Nitric Oxide Acts as an Antioxidant and Delays Programmed Cell Death in Barley Aleurone Layers

Abstract

Nitric oxide (NO) is a freely diffusible, gaseous free radical and an important signaling molecule in animals. In plants, NO influences aspects of growth and development, and can affect plant responses to stress. In some cases, the effects of NO are the result of its interaction with reactive oxygen species (ROS). These interactions can be cytotoxic or protective. Because gibberellin (GA)-induced programmed cell death (PCD) in barley (Hordeum vulgare cv Himalaya) aleurone layers is mediated by ROS, we examined the effects of NO donors on PCD and ROS-metabolizing enzymes in this system. NO donors delay PCD in layers treated with GA, but do not inhibit metabolism in general, or the GA-induced synthesis and secretion of-amylase.-Amylase secretion is stimulated slightly by NO donors. The effects of NO donors are specific for NO, because they can be blocked completely by the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. The antioxidant butylated hydroxy toluene also slowed PCD, and these data support our hypothesis that NO is a protective antioxidant in aleurone cells. The amounts of CAT and SOD, two enzymes that metabolize ROS, are greatly reduced in aleurone layers treated with GA. Treatment with GA in the presence of NO donors delays the loss of CAT and SOD. We speculate that NO may be an endogenous modulator of PCD in barley aleurone cells.

The Arabidopsis PARAQUAT RESISTANT2 gene encodes an S-nitrosoglutathione reductase that is a key regulator of cell death

“…Likewise, a similar mechanism may be operating in par2-1, and the NO donor SNP confers paraquat resistance, presumably by exerting an antagonistic effect against the oxidative stress through increasing the NO level. This view is supported by the observation that SNP also confers paraquat resistance to potato leaves [52], and acts as an antioxidant to delay PCD induced by gibberellin in barley aleurone layers [33]. Again, consistent with the reciprocal regulation of NO and ROS, the accumulation of GSNOR1/HOT5/PAR2 protein is induced by paraquat, but is reduced when treated by SNP and GSNO.…”

“…Because NO has been reported to act as an antioxidant [28,32,33], we reasoned that the paraquat-resistance phenotype of par2-1 may be related to the increased intracellular NO level in the mutant. To test this possibility, wild type, par2-1 and gsnor1-3 were germinated and grown in the presence of NO donors, sodium nitroprusside (SNP) and GSNO, or the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidadazoline-1-oxy-3-oxide (CPTIO).…”

“…The balance between intracellular NO and ROS levels has been shown to be a key determinant for HR [26][27][28][29][30]. The ROS and NO levels appear to be reciprocally controlled through, at least partly, related scavenging enzymes, and NO has also been proposed to function as an antioxidant under certain conditions [28,29,[31][32][33]. Moreover, S-nitrosylation, the covalent addition of an NO molecule to a cysteine thiol of a protein or a peptide, is a key destination of the gaseous hormone and a redox-based posttranslational modification mechanism.…”

Effect of nitric oxide and putrescine on antioxidative responses under NaCl stress in chickpea plants

“…Tu et al (2003) reported that wheat leaves treated with 0.10 m mol/L SNP reduced H 2 O 2 by activating catalase in ageing wheat leaves. Beligni et al (2002) found that SNAP (Snitroso-N-acetyl-DL-pericillamine), another NO donor, could delay the GA-induced loss of Cat2 mRNA and protein in barley aleurone. also reported that SNP increased the activity of peroxidase but had little effect on SOD in drought stressed poplar leaves.…”

N-3-Oxo-Decanoyl-l-Homoserine-Lactone Activates Auxin-Induced Adventitious Root Formation via Hydrogen Peroxide- and Nitric Oxide-Dependent Cyclic GMP Signaling in Mung Bean

“…S3C). Butylated hydroxytoluene (BHT) and ascorbate acid (AsA) are efficient antioxidants (Beligni et al, 2002), and diphenylene iodonium (DPI) is an inhibitor of the plasma membrane NADPH oxidase that is one of the main sources of H 2 O 2 generation after an environmental stress (Neill et al, 2002;Torres and Dangl, 2005). BHT, AsA, and DPI suppressed 3-O-C10-HL-induced H 2 O 2 accumulation ( Three-day-old mung bean explants were subjected to 100 nM 3-O-C10-HL or a donor (100 nM C10-HL, 10 mM IAA, 100 mM H 2 O 2 , 50 mM GSNO, or 1 mM 8-Br-cGMP) treatment for 3 d or were pretreated with different inhibitors or scavengers (10 mM NPA, 1 mM DPI, 1 mM BHT, 1 mM AsA, 50 mM cPTIO, 10 mM LY83583, or 50 mM ODQ) for 2 h. This treatment was followed by the addition of 100 nM 3-O-C10-HL for 24 h, and H 2 O 2 (A) and NO (B) contents were determined.…”