N. B. Troshina

Effects of salicylic and jasmonic acids on the components of pro/antioxidant system in potato plants infected with late blight

The effects of salicylic acid (SA) and jasmonic acid (JA) on plant defense responses were studied with aseptic potato (Solanum tuberosum L.) plantlets infected with Phytophthora infestans (Mont.) de Bary. Plant treatment with 10−6 M SA or 10−7 M JA induced plant resistance; the mixture of these acids was most efficient. After treatment with these compounds, phenolic compounds were accumulated and peroxidase was activated in the sites of pathogen localization, and this might be the reason of resistance enhancement. In addition, more H2O2 was accumulated in infected plants treated with JA or its mixture with SA but not in plants treated with SA alone. It might occur because of observed inhibition of catalase and activation of isoperoxidase with the isoelectric point (pI) of ∼9.3, which manifests an affinity for the pathogen cell wall. The data obtained allow us to recommend the application of these compounds for potato plant protection against late blight.

Changes in the Phytohormone Levels in Wheat Calli as Affected by Salicylic Acid and Infection with Tilletia caries, a Bunt Pathogenic Agent

The role of salicylic acid (SA) in growth regulation and the change in the levels of phytohormones (IAA, ABA, and cytokinins) were studied in the wheat calli co-cultured with bunt pathogen Tilletia caries. Calli infection with T. caries resulted in the hypertrophied callus growth and simultaneous increase in phytohormone level. The addition of SA to the nutrient media decreased the callus growth induced by the pathogen, whereas the level of investigated phytohormones was not affected. In the SA-treated infected calli, the formation of necrotic lesions was observed in the zones of contact of the fungal mycelium with callus cells that limited pathogen growth. The authors suggest that the stabilization of the hormonal balance of plant cells at pathogenesis is one of the possible mechanisms of the SA protective action in vitro and in vivo. Hence, co-culturing wheat calli and T. caries fungus appeared to be a convenient model for assessing SA protective action.

Salicylic acid increases the defense reaction against bunt and smut pathogens in wheat calli

The role of salicylic acid (SA) in regulating wheat calli growth and peroxidase activity in the co-culture with bunt (Tilletia caries (D.C.) Tul.) and smut (Ustilago tritici Pers.) pathogens was studied in this work. We found that the influence of SA increased the number of globular high-density sites with meristema-like cells and reduced the number of low-structured sites with parenchyma-like cells in wheat calli. SA inhibited fungi spores germination, mycelium growth, and formation of its new spores during the co-cultivation of wheat calli with bunt or smut agent. Interaction of fungi mycelium with wheat calli treated by SA led to formation of zones with hypersensitive reaction in calli high-structured sites with meristema-like cells. The obtained data about the influence of SA on activation of wheat calli growth and the peroxidases with pI ~3.5 and ~9.8, which can bind to the mycelium of T. caries or U. tritici are discussed in this paper.

Salicylic acid induces resistance to Septoria nodorum Berk. in wheat

The effect of salicylic acid (SA) on oxalate oxidase and peroxidase activities and hydrogen peroxide (H2O2) production in leaf cells has been studied in wheat of the susceptible cultivar Zhnitsa infected by Septoria nodorum, a pathogen of wheat leaf blotch. The results show that fungal hyphae spread into interstices between mesophyll cells and that infected tissues contain H2O2. Treatment with SA results in enhanced H2O2 production in mesophyll cells, which is due to activation of oxalate oxidase and peroxidase in the cell wall. It is proposed that the modulating effect of SA on oxidoreductase activities is involved in the induction of protective response to fungal infection in wheat plants.

The effect of pathogens and phytohormones on the rate of oxidation of phenols by oxalate oxidase in wheat seedlings

We studied the effect of various fungal phytopathogens and exogenous phytohormones on the rate of o-phenylenediamine oxidation mediated by oxalate oxidase, which is one of protective proteins of wheat. The pattern of changes in o-phenylenediamine oxidation rate depended on pathogen type, cultivar resistance, and phytohormone class. This reaction is proposed as a model reaction for studying plant response to infection and effects of various physiologically active compounds.

The Effect of the Common Bunt on the Growth of Wheat Seedlings and Calluses

The growth of wheat (Triticum aestivum L., cv. Zhnitsa) seedlings and calluses infected with spores of common bunt causal agent Tilletia caries (DC) Tul. was studied. Inoculation with the pathogenic fungus enhanced both in vivo and in vitro growth due to cell division activation and cell expansion. These growth characteristics were also retained in wheat calluses infected with T. caries and grown on the hormone-free Murashige and Skoog nutrient medium. This implies the production of hormone-like substances by the fungus itself or by the infected plant. At the phase of fungal penetration into the plants, infection resulted in IAA accumulation in seedlings. Later, the IAA content reduced to a control level and the phytohormone balance was shifted toward cytokinins. Similar changes in the IAA and cytokinin levels were observed during early fungus development on wheat callus tissues. Such a sequence of events is supposed to be required for successful fungal penetration and localization in plant tissues and for the establishment of compatible interactions between the pathogen and the host plant.

Salicylic and Jasmonic acids in regulation of the proantioxidant state in wheat leaves infected by Septoria nodorum Berk

Influence of mediators of the signal systems of salicylic (SA) and jasmonic (JA) acids and their mixture on reactive oxygen species’ (ROS) (superoxide radical and O2·− H2O2) generation and activity of oxidoreductases (oxalate oxidase, peroxidase and catalase) in leaves of wheat Triticum aestivum L. infected by Septoria leaf blotch pathogen Septoria nodorum Berk has been studied. Presowing treatment of seeds by SA and JA decreased the development rate of fungus on wheat leaves. SA provided earlier inductive effect on production of O2·− and H2O2 compared with JA. The protective effect of the salicylic and jasmonic acids against Septoria leaf blotch pathogen was caused by activation of oxalate oxidase, induction of anion and cation peroxidases, and decrease of catalase activity. Ability of compounds to stimulate ROS in the plant tissues can be used as criteria for evaluation of immune-modulating activity of new substances for protection of the plants.

Effect of hydrogen peroxide on morphological characteristics and resistance of wheat calluses to T. caries Tul.

We studied the effect of hydrogen peroxide on morphological characteristics and resistance of common wheat calluses ( Triticum aestivum L.) to Tilletia caries Tul. The induction of the defense response and morphogenesis in calluses depended on H2O2 concentration. A correlation was revealed between the elevated concentration of hydrogen peroxide in wheat calluses and high activity of oxalate oxidase in the cell wall. Administration of H2O2 into the callus culture medium was followed by rhizogenesis, induced the formation of dense regions, and inhibited fungal growth on calluses. Hydrogen peroxide at high concentrations was less potent in inhibiting the growth of fungi. A relationship was found between oxalate oxidase activity, H2O2 concentration, and morphogenetic and defense responses of calluses induced by exogenous hydrogen peroxide. These data suggest that the induction of H2O2 generation is one of the approaches to increase callus resistance.

Influence of Ca2+ ions on metabolism of active oxygen species in wheat calli cocultured with the bunt pathogen Tilletia caries

The effect of Ca2+ on morphophysiological parameters of wheat calli (Triticum aestivum L.) infected by the bunt pathogen Tilletia caries, in particular on the level of active oxygen species, activity of oxalate oxidase, peroxidase, and catalase is investigated. The concentration of O2−, H2O2, and activity of oxidoreductases (oxalate oxidase, peroxidase, and catalase) depended on the content of Ca2+ in the culture medium of calli. The increase of the concentration of Ca2+ ions in the culture medium led to forming of calli with high structure, induction of activity of oxalate oxidase and of some isoperoxidase, and to accumulation of active oxygen species. These changes contributed to inhibition of development of the fungus. So this dependence confirm the role of calcium as the intermediant in biochemical reactions related to the formation of the protective response of plant cells to biotic stress.