Kokorev O. Stress-protective effect of polyamines on plants and its functional relationship with signaling mediators

PhD thesis is devoted to study the role of key signaling mediators, in particular, ROS, nitric oxide, hydrogen sulfide and calcium ions in the implementation of the stress-protective effect of di- and tetraamines on plants during hyperthermia and dehydration. The main objectives were to exemine the effect of exogenous polyamines on plants resistance to hyperthermia and lack of moisture due to the modification of antioxidant enzymes activity and the content of low molecular weight polyfunctional protective compounds; establishing the participation of ROS, nitric oxide, hydrogen sulfide and calcium ions in the implementation of the protective effect of polyamines on wheat seedlings under conditions of hyperthermia; establishing the effect of diamines on the activity of diamine oxidase (DAO) and nitrate reductase as possible enzymes of NO synthesis and the establishment of functional relationships between nitric oxide and hydrogen peroxide in the implementation of the stress-protective effects of putrescine and cadaverine; determining the effect of exogenous polyamines on the functioning of plant stomatal system and the study of the participation of calcium ions and lipid signaling components in the implementation of their effects. It was found that the studied polyamines (putrescine, cadaverine and spirmine) caused an increase in heat resistance of wheat seedlings. The minimum concentration of putrescine, which caused a probable increase in seedling survival, was 0.25 mM. The highest protective effect of all polyamines was found at a concentration of 1 mM. The protective effect of spermine was expressed slightly more than the effects of putrescine and cadaverine. At the same time, the stress-protective effect of the two diamines in the concentration range of 0.5 – 2.5 mM almost did not differ. The obtained results also indicate the participation of polyamines in the regulation of the condition of the stomata in plants. It has been shown that incubation of pea leaf epidermis in medium with the addition of putrescine or spermine caused a decrease in the size of the respiratory aperture. The effect of polyamines on the functioning of the respiratory system is calcium-dependent. In the presence of a calcium channel blocker LaCl3, the effect of putrescine and spermine on the condition of the stomata was weak. Their effects were partially offset by the extracellular calcium chelator EGTA, but completely eliminated by the phospholipase C inhibitor neomycin. Data were obtained that also indicate on the involvement of LPO in the regulatory effect of polyamines on the condition of the stomata. The effect of putrescine and spermine on the value of the aperture of the stomata was not detected in presence of n-butanol – an inhibitor of phospholipase D-dependent formation of phosphatidic acid, but not its inactive isomer of butanol-2. Thus, the results indicate the possible role of calcium in the cytosol from intracellular compartments and the importance of signaling intermediates formed by phospholipases C and D in the implementation of the respiratory effects of polyamines. Thus, the dissertation research deepens the understanding of the mechanisms of stress-protective action of polyamines on plants associated with their involvement in cellular signaling processes. This creates a basis for the inclusion of polyamines in the group of practically significant physiologically active substances with stress-protective effects. Established in soil culture under drought conditions close to natural, the stress-protective effect of foliar treatment with putrescine and spermine on intact green wheat plants allows us to consider this technique as promising for increasing drought resistance of plants in the field.