Salt Stress Tolerance and Calcium Signalling Components: Where We Stand and How Far We can Go?

Soil salinization emerges as a pervasive global challenge, impeding plant growth and exerting substantial constraints on agricultural development and food security. Excessive salt concentration causes ionic stress, osmotic stress, and ultimately oxidative stress to the plants. To navigate salinity challenges, plants deploy an array of coping strategies, like ion homeostasis, osmoregulation, ROS homeostasis, etc. Halophytes have evolved intricate mechanisms to tolerate salt, enabling them to complete their lifecycle in the extreme saline environment (>= 200 mM NaCl). However, glycophytes are able to tolerate only small concentration of salt. In the typical salt tolerance mechanism in plants, calcium (Ca2+) signature plays an important role, and the signalling is dependent upon the interaction of various Calcineurin B-like (CBL) proteins, CBL-interacting protein kinases, Calcium-dependent protein kinases, and Calmodulins. Here, we compare the calcium-dependent responses to salt stress in halophytes and glycophytes with a special reference to the Salt Overly Sensitive (SOS) pathway. This will help to understand the genes and genetic pathways involved in molecular basis of halophytic salt tolerance, and hence, future studies could provide a solution to impart salt tolerance in glycophytes with the tools of genetic and genome engineering.