Nitric oxide influences glycine betaine content and ascorbate peroxidase activity in maize

• The activity of ascorbate peroxidase isoforms was differentially affected by Nω-Nitro-L-arginine methyl.
• Nitric oxide synthase inhibition also altered all the parameters investigated.
• These changes were reversed by simultaneous treatment of the plants with nitric oxide donor 2,2′- (hydroxynitrosohydrazono) bis-ethanimine.
• Nitric oxide produced from nitric oxide synthase activity plays a role in glycine betaine accumulation.

Compatible solutes, such as glycine betaine (GB), are involved in improving plant tolerance to abiotic stress. In this study, we investigated the effects of exogenously applied nitric oxide (NO) donor 2,2′-(hydroxynitrosohydrazono) bis-ethanimine and nitric oxide synthase (NOS) inhibitor Nω-Nitro-L-Arginine methyl ester (L-NAME) on GB content and its influence on ascorbate peroxidase (APX) enzymatic activity in roots and leaves of maize seedlings. Application of L-NAME (2 mM L-NAME or in combination with 200 μM DETA) significantly increased cell death, H2O2 content, and lipid peroxidation but reduced GB content and APX activity. The effects of L-NAME treatment on maize were reversed by application of the NO donor 2, 2′-(hydroxynitrosohydrazono) bis-ethanimine (DETA/NO). Application of the NO donor to plants treated with L-NAME reversed the effects of L-NAME on GB content and APX activity, which were increased to levels higher than those in plants treated with L-NAME alone. These results show that exogenous application of the NOS inhibitor reduces APX activity and GB accumulation. Our data suggest that NOS activity plays a role in regulating the antioxidant defense mechanism and osmoprotection in plants.