Exogenous nitric oxide pretreatment protects Brassica napus L. seedlings from paraquat toxicity through the modulation of antioxidant defense and glyoxalase systems.
To investigate the physiological and biochemical mechanisms of nitric oxide (NO)-induced paraquat (PQ) tolerance in plants, we pretreated a set of 10-day-old Brassica napus seedlings with 500 μM sodium nitroprusside (SNP - a NO donor) for 24 h. Then, three doses of PQ (62.5, 125 and 250 μM) were applied separately, as well as to SNP-pretreated seedlings, and the seedlings were allowed to grow for an additional 48 h. The seedlings treated with PQ showed clear, dose-dependent signs of oxidative stress, with elevated levels of lipid peroxidation (MDA, malondialdehyde), H2O2 and O2- generation, and lipoxygenase (LOX) activity. Paraquat treatment disrupted pools of water-soluble antioxidants (ascorbate-AsA and reduced glutathione-GSH). Paraquat had different effects on the activities of antioxidant enzymes. The activities of glutathione reductase (GR) and catalase (CAT) decreased after PQ treatment in a dose-dependent manner, while the activities of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glyoxalase (Gly I and Gly II) decreased only with high doses of PQ (125 and 250 μM). By contrast, the activities of monodehydroascorbate reductase (MDHAR), glutathione S-transferase (GST) and glutathione peroxidase (GPX) increased after PQ treatment. A higher dose of PQ reduced chlorophyll and leaf water content but increased the methylglyoxal (MG) and proline (Pro) content. Compared to PQ alone, PQ supplemented with exogenous NO reduced LOX activity, the AsA-GSH pool, and the activities of APX, DHAR, GR, GPX, Gly I and Gly II. These effects helped to reduce oxidative stress and MG toxicity and were accompanied by reduced chlorosis and increased relative water content. Given these results, exogenous NO was found to be a key player in the mitigation of PQ toxicity in plants.
['Hasanuzzaman|Mirza|M|', 'Nahar|Kamrun|K|', 'Alam|Md Mahabub|MM|', 'Bhuyan|M H M Borhannuddin|MHMB|', 'Oku|Hirosuke|H|', 'Fujita|Masayuki|M|']
D000975:Antioxidants D029688:Brassica napus D013437:Carbon-Sulfur Lyases D009569:Nitric Oxide D010088:Oxidoreductases D010269:Paraquat D018515:Plant Leaves D010940:Plant Proteins D036226:Seedlings
MethylGlyoxal Abiotic stress Herbicide toxicity Reactive oxygen species Signaling molecule Xenobiotics