Figure 3.

Metabolic scheme for regulation of salt stress responses by polyamines (PAs), nitric oxide (NO) and proline mediated by cytosolic Ca²⁺ signaling. Under salt stress, elevated PAs content affect Ca²⁺ level in the cell by either direct activation of PMCA and contributes to Ca²⁺ excursion (this will result in a steady state level of Ca²⁺ for normal metabolism in the cell); or indirectly by stimulation of NO and ROS production that results in downstream Ca²⁺ signaling. Similarly by salt shock, enhanced proline content influences the Ca²⁺ read out by ROS engagement; while NO is multiply associated with Ca²⁺ signaling comprising: direct manipulation of the Ca²⁺ signaling, effect on Ca²⁺ channels and regulation of MAPKs. CR: Cysteine residue, cGMP: Cyclic GMP, cADPR: Cyclic ADP ribose (cADPR), CaM: Calmodulin, CDPK: Ca²⁺ dependent protein kinases, MAPK: mitogen-activated proteins kinase, NO: Nitric oxide, PAs: Polyamines, PMCA: plasma membrane-Ca^2+-ATPase, Pro: Proline, ROS: Reactive oxygen species, SR: Salt responses, SRR: Salt responsive receptors.