L. G. Yarullina

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.

Molecular peculiarities of the chitin-binding peroxidases of plants

The chitin-binding ability of isoperoxidases isolated from 23 plants of different species was studied. The activation of peroxidases in a protein extract in the presence of this polysaccharide was found for 14 of the studied plants. Anionic isoperoxidases were shown to be sorbed on chitin and eluted from them with 1M NaCl for 16 of the plant species. Cationic isoforms of the peroxidases of some species of the Fabaceae and Cucurbitaceae plant families also bound to chitin. An immunochemical similarity was found between the chitin-binding isoperoxidases of taxonomically distant plant species (the Pomaceous, Fabaceae, and Cucurbitaceae). Moreover, a high homology of the molecular structures of the polysaccharide-binding sites was revealed for the anionic peroxidases of rice, wheat, oat, zucchini, cucumber, and radish. We propose the existence of a special class of plant peroxidases that bind with polysaccharides (chitin) and participate in the protective reactions of plants against pathogens.

Hydrogen peroxide production in wheat leaves infected with the fungus Septoria nodorum Berk. Strains with different virulence

The effect of two strains of the phytopathogenic fungus Septoria nodorum Berk. of different virulence on the intensity of local generation of hydrogen peroxide in common wheat leaves and the role of oxidoreductases in this process was studied. Differences in the pattern of hydrogen peroxide production in wheat plants infected with high- and low-virulence pathogen strains have been found. The low-virulent S. nodorum strain caused a long-term hydrogen peroxide (H2O2) generation in the infection zone, whereas the inoculation of leaves with the highly virulent strain resulted in a transient short-term increase in the H2O2 concentration at the initial moment of contact between the plant and the fungus. It was shown that the low level of H2O2 production by plant cells at the initial stages of pathogenesis facilitates S. nodorum growth and development. The decrease in the H2O2 concentration induced by the highly virulent S. nodorum strain is determined by inhibition of the oxalate oxidase activity in plant tissues and by the ability of the fungus to actively synthesize an extracellular catalase. The pattern of hydrogen peroxide generation at the initial stages of septoriosis may serve as an index of virulence of S. nodorum population.

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.

Hydrolytic enzymes and their proteinaceous inhibitors in regulation of plant–pathogen interactions

This review considers the main groups of hydrolytic enzymes associated with plant pathogens, as well as proteinaceous inhibitors of these enzymes, acting as the components of plant defense system. The role of hydrolases is described in the development of a pathological process in plant tissues. Significance of hydrolase inhibitors in the development of plant resistance to pathogens is analyzed. It is proposed that specific interactions in the “host plant–pathogen” system, involving hydrolytic enzymes and their proteinaceous inhibitors, depend on the nutritional specialization of fungi.

Relationship between the aggressiveness and catalase activity of Septoria nodorum Berk. in wheat

A comparative study of hydrogen peroxide (H2O2) generation, the character of a fungal catalase SNOG_03173.1 gene expression, and the catalase activity in wheat plants, infected with Septoria nodorum Berk. strains differing in their aggressiveness, has been carried out. The decreased intensity of H2O2 accumulation in infected tissues, influenced by an aggressive S. nodorum strain and caused by the enhanced transcriptional activity of the fungal catalase gene and the heightened synthesis of its product, has been revealed to be more expressed compared to a similar decrease influenced by a less aggressive strain. An assumption was made that the transcriptional activity of the fungi catalase gene and, therefore, the activity of catalase involved in the regulation of the H2O2 content in the infected zone of wheat plants represent important factors providing high aggressiveness and pathogenicity of S. nodorum.

Activity of Protective Proteins in Wheat Plants Treated with Chitooligosaccharides with Different Degrees of Acetylation and Infection with Bipolaris sorokiniana

The influence of chitooligosaccharides (COS) with different degrees of acetylation (DA) on the production of hydrogen peroxide (H2O2) and changes in the level of gene expression of pathogenesis-related (PR) proteins (oxalate oxidase AJ556991.1, peroxidase TC 151917, chitinase AV029935.1, proteinase inhibitor EU 293132.1) in the roots of the wheat Triticum aestivum L. inoculated with root rot pathogen Bipolarissorokiniana (Sacc.) Shoenaker was investigated. Differences were detected in plant responses to infection. These differences were due to the pretreatment of COS seeds with differing DA. Our results demonstrated that COS with a DA over 65% more effectively induced accumulation of H2O2 and increased the transcriptional activity of genes of PR-proteins as compared to COS with a DA of 30%. These data suggest an important role for DA in the manifestation of eliciting properties of COS, also in the presence of H2O2.

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.

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.

The effect of salicylic and jasmonic acids on the activity and range of protective proteins during the infection of wheat by the septoriosis pathogen

The influence of salicylic (SA) and jasmonic (JA) acids as signaling systems mediators on the generation of H2O2 and expression of genes encoding protective proteins was studied in the leaves of wheat Triticum aestivum L. upon infection with the pathogen of septoriosis Septoria nodorum Berk. It was found that presowing treatment of seeds with SA and JA decreased the development of the fungus on the leaves of wheat and had a stimulating effect on the production of H2O2 in the area of infection. An increased expression of genes encoding oxalate oxidase AJ556991.1 and anionic peroxidase TC 151917 was shown in infected tissues with the method of polymerase chain reaction.