Increasing climatic instability, along with increasing technogenic pressure on the natural environment, necessitate the search for new approaches to increasing the resistance of wheat to abiotic factors, primarily to low temperature. A promising direction is the use of metal nanoparticles, which have the ability to positively influence plant metabolism in low concentrations. Due to their small size (less than 100 nm) and special physicochemical, optical, and electrical properties, nanoparticles penetrate cellular barriers, spread throughout the plant organism, affecting almost all processes in it. With wheat as an example (Triticum aestivum L., variety Zlata), it was shown for the first time that gold nanoparticles (GNPs) can act as adaptogens, increasing the cold resistance of plants. The study used priming—soaking of seeds in GNP solutions with concentrations 5–50 μg/mL for 24 h. The plants grown from seeds treated with GNPs differed from the control (untreated) ones in a number of physiological, biochemical, and molecular genetic parameters. Their growth processes and activity of the photosynthetic apparatus were significantly enhanced, and the expression of genes encoding large (rbcL) and small (rbcS) Rubisco subunits, as well as COR genes, Wcor726 and Wcor15, were increased. Moreover, wheat plants obtained from GNP-treated seeds differed from control ones in their increased resistance to low temperatures, and the effect was manifested both under control conditions and after low-temperature hardening. Concentration tests showed that the maximum effect was achieved when using GNPs at a concentration of 10 μg/mL. It is concluded that GNPs are able to influence plant metabolism and the expression of stress response genes, which leads to a significant increase in cold resistance. Possible mechanisms of GNP action on low temperature resistance are discussed.

Changes in the ultrastructural organization of mesophyll cells during low-temperature adaptation (4°C, 7 days) were studied on seedlings of a frost-resistant variety of winter wheat ( Triticum aestivum L.). It was found that, under the influence of low hardening temperature, wheat leaf cells increased in size, while the area of the cytoplasm increased and the size of the vacuole decreased. The electron density of the cytoplasm visually increased, and numerous vesicles appeared in it. In addition, the size of chloroplasts, as well as the number of chloroplasts, mitochondria, and peroxisomes per unit area of a cell section, increased. Accumulations of mitochondria and peroxisomes in the form of chains were noted near chloroplasts in the cells of hardened seedlings, and the mitochondria themselves changed their shape from round to elongated or dumbbell-shaped. The low temperature also affected the shape of chloroplasts, which became more rounded from lenticular, and outgrowths (stromules) were found in them. Significant changes under the influence of low temperature occurred in the ultrastructure of chloroplasts: the number and size of plastogbules increased; starch inclusions completely disappeared; the number of grana, the average number of thylakoids per grana, the height and area of the grana, the density of photosynthetic membranes in the chloroplast, and the index of grana stacking (ratio length of appressed membranes to the length of non-appressed membranes) decreased. At the same time, in the process of low-temperature hardening, an increased frost resistance of wheat was formed, which was analyzed by the survival rate of seedlings and the release of electrolytes from leaf tissues after testing freezing. The relationship between the found structural transformations in wheat leaf cells and functional and physiological-biochemical changes occurring in cold-tolerant plants in the process of low-temperature adaptation is shown. It is assumed that the observed ultrastructural reorganization of cells is one of the important components in a complex adaptation program as well as a link necessary for the formation of increased resistance of winter cereals to low temperatures.

The review is focused on a comparative analysis of the literature data on the ultrastructural reorganization of leaf cells of higher plants, which differ in their response to low sub-damaging temperatures. The importance of adaptive structural reorganization of cells as a special feature contributing to the surviving strategy of plants existing under changed conditions is emphasized. The adaptive strategy of cold-tolerant plants combines the structural, functional, metabolic, physiological and biochemical reorganization of cells and tissues. These changes constitute a unified program directed to protecting against dehydration and oxidative stress, as well as maintaining basic physiological processes, and above all, photosynthesis. The ultrastructural markers of coldtolerant plants adaptation to low sub-damaging temperatures include some particular changes in cell morphology. Namely: the following: an increase in the volume of the cytoplasm; the formation of new membrane elements in it; an increase in the size and number of chloroplasts and mitochondria; concentration of mitochondria and peroxisomes near chloroplasts; polymorphism of mitochondria; an increase in the number of cristae in them; the appearance of outgrowths and invaginations in chloroplasts; lumen expansion in the thylakoids; the formation in chloroplasts "sun type" membrane system with reduction in the number and size of grana and domination of non-appressed thylakoids membranes. Due to this adaptive structural reorganization cold-tolerant plants are able to function actively during chilling. On the contrary, structural reorganization of leaf cells of coldsensitive plants under chilling is aimed at maintaining the basic functions at a minimum level. Cold-sensitive plants "wait out" low temperature stress, and with prolonged exposure to cold, they die from dehydration and intensification of oxidative stress.

It was shown for the first time that the treatment of winter wheat ( Triticum aestivum L.) seeds with gold nanoparticles (average diameter 15.3 nm; solution concentration 20 μg/mL) increases plant tolerance to low temperature. It was found that an increase in tolerance under the influence of nanoparticles is accompanied by a number of changes depending on temperature conditions. In optimal temperature conditions, gold nanoparticles stimulated plant growth and the activity of the photosynthetic apparatus, whereas in conditions of low-temperature hardening (2°C, 7 days) they inhibited growth but maintained photosynthetic activity, contributing to the accumulation of soluble sugars (cryoprotectants) in the leaves. It is concluded that gold nanoparticles can be considered as adaptogens that increase plant tolerance to low temperatures; however, their effectiveness in this role and the subtle mechanisms of action require further study.

The effects of gold nanoparticles (GNPs) on the redox status and freezing tolerance of wheat seedlings were studied. Here we show that treatment of winter wheat seedlings (Triticum aestivum L., var. Moskovskaya 39) with GNPs via their roots increased freezing tolerance by affecting the redox status of plants. Based on the assays with colloidal solutions of gold nanospheres (diameter 15 nm, concentrations of 5, 10, 20, and 50 μg ml−1), a GNPs concentration of 20 μg ml−1 had the most pronounced beneficial effect on the growth and survival rate (after freezing at – 3 °C for 24 h) of the seedlings. The indices of the intensity of peroxide processes, general antioxidant activity and the content of photosynthetic pigments in wheat leaves in seedlings treated with GNPs were evaluated. The possibility of GNPs to affect the redox status of plants is discussed.

The activity of natural 5,6-Dihydroxy-eicosatetraenoic acid (5,6-DiHETE; 2 isomers), 5S,15S-DiHETE, 8S,15S-DiHETE, 5S,12S-DiHETE, delta 6-trans-leukotriene B4, 12-epi-delta 6-trans-leukotriene B4, omega-hydroxy-leukotriene B4, omega-carboxy-leukotriene B4, 15S-hydroxyeicosatetraenoic acid (15S-HETE), 12S-HETE, 5S-HETE and 12S-hydroxy-heptadecatrienoic acid was compared to LTB4 on the guinea-pig lung parenchymal strip and on the release of prostaglandins and thromboxanes by the perfused guinea-pig lungs. The omega-hydroxy-LTB4 appeared more potent than LTB4 both for inducing a contraction and for releasing prostanoids whereas the omega-carboxy-LTB4 was much less active on the parenchyma and did not release prostanoids at the dose used. All other hydroxy acids tested were either very weakly active or inactive in the two systems used with the exception of the 5,6-DiHETEs which showed significant activity. These di-hydroxy acids induced contractions of the lung parenchymal strip which could be blocked by FPL-55712 but were inactive on the guinea-pig ileum. The 5S-HETE, 12S-HETE and 15S-HETE were also tested for possible myotropic activity on selected smooth muscle preparations. Our results provide further informations on the structural requirements for LTB4 (and other hydroxy acids) actions on the guinea-pig lungs.

Gold nanoparticles are widely used in a variety of biomedical practice. In this chapter we discuss the properties of gold nanoparticles, the main methods of their synthesis, possible routes of uptake and translocation within a plant and some effects on the plants. The influence of gold nanoparticles on plants depends on many factors: size and concentration of gold nanoparticles, plant species and experimental conditions. The data obtained suggest that a coordinated research program is required to study correlations between particle parameters, experimental design, and the observed biological effects. As it was shown in numerous works, gold nanoparticles affect the growth rate and water metabolism, the activity of the photosynthetic apparatus and antioxidant system as well as the level of expression of some genes which are important for the functioning of higher plants both under optimal and unfavorable conditions. It is concluded that gold nanoparticles might be recommended for usage not only as stimulators of growth and development, but also as adaptogens that increase the tolerance of plants to various adverse effects.

The intensive development of nanotechnology led to the widespread application of various nanoparticles and nanomaterials. As a result, nanoparticles enter the environment and accumulate in ecosystems and living organisms. The consequences of possible impact of nanoparticles on living organisms are not obvious. Experimental data indicate that nanoparticles have both toxic and stimulating effects on organisms. In this study, we demonstrated for the first time that gold nanoparticles can act as adaptogens increasing plant freezing tolerance. Priming winter wheat (Triticum aestivum L., var. Moskovskaya 39, Poaceae) seeds for 1 day in solutions of gold nanoparticles (15-nm diameter, concentrations of 5, 10, 20, and 50 µg/ml) led to an increase in freezing tolerance of 7-day-old wheat seedlings. A relationship between an increase in wheat freezing tolerance and changes in some important indicators for its formation-growth intensity, the activity of the photosynthetic apparatus and oxidative processes, and the accumulation of soluble sugars in seedlings-was established. Assumptions on possible mechanisms of gold nanoparticles effects on plant freezing tolerance are discussed.

This review deals with the influence of gold nanoparticles on physiological processes (responses) in higher plants. Gold nanoparticles can affect a lot of processes in the plant organism, including growth rate, parameters of water exchange, activity of the photosynthetic apparatus and the antioxidant system, and expression of some genes important for the functioning of plants under optimal and adverse conditions, which was shown in plants belonging to different taxonomic groups. Analysis of literature data suggests that gold nanoparticles may be used not only as stimulators of growth and development but also as adaptogens improving plant resistance to various adverse influences.

— A comparative survey of the published data concerning the effects of the most frequently used metal nanoparticles and their oxides on the main parameters of the photosynthetic apparatus activity and the chloroplast ultrastructure of higher plants is presented. It is demonstrated that metal nanoparticles are capable of both stimulating and suppressing activities towards the photosynthetic apparatus. Possible mechanisms of the effects of metal nanoparticles on the plant organism are discussed.

Arabidopsis thaliana Heynh . (L.) plants of the Columbia ecotype (Col-0) and its ethylene-insensitive etr1-1 (ethylene resistant 1) and ein2-1 (ethylene insensitive 2) mutants were studied. The plants were compared in respect to their cold tolerance conferred by cold acclimation. The tolerance to negative temperature increased in all the three genotypes after 5-day cooling of the plants at 2°C. Meanwhile, a quantitative difference was observed between them: the Col-0 plants survived better than the mutants, and the electrolyte leakage from the tissues reached 50% at higher (by 1°C and more) temperature in the hardened mutants than in the Col-0. Only the mutants manifested the increased lipid peroxidation over the hardening period; this indicates ROS production and general oxidative stress. From this point, we speculated that the tested Arabidopsis genotypes are different in the efficiency of their antioxidant systems. For testing, the total activities of the chief antioxidant enzymes superoxide dismutase (SOD) and catalase, including their isoenzymes, were monitored in the course of hardening. The total SOD activity was found to be lower in the mutants than in the Col-0 both at the normal growing temperature and over the whole time of the cold hardening. The isozyme analysis revealed the link of the reduced total SOD activity of the mutants with the reduced activity of their Cu/Zn-SOD isoforms at 22°C and at the beginning of the hardening. This relationship was supported by the lower relative content of the CSD1 and CSD2 gene transcripts of Cu/Zn-SOD in the mutants in comparison with the Col-0. The decrease in the total catalase activity was also observed and would be ascribed to the lowered activity of the CAT2 isoform. The reported results evidence to the principal feasibility of the ethylene signaling control of the Cu/Zn-SOD and catalase activities associated with the cold acclimation of Arabidopsis .

Recent studies indicate direct links between molecular cell cycle and cell differentiation machineries. Ethylene and abscisic acid (ABA) are known to affect cell division and differentiation, but the mechanisms of such effects are poorly understood. As ethylene and ABA signaling routes may interact, we examined their involvement in cell division and differentiation in cell tissue cultures derived from several Arabidopsis thaliana plants: wild type (Col-0), and ethylene-insensitive mutants etr1-1, ctr1-1, and ein2-1. We designed an experimental setup to analyze the growth-related parameters and molecular mechanisms in proliferating cells upon short exposure to ABA. Here, we provide evidence for the ethylene–ABA signaling pathways’ interaction in the regulation of cell division and differentiation as follows: (1) when the ethylene signal transduction pathway is functionally active (Col-0), the cells actively proliferate, and exogenous ABA performs its function as an inhibitor of DNA synthesis and division; (2) if the ethylene signal is not perceived (etr1-1), then, in addition to cell differentiation (tracheary elements formation), cell death can occur. The addition of exogenous ABA can rescue the cells via increasing proliferation; (3) if the ethylene signal is perceived, but not transduced (ein2-1), then cell differentiation takes place—the latter is enhanced by exogenous ABA while cell proliferation is reduced; (4) when the signal transduction pathway is constitutively active, the cells begin to exit the cell cycle and proceed to endo-reduplication (ctr1-1). In this case, the addition of exogenous ABA promotes reactivation of cell division.

Arabidopsis thalianaHeynh.(L.) plants of the Columbia ecotype (Col-0) and its ethylene-insensitiveetr1-1(ethylene resistant 1) andein2-1(ethylene insensitive 2) mutants were studied. The plants were compared in respect to their cold tolerance conferred by cold acclimation. The tolerance to negative temperature increased in all the three genotypes after 5-day cooling of the plants at 2 degrees C. Meanwhile, a quantitative difference was observed between them: the Col-0 plants survived better than the mutants, and the electrolyte leakage from the tissues reached 50% at higher (by 1 degrees C and more) temperature in the hardened mutants than in the Col-0. Only the mutants manifested the increased lipid peroxidation over the hardening period; this indicates ROS production and general oxidative stress. From this point, we speculated that the testedArabidopsisgenotypes are different in the efficiency of their antioxidant systems. For testing, the total activities of the chief antioxidant enzymes superoxide dismutase (SOD) and catalase, including their isoenzymes, were monitored in the course of hardening. The total SOD activity was found to be lower in the mutants than in the Col-0 both at the normal growing temperature and over the whole time of the cold hardening. The isozyme analysis revealed the link of the reduced total SOD activity of the mutants with the reduced activity of their Cu/Zn-SOD isoforms at 22 degrees C and at the beginning of the hardening. This relationship was supported by the lower relative content of theCSD1andCSD2gene transcripts of Cu/Zn-SOD in the mutants in comparison with the Col-0. The decrease in the total catalase activity was also observed and would be ascribed to the lowered activity of the CAT2 isoform. The reported results evidence to the principal feasibility of the ethylene signaling control of the Cu/Zn-SOD and catalase activities associated with the cold acclimation ofArabidopsis.

The problem of the survival of plants under low temperatures becomes more relevant in the light of global climate change and the growing needs of the population. In this regard, studies of the impact of hypothermia on plants are not only fundamental, but also applied. Potatoes are an important food crop, ranking fourth in the world in terms of growing. The actual yield of potatoes is significantly lower than its potential productivity, and one of the limiting factors is the lack of resistance of many modern varieties to spring frosts. Decoding of the potato genome made it possible to use advances in molecular biology to study the role of individual genes and identify key proteins that can increase resistance to low temperature. It is widely known that under the action of low temperatures, there is a phase transition of membrane lipids, which is accompanied by a decrease in membrane fluidity and loss of their barrier properties and, as a result, by inactivation of enzymes. In response to changes in physical properties of membranes, cells activate protection systems, among which an important role is played by the cold-induced increase in the degree of unsaturation of fatty acids of membrane lipids. Therefore, one of the main goals of adaptation is the stabilization of membranes, for example, due to the work of enzymes, fatty acid desaturase (encoded by genes FAD), catalyzing the conversion of saturated fatty acids (FA) into unsaturated. Among all plant cell membranes, chloroplast membranes play a special role in the formation of plant resistance to low temperatures, since it is in chloroplasts that photosynthesis, the main source of energy necessary for the restructuring of metabolism during the adaptation period, takes place. The aim of the research was to study the role of chloroplast localized Delta 9-, Delta 12 - and omega 3(Delta 15)-desaturases in adaptive transformations of the fatty acid composition of chloroplast membranes when forming potato plant cold resistance during hardening. The object of the study was potato plants (Solanum tuberosum L., cultivar Jubilee Zhukov), 3 weeks of age, grown in soil culture at a temperature of 22 degrees C, illumination of 100 mu mol/(m(2) c) and 16-h photoperiod. Hardening of plants was carried out in the climatic chamber KBW-240 "Binder" (Germany) under 16-h photoperiod and illumination of 100 mu mol/(m(2)c) at a temperature of 3 degrees C for 7 days. Controls were nonhardened plants. To assess the effectiveness of adaptation, whole plants were frozen at a temperature of 2 degrees C for 18 hours in the climatic chamber MIR-153 "Sanyo" (Japan), and then transferred to the growing conditions to determine survival. The following genes of FA desaturases were selected for the study: SAD (encodes one of the soluble Delta 9-ACP-), FAD6 (encodes membrane-bound acyl-lipid Delta 12-), FAD7 (encodes membrane- bound acyl-lipid Delta 15(omega 3)-desaturase). Protein products of these genes are localized in chloroplasts. Total RNA from leaves was isolated using Spectrum Plant Total RNA Kit "Sigma" (USA). The reverse transcription reaction was performed using a set of reagents and the Protocol MMLV RT Kit "Eurogen" (Russia). The resulting cDNA was used for real-time PCR (q-PCR) using the amplifier CFX96 Touch Real-Time PCR Detection System "Bio-Rad" (USA), using a set of reagents qPCRmix-HS SYBR kit "Eurogen" (Russia). The relative transcript content was calculated by calculating the normalized expression (Delta Delta C-T). Primers for the genes of FA desaturases were selected using the database NCBI and Internet resource Primer3Plus. Intact chloroplasts were isolated by centrifugation in a percol step gradient. Chloroplast lipids were methylated by boiling in a mixture of CH3OH and CH3COCl. The obtained LC methyl esters were analyzed by GL-MS using Agilent 7890A GC (USA). The experiments were conducted in 5-6 biological replicates and 3-4 analytical ones. Statistical data processing was performed using the program SigmaPlot 11. The data are presented as means and their standard errors. We showed that the hardened potato plants survived after -2 degrees C for 18 h, which indicates the successful hardening of S. tuberosum, Jubilee Zhukov cultivar (See Fig. 1). Among the studied genes Delta 9-, Delta 12- and omega 3-desaturases of chloroplasts, a short-term (after 2 h of adaptation) increase in the transcripts of the FAD6 gene encoding acyl-lipid Delta 12-desaturase was found. The relative content of FAD7 gene transcripts encoding omega 3-desaturase remained stable and maintained at the level of control. The character of SAD gene expression encoding Delta 9-ACP desaturase differed from the others: the relative transcript content decreased during adaptation (See Fig. 2). It should be noted that potatoes have 13 soluble Delta 9-ACP-desaturase genes forming the first double bond, whose proteins are localized in the stroma of chloroplasts. Perhaps, the studied gene is not cold-inducible. The total percentage of polyunsaturated fatty acids (PUFA) of lipids in chloroplasts of potato was high and constitutive in non-hardened plants accounted for almost 90% of the total content of all FA (See Table). Probably, therefore, in the process of adaptation there was no noticeable increase in the relative content of the transcripts of the studied genes Delta 12- and omega 3-desaturases of chloroplasts. During the period of low-temperature hardening, the part of PUFA, and especially alpha-linolenic acid, was maintained at a high level; there was an increase in the content of palmitic acid, which may indicate an increase in the intensity of synthesis of FA de novo. In addition, an increase in the content of C-16(:1) (Delta 7) acid was observed, which is also important for adaptation. It is known that the fluidity of membranes with decreasing temperature is determined not only by the content of FA with a larger number of double bonds, but also by the content of FA with a smaller number of carbon atoms. Maintaining a high amount of PUFA helped to maintain the thylakoid membranes of chloroplasts in a functional state during the hardening process, which, in turn, allowed the potato plants to realize other processes of adaptation.