sitl1 mutant reduces Na+ and
Mg2+ uptake and root-to-shoot translocation
In order to investigate the mechanistic basis of salinity tolerance and
the observed reduction in root development and leaf chlorophyll content,
the ion concentrations of the sitl1 and WT plants grown for 1
week under 0 mM or 50 mM NaCl stress conditions were measured (Figure
5a-e). Under unstressed conditions, K content was increased by 1.38-fold
and Mg was reduced by 0.61-fold, respectively, in the root ofsitl1 compared to that of WT (Figure 5a,b). Mg content in leaf
tissues was also reduced by 0.76-fold in sitl1 , whereas, Na, Ca,
and P content were not changed in both root and leaf tissues (Figure
5c-e). Under salinity stress conditions, K content was increased
1.75-fold, however, Mg and Na content were reduced 0.82-fold and
0.67-fold, respectively, in the root of sitl1 . Notably,
significant reduction of Mg and Na content were observed in both roots
and leaves of the sitl1 under 100 mM NaCl treatment (Figure
5b,c).
Next, we analyzed Mg, Na, and K concentrations in xylem sap (Figure
5a-e). The Mg and Na concentrations in xylem sap were significantly
reduced 0.56-fold and 0.64-fold, respectively, compared to the WT,
whereas K concentration in xylem sap was not changed under normal
condition (Figure 5f-h). Mg and Na concentrations in xylem sap were also
significantly lower in the sitl1 than in the WT under 100 mM NaCl
stress (Figure 5f,g). Collectively, these results demonstrate that
improved salinity tolerance, and reduced root growth and leaf
chlorophyll content in sitl1 caused major changes to the Mg and
Na content in both roots and leaves.