Effect of common sage plant treatment with polyamines on the contents of proline and free and conjugated polyamines under oxidative stress

Common sage (Salvia officinalis L.) plants grown in water culture to the stage of 4–5 true leaves were treated with paraquat (PQ) ( 1 ml of the solution containing 0.1 μM PQ in 0.05% Tween 80), putrescine (Put), spermidine (Spd), or Spermine (Spm) (all polyamines (PA) at the concentration of 0.5 mM in 0.05% Tween 80) or PA plus PQ for 6, 12, 24, 36, or 48 h. Under normal conditions, treatment with individual PA did not induce any changes in the content of free proline. Under oxidative stress induced by PQ, oxidation of proline and free PA by ROS resulted in their spending and demanded restoration of free PA due to hydrolysis of their insoluble conjugates. As distinct from treatment with PQ only, its combination with PA in the light was accompanied by proline accumulation. Treatment with Put plus PQ induced accumulation of intracellular Put and its soluble and insoluble conjugates. Treatments with Spd and Spm in combination with PQ resulted similarly in the increase in the levels of their intracellular soluble and insoluble conjugates. In treatments with these high-molecular PA, polyamine oxidase was activated and diaminopropan formation was observed. It seems likely that, for restoration of high-molecular PA homeostasis, their degradation by polyamine oxidase or production of insoluble conjugates is induced. Thus, the amount of free and conjugated particular PA is under strict control and is maintained at a definite level. A decrease in the content of a particular free PA induces primarily a decrease in the content of its soluble and then insoluble conjugates. The data obtained demonstrate the effects of exogenous PA on the content of intracellular proline under oxidative stress but do not allow a conclusion about direct regulation of its content by PA.