Overexpression of SOS (Salt Overly Sensitive) Genes Increases Salt Tolerance in Transgenic Arabidopsis

Soil salinity is a major abiotic stress that decreases plant growth and productivity. Recently, it was reported that plants overexpressing AtNHX1 or SOS1 have significantly increased salt tolerance. To test whether overexpression of multiple genes can improve plant salt tolerance even more, we produced six different transgenic Arabidopsis plants that overexpress AtNHX1, SOS3, AtNHX1 + SOS3, SOS1, SOS2 + SOS3, or SOS1 + SOS2 + SOS3. Northern blot analyses confirmed the presence of high levels of the relevant gene transcripts in transgenic plants. Transgenic Arabidopsis plants overexpressing AtNHX1 alone did not present any significant increase in salt tolerance, contrary to earlier reports. We found that transgenic plants overexpressing SOS3 exhibit increased salt tolerance similar to plants overexpressing SOS1. Moreover, salt tolerance of transgenic plants overexpressing AtNHX1 + SOS3, SOS2 + SOS3, or SOS1 + SOS2 + SOS3, respectively, appeared similar to the tolerance of transgenic plants overexpressing either SOS1 or SOS3 alone.