Synergism between polyamines and ROS in the induction of Ca2+ and K+ fluxes in roots

Stress conditions cause increases in ROS and polyamines levels, which are not merely collateral. There is increasing evidence for the ROS participation in signaling as well as for polyamine protective roles under stress. Polyamines and ROS, respectively, inhibit cation channels and induce novel cation conductance in the plasma membrane. Our new results indicate that polyamines and OH^• also stimulate Ca²⁺ pumping across the root plasma membrane. Besides, polyamines potentiate the OH^•-induced non-selective current and respective passive K⁺ and Ca²⁺ fluxes. In roots this synergism, however, is restricted to the mature zone, whereas in the distal elongation zone only the Ca²⁺ pump activation is observed. Remodeling the plasma membrane ion conductance by OH^• and polyamines would impact K⁺ homeostasis and Ca²+ signaling under stress.