Juan Chen, Duan-Ye Xiong, Wen-Hua Wang, Wen-Jun Hu, Martin Simon, Qiang Xiao, Juan Chen,Ting-Wu Liu, Xiang Liu, Hai-Lei Zheng.Plos One,2013.8(8): e71543.

It is well known that nitric oxide (NO) enhances salt tolerance of glycophytes. However, the effect of NO on modulating ionicbalance in halophytes is not very clear. This study focuses on the role of NO in mediating K+/Na+ balance in a mangrovespecies, Kandelia obovata Sheue, Liu and Yong. We first analyzed the effects of sodium nitroprusside (SNP), an NO donor, onion content and ion flux in the roots of K. obovata under high salinity. The results showed that 100 mM SNP significantlyincreased K+ content and Na+ efflux, but decreased Na+ content and K+ efflux. These effects of NO were reversed by specificNO 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 andvacuolar Na+/H+ antiporter, which were crucial proteins for ionic balance. To further clarify the molecular mechanism of NOmodulatedK+/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 showedthat NO increased the relative expression levels of these genes, while this increase was blocked by NO synthesis inhibitorsand 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.