Nitric Oxide Functions as a Signal in Salt Resistance in the Calluses from Two Ecotypes of Reed

Abstract

Calluses from two ecotypes of reed (Phragmites communis Trin.) plant (dune reed [DR] and swamp reed [SR]), which show different sensitivity to salinity, were used to study plant adaptations to salt stress. Under 200 mm NaCl treatment, the sodium (Na) percentage decreased, but the calcium percentage and the potassium (K) to Na ratio increased in the DR callus, whereas an opposite changing pattern was observed in the SR callus. Application of sodium nitroprusside (SNP), as a nitric oxide (NO) donor, revealed that NO affected element ratios in both DR and SR calluses in a concentration-dependent manner. N -nitro-l-arginine (an NO synthase inhibitor) and 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxyde (a specific NO scavenger) counteracted NO effect by increasing the Na percentage, decreasing the calcium percentage and the K to Na ratio. The increased activity of plasma membrane (PM) H ϩ -ATPase caused by NaCl treatment in the DR callus was reversed by treatment with N -nitro-l-arginine and 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxyde. Western-blot analysis demonstrated that NO stimulated the expression of PM H ϩ -ATPase in both DR and SR calluses. These results indicate that NO serves as a signal in inducing salt resistance by increasing the K to Na ratio, which is dependent on the increased PM H ϩ -ATPase activity.When plants are exposed to NaCl, cellular ion homeostasis may be impaired. Under salinity conditions, tolerant plants typically maintain high potassium (K ϩ ) and low sodium (Na ϩ ) in the cytosol of cells (Greenway and Munns, 1980; Jeschke, 1984). Such mechanisms involve Na ϩ compartmentalization into vacuoles and/or extrusion to the external medium and K ϩ accumulation in the cytoplasm. These processes appear to be mediated by several transport systems, such as H ϩ -ATPase, carriers (symporters and antiporters), and channels associated with plasma membranes (PMs) and tonoplasts (Niu et al., 1995; Rausch et al., 1996).Control of Na ϩ movement across the PM and tonoplast to maintain a low Na ϩ concentration in the cytoplasm is a key factor of cellular adaptation to salt stress (Niu et al., 1995; Rausch et al., 1996). Na ϩ transport across the PM is dependent on the electrochemical gradient created by the PM H ϩ -ATPase (Serrano, 1996). PM H ϩ -ATPase belongs to a family of P-type ATPase, which has a catalytic subunit of approximately 100 kD. This enzyme is a proton pump, whose major role couples ATP hydrolysis to proton transport and creates electrochemical gradient across the PM used by secondary transporters (Serrano, 1989). In addition, this membrane protein is involved in many physiological processes, including salt tolerance, intracellular pH regulation, stomatal opening, and cell elongation (Rayle and Cleland, 1992;Niu et al., 1993; Michelet and Boutry, 1995; Cosgrove, 1997; Kerkeb et al., 2001; Yang et al., 2003). The PM H ϩ -ATPase is encoded by a multigene family, and at least 10 isoforms of the H ϩ -ATPase exist in plants. Krysan et al. (1996) analyzed T-DNA knockout Arab...

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).…”

“…NO has also been reported to act as a signal molecule; mediating responses to biotic and abiotic stresses in the plant kingdom and it appears to be present in most of the stress reactions (Gould et al, 2003). It has been reported to exert a protective effect in response to drought stress (Wang et al, 2004b), salt stress (Kopyra and Gwozdz, 2003;Zhao et al, 2004;Chen et al, 2004), heavy metal stress (Hsu and Kao, 2005;Wang and Yang, 2005) and UV radiation stress (Shi et al, 2005). However experimental evidence for NO as a signal molecule for oxidative metabolism under salt stress is still preliminary.…”

Nitric oxide negatively regulates AKT1-mediated potassium uptake through modulating vitamin B6 homeostasis in Arabidopsis

“…However, more external applied K + has been proved to reduce the negative effects of several stresses (54), but the involvement and/or mechanism of NO under these high K + situations is unclear. Recent reports suggest that NO enhances plant salt tolerance in different species through various mechanisms (18,20,55,56). In a mangrove species resistant to high salinity, NO enhanced K + content through decreasing the cytosolic K + loss and increasing K + uptake from the environment, and the transcript of AKT1 was increased under high salt condition (55).…”

Nitric oxide affects salt-induced changes in free amino acid levels in maize

“…NO was found to serve as a signal inducing salt tolerance in reed (Zhao et al, 2004). NO enhanced salt tolerance in maize due to the activation of proton pumps and the Na + /H + antiport, as indicated by improved growth, increased dry matter accumulation and greater chlorophyll content (Zhang et al, 2006).…”