Differential response of antioxidant compounds to salinity stress in salt-tolerant and salt-sensitive seedlings of foxtail millet (Setaria italica)

The modulation of antioxidant components was comparatively analysed in a sa lt-tolerant (cv. Prasad) and salt-sensitive (cv. Lepakshi) cultivar of foxt ail millet (Setaria italica L.) under different NaCl concentrations. Under conditions of salt stress, the salt-tolerant cultivar exhibited increased t otal superoxide dismutase (SOI) and ascorbate peroxidase (APX) activity whe reas both enzyme activities decreased in acutely salt stressed seedlings of the sensitive cultivar. At 200 mM NaCl, the tolerant foxtail millet cultiv ar responded with induction of cytosolic Cu/Zn-SOD and the Mn-SOD isoform a t the protein level, The induced accumulation of the cytosolic Cu/Zn-SOD pr otein/activity is positively correlated with an elevated level of the cytos olic APX gene activity. The elevated cytosolic Cu/Zn-SOD and cytosolic APX activity correlates with an induced accumulation of their transcripts. Tole rant 5-day-old seedlings grown during high salinity treatment (200 mM NaCl) contained a lower amount of Na+ ions and showed a lower electrolyte leakag e than sensitive seedlings. In conclusion, our comparative studies indicate that salt-induced oxidative tolerance is conferred by an enhanced compartm ent-specific activity of the antioxidant enzymes in response to compartment -specific signals.