Nitrate reductase‐mediated early nitric oxide burst alleviates oxidative damage induced by aluminum through enhancement of antioxidant defenses in roots of wheat (Triticum aestivum)

Abstract

SummaryNitric oxide (NO) is an important signaling molecule involved in the physiological processes of plants. The role of NO release in the tolerance strategies of roots of wheat (Triticum aestivum) under aluminum (Al) stress was investigated using two genotypes with different Al resistances.An early NO burst at 3 h was observed in the root tips of the Al-tolerant genotype Jian-864, whereas the Al-sensitive genotype Yang-5 showed no NO accumulation at 3 h but an extremely high NO concentration after 12 h. Stimulating NO production at 3 h in the root tips of Yang-5 with the NO donor relieved Al-induced root inhibition and callose production, as well as oxidative damage and ROS accumulation, while elimination of the early NO burst by NO scavenger aggravated root inhibition in Jian-864.Synthesis of early NO in roots of Jian-864 was mediated through nitrate reductase (NR) but not through NO synthase. Elevated antioxidant enzyme activities were induced by Al stress in both wheat genotypes and significantly enhanced by NO donor, but suppressed by NO scavenger or NR inhibitor.These results suggest that an NR-mediated early NO burst plays an important role in Al resistance of wheat through modulating enhanced antioxidant defense to adapt to Al stress.

Ascorbic acid improves the tolerance of wheat plants to lead toxicity

“…Both enzymes activity could be helpful in improving the tolerance of wheat plants to Pb-toxicity. It is reported that NR induced nitric oxide (NO) synthesis that protects plants against abiotic stress (Sun et al, 2014;Khan et al, 2017).…”

Early generation of nitric oxide contributes to copper tolerance through reducing oxidative stress and cell death in hulless barley roots

“…The burst of NO as a cell-signaling molecule during metal treatment reflects the specific role of NO in plant response to metal stress. For instance, in many reports of NO production found in plants under metal stress, NO was suggested to have an important protective effect on plant cells against metal toxicity (Kazemi 2012;Sun et al 2014;Yu et al 2012;Zhou et al 2012). However, the enhanced stress signal might be a result of higher levels of NO acting as a negative regulator of the resistance response in plants against metals.…”

“…Metals treatment alters NO concentrations in plants. It has been widely reported that NO contents significantly increased in plants exposed to metal treatments, including Al (Sun et al 2014), Cd (Alemayehu et al 2015;Ye et al 2013), Zn (Xu et al 2010b), Ni (Kazemi 2012), Pb (Yu et al 2012) and As (Singh et al 2009). However, metal stress can also decrease NO accumulation; for example, in the roots of rice (Xiong et al 2009) and Medicago truncatula (Xu et al 2010a) after treatment with Cd.…”

“…Cell viability in root tips after different treatments was determined by Evans blue staining according to Sun et al (2014). The roots were incubated for 20 min in Evans blue solution (25 %, w/v), and then washed for 30 min to remove excess and unbound dye.…”

“…Therefore, plants can utilize enzymatic and non-enzymatic antioxidant pathways to scavenge ROS and subsequently protect plant cells against oxidative damage under Cu stress (Cobbett and Goldsbrough 2002). These include several ROS-removing enzymes such as catalase (CAT EC 1.11.1.6), peroxidase (POD EC 1.11.1.7), superoxide dismutase (SOD EC 1.15.1.1), ascorbate peroxidase (APX EC 1.11.1.11), glutathione reductase (GR), guaiacol peroxidase (GPX), and the non-enzymatic antioxidants scavengers such as ascorbate (ASC), glutathione (GSH), and hydrophobic molecules (tocopherols, carotenoids, xanthophylls, and polyamines), which are reported to be involved in minimizing ROS damage or oxidative bursts during heavy metal stress responses (Foyer and Noctor 2005;İşeri et al 2011;Sun et al 2014; Thounaojam et al 2012;Xu et al 2010a). However, the mechanisms regulating Cu toxicity and tolerance still remain unclear.…”