Nitric oxide improves tolerance to arsenic stress in Isatis cappadocica desv. Shoots by enhancing antioxidant defenses

Abstract

Arsenic (As) is a toxic metalloid that severely hampers plant growth and also poses health risks for humans through the food chain. Although nitric oxide (NO) is known to improve plant resistance to multiple stresses including metal toxicity, little is known about its role in the As tolerance of hyperaccumulator plants. This study investigates the role of the exogenously applied NO donor, sodium nitroprusside (SNP), in improving the As tolerance of Isatis cappadocica, which have been reported to hyperaccumulate As. Exposure to toxic As concentrations significantly increases NO production and causes damage to the cell membrane, as indicated by increased hydrogen peroxide (H2O2) and malondialdehyde (MDA) concentration, thereby reducing plant growth. However, the addition of SNP improves growth and alleviates As-induced oxidative stress by enhancing the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione S-transferase (GST), glutathione (GSH), as well as proline and thiol concentration, thereby confirming the beneficial role played by NO in enhancing As stress tolerance. Furthermore, the As-induced decrease in growth and the increase in oxidative stress were more marked in the presence of bovine hemoglobin (Hb; a NO scavenger) and N(G)-nitro-L-arginine methyl ester (L-NAME; a NO synthase inhibitor), thus demonstrating the protective role of NO against As toxicity. The reduction in NO concentration by L-NAME suggests that NOS-like activity is involved in the generation of NO in response to As in I. cappadocica.

Characterization of mechanisms involved in tolerance and accumulation of Cd in Biscutella auriculata L

“…The antioxidant GSH plays an important role in several physiological processes, including signal transduction, conjugation of metabolites, detoxification, as a substrate for enzymatic antioxidants and in the regulation of stress-responsive gene expression (Ali et al, 2019), but it is also the precursor of phytochelatins (Yadav, 2010). A significant increase in the concentration of GSH was observed in B. auriculata leaves in response to Cd treatment, which in addition to contributing to phytochelatin production could participate directly in chelating Cd, as reported for other plant species in response to different metals such Cd (Domínguez-Solis et al, 2004) and As (Souri et al, 2020) and improving antioxidant defenses. Arabidopsis mutants overexpressing the enzyme adenosine 5′-phosphosulfate reductase 2 (APR2), which plays an important role in the reductive sulfate assimilation pathway, positively regulated Cd tolerance via the glutathione-dependent pathway, thus improving GSH-dependent antioxidant capability and Cd-chelation by PCs (Xu et al, 2020).…”

“…The production of endogenous NO in response to heavy metals in plants has been extensively analysed, with NO increasing under short periods of treatment while longterm Cd treatment and high concentrations of metals give rise to a reduction of this molecule (Xiong et al, 2009, Pérez-Chaca et al, 2014, Romero-Puertas et al, 2018Terrón-Camero et al, 2019). Several studies have shown that NOdependent post-transcriptional modifications of proteins can regulate ROS metabolism, phytochelatins and proteolysis processes in plant response to Cd and other heavy metals (Terrón-Camero et al, 2019, Souri et al, 2020. In our study, long term Cd treatment produced a reduction in the NO content in B. auriculata roots but changes were not observed in leaves, which suggest a differential regulation of NO in both organs.…”

“…Nitric oxide (NO) is attracting increasing attention as a regulator of many physiological processes in plants, including the defence against heavy metal (Gill et al, 2013, Terrón-Camero et al, 2019. It has been reported that NO can improve antioxidant defences by inducing the expression of genes that encode antioxidant enzymes and it is a key factor in the tolerance of cells to oxidative stress caused by Cd and other metals (Romero-Puertas and Sandalio, 2016, Romero-Puertas, et al, 2018, Souri et al, 2020. S-Nitrosoglutathione reductase (GSNOR) is an important enzyme that regulates intracellular levels of S-nitrosoglutathione (GSNO) and also indirectly regulates NO levels and protein S-nitrosylation, a post-translational modification that affects the activity, location, and stability of proteins (Frungillo et al, 2014, Hu et al, 2019.…”

Flavonoid Naringenin Alleviates Short-Term Osmotic and Salinity Stresses Through Regulating Photosynthetic Machinery and Chloroplastic Antioxidant Metabolism in Phaseolus vulgaris

“…The high ratio in GSH/GSSG and the elevated GSH content/redox state, which was detected in Nar-treated bean chloroplasts in response to salinity, showed that it could have a role in recycling of AsA and GSH by providing a redox state and reducing oxidative stress, as mentioned by Wang et al (2013) and Garg and Singla (2015). Another enzyme, GST detoxifies toxic lipid peroxides and reduces dehydroascorbate with GSH-dependent reductase activity (DHAR) and so maintains the reductant pools such as AsA (Souri et al, 2020). In the current study, induced GST activity was continued by Nar applications with NaCl or PEG.…”

Nitric oxide is essential for cadmium‐induced peroxule formation and peroxisome proliferation

“…This suggests that NO modifies H 2 O 2 content and its dependent signalling. The exogenous addition of NO donors is well known to increase antioxidant activities such as GST after treatment with paraquat, As or Cd (Hasanuzzaman et al, 2018; Nahar et al, 2016; Souri, Karimi, Farooq, & Sandalio, 2020), while an excess of endogenous NO may inhibit antioxidant activity under Cd stress conditions (Terrón‐Camero et al, 2020).…”