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.

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