Deciphering the nitric oxide, cyanide and iron-mediated actions of sodium nitroprusside in cotyledons of salt stressed sunflower seedlings.

Nitric oxide (NO) is an endogenous signaling molecule in plants. Sodium nitroprusside (SNP), an established NO donor used in plant science research, simultaneously releases NO, cyanide (CN-) and iron (Fe) in solution. Since cyanide and iron mask NO effect of SNP, its use in NO research is debatable. Deciphering the action of SNP through NO, CN- or Fe has been undertaken in the present work. Cotyledons from salt stressed sunflower seedlings grown in the presence of NO donors were subjected to spectrofluorometric analysis of NO, CN- and Fe contents, and proteome and biochemical analyses. Diethylenetriamine NONOate (DETA) proved to be a better NO source since SNP enhanced ROS accumulation in the tissue. Abundance of 127 proteins is modulated by salt stress. SNP and exhausted SNP (exSNP) alter the abundance of 117 and 129 proteins, respectively. These proteins belong to primary metabolism, stress-response, transport, translation, proteolysis, chaperone, regulatory, and storage. Salt-responsive proteins, such as, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoglycerate kinase (PGK) and isocitrate dehydrogenase are negatively modulated. DETA and SNP lower the activities of GAPDH and S-adenosylmethionine synthase (SAMS). Abundance of heat shock 70 kDa protein and actin are sensitive to both NaCl and NO. SNP affects plant growth by modulating proteome though iron, cyanide and NO. Its use only as an NO donor is thus debatable. exSNP control also releases substantial amount of cyanide and iron, thus questioning its use as control in NO research.