Involvement of nitric oxide synthase-dependent nitric oxide and exogenous nitric oxide in alleviating NaCl induced osmotic and oxidative stress in Arabidopsis thaliana

To elucidate the roles of endogenous nitric oxide on Arabidopsis thaliana tolerance to salt stress, a moderate concentration of NaCl was applied to wild-type (WT) and mutant (Atnoa1) plants which have an impaired in vivo nitric oxide synthase and reduced endogenous nitric oxide content due to T-DNA insertion in the first exon of the NOA1 gene. The exhibited greater inhibition of root growth, higher leaf water loss (LWL), lower contents of chlorophyll, soluble protein, proline, higher activities of peroxidase (POD), ascorbate peroxide (APX), and gluthinone reductase (GR), it also showed lower activities of superoxide dismutase (SOD) and catalase (CAT) than wild-type plants under NaCl stress. The nitric oxide synthase (NOS) inhibitor NG-nitro-L-Arg (L-NNA) enhanced NaCl induced growth inhibition, osmotic stress, and oxidative stress in wild-type plants. Meanwhile the NO donor, sodium nitroprusside (SNP), alleviated the NaCl induced damages in Atnoa1 plants. These results indicate that both NOSdependent endogenous NO and exogenous NO were involved in salt resistance in A. thaliana.