[Elicitor activity of chitosan and arachidonic acid: their similarity and distinction].

Two elicitors-chitosan and arachidonic acid-induced the same defense responses in potatoes, stimulating the processes of wound reparation and inducing the formation of phytoalexins, inhibitors of proteinase, and active forms of oxygen. However, chitosan induced the defense potential of plant tissues at concentrations higher than those of arachidonic acid. The protective action of chitosan was defined by two parameters, i.e., the ability to induce the immune responses in plant tissues and to exhibit a toxic effect on the pathogen development, causing late blight and seedling blight, whereas the elicitor effect of arachidonic acid depended on its ability to induce the defense potential of plant tissues only.

[Involvement of salicylic acid in induction of nematode resistance in plants].

The role of salicylic acid (SA) as a possible signaling component in the case of the infection of plants with nematodes has been studied using a model system consisting of the tomato (Lycopersicon esculentum (Mill.) and race 1 of the gall eelworm Meloidogyne incognita (Kofoid and White, 1919; Chitwood, 1949). The pre-planting SA treatment of tomato seeds results in an increased nematode resistance of susceptible tomato cultivars; the protective effect is higher in the case of SA combined with chitosan, a biogenic elicitor of plant resistance. The studied preparations stimulate the growth and development of the plants. The increase in the resistance of tomato plants is related to the increased activity of phenylalanine ammonia-lyase and an increased SA content in plant tissues infected with nematodes; both these factors significantly influence nematode development.

[Wound repair in plant tissues (Review)].

Signaling systems responsible for repair processes in plants and manifestation of defensive effects in plant tissues were analyzed. Special attention was given to jasmonic acid, a mobile systemic repair signal, as well as to jasmonate biosynthesis and signal transport to the areas where protective responses of plants are induced. The main defense responses of potato tubers induced by wounding were considered.

[Immunomodulating activity of chitosan derivatives with salicylic acid and its fragments].

A study of biological activity of the derivatives of the chitin-chitosan oligomer with salicylic acid and its fragments showed that chitosan salicylate actively protected potato tubers against Phytophthora infestans but sharply inhibited reparation of potato tissues. N-(2-Hydroxybenzyl)chitosan exhibited good protective properties but did not influence wound reparation. N-(2-Hydroxy-3-methoxybenzyl)-N-pyridox-chitosan, which contained the pyridoxal and 2-hydroxy-3-methoxy fragments, was the most efficient, stimulating both defense against late blight and wound reparation in potato tissues.

[The inhibition of potato tubers wound reparation].

The multiple washing of the wound surface of potato tubers by water adversely affected the protective properties of wound periderm. Immune inhibitor beta-1,3-beta-1,6 glucan had a property of local effect and inhibited the process of wound healing. The pentasaccharide of xyloglucan caused necrosis of potato tuber tissue and prevented the wound reparation process.

[Wound healing and induced resistance in potato tubers].

It was demonstrated that biogenic elicitors, arachidonic acid and chitosan, locally and systemically stimulated wound healing in potato tuber tissues by increasing the number of wound periderm layers, accelerating the development of cork cambium (phellogen), and inducing proteinase inhibitors. The signal molecules, jasmonic and salicylic acids, had different effects on the development of wound periderm: jasmonic acid locally and systemically stimulated potato wound healing and elevated the level of proteinase inhibitors, whereas salicylic acid did not have any effect on wound healing and even blocked the formation of proteinase inhibitors.

[Activation of elicitor defensive properties by systemic signal molecules during the interaction between potato and Phytophthora].

The elicitor arachidonic acid in combination with jasmonic acid (JA) induced a higher level of defense against the late blight agent in potato (Solanum tuberosum L.) tissues than in combination with salicylic acid (SA). On the contrary, the elicitor chitosan displayed a higher inductive effect in combination with SA as compared with JA. The optimal concentrations of tested compounds were selected for designing the compositions activating wound repair, induction of proteinase inhibitors, and resistance to the biotrophic pathogen Phytophthora infestans (Mont.) de Bary. It was demonstrated that the compositions of elicitor and systemic signal molecules provided a faster spreading of an inducing effect in the potato tissues.

[Induced plant resistance and salicylic acid: a review].

Current understanding of the involvement of salicylic acid (SA) in the formation of plant resistance has been reviewed. SA acts as a signal molecule in the SA-dependent pathway. The so-called salicylate burst observed in tissues of plants after stress increases their resistance. The mechanism whereby SA induces plant resistance depends on the ability of this compound to inhibit the enzymes of the antioxidant system of plants, which results in the accumulation of active oxygen species and expression of defense genes.

[Free and conjugated forms of salicylic acid: content and role in potato].

Hydrolysis of conjugated forms of salicylic acid and accumulation of its free form was observed after infection of potato tubers (Solanum tuberosum L.) with an incompatible race of phytophthora or treatment with an elicitor (chitosan). Infection of tubers with a compatible race of the pathogen or treatment with a suppressor (laminarin) decreased both the degree of hydrolysis of conjugated forms of salicylic acid and the accumulation of its free form.

[Role of L-phenylalanine ammonia lyase in the induced resistance and susceptibility of potato plants].

Biogenic elicitors (chitosan and its complex with salicylic acid) and an immunosuppressor (laminarin) were shown to increase the activity of L-phenylalanine ammonia lyase (EC 4.3.1.5) and protein synthesis in potato tubers. Laminarin did not decrease L-phenylalanine ammonia lyase activity. It is unlikely that the activity of this enzyme may serve as a criterion for the induced resistance.

[Biochemical aspects of plant interactions with parasite nematodes. (A review)]. / Biokhimicheskie aspekty vzaimodeistviia rastenii s paraziticheskimi nematodami. (Obzor).

The review summarizes reports on molecular aspects of interactions of phytoparasitic nematodes with plant hosts. Data on the secrets of nematodes affecting plants (elicitors, toxins, products of parasitism genes, etc.) are analyzed and information flow pathways comprising all elements of the plant-parasite interaction (from elicitors to defense responses of plant cells), described. Emphasis is placed on the mechanisms whereby plants are protected from nematode invasion (hypesensitivity reactions, apoptosis, phytoalexins, proteinase inhibitors, PR-proteins, etc.). Consideration is given to genetic aspects of plant-parasite relationships. Promising practical approaches to defending plants from phytoparasitic nematodes, developed based on the results of studies of molecular mechanisms of plant-parasite interactions are provided in conclusion.

[Exoproteinases of the oomycete Phytophthora infestans]. / Ekzoproteinazy oomitseta Phytophthora infestans.

When grown in a medium containing heat-stable potato tuber proteins, the oomycete Phytophthora infestans (Mont.) de Bary produces a set of exoproteinases active at neutral and mildly basic pH values. These extracellular proteinases have been shown by SDS-PAGE with the presence of gelatin to include at least six components differing in molecular weight. Inhibitory analysis and study of the effects of the enzymes on various synthetic substrates show that the culture liquid of P. infestans contains mainly serine proteinases specific to trypsin and subtilisin and metalloproteinases. Their activity is suppressed by proteinase-inhibitor proteins from potato tubers. It is suggested that P. infestans exoproteinases may be the metabolic target for natural proteinase inhibitors from potato.

[Effect of systemic signaling molecules on the rate of spread of the immunizing effect of elicitors over potato tissues]. / Vozdeistvie sistemnykh signal'nykh molekul na skorost' rasprostraneniia po tkaniam kartofelia immuniziruiushchego éffekta élisitorov.

Mobile systemic signaling molecules (salicylic and jasmonic acids) enhance and accelerate the spread of systemic immunizing effect of elicitors (arachidonic acid and chitosan) over potato tuber tissues (Solanum tuberosum L.).

[Role of proteinase inhibitors in potato protection]. / Rol' ingibitorov proteinaz v zashchite kartofelia.

Mechanical damage or infection of potatoes with Phytophthora infestans caused an accumulation of only serine protease inhibitors in exudates of potato tubers. Among them, proteins prevailed that are structurally similar to those present in healthy tubers: a 22-kDa trypsin inhibitor, a 21-kDa serine protease inhibitor consisting of two polypeptide chains, and a 8-kDa potato chymotrypsin I inhibitor produced de novo. The accumulated proteins inhibited the growth of hyphae and germination of zoospores of P. infestans. Treatment with elicitors, jasmonic and arachidonic acids, intensified the accumulation of these inhibitors in tubers in response to the wound stress, whereas salicylic acid blocked this process. These results suggest that the lipoxygenase metabolism plays a substantial role in signal transduction of the protective system of resting potato tubers.

[Regulation of potato immune responses by laminarin]. / Reguliatsiia immunnykh otvetov kartofelia laminarinom.

Laminarin blocks potato immune responses by inhibiting the reaction of oversensitivity, formation of phytoalexins, wound repair, and the activity of proteinase inhibitors. It was found that laminarin exhibits antielicitor activity. Addition of salicylic acid to laminarin enhances its immunosuppressing effect, which becomes systemic.

[Induced phytophthora resistance in transgenic potato tubers]. / Indutsirovanie fitoftoroustoichivosti u klubnei transgennogo kartofelia.

Resistance of transgenic cultivars based on the expression of one or more resistance genes is sooner or later broken by pathogens whose race-producing rates are high. Thus, combining transgenesis with elicitor-induced resistance is a promising approach. The elicitor-induced resistance is based on the expression of multiple resistance genes, which can prevent the adaptation of pathogens to transgenic races, maintain the stability of cultivars, and increase their lifespan. In this work, we used transgenic potato cultivars Temp and Superior transformed with Bacillus thuringiensis delta-endotoxin gene and Lukyanovskii transformed with leukocyte alpha-interferon gene. Arachidonic acid (10(-8) M) and soluble chitosan (5 kDa, 100 micrograms/ml) were used as elicitors for tuber treatment. Our data showed that pretreatment with elicitors causes a 15-25% increase in both the systemic prolonged resistance of potato tubers to Phytophthora infestans and their ability to repair mechanical damage.

[The use of elicitors for defense of agricultural plants demands caution]. / Pri ispol'zovanii élisitorov dlia zashchity sel'skokhoziaistvennykh rastenii neobkhodima ostorozhnost'.

Hazards of the use of biogenic elicitors for inducing protective mechanisms in plants without considering the possible negative effects of the elicitors are considered.

[Immunosuppressors in pathogenesis of potato-pathogen blight]. / Immunosupressory v patosisteme kartofel'-vozbuditel' fitoftoroza.

The properties and effects of two plant resistance suppressors (1,3-beta-1,6-beta-glucan and a pentasaccharide of xyloglucan origin) involved in the pathosystem of potato (Solanum tuberosum) and the causal agent of blight (Phytophthora infestans (Mont) de Bary) were compared. The microbial 1,3-beta-1,6-beta-glucan suppressed the defense response over a narrow concentration range (10(-2) M), whereas the plant pentasaccharide had a broad range of effective concentrations (10(-12) to 10(-6) M). In the pathosystem of potato-causal agent of late blight, the beta-glucan caused a local and race-specific suppressor effect on the plant host defense response. In contrast, the pentasaccharide caused both local and systemic suppression of potato resistance, and the presence of terminal fucosyl residue in the xyloglucan oligosaccharine played a decisive role in its effect. The recognition of both suppressors by potato cell membrane sites is discussed.

[Effect of arachidonic acid on potato tubers during storage]. / Vozdeistvie arakhidonovoi kisloty na klubni kartofelia v period khraneniia.

Potato (Solanum tuberosum L.) tubers were treated with various concentrations (10(-9) to 10(-4) M) of the biogenic elicitor arachidonic acid during the period of storage (from October to July). The data showed that the resistance-inducing concentration of arachidonic acid was 10(-6) M in autumn and 10(-9) M in spring. Possible causes of the change in the immunizing concentration of arachidonic acid during storage of potato tubers are discussed.

[Modulation of plant resistance to diseases by water-soluble chitosan]. / Modulirovaniebolezneustoichivosti rastenii s pomoshch'iu vodorastvorimogo khitozana.

Low-molecular-weight water-soluble chitosan with a molecular weight of 5 kDa obtained after enzymatic hydrolysis of native crab chitosan was shown to display an elicitor activity by inducing the local and systemic resistance of Solanumi tuberosum potato and Lycopesicon esculentum tomato to Phytophthora infestans and nematodes, respectively. Chitosan induced the accumulation of phytoalexins in tissues of host plants, decreased the total content and changed the composition of free sterols producing adverse effects on infesters, activated chitinases, beta-glucanases, and lipoxygenases, and stimulated the generation of reactive oxygen species. The activation of protective mechanisms in plant tissues inhibited the growth of taxonomically different pathogens (parasitic fungus Phytophthora infestans and root knot nematode Meloidogyne incognita).