Wheat germ agglutinin (WGA) is an active participant in ABA-controlled plant reactions to biotic and abiotic stresses; part of this wheat lectin is excreted in the area of the root apical meristem and becomes an exogenous agent for the plant. We have previously shown that 24-epibrassinolide (EBR) increased the WGA mRNA level independently of ABA because it did not change ABA content. The 0.4 μM EBR root pretreatment of wheat seedlings under the influence of 1 mM cadmium acetate in the presence of fluridone was found to inhibit the stress-induced accumulation of ABA, while the WGA content in plants was higher than in stressed EBR-untreated wheat roots. This indicates the possible existence of ABA-independent ability of EBR to regulate the quantitative level of WGA in wheat roots under cadmium stress. The protective effect of EBR is also proved by the prevention of cadmium growth-inhibiting effect on mitotic index. Moreover, EBR-pretreated wheat plants under cadmium stress form in the root cell walls Casparian bands and suberin lamellae, the critical places in the apoplastic barriers of endo- and exodermis. Thus we have demonstrated the involvement of wheat lectin in the realization of EBR-induced protective effect on plants under cadmium stress. An important contribution to the EBR-induced strengthening the barrier properties of the cell walls of the studied tissues have the ability of EBR to induce ABA-independent accumulation of WGA, which further promotes the increasing lignin and suberin biopolymers deposition in the cell walls of wheat roots.

This work was supported by the Russian Foundation for Basic Research (grant no. 20-04-00904 a), partly within the framework of the state assignment (theme no. AAAA-A16-116020350029-1).