Nitric oxide enhances salt tolerance in maize seedlings through increasing activities of proton-pump and Na+/H+ antiport in the tonoplast

Abstract

Nitric oxide (NO), an endogenous signaling molecule in animals and plants, mediates responses to abiotic and biotic stresses. Our previous work demonstrated that 100 microM sodium nitroprusside (SNP, an NO donor) treatment of maize seedlings increased K(+) accumulation in roots, leaves and sheathes, while decreasing Na(+) accumulation (Zhang et al. in J Plant Physiol Mol Biol 30:455-459, 2004b). Here we investigate how NO regulates Na(+), K(+) ion homeostasis in maize. Pre-treatment with 100 muM SNP for 2 days improved later growth of maize plants under 100 mM NaCl stress, as indicated by increased dry matter accumulation, increased chlorophyll content, and decreased membrane leakage from leaf cells. An NO scavenger, methylene blue (MB-1), blocked the effect of SNP. These results indicated that SNP-derived NO enhanced maize tolerance to salt stress. Further analysis showed that NaCl induced a transient increase in the NO level in maize leaves. Both NO and NaCl treatment stimulated vacuolar H(+)-ATPase and H(+)-PPase activities, resulting in increased H(+)-translocation and Na(+)/H(+) exchange. NaCl-induced H(+)-ATPase and H(+)-PPase activities were diminished by MB-1. 1-Butanol, an inhibitor of phosphatidic acid (PA) production by phospholipase D (PLD), reduced NaCl- and NO-induced H(+)-ATPase activation. In contrast, applied PA stimulated H(+)-ATPase activity. These results suggest that NO acts as a signal molecule in the NaCl response by increasing the activities of vacuolar H(+)-ATPase and H(+)-PPase, which provide the driving force for Na(+)/H(+) exchange. PLD and PA play an important role in this process.

Effect of nitric oxide and putrescine on antioxidative responses under NaCl stress in chickpea plants

“…In the present investigations also, SNP could completely ameliorate the adverse effect of NaCl treatment on membrane injury and lipid peroxidation. A protective effect of NO on relative membrane injury has been reported under drought stress (Garcia-Mata andLamattina, 2001, Wang et al, 2004a), salt stress (Zhao et al, 2004, Zhang et al 2006, ageing and senescence (Tu et al, 2003, Hung and and heavy metal stress (Hsu and Kao, 2005). Lower concentrations of NO might act as an antioxidant (Zhang et al, 2006).…”

“…Krishnamurthy (1991) reported a 63 % decrease in chlorophyll content, with long term salinization treatments in wheat, and putrescine was effective in partially overcoming the reduction of chlorophyll. NO has also been reported to overcome the age induced decline in chlorophyll content in wheat seedlings (Tu et al, 2003) under oxidative stress (Belgini and Lamattina, 1999) and salt stress (Zhang et al, 2006). Lipid peroxidation and electrolyte leakage can be considered as indices of stress under short term NaCl treatments and both NO and putrescine were effective in ameliorating the salt induced negative effects on these parameters.…”

“…A protective effect of NO on relative membrane injury has been reported under drought stress (Garcia-Mata andLamattina, 2001, Wang et al, 2004a), salt stress (Zhao et al, 2004, Zhang et al 2006, ageing and senescence (Tu et al, 2003, Hung and and heavy metal stress (Hsu and Kao, 2005). Lower concentrations of NO might act as an antioxidant (Zhang et al, 2006). Polyamines are also known for their anti-stress and antisenescence effects due to their membrane stabilizing and antioxidant properties (Kaur- Sawhney andGalston, 1991, Borell et al, 1997).…”

“…Relative membrane injury was analysed according to the method of Zhang et al (2006). 250 mg of fully expanded leaves were rinsed with distilled water and immersed in 10 ml de-ionised water in vials and incubated at 25 °C for 4 h. Electrical conductivity (EC) of the bathing medium was measured at 25 °C (Xi).…”

“…Increasing the concentration of free radical scavengers by exogenous application could help in the detoxification of stress-induced free radical production (Velikova et al, 2000;Shalata and Neuman, 2001;Verma and Mishra, 2005;Wang et al, 2004a;Wang and Yang, 2005;Zhang et al, 2006). In this study, we have tested two antioxidant compounds, putrescine and nitric oxide donor sodium nitroprusside.…”