The Effect of Arachidonic Acid and Viral Infection on the Phytohemagglutinin Activity during the Development of Tobacco Acquired Resistance

The effects of arachidonic acid (AA) on the development of viral infection and the activity of phytohemagglutinins in Nicotiana tabacum L. plants were studied. Cv. Samsun NN was used, which displayed a genotypically determined hypersensitive response to tobacco mosaic virus (TMV) infection. When tobacco leaf disks were treated with 10^–9 to –10^–7 M AA, viral reproduction was suppressed by 90–100%. The AA concentration of 10^–8 M was optimal for the improvement of plant virus resistance. Tobacco leaves maintained virus resistance for at least two weeks. Both AA treatment and TMV inoculation were accompanied by an enhanced lectin activity, which may indicate the involvement of lectins in the development of plant defense responses. Lectin accumulation was observed in the intact plants developing systemic resistance and in the detached leaves characterized by local resistance.     

Induction of Phytohemagglutinin Activity by Arachidonic Acid in in vitro Potato Plants

Tube-grown potato (Solanum tuberosum L., cv. Nevskii) plants treated with arachidonic acid (AA) were used as a model to study the activity of phytohemagglutinins (PHA) during induction of the plant antiviral defense system. Plant treatment with 10^–8 M AA and also their inoculation with potato viruses X, Y, and M resulted in the increased activity of PHAs in potato shoots. The inducer of antiviral resistance behaved as a modulator of the PHA activity providing for its various levels during the development of viral infection. During the development of AA-induced systemic resistance, the level of phytohemagglutinin activity did not essentially depend on the nature of the viral pathogen. We suggested that the mechanism of AA-induced plant antiviral defense was connected with changes in the PHA activity.     

高等植物病原相关蛋白

在过去的三十年中,人们对诱导系统性抗性——这一普遍存在于高等植物抗病过程中的现象——进行了深入研究。被真菌、细菌或病毒侵染后,植物表现出广泛的、长时间的系统性抗性。在这一过程中,植物细胞壁组成成分发生改变,表达各种病原相关蛋白(PR蛋白),并合成多种植物抗毒素。本文就主要的PR蛋白家族的结构和功能特性,PR蛋白的发现和分类,及PR蛋白的应用作一综述。     

Protein composition of tobacco leaves with antiviral resistance induced by activators of defense responses and TMV infection

In tobacco (Nicotiana tabacum L.) plants of hypersensitive cv. Samsun NN, a capability of necrosis lesion formation and protein patterns were studied after induction of antiviral resistance by defense responses activators (DRA) (arachidonic acid, ubiquinone 50, and vitamin E) and by infection with tobacco mosaic virus (TMV). DRA and TMV improved both local and systemic leaf resistance to TMV. Native protein electrophoresis demonstrated differences in the composition of leaf proteins extracted under acidic and alkaline conditions. SDS-PAGE revealed proteins accumulated during the development of systemic antiviral resistance after lower leaf treatments with DRA and of local resistance induced by pretreatment with TMV. It was shown that various DRA affected protein patterns similarly, whereas TMV infection resulted in other changes. It is supposed that different pathways function in tobacco plants during induction of systemic resistance by DRA and TMV infection.     

Effect of Plant Oligoadenylates on Viral Infection and Antistress and Growth-Regulating Properties in Potato Plants Grown in vitro

Biological properties of plant oligoadenylates (POA) were studied in in vitro grown potato (Solanum tuberosum L.) plants. POA were synthesized by ATP polymerization in the presence of an enzyme preparation isolated from leaves of wild potato Solanum chacoense Bitt. treated with resistance inducers. The concentration of viral antigen was determined by the method of immunoenzyme analysis. In the course of virus elimination by the apical meristem method, pretreatment of potato tuber sprouts with POA increased the survival rate of meristem explants and, in several cultivars, enhanced morphogenesis and increased the yield of virus-free regenerants. Prolonged application of POA in the nutrient medium for microcutting of potato tube plants infected in vitro with X-, S-, and M-viruses increased their height due to internode lengthening. The effect of this treatment on virus reproduction was ambiguous: various combinations of virus species, the duration of growth on POA-containing media, and POA concentration resulted in either statistically significant inhibition or a significant enhancement of virus reproduction. Possible mechanisms of the antistress effect of POA, in connection with their effect on virus reproduction, are discussed.     

Boosting the Immune System of Solanaceous Plants by Lysophosphatidylcholine

An in vitro treatment of solanaceous plants, viz. potato (Solanum tuberosum L.) and tobacco (Nicotiana tabacum L.), with lysophosphatidylcholine promoted their resistance to phytopathogens, such as Phytophthora infestans (Mont.) de Bary and potato virus Y. The systemic and long-term lysophospholipid-induced response was independent of the phytopathogen type. It was concluded that lysophosphatidylcholine, a product of phosphatidylcholine hydrolysis with phospholipase A₂, plays an important role in the regulation of plant immune system.     

Effect of Zinc Sulfate and Boric Acid on the Hormonal Status of Potato Plants in Relation to Tuberization

Potato (Solanum tuberosum L.) plants were grown in a greenhouse using zinc- and boron-deficient soil. The effects of seed-tuber treatment with 3 mM zinc sulfate and 8 mM boric acid on the content and ratio of phytohormones in the leaves and mature tubers, the indices of photosynthetic activity, the rate and NaF-sensitivity of respiration, and the tuber growth were studied. Zinc-sulfate treatment shifted the hormonal balance toward a substantial increase in the cytokinin content and the cytokinin/ABA ratio, as well as a decrease in the IAA/cytokinin ratio. Boric-acid treatment resulted in an increase in the IAA content and IAA/cytokinin ratio. Zinc-sulfate treatment abolished the apical dominance and increased the tuber weight due to their increased number and the number of phellem (cork) cell layers. Boric-acid treatment increased cell diameter in the tuber perimedullary zone; an increase in tuber weight per plant was related to tuber growth. A relationship between changes in the plant hormonal status induced by zinc-sulfate and boric-acid treatments and the activity of physiological processes is discussed.     

Kinetics of the Accumulation of Jasmonic Acid and Its Derivatives in Systemic Leaves of Tobacco (Nicotiana tabacum cv. Xanthi nc) and Translocation of Deuterium-Labeled Jasmonic Acid from the Wounding Site to the Systemic Site

In plants, the mobile signal needed for wound-induced systemic acquired resistance (WSR) has been elusive. The signal compound involved in WSR is supposed to be JA or its derivatives. On the basis of kinetic study of the accumulation of JA or its derivatives, it was discovered that JA, JA-Ile, tuberonic acid (TA, 12-OH epi-JA), and tuberonic acid glucoside (TAG) accumulated in systemic tissues in response to mechanical wounding stress in the tobacco plant (Nicotiana tabacum). Attempts to recover deuterium-labeled JA in systemic leaves after feeding the wounded leaves with deuterium-labeled JA were successfully done. It was also found that the translocated deuterium-labeled JA was metabolized to TA in systemic leaves under feeding of deuterium-labeled JA to the wounding leaves.     

The role of salicylic acid and jasmonic acid in pathogen defence

Phytohormones are not only instrumental in regulating developmental processes in plants but also play important roles for the plant's responses to biotic and abiotic stresses. In particular, abscisic acid, ethylene, jasmonic acid, and salicylic acid have been shown to possess crucial functions in mediating or orchestrating stress responses in plants. Here, we review the role of salicylic acid and jasmonic acid in pathogen defence responses with special emphasis on their function in the solanaceous plant potato.     

Effect of Chitosan on Systemic Viral Infection and Some Defense Responses in Potato Plants

The development and the possible mechanism of the chitosan-induced resistance to viral infection were investigated in potato plants. The plants were sprayed with a solution of chitosans (1 mg/ml) with the mol wt of 3, 36, and 120 kD. After 1, 2, 3, or 4 days, the treated leaves were cut off and mechanically infected with the potato virus X (PVX). The disks cut out from the inoculated leaves were used for determining virus accumulation, callose content, and ribonuclease and -1,3-glucanase activities. In another set of experiments, the plants were infected with PVX within 1, 4, or 8 days after chitosan treatment, and the number of systemically infected plants was determined. It was found that, a day after treatment, the plants acquired a resistance to viral infection. The disks from the chitosan-treated leaves, as compared to the control, accumulated less amount of virus. The chitosan treatment also significantly decreased the number of systemically infected plants as compared to the control. After 2–3 days, the resistance disappeared or even gave way to an increased susceptibility to the infection; subsequently, the resistance increased again. The extent of the resistance correlated with the callose content and the level of ribonuclease activity observed on the infection day. The resistance towards the infection with PVX is probably mediated by the callose and ribonuclease induction. The cultivation of test-tube potato plants from the cuttings previously infected with PVX on the chitosan-containing nutrient medium did not eradicate the viral infection from the plants.     

Salicylic Acid and Phenylalanine Ammonia-Lyase in Potato Plants Infected with the Causal Agent of Late Blight

In tuber tissues of potato (Solanum tuberosum L.) infected with an incompatible race of Phytophthora infestans (Mont.) de Bary, the activity of phenylalanine ammonia-lyase and the contents of free and bound salicylic acid (SA) considerably exceeded the corresponding indices in the tissues infected with a compatible race of the oomycete. The accumulation of the free form of SA apparently resulted from both enhanced SA biosynthesis and the liberation from the bound SA forms. SA accumulation in the incompatible host-pathogen combination presumes that SA participated in the local potato resistance to late blight.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 573–577.Original Russian Text Copyright © 2005 by Panina, Gerasimova, Chalenko, Vasyukova, Ozeretskovskaya.     

Growth-Coupled Lipid Synthesis in Mortierella alpina LPM 301, a Producer of Arachidonic Acid

Mortierella alpina LPM 301, a producer of arachidonic acid (ARA), was found to possess a unique property of intense lipid synthesis in the period of active mycelium growth. Under batch cultivation of this strain in glucose-containing media with potassium nitrate or urea, the bulk of lipids (28–35% of dry biomass) was produced at the end of the exponential growth phase and remained almost unaltered in the stationary phase. The ARA content of lipids comprised 42–50% at the beginning of the stationary phase and increased continuously after glucose depletion in the medium due to the turnover of intracellular fatty acids; by the end of fermentation (189–210 h), the amount of ARA reached 46–60% of the total fatty acids (16–19% of dry mycelium). Plausible regulatory mechanisms of the growth-coupled lipid synthesis in microorganisms are discussed.     

Functional Domains within Fusion Proteins: Prospectives for Development of Peptide Inhibitors of Viral Cell Fusion

The entry of enveloped viruses into host cells is accomplished by fusion ofthe viral envelope and target plasma membrane and is mediated by fusionproteins. Recently, several functional domains within fusion proteins fromdifferent viral families were identified. Some are directly involved inconformational changes after receptor binding, as suggested by the recentrelease of crystallographically determined structures of a highly stablecore structure of the fusion proteins in the absence of membranes. However,in the presence of membranes, this core binds strongly to the membrane'ssurface and dissociates therein. Other regions, besides the N-terminal fusionpeptide, which include the core region and an internal fusion peptide inparamyxoviruses, are directly involved in the actual membrane fusion event,suggesting an umbrella like model for the membrane inducedconformational change of fusion proteins. Peptides resembling these regionshave been shown to have specific antiviral activity, presumably because theyinterfere with the corresponding domains within the viruses. Overall, thesestudies shed light into the molecular mechanism of membrane fusion induced byenvelope glycoproteins and suggest that fusion proteins from different viralfamilies share common structural and functional motifs.     

Induced systemic resistance (ISR) against pathogens in the context of induced plant defences

Induced systemic resistance (ISR) of plants against pathogens is a widespread phenomenon that has been intensively investigated with respect to the underlying signalling pathways as well as to its potential use in plant protection. Elicited by a local infection, plants respond with a salicylic-dependent signalling cascade that leads to the systemic expression of a broad spectrum and long-lasting disease resistance that is efficient against fungi, bacteria and viruses. Changes in cell wall composition, de novo production of pathogenesis-related-proteins such as chitinases and glucanases, and synthesis of phytoalexins are associated with resistance, although further defensive compounds are likely to exist but remain to be identified. In this Botanical Briefing we focus on interactions between ISR and induced resistance against herbivores that is mediated by jasmonic acid as a central signalling molecule. While many studies report cross-resistance, others have found trade-offs, i.e. inhibition of one resistance pathway by the other. Here we propose a framework that explains many of the thus far contradictory results. We regard elicitation separately from signalling and from production, i.e. the synthesis of defensive compounds. Interactions on all three levels can act independently from each other.     

Induction of Systemic Acquired Resistance by Heat Shock Treatment in Arabidopsis

A 3,6-di-O-benzylated demethylallosamizoline derivative was glycosylated at the 4-position with an N, N′-diphthaloylchitobiosyl moiety by using the thioglycoside method. After de-protections, the resulting demethylallosamidin-like pseudotrisaccharide was evaluated as an inhibitor against a couple of chitinases.     

Induction of systemic acquired resistance in cotton by BTH has a negligible effect on phytophagous insects

Whether or not chemical changes in plants in response to pests (insects and pathogens) are general or specific remains unclear. Some evidence indicates that an induced response (IR) to arthropods via the octadecanoid pathway represents a distinct mechanism from the salicylic acid-based pathway of systemic acquired resistance (SAR) to pathogens. To further test this hypothesis, young cotton seedlings were activated with benzo (1,2,3) thiadiazole-7-carbothioic acid (S) methyl ester (BTH), an elicitor of SAR. The enzymatic activities of a number of pathogenesis-related (PR) proteins in young and old leaves of control and BTH treated plants were measured. BTH applications elicited marked increases in the activity levels of chitinase, peroxidase, and -1,3-glucanase both locally and systemically. The highest levels of induction were detected systemically in young leaves. Except for some local effects on whitefly oviposition, the induction of SAR by BTH had no effect on either host preference of whiteflies Bemisia tabaci (Gennadius) or on feeding efficiency of cotton bollworms Helicoverpa armigera (Hübner). We conclude that SAR induction via the salicylic acid pathway in Acala cotton has negligible effect on the tested insect herbivores.     

维生素A酸诱导小鼠F9-1胚胎性癌细胞分化过程中蛋白质的变化

本文报道了用双向凝胶电泳和彩色银染技术,分析小鼠F9-1胚胎性癌细胞在维生素A酸诱导分化过程中蛋白质的变化。发现维生素A酸处理细胞72小时后,全细胞蛋白质中有9种蛋白质消失,而新出现11种蛋白质。对细胞核蛋白质进行了双向电泳分析,观察到诱导分化后新出现8种蛋白质,其中有一些与全细胞蛋白质图谱上出现的变化完全对应。对核内低迁移率非组蛋白的分析发现,经维生素A酸处理后,一些低迁移率非组蛋白消失。蛋白质的这些变化可能与维生素A酸诱导细胞分化过程中基因活性的变化有关。     

Effect of Comenic Acid on the Activation of G Proteins by Agonists of Opioid Receptors in Plasma Membranes from the Rat Brain

We studied the effect of comenic acid on transmembrane opioid signaling (in particular, on that mediated by -opioid receptors, with the use of an agonist of these receptors, [D-Ala²]-leucine enkephalin (DALE), and mediated by -opiate receptors, with the use of morphine). It was demonstrated that comenic acid modulates agonist-dependent binding of [³⁵S]GTPS in plasma membranes from the rat brain. The effect of comenic acid on the activation of G proteins via -opioid receptors possessing high affinity for DALE depended on the ion composition of the medium: in the presence of K⁺ the activation decreased, while in the presence of Na⁺ it remained invariable. Under the influence of comenic acid, the agonist-dependent activation of G proteins mediated by receptors with low affinity for DALE was intensified in the presence of both Na⁺ and K⁺. Using morphine, we observed opposite effects: in the presence of Na⁺ or K⁺ comenic acid decreased or increased, respectively, the agonist-dependent activation of G proteins. We suggest that due to the comenic acid-induced modulation the relative intensity of activation of G proteins, which control signal pathways activated by opioid receptors of different types, can be significantly changed.     

Induced Resistance in Cucumbers against Fusarium oxysporum f. sp. cucumerinum and Rhizoctonia solani AG2–2 by Infection of the Cotyledons

Localized infection in cucumber cotyledons with Colletotrichum lagenarium induced resistance against infection after challenge inoculation with Rhizoctonia solani AG2–2 and Fusarium oxysporum f. sp. cucumerinum in the roots. The plants were unprotected in soil that was infested heavily with R. solani or in contact with the mycelium, and induced resistance was not observed. Wounding of the root also negated the effect of induced resistance to F. oxysporum .