Figure 1.

Activation of rice SOS1 by the Arabidopsis SOS2/SOS3 kinase complex. A, AXT3K cells transformed with an empty vector (0) or with the indicated combination of SOS genes (1, OsSOS1; 2, AtSOS2; 3, AtSOS3) were grown overnight in selective synthetic dextrose medium. Five microliters of serial decimal dilutions were spotted onto plates of AP medium with 1 mm KCl and supplemented with 0 (data not shown), 100, or 200 mm NaCl. Plates were incubated at 28°C for 3 d. Plasmids used for expression of the SOS proteins were pDR195 for OsSOS1, pFL2T for AtSOS2, pFL3T for AtSOS3, and pFL32T for coexpression of AtSOS2 and AtSOS3. B, Intracellular Na⁺ content as determined by atomic emission spectrometry. Cells were grown in AP medium with 1 mm KCl and 30 mm NaCl and collected at OD₅₅₀ = 0.2 to 0.3. Values are the mean and se of three independent cultures of each combination of SOS genes. Units are nanomols of ions per milligram dry weight of cell samples. [See online article for color version of this figure.]