsHb is also capable of catalyzing protein nitration through a nitrite- and hydrogen peroxide-dependent process. The physiological significance of the described findings under abiotic and biotic stress conditions will be discussed with a special emphasis on pathogen-induced programmed cell death (PCD).

Mitigation of sodium chloride toxicity inSolanum lycopersicumL. by supplementation of jasmonic acid and nitric oxide

“…Both CAT and APX mediate the breakdown of H 2 O 2 produced from SOD action, and further enhancement in CAT and APX by application of JA and NO may have strengthened the antioxidant defense system to reduce the oxidative damage. Exogenously sourced NO could promote the expression of antioxidant-coding genes (Groß et al 2013). The relative expression of antioxidant enzymes by exogenous application of JA has also been studied in soybean (Sirhindi et al 2016) and with NO in chickpea (Ahmad, Abdel Latef, et al 2016).…”

Low-molecular-weight metabolite systems chemistry

“…The latter enzyme has not yet been identified in plants although being suspected to be involved in most of its formation processes. Nitric oxide can be highly toxic because it can more or less react with ROS, for example with peroxynitrite ( Figure 5) and also every pro-and antioxidant LMWM (Groß et al, 2013). Furthermore, proteome wide-scale analyses revealed that nitric oxide can nitrosylate sulfur groups besides of cysteine in proteins, which has a fundamental effect on their functions (Astier et al, 2012).…”

“…In attempts of keeping the threat of the high ROS reactivity at minimum, various LMWM antioxidants and enzymes have evolved (Fridovich, 1998;Apel and Hirt, 2004;Halliwell and Gutteridge, 2007). Besides reactive oxygen species, we also know reactive nitrogen species (RNS), for example nitric oxide ( • NO), and sulfur reactive species, for example thiols, disulfides, sulfenic acid derivatives, thio-sulfinates and -sulfonates, and thiyl radicals, the latter presently being less in the research focus compared to RNS (Giles and Jacob, 2002;Gruhlke and Slusarenko, 2012;Groß et al, 2013). The radical • NO can arise by the following routes: (I) by compartment-specific reactions; (II) in chloroplasts and plant mitochondria from nitrite (NO 2 ) reduction by electron transport chain deficient processes (accidental one-electron transfers); (III) in plant peroxisomes from nitrite reduction by xanthine oxidoreductase; (IV) in the plant cytoplasm by nitrite reduction; (V) in the plant apoplast spontaneously at low pH by membrane-bound nitrite and nitrate reductases; and (VI) in mammalian cells nitric oxide synthase (NOS, Figure 5) oxidizes the amino acid arginine.…”

“…Figure 5 presents a summary of the various oxygen, nitrogen and sulfur reactive species, and chemical reactions involved in their formation. The various radicals can readily react with each other, as well as with LMWMs, proteins and membranes in the cell (Giles and Jacob, 2002;Halliwell, 2006;Møller et al, 2007;Groß et al, 2013). The ability of some LMWMs to reduce molecular oxygen by one-electron transfers is regarded as the major mechanism contributing to their cytotoxicity (Kappus and Sies, 1981).…”

Antioxidant Enzymes Activity in the Elaeis guineensis Jacq. Submitted to Drought

“…8; genotypes as a response to metabolize the radicals produced superoxides (Jaleel et al, 2007). SOD, which may be mitochondrial, cytosolic or chloroplastidic, is responsible for the dismutation of O 2 converting it to hydrogen peroxide and oxygen (Grob et al, 2013).…”