Nitric oxide mitigates salt-induced oxidative stress in Brassica juncea seedlings by regulating ROS metabolism and antioxidant defense system.

The present investigation was designed to determine the interaction of nitric oxide with other antioxidants in relieving oxidative stress induced by NaCl at morphological, physiological and molecular level. 15 days old seedlings of B. juncea were subjected to 50 mM NaCl alone, 100 μM SNP alone and in combination (SNP + NaCl) in hoagland growth medium for 96 h and to analyze the cellular homeostasis and salt tolerance mechanism via examining growth, stress parameters, enzymatic and non enzymatic antioxidants and expression level of NR. Exposure of 100 μM sodium nitroprusside to mustard seedling enhanced photosynthetic pigment content and prevented plant growth inhibition. Accumulation of MDA and H2O2 was more pronounced in individual NaCl treated seedling than in the combination of NaCl and SNP. Applying SNP enhanced NR activity by 1.70 folds and increased NO production by 2.26 folds than individual salt treated roots. Furthermore, the activities of CAT, GPX and NR act synergistically with endogenous NO level whereas APX work antagonistically. In addition, the study also demonstrates that NO regulated NaCl induced transcriptional expression of NR. Induction of BjNR in Indian mustard roots lead to enhanced the plant resistance against salinity stress. The present finding revealed that NO confers increased B. juncea tolerance to salt stress by stimulation of antioxidants and reestablishment of cellular redox status.