Nitric Oxide Mediates Root K+/Na+ Balance in a Mangrove Plant, Kandelia obovata, by Enhancing the Expression of AKT1-Type K+ Channel and Na+/H+ Antiporter under High Salinity
It is well known that nitric oxide (NO) enhances salt tolerance of glycophytes. However, the effect of NO on modulating ionic balance in halophytes is not very clear. This study focuses on the role of NO in mediating K+/Na+ balance in a mangrove species, Kandelia obovata Sheue, Liu and Yong. We first analyzed the effects of sodium nitroprusside (SNP), an NO donor, on ion content and ion flux in the roots of K. obovata under high salinity. The results showed that 100 μM SNP significantly increased K+ content and Na+ efflux, but decreased Na+ content and K+ efflux. These effects of NO were reversed by specific NO synthesis inhibitor and scavenger, which confirmed the role of NO in retaining K+ and reducing Na+ in K. obovata roots. Using western-blot analysis, we found that NO increased the protein expression of plasma membrane (PM) H+-ATPase and vacuolar Na+/H+ antiporter, which were crucial proteins for ionic balance. To further clarify the molecular mechanism of NO-modulated K+/Na+ balance, partial cDNA fragments of inward-rectifying K+ channel, PM Na+/H+ antiporter, PM H+-ATPase, vacuolar Na+/H+ antiporter and vacuolar H+-ATPase subunit c were isolated. Results of quantitative real-time PCR showed that NO increased the relative expression levels of these genes, while this increase was blocked by NO synthesis inhibitors and scavenger. Above results indicate that NO greatly contribute to K+/Na+ balance in high salinity-treated K. obovata roots, by activating AKT1-type K+ channel and Na+/H+ antiporter, which are the critical components in K+/Na+ transport system.
References
[1]
Chen Z, Pottosin II, Cuin TA, Fuglsang AT, Tester M, et al. (2007) Root plasma membrane transporters controlling K+/Na+ homeostasis in salt-stressed barley. Plant Physiol 145: 1714–1725.
[2]
Shabala S, Cuin TA (2008) Potassium transport and plant salt tolerance. Physiol Plantarum 133: 651–669.
[3]
Zhu JK (2003) Regulation of ion homeostasis under salt stress. Curr Opin Plant Biol 6: 441–445.
[4]
Sun J, Wang MJ, Ding MQ, Deng SR, Liu MQ, et al. (2010) H2O2 and cytosolic Ca2+ signals triggered by the PM H+-coupled transport system mediate K+/Na+ homeostasis in NaCl-stressed Populus euphratica cells. Plant Cell Environ 33: 943–958.
[5]
Wu C, Gao X, Kong X, Zhao Y, Zhang H (2009) Molecular cloning and functional analysis of a Na+/H+ antiporter gene ThNHX1 from a halophytic plant Thellungiella halophila. Plant Mol Biol Rep 27: 1–12.
[6]
Chen J, Xiao Q, Wu F, Dong X, He J, et al. (2010) Nitric oxide enhances salt secretion and Na+ sequestration in a mangrove plant, Avicennia marina, through increasing the expression of H+-ATPase and Na+/H+ antiporter under high salinity. Tree Physiol 30: 1570–1586.
[7]
Silva P, Fa？anha AR, Tavares RM, Gerós H (2010) Role of tonoplast proton pumps and Na+/H+ antiport system in salt tolerance of Populus euphratica Oliv. J Plant Growth Regul 29: 23–34.
[8]
Sun J, Chen SL, Dai SX, Wang RG, Li NY, et al. (2009) NaCl-induced alternations of cellular and tissue ion fluxes in roots of salt-resistant and salt-sensitive poplar species. Plant Physiol 149: 1141–1153.
[9]
Chen Z, Newman I, Zhou M, Mendham N, Zhang G, et al. (2005) Screening plants for salt tolerance by measuring K+ flux: a case study for barley. Plant Cell Environ 28: 1230–1246.
Sentenac H, Bonneaud N, Minet M, Lacroute F, Salmon JM, et al. (1992) Cloning and expression in yeast of a plant potassium ion transport system. Science 256: 663–665.
[12]
Buschmann PH, Vaidyanathan R, Gassmann W, Schroeder JI (2000) Enhancement of Na+ uptake currents, time-dependent inward-rectifying K+ channel currents, and K+ channel transcripts by K+ starvation in wheat root cells. Plant Physiol 122: 1387–1398.
Martínez-Cordero M, Martínez V, Rubio F (2005) High-affinity K+ uptake in pepper plants. J Exp Bot 56: 1553–1562.
[15]
Ardie SW, Liu S, Takano T (2010) Expression of the AKT1-type K+ channel gene from Puccinellia tenuiflora, PutAKT1, enhances salt tolerance in Arabidopsis. Plant Cell Reports 29: 865–874.
[16]
Qi Z, Spalding EP (2004) Protection of plasma membrane K+ transport by the salt overly sensitive1 Na+-H+ antiporter during salinity stress. Plant Physiol 136: 2548–2555.
[17]
Parida AK, Jha B (2010) Salt tolerance mechanisms in mangroves: a review. Trees-Struct Funct 24: 199–217.
[18]
Wilson ID, Neill SJ, Hancock JT (2008) Nitric oxide synthesis and signalling in plants. Plant Cell Environ 31: 622–631.
[19]
Wendehenne D, Durner J, Klessig DF (2004) Nitric oxide: a new player in plant signalling and defence responses. Curr Opin Plant Biol 7: 449–455.
[20]
Zhang YY, Wang LL, Liu YL, Zhang Q, Wei QP, et al. (2006) Nitric oxide enhances salt tolerance in maize seedlings through increasing activities of proton-pump and Na+/H+ antiport in the tonoplast. Planta 224: 545–555.
[21]
Zhao LQ, Zhang F, Guo JK, Yang YL, Li BB, et al. (2004) Nitric oxide functions as a signal in salt resistance in the calluses from two ecotypes of reed. Plant Physiol 134: 849–857.
[22]
Sheue CR, Liu HY, Yang WH (2003) Kandelia obovata (Rhizophoraceae), a new mangrove species from Eastern Asia. TAXON 52: 287–294.
[23]
Scholander PF (1968) How mangroves desalinate seawater. Physiol Plantarum 21: 251–261.
[24]
Li NY, Chen SL, Zhou XY, Li CY, Shao J, et al. (2008) Effect of NaCl on photosynthesis, salt accumulation and ion compartmentation in two mangrove species, Kandelia candel and Bruguiera gymnorhiza. Aquat Bot 88: 303–310.
[25]
Lu Y, Li N, Sun J, Hou P, Jing X, et al. (2013) Exogenous hydrogen peroxide, nitric oxide and calcium mediate root ion fluxes in two non-secretor mangrove species subjected to NaCl stress. Tree Physiol 33: 81–95.
[26]
Leigh RA (2001) Potassium homeostasis and membrane transport. J Plant Nutr Soil Sci 164: 193–198.
[27]
Maathuis FJM (2006) The role of monovalent cation transporters in plant responses to salinity. J Exp Bot 57: 1137–1147.
[28]
Carden DE, Walker DJ, Flowers TJ, Miller AJ (2003) Single-cell measurements of the contributions of cytosolic Na+ and K+ to salt tolerance. Plant Physiol 131: 676–683.
[29]
Hariadi Y, Marandon K, Tian Y, Jacobsen SE, Shabala S (2011) Ionic and osmotic relations in quinoa (Chenopodium quinoa Willd.) plants grown at various salinity levels. J Exp Bot 62: 185.
[30]
Sun J, Dai S, Wang R, Chen S, Li N, et al. (2009) Calcium mediates root K+/Na+ homeostasis in poplar species differing in salt tolerance. Tree Physiol 29: 1175–1186.
[31]
Alemán F, Nieves-Cordones M, Martínez V, Rubio F (2011) Root K+ acquisition in plants: the Arabidopsis thaliana model. Plant Cell Physiol 52: 1603–1612.
[32]
Fuchs I, St？lzle S, Ivashikina N, Hedrich R (2005) Rice K+ uptake channel OsAKT1 is sensitive to salt stress. Planta 221: 212–221.
[33]
Kaddour R, Nasri N, M'rah S, Berthomieu P, Lachaal M (2009) Comparative effect of potassium on K and Na uptake and transport in two accessions of Arabidopsis thaliana during salinity stress. CR Biol 332: 784–794.
[34]
Berthomieu P, Conejero G, Nublat A, Brackenbury WJ, Lambert C, et al. (2003) Functional analysis of AtHKT1 in Arabidopsis shows that Na+ recirculation by the phloem is crucial for salt tolerance. EMBO J 22: 2004–2014.
[35]
Niu X, Bressan RA, Hasegawa PM, Pardo JM (1995) Ion homeostasis in NaCl stress environments. Plant Physiol 109: 735–742.
[36]
Arasimowicz M, Floryszak-Wieczorek J (2007) Nitric oxide as a bioactive signalling molecule in plant stress responses. Plant Sci 172: 876–887.
[37]
Shi H, Lee B, Wu SJ, Zhu JK (2002) Overexpression of a plasma membrane Na+/H+ antiporter gene improves salt tolerance in Arabidopsis thaliana. Nat Biotechnol 21: 81–85.
[38]
Wang CM, Zhang JL, Liu XS, Li Z, Wu GQ, et al. (2009) Puccinellia tenuiflora maintains a low Na+ level under salinity by limiting unidirectional Na+ influx resulting in a high selectivity for K+ over Na+. Plant Cell Environ 32: 486–496.
[39]
Qiu QS, Barkla BJ, Vera-Estrella R, Zhu JK, Schumaker KS (2003) Na+/H+ exchange activity in the plasma membrane of Arabidopsis. Plant Physiol 132: 1041–1052.
[40]
Tester M, Davenport R (2003) Na+ tolerance and Na+ transport in higher plants. Ann Bot 91: 503–527.
[41]
Fukuda A, Nakamura A, Hara N, Toki S, Tanaka Y (2011) Molecular and functional analyses of rice NHX-type Na+/H+ antiporter genes. Planta 233: 175–188.
[42]
Chen S, Polle A (2010) Salinity tolerance of Populus. Plant Biol 12: 317–333.
[43]
Kao WY, Tsai HC, Tsai TT (2001) Effect of NaCl and nitrogen availability on growth and photosynthesis of seedlings of a mangrove species, Kandelia candel (L.) Druce. J Plant Physiol 158: 841–846.
[44]
Fritz E (1989) X-ray microanalysis of diffusible elements in plant cells after freeze-drying, pressure-infiltration with ether and embedding in plastic. Scanning Microsc 3: 517–526.
[45]
Vázquez MD, Poschenrieder C, Corrales I, Barceló J (1999) Change in apoplastic aluminum during the initial growth response to aluminum by roots of a tolerant maize variety. Plant Physiol 119: 435–444.
[46]
Xu Y, Sun T, Yin LP (2006) Application of non-invasive microsensing system to simultaneously measure both H+ and O2 fluxes around the pollen tube. J Integr Plant Biol 48: 823–831.
[47]
Xu RR, Qi SD, Lu LT, Chen CT, Wu CA, et al. (2011) A DExD/H box RNA helicase is important for K+ deprivation responses and tolerance in Arabidopsis thaliana. FEBS J 278: 2296–2306.
[48]
Bradford MM (1976) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem 72: 248–254.
[49]
Livak KJ, Schmittgen TD (2001) Analysis of relative gene expression data using real-time quantitative PCR and the 2-[Delta][Delta] CT method. Methods 25: 402–408.
