Understanding and improving salt tolerance in plants

One-fifth of irrigated agriculture is adversely affected by soil salinity. Hence, developing salt-tolerant crops is essential for sustaining food production. Progress in breeding for salt-tolerant crops has been hampered by the lack of understanding of the molecular basis of salt tolerance and lack of availability of genes that confer salt tolerance. Genetic evidence suggests that perception of salt stress leads to a cytosolic calcium-signal that activates the calcium sensor protein SOS3. SOS3 binds to and activates a ser/thr protein kinase SOS2. The activated SOS2 kinase regulates activities of SOS1, a plasma membrane Na+/H+ antiporter, and NHX1, a tonoplast Na+/H+ antiporter. This results in Na+ efflux and vacuolar compartmentation. A putative osmosensory histidine kinase (AtHK1)-MAPK cascade probably regulates osmotic homeostasis and ROS scavenging. Osmotic stress and ABA (abscisic acid)-mediated regulation of LEA (late-embryogenesis-abundant)-type proteins also play important roles in plant salt tolerance. Genetic engineering of ion transporters and their regulators, and of the CBF (C-repeat-binding factor) regulons, holds promise for future development of salt-tolerant crops.