Regulates negatively salt stress responses and Na(+) homeostasis (PubMed:29272523, PubMed:30701352). Prevents Na(+) efflux, disturbs reactive oxygen species (ROS) homeostasis, and represses the expression of nuclear salt stress-responsive genes (PubMed:30701352). Involved in resistance to abiotic stress (PubMed:29272523). Heterodimers (PubMed:29272523). Interacts with CYSTM7 and WIH1/CYSTM13 (PubMed:29272523). Mostly expressed in leaves and flowers and, to a lower extent, in stems, siliques, shoots and roots. Induced by salt, cold and drought. Increased tolerance to high salinity with reduced reactive oxygen species (ROS) levels and associated with an over-activation of nuclear salt stress-responsive genes. Belongs to the CYSTM1 family.