E. A. Cherepanova

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.

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.

The Effect of Salicylic Acid on Peroxidase Activity in Wheat Calli Cocultured with the Bunt Pathogen Tilletia caries

The effect of salicylic acid (SA) on peroxidase activity in wheat (Triticum aestivum L.) calli cocultured with the bunt pathogen Tilletia caries was studied. Fungal infection was shown to activate cytoplasmic peroxidase. SA suppressed total peroxidase activity but did not inhibit the peroxidase with pI ∼9.8. A novel chitin-specific peroxidase with pI ∼3.5 appeared after the SA treatment. The infection of SA-treated cells with Tilletia caries activated the isoenzymes with pI ∼3.5, ∼4.8, and ∼7.5 and stimulated their secretion into the culture medium. The ability of SA to control wheat peroxidase activity during pathogenesis is discussed. The important role of this control in plant defense responses to the bunt pathogen is emphasized.

Structural-functional features of plant isoperoxidases.

Current data on structural-functional features of plant peroxidases and their involvement in functioning of the pro-/antioxidant system responding to stress factors, especially those of biotic origin, are analyzed. The collection of specific features of individual isoforms allows a plant to withstand an aggressive influence of the environment. Expression of some genes encoding different isoperoxidases is regulated by pathogens (and their metabolites), elicitors, and hormone-like compounds; specific features of this regulation are considered in detail. It is suggested that isoperoxidases interacting with polysaccharides are responsible for a directed deposition of lignin on the cell walls, and this lignin in turn is concurrently an efficient strengthening material and protects the plants against pathogens.

Effect of chitooligosaccharides with different degrees of acetylation on the activity of wheat pathogen-inducible anionic peroxidase

The effect of chitooligosaccharides (COSs) with a molecular weight of 5–10 kDa and a degree of acetylation (DA) of 65 and 13% at a concentration of 1.0 mg/L on the expression of the TC151917 gene, which encodes wheat anionic peroxidase, and the activity of “anionic” isoperoxidases in common wheat plants infected with Septoria nodorum Berk.—the agent of Septoria leaf blotch were studied. Treatment with COSs with a 65% DA and infection promoted the transcription of the anionic peroxidase gene and increased the enzymatic activity of the anionic peroxidase with an isoelectric point (pI) of 3.5 in soluble and ion-bound to cell walls protein fractions. Chitooligosaccharides with a 13% DA change these parameters to a lesser extent. These data suggest the importance of the degree of acetylation of COSs in the development of wheat defense response with the peroxidases.

Polysaccharide-Specific Isoperoxidases as an Important Component of the Plant Defence System

The plant cell wall is a very complex and dynamic system, similar in importance to both the extracellular and intracellular processes which are recognised nowadays. The cell wall is a “vanguard” an effective barrier in the way of different negative chemical and biotic factors, including pathogens and wounding. The defence functions of plant cell walls are associated with the construction of physical barriers consisting of ligninand suberincontaining polymers on the path of pathogens inside a plant. This reaction develops more or less automatically, and barriers are only formed in the zone of pathogen penetration during active pathogen expansion into the host plant’s tissues. Yet the mechanisms of these events are still unclear. It is well-known that peroxidases (PO) are key enzymes involved in lignification (Cosio & Dunand, 2009) and one of the few proteins secreted into the plant cell wall. However, POs have numerous applications in industry and one of the most important of these is the use of POs for lignin degradation. Therefore, both analytics and industry require a great volume of stable PO preparations of a high quality and at a low price, and the search for new methods and substrates for their extraction and purification has great commercial importance. Thus, the ability of plant oxidoreductases to interact with the biopolymers of the cell walls of plants and fungi has been studied for several decades (Siegel, 1957; McDougall, 2001). Moreover, it has been shown that plant POs can bind electrostatically with calcium pectate (Dunand et al., 2002) and chitin (Khairullin et al., 2000). Plants are likely to contain a whole subclass of these “polysaccharide-specific” isoPOs and their encoding genes. This subclass should be characterised by the ability to bind with polysaccharides and the defence function focused on strengthening the cell wall of the host and isolating the non-infected host tissues from the pathogen with the help of lignin. We suppose that the ability of plant POs to interact with some biopolymers without losing their activity can be applied for the isolation and purification of these enzymes. The possibility of the application of chitin in agriculture, biomedicine, biotechnology and the food industry has received much attention due to its biocompactibility, biodegradability and bioactivity. The low price and the ecological safety of this biopolymer define it as an available matrix for technological processes. As such, it may be possible to produce the high-quality preparations of POs that are needed for various fields of industry and analytical methods with the use of chitin (or other

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.

Inhibition of IAA oxidase activity of wheat anionic peroxidase by chitooligosaccharides

The study demonstrated that chitooligosaccharides with a molecular weight of 5–10 kDa and a degree of acetylation of 65% exhibited an auxin-like effect in wheat plants and also played an important role in regulating the activity of polysaccharide (chitin)–specific anion isoenzymes of peroxidase oxidizing indole acetic acid. Changes in the kinetic parameters of the interaction of the wheat anionic chitin-specific peroxidase with pI ∼3.5 with chitin oligomers in the presence of indoleacetic acid were pH-depended and indicated that chitooligosaccharides significantly impair the ability of the enzyme for oxidation at pH levels of 4.2 and 6.0. It can be assumed that chitooligosaccharides not only induce protective plant systems but also increase the accumulation of auxin in plant tissues, thus adversely affecting a number of components of the plant protective system against pathogens.

Effect of chitooligosaccharides on peroxidase isoenzyme composition in wheat calli cocultured with bunt causal agent

Effects of chitooligosaccharides (COS) on the activity of peroxidase and its isoenzyme composition were investigated in cocultures of wheat calli (Triticum aestivum L.) with common bunt fungal pathogen (Tilletia caries (DC) Tul.). COS elevated the activity of readily soluble form of peroxidase: at concentrations of 0.01 and 1 mg/l, peroxidases with isoelectric points (pI) of about 3.5 and 9.8 and at concentration of 100 mg/l—those with pI of 4.3–5.2 were activated. It was shown that treatment with COS boosted the resistance of wheat calli to T. caries, inducing the accumulation in the cell wall of pathogen-specific isoperoxidases, especially its anionic isoform with pI ∼ 3.5. The ultimate indicator of defense responses is quick lignification of cultured cell walls under the effect of COS in the contamination area.

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.