As much as there is known about the function of the sodium/proton antiporter SOS1 in plants, recent studies point towards a more general role for this protein. The crucial involvement in salt stress protection is clearly one of its functions -confined to the N-terminus, but the modular structure of the protein includes a segment with several domains that are functionally not studied but comprise more than half of the protein's length. Additional functions of the protein appear to be an influence on vesicle trafficking, vacuolar pH and general ion homeostasis during salt stress. Eliminating SOS1 leads to the expression of genes that are not strictly salinity stress related. Functions that are regulated in sos1 mutants included pathogen responses, and effects on circadian rhythm.