PhD thesis is devoted to the study of the effects of functional interaction of key gas transmitters (NO, H2S, CO) with each other, with other signaling mediators and individual components of the hormonal system of plants in connection with their adaptation to hyperthermia and salt stress.
In the study of the effect of exogenous carbon monoxide on heat resistance, it was found that treatment of wheat seedlings with CO donor hemin induced the development of their heat resistance. It was found that the CO donor increased the activity of SOD, catalase, and guaiacol peroxidase in the roots of wheat seedlings. The effects of inducing heat resistance of seedlings by hemin treatment and increasing the activity of antioxidant enzymes in them were eliminated by calcium antagonists (EGTA and neomycin) and hydrogen peroxide scavenger DMTU. The CO donor-induced increase in seedlings' survival after heat stress was also eliminated by the NO scavenger PTIO.
Increased formation of hydrogen peroxide in roots of wheat seedlings under the action of hemin was transient. Its maximum was observed after a previous increase in extracellular peroxidase activity. The increase in H2O2 caused by the CO donor was eliminated by the peroxidase inhibitor sodium azide. The increase in peroxidase activity and hydrogen peroxide content induced by the action of hemin was not manifested in the presence of antagonists of calcium and NO. This shows the role of calcium and nitric oxide in enhancing the formation of hydrogen peroxide by peroxidase under the action of the CO donor on wheat seedlings root cells.
The NO content during treatment of wheat seedling roots with hemin also increased transiently. This effect was eliminated by nitrate reductase inhibitor sodium tungstate that shows the role of nitrate reductase as the main enzymatic source of NO, which is activated by the action of hemin on root cells of wheat seedlings. At the same time, the process of NO formation activated by the CO donor turned out to be dependent on calcium homeostasis, as it was eliminated by the action of calcium antagonists EGTA and neomycin. On the other hand, the carbon monoxide donor-induced increase in nitrate reductase activity and increase in NO content in wheat seedling roots was not eliminated by the antioxidant DMTU. This shows that in the signal chain activated by carbon monoxide, NO is located above hydrogen peroxide.
It was found that the treatment of seedlings with SA or NaHS caused an increase in their resistance to damaging heating. At the same time, under the influence of SA, there was a transient increase in the hydrogen sulfide content in roots with the maximum effect in 2-3 hours after the start of treatment. Treatment of roots with SA caused an increase in the activity of SOD, catalase, and guaiacol peroxidase. Hydrogen sulfide synthesis inhibitors hydroxylamine and potassium pyruvate partially eliminated the SA-induced effects of increasing the activity of antioxidant enzymes and the development of heat resistance of seedlings. At the same time, the combined treatment with SA and NaHS contributed to an additional increase in the activity of antioxidant enzymes and increase the survival of wheat seedlings after heating. The combined treatment of 24-EBL and SNP in optimal concentrations caused a more significant protective effect compared to the treatment of each compound separately. At the same time, the combined effect of high concentrations reduced the heat resistance of seedlings. Therefore, the stress-protective effect of phytohormones SA and BS can be enhanced by their use in combination with donors of gasotransmitters - hydrogen sulfide and nitric oxide, respectively.
Donors of gasotransmitters had a similar positive effect on the salt resistance of wild-type Arabidopsis plants, which was manifested in the reduction under their influence of water deficiency of leaves, reduction of oxidative damage, stabilization of membrane permeability, and chlorophyll content during the influence of NaCl. Pre-treatment of coi1 and jin1 Arabidopsis mutants with NO, H2S, and CO donors did not prevent NaCl-induced enhancement of lipid peroxidation, did not reduce membrane permeability, and preserve the chlorophyll pool under stress. The obtained results indicate the involvement of jasmonate signaling components (COI1 and JIN1/MYC2 proteins) in implementing the stress-protective effect of hydrogen sulfide, nitric oxide, and carbon monoxide on Arabidopsis plants under salt stress.
The dissertation research significantly complements the fundamental knowledge about the mechanisms of functional interaction between signaling mediators-gasotransmitters (CO, NO, H2S) and separate stress phytohormones (jasmonic and salicylic acids and brassinosteroids). The obtained results can become a theoretical basis for the development of new methods to increase the resistance of wheat plants to adverse environmental factors, in particular, high temperatures and salinity.
