Exogenous Nitric Oxide Confers Tolerance to Cr(VI) in Maize (Zea mays L.) Seedlings by Modulating Endogenous Oxido-Nitrosative Events

Abstract

The use of exogenous compounds such as 'gasotransmitter' molecules is a well-established agronomic strategy to improve the crop tolerance to environmental stresses. In this current work, when Cr (200 µM) was combined with the nitric oxide (NO) generator sodium nitroprusside SNP, 500 µM) there was a suppression of metal-induced alterations in embryo growth. Exogenous NO produced by SNP reduced the accumulation of toxic hydrogen peroxide and methylglyoxal and stress-linked proline in Cr-treated seedlings. Chromium increased thiol and S-nitrosothiol levels but this was restored to control levels by SNP, in spite of a competing NO reaction leading to increase of S-nitrosoglutathione content. However, added complexity was indicated by addition of arginine analogue N (ω)-nitro-L-arginine methyl ester ( L -NAME, 500 µM) in the germinating medium to suppress endogenous NO production. This suppressed endogenous NO production but superoxide dismutase (SOD) was suppressed not enhanced in Cr + L -NAME treatments. In addition, Cr + L -NAME significantly decreased the content of spermidine and spermine in epicotyls as compared to Cr treatment alone. Similarly, exposure to Cr + SNP decreased spermidine and spermine levels in both radicles and epicotyls. This is important as polyamines have been suggested as route for NO production. Thus, our observations suggest that exogenous NO mitigates Cr-induced damage and confers seedling tolerance to Cr through suppression of NADPH oxidase activity and increased GSNO contents. This may act to prevent an excess of methylglyoxal and hydrogen peroxide. However, the reduction in polyamine mediated cellular NO generation could also promote increased viability under Cr stress.

Metabolic profiles in the xylem sap of Brassica juncea exposed to cadmium

“…In Cd‐exposed pea plants ( Pisum sativum L., cv Lincoln), Barroso et al (2006) observed that the content of GSNO in collenchyma cells showed a marked decrease ( P < 0.05). Cr treatments reduced GSNO levels for radicles of maize ( Zea mays L.) (Kharbech et al, 2022). Application of GSNO‐reduced cell death, H 2 O 2 level, oxidative damage, and elevated proline content, indicating that NO donor GSNO mitigated the toxicity of Cd in plants (Xu et al, 2011).…”

S-Nitrosoglutathione (GSNO)-Mediated Lead Detoxification in Soybean through the Regulation of ROS and Metal-Related Transcripts

“…NO can increase the activity of both enzymatic and non-enzymatic antioxidants to scavenge ROS and lipid peroxidative substrates, and therefore, protect cells from oxidative damage against heavy metal stress by reducing their uptake accumulation, and translocation. Consequently, NO improves ionic homeostasis and provides tolerance to metal stress [ 16 ]. Moreover, NO is a signaling and highly reactive biomolecule that has the ability to alter the structure and activity of proteins [ 12 ].…”

“…In addition, depending on the type of donor and the concentration when supplied exogenously, NO can function as a beneficial or harmful molecule in plants. S-nitrosoglutathione (GSNO) is an S-nitrosylated derivative of cellular thiol glutathione (GSH) and is considered to be one of the most important NO donors [ 16 ]. GSNO has been found to have a positive affect for long periods as a NO source against water stress in sugarcane [ 17 ].…”