Exogenous Nitric Oxide Mitigates Nickel-Induced Oxidative Damage in Eggplant by Upregulating Antioxidants, Osmolyte Metabolism, and Glyoxalase Systems.

Mona Soliman,Amr Elkelish,Haifa A Alhaithloul,Basmah M Alharbi,Mohamed El-Esawi,Khalid Rehman Hakeem

doi:10.3390/plants8120562

Abstract

Nitric oxide (NO) at optimal levels is considered beneficial to plant functioning. The present study was carried out to investigate the role of exogenously applied NO (100 and 150 µM sodium nitropurusside, SNP) in amelioration of nickel (Ni)-mediated oxidative effects in eggplant. Ni stress declined growth and biomass production, relative water content (RWC), and chlorophyll pigment synthesis, thereby affecting the photosynthetic efficiency. Exogenously applied SNP proved beneficial in mitigating the Ni-mediated growth restrictions. NO-treated seedlings exhibited improved photosynthesis, stomatal conductance, and chlorophyll content with the effect of being apparent at lower concentration (100 µM SNP). SNP upregulated the antioxidant system mitigating the oxidative damage on membranes due to Ni stress. The activity of superoxide dismutase, catalase, glutathione S-transferase, ascorbate peroxidase, and glutathione reductase was upregulated due to SNP which also increased the ascorbate and reduced glutathione content. SNP-supplied seedlings also showed higher proline and glycine betaine accumulation, thereby improving RWC and antioxidant system. Glyoxalase I activity was induced due to SNP application declining the accumulation of methylglyoxal. NO-mediated mitigation of Ni toxicity was confirmed using NO scavenger (PTIO, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), which reversed the influence of SNP almost entirely on the parameters studied. Uptake of nitrogen (N), potassium (K), and calcium (Ca) was increased due to SNP application and Ni was reduced significantly. Therefore, this study revealed the efficiency of exogenous SNP in enhancing Ni stress tolerance through upregulating antioxidant and glyoxalase systems.

Highlights

Accumulation of heavy metals in agricultural land significantly reduces soil fertility and the yield potential of crop plants, thereby imparting threat to global food security
Relative to control, applied SNP increased plant height and dry weight and ameliorated the reduction induced by Ni treatment
Maximal enhancement of 15.81% in height and 29.80% in dry weight was observed in 100 μM Nitric oxide (NO)-treated plants and amelioration of 17.86% and 46.15% was observed in plants treated with Ni + 100 μM SNP over the

Summary

Introduction

Accumulation of heavy metals in agricultural land significantly reduces soil fertility and the yield potential of crop plants, thereby imparting threat to global food security. Metal toxicity imbalances cellular redox homeostasis and mineral uptake, inhibits photosynthesis, damage nucleic acids, and mediate protein oxidation [6] These damaging effects result from the excessive reactive oxygen species (ROS) thereby imparting oxidative damage, and toxic metals have been reported to alter the phytohormone profile, chloroplast structure and functioning [7,8]. The antioxidant system is comprised of enzymatic and nonenzymatic components, which neutralize excess ROS [10], and osmolytes, including proline, glycine betaine (GB), sugars, etc., leading to protection of water relations and enzyme activity [11] Another important mechanism i.e., glyoxalase system includes two key enzymes: glyoxalase I and II mediating the detoxification of methylglyoxal (MG) [9]. Exogenous supplementation of phytohormones strengthen the tolerance mechanisms and improve tolerance of crop plants to a variety of stresses [5,8,12,13,14]

Results

Discussion

Conclusion