Effect of chitosan conjugates with oxycinnamic acids and <i>Bacillus subtilis</i> bacteria on the activity of protective proteins and resistance of potato plants to <i>Phytophthora infestans</i>

The effect of chitosan conjugates with caffeic (ChCA) and ferulic (ChFA) acids in combination with Bacillus subtilis bacteria on the transcriptional activity of PR protein genes and proteome changes in potato plants during infection with Phytophthora infestans (Mont.) de Bary was studied. Plants grown from mini tubers of the Luck variety were sprayed with solutions of ChCA and ChFA, suspension of B. subtilis bacteria strains 26D and 11 VM, composites of ChCA of ChFA together with bacteria. 3 days after treatment, some of the plants were infected with P. infestans. A decrease in the degree of development of the pathogen of late blight on potato leaves in all treatment options was revealed. The maximum protective effect was manifested when plants were treated with bacteria B. subtilis strain 26D in combination with conjugates of chitosan and oxycinnamic acids. The mechanisms of increasing the resistance of potato plants to P. infestans were associated with the activation of transcriptional activity of genes encoding the main protective protein (PR‑1), chitinase (PR‑3), thaumatin-like protein (PR‑5), protease inhibitor (PR‑6), peroxidase (PR‑9), ribonuclease (PR‑10). The revealed activation of the expression of marker genes of systemic acquired resistance and induced systemic resistance under the influence of joint treatment of plants with B. subtilis and chitin conjugates with oxycinnamic acids indicate the synergistic development of protective reactions in potato plants in this variant. By the method of two-dimensional electrophoresis of S. tuberosum leaf proteins followed by MALDI-TOF analysis, 12 proteins were identified, the presence of which in the leaves differed depending on the variant of the experiment. In all treatment variants, suppression of serine-threonine protein phosphatase activity was observed, reflecting the development of the hypersensitivity reaction. Different variants of the experiment formed weakly expressed clusters, which indicates multiple mechanisms of regulation of the synthesis of protective proteins involved in the reaction to treatment with bacteria, chitosan conjugates and infection with P. infestans.