Zh. V. Udalova

Correlation between the Structure of Plant Steroids and Their Effects on Phytoparasitic Nematodes

The effects of certain plant steroids (belonging to furostanol glycosides or glycoalkaloids) and α-ecdysone on growth and development of phytoparasitic nematodes were studied. It was shown using an experimental system including tomato Lycopersicon esculentum Mill. and root-knot nematode, Meloidogyne incognita Kofoid et White, that a steroid molecule exhibits significant nematicidal activity if it contains a carbohydrate moiety and an additional heterocycle in the steroid core. The maximum nematicidal activity is inherent in glycosides containing chacotriose as the carbohydrate moiety of the molecule. Some compounds tested in this work could be used for protecting plants against phytoparasitic nematodes.

Role of Isoprenoids in Plant Adaptation to Biogenic Stress Induced by Parasitic Nematodes (Review)

Parasitic nematodes are considered a biogenic stress factor in plants. The effects of various plant isoprenoids, including mono-, sesqui-, di-, and triterpenoids, sterols, and steroid glycosides, on parasitic nematodes are reviewed. Certain isoprenoids can be placed in the class of natural plant adaptogens.

The Participation of salicylic and jasmonic acids in genetic and induced resistance of tomato to Meloidogyne incognita (Kofoid and White, 1919)

Salicylic (SA) and jasmonic (JA) acids are the best known mediators of signal systems in plants. In this investigation the participation and character of interactions between SA- and JA-signals under the induced and genetic resistance of plants to nematodes was investigated on the model system tomato (Lycopersicon esculentum) and the root-knot nematode Meloidogyne incognita. This study demonstrates that application of JA and SA to tomato foliage induces systemic effects that suppress root-knot nematode infestation, inhibition of nematode reproduction, and also increased activity of LOX and PAL, the enzymes of biosynthesis of JA and SA. JA treatment did not inhibit Mz-mediated resistance, which suggests a lack of signaling conflicts between these two forms of defense.

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 preplanting 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.

Adaptogenic Effects of Furostanol Glycosides of Dioscorea deltoidea Wall on Oxidative Processes in Tomato Plants during Biotic Stress

The effect of furostanol glycosides of a cell culture of Dioscorea deltoidea Wall on oxidative processes in tomato plants subjected to invasion with the gall nematode Meloidogyne incognita Kofoid et White was studied. We showed that furostanol glycosides induce a nonspecific defensive response in plants. Exposure of cell membranes to furostanol glycosides causes rearrangements in fatty acids, resulting in the formation of conjugated dienes, which makes molecules thermodynamically more stable under stress conditions. The study of changes in the activity of peroxidases of intact plants and plants affected with the nematode, which were treated with furostanol glycosides, showed that the protective effect of the guaiacol-dependent peroxidase is more long-term than the effect of the benzidine-dependent peroxidase.

Photosynthetic Pigments of Tomato Plants under Conditions of Biotic Stress and Effects of Furostanol Glycosides

The adaptogenic effect of furostanol glycosides (FG) on biosynthesis of photosynthetic pigments in tomato plants (Lycopersicon esculentum Mill.) was studied under conditions of biotic stress caused by root-knot nematode (Meloidogyne incognita Kofoid et White). Treatment of plants with 5 × 10–4 M FG was accompanied by an increase in the rate of biosynthesis of pigments (particularly, chlorophyll b and carotenoids), which was observed against the background of a decrease in the relative contribution of β-carotene and an increase in the relative contribution of pigments of the violaxanthin cycle (VXC) to the overall pool of carotenoids. It was suggested that FG stimulated phytoimmunity by shifting metabolism of carotenoids toward enhanced biosynthesis of VXC pigments. These pigments play a protective role and facilitate stabilization of the photosynthetic apparatus, which is particularly important under stress conditions.

PR proteins in plants infested with the root-knot nematode Meloidogyne incognita (Kofoid et White, 1919) Chitwood 1949.

Production of pathogenesis-related proteins (PR proteins) is an important protective response of plants to pathogenic factors. It was suggested [1, 2] that this group of plant-encoded inducible proteins is related to specific forms of resistance to pathogens and stresses. PR proteins isolated from tobacco plants infected with tobacco mosaic virus have been studied in most detail. These proteins are arbitrarily divided into five groups. The properties of hydrolytic proteins of groups 2 and 3 ( β -1,3-glucanases and chitinases) has been described most comprehensively [3]. There are grounds to assume that these enzymes fulfil at least two functions in plant disease control. First, they are capable of catalyzing degradation of cell walls of pathogenic agents, because β -1,3-glucanes and chitin are essential components of the pathogen cell walls [4, 5]. Second, these enzymes catalyze hydrolysis of the corresponding substrates, thereby releasing biologically active oligosaccharides (elicitors and suppressors) capable of regulating the immune status of plant tissues [6]. The content of PR proteins in healthy plant tissues is insignificant, and these proteins were found in healthy plants only at certain stages of development [7]. The process of the pathogen-induced production of PR proteins should be regarded as systemic, because these proteins are accumulated not only at the site of pathogen localization, but also in noninoculated parts of plant. The information about protective effects of PR proteins against parasitic nematodes is scarce and contradictory. Some authors reported an absence of induction of PR proteins in plants infested with the nematode [8]. On the other hand, it was shown that nematode infestation induces an increase in the activity of glucanase and chitinase. Although no quantitative correlation of the activity of the enzymes with the degree of plant resistance was found in [8–10], there is evidence for contribution of PR proteins to plant protection against parasitic nematodes [11]. The goal of this work was to study the role of β -1,3glucanase and chitinase in the interaction between cucumber ( Cucumis sativum L.) and the root-knot nematode Meloidogyne incognita (Kofoid et White, 1919) Chitwood 1949 race 1. The cucumber cultivar TSKh211 was used. The degree of plant damage was four points on an invasion scale. Water-soluble chitosan (molecular weight, 5 kD; degree of acetylation, 15%) at a concentration of 50 μ g/ml and ascorbic acid (AA; Sigma) at a concentration of 10 − 7 M were used as elicitors for modulating the immune status of plants [12]. Before planting into soil, cucumber seeds were treated for 2 h with aqueous solutions of AA and chitosan. The morphological and physiological states of the nematodes and plants were assessed 40 days after infestation of roots. The chitinase and glucanase activities in cucumber leaves and roots were measured 21 days after infestation as described in [13, 14]. Colloid chitin (10 mg/ml) and laminarin (2 mg/ml) were used as substrates of chitinase and β -1,3-glucanase, respectively. The specific activity was expressed in μ mol of the reaction product per min per mg protein. The β -1,3-glucanase and chitinase reaction products were glucose and N-acetylglucoosamine, respectively. The results shown in Table 1 indicate that treatment with either of the elicitors caused a decrease in the degree of infestation of cucumber roots with nematodes. This decrease correlated with an acceleration of plant growth and an increase in the weight of their aboveground organs. It should be noted that chitosan was a more effective suppressor of nematodes than AA. For example, treatment with chitosan or AA caused a threefold or only a 13% decrease in the number of cucumber root knots, respectively. The effect of chitosan on nematode development was particularly notable. Indeed, at the end of the experiment, mature female nematodes were entirely absent in plants treated with chitosan, whereas in plants treated with AA, the number of mature female nematodes was no less than 40% GENERAL BIOLOGY

Mi-1 gene expression in tomato plants under root-knot nematode invasion and treatment with salicylic acid

The dynamics of expression of two homologous genes Mi-1.1 and Mi-1.2 in the roots of resistant and susceptible tomato plants in non-invasion conditions and during invasion with the root-knot nematode M. incognita was studied. Nematode invasion was accompanied by a significant increase in the expression level of both genes; however, the accumulation of transcripts at the early stages of nematode invasion in the penetration of nematode juveniles to the roots was observed only in plants that contained the Mi-1.2 gene, which explains the resistance of tomatoes to this root-knot nematode, caused by only this gene. We reveal a change in the Mi-1 gene activity under exogenous salicylic acid treatment, which contributed to the formation of induced resistance to root-knot nematode in the susceptible plants.

Steroid furostanol glycosides: A new class of natural adaptogenes (Review)

The present review summarizes experimental data revealed while studying the mechanism of the adaptogenic effect of furostanol glycosides (FG) extracted from Dioscorea deltoidea Wall cell culture under the conditions of biotic stress in tomato plants Lycopersicon esculenium Mill. induced by the gall nematode Meloidogyne incognita Kofoid et White. Comparison of changes in isoprene content (phytosterines, tomatin, and carotenoids) and in the rate of oxidative processes in the leaves and roots of intact and treated plants evidence that FG cause nonspecific defense reactions resulting in the formation of systemic acquired resistance. This formation is presented by the enhancement in photosynthetic apparatus pigment fund, pigments of the violaxanthin cycle in particular, by activation of processes related to POL, and by increase in peroxidase activity—enzyme of antioxidant protection.

The immunocorrection properties of 1-->3-beta-glucans in the interaction of plants of the family solanaceae with phytopathogens.

Certain parasitic fungi are also sources of β -glucans. It was shown earlier by Ayers et al. [3] that metabolites of Phytophthora megasperma var. soja contained hepta1 → 3 ; 1 → 6 β -D-glucan, an elicitor of soybean defense mechanisms. The elicitor activity is observed if the heptaglucoside molecule contains three terminal glucose residues, two specifically oriented branches, and 1 → 6 β bonds in the main backbone chain of the elicitor.