Change of Antioxidant Enzyme Activity during Low-Temperature Hardening of Nicotiana tabacum L. and Secale cereale L.

Russian Journal of Plant Physiology - Changes in the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) for the plants Nicotiana tabacum L. and Secale cereale L....     

Processes hindering activation of lipid peroxidation in cold-tolerant plants under hypothermia

The reasons why the rate of lipid peroxidation (POL) associated with a long-term action of low above-zero temperature (5°C, 6 days) on 6-week-old plants of two potato (Solanum tuberosum L.) cultivars (cold-tolerant cv. Desnitsa and less tolerant cv. Desiree) did not rise were investigated. Upon a long-term action of low hardening temperatures on the plants of both cultivars, there was an equilibrium between the rate of generation of superoxide anion (O₂^·− and activity of superoxide dismutase (SOD), which inactivated it with the formation of H₂O₂. Among the enzymes breaking up hydrogen peroxide, the highest activity was observed for guaiacol peroxidases, which was an order of magnitude greater than the activity of catalase. In potato cultivars, POL processes were not considerably activated; however, activities of antioxidant enzymes (SOD, catalase, and guaiacol peroxidases) in cold-tolerant cv. Desnitsa and less tolerant cv. Desiree differed. It was concluded that, upon a long-term action of hardening temperatures, cold-tolerant plants could sup-press POL processes. Moreover, a test for tolerance to damaging temperature (−3°C, 18 h) showed that detected preservation of the prooxidant/antioxidant equilibrium not only maintained vital activities at low above-zero temperatures but also elevated tolerance to short-term frosts, with this adaptability being cultivar-specific.     

Changes in the activity of superoxide dismutase isoforms in the course of low-temperature adaptation in potato plants of wild type and transformed with Δ12-acyl-lipid desaturase gene

We investigated the changes in the total activity of superoxide dismutase (SOD) and the role of its isoforms in hardening potato (Solanum tuberosum L., cv. Desnitsa) plants of wild type and transformed with desA gene of Δ12-acyl-lipid desaturase from Synechocystis sp. PCC 6803. Hydroponically grown 8-week-old plants were exposed for six days to hardening temperature of 5°C. Before chilling, the total SOD activity in the transformed plants was somewhat greater than in the control plants. By the first day of hardening, SOD activity in both potato genotypes rose almost 1.5 times; however, the absolute value of SOD activity was considerably greater in the transformed plants. Subsequently, the total SOD activity in both genotypes decreased and by the end of the 6th day, it almost returned to the initial level. Electrophoretic and inhibitor analyses of potato plants revealed three types of SOD with one isoform of Mn-SOD, four isoforms of Fe-SOD, and two isoforms of Cu/Zn-SOD. In both genotypes, Fe-SOD3 manifested the greatest activity before chilling and in the course of hardening. Such changes in SOD activity corresponded to the rate of generation of superoxide anion radical and elevation of the content of products of peroxide oxidation of lipids (POL). Our data suggest that in the course of hardening of cold-resistant potato plants, the total SOD activity changed mostly due to Fe-SOD3 and to some extent as a result of elevated Cu/Zn-SOD2 activity, which was particularly evident at the beginning of hardening and more pronounced in the transformed plants. We assume that such temporal pattern is related to a greater rate of superoxide anion generation in the transformed plants as compared with control plants.     

The Difference in Low-Temperature Tolerance of Arabidopsis thaliana Plants and Its Ethylene-Insensitive Mutants Is Related to Activities of Antioxidant Enzymes

Russian Journal of Plant Physiology - Arabidopsis thaliana Heynh. (L.) plants of the Columbia ecotype (Col-0) and its ethylene-insensitive etr1-1 (ethylene resistant 1) and ein2-1 (ethylene...     

Activities of Hydrogen Peroxide-Scavenging Enzymes during Low-Temperature Hardening of Potato Plants Transformed by the <Emphasis Type="Italic">desA</Emphasis> Gene of Δ12-Acyl-Lipid Desaturase

Activities of enzymes decomposing hydrogen peroxide (H₂O₂) under long exposure to hardening low temperatures and the effect of Δ12-acyl-lipid desaturase on these processes were studied on potato (Solanum tuberosum L., cv. Desnitsa), which typically represents cold-tolerant plants. We compared nontransformed plants (control) and the line transformed with the construction carrying the target desA gene of the mentioned desaturase from cyanobacterium Synechocystis sp. PCC (desA-licBM3 plants). The plants were hardened at 5°C for six days under illumination of 50 μmol/(m² s). The hardening was found to favor plant tolerance to the subsequent frost, and the desA-licBM3 plants exceed the controls in this property. Of the studied H₂O₂-scavenging enzymes, soluble type III peroxidases (guaiacol peroxidases) displayed the most activity, and type I peroxidase (ascorbate peroxidase) was the least active in the two potato lines over the hardening period. The activity of catalase increased twofold in the control and fourfold in the transformed plants in the first day of the hardening. However, the doubled catalase activity did not appear to compensate the H₂O₂ accumulation over this period. The recorded rise in catalase activity in the desA-licBM3 plants, together with the high activity of guaiacol peroxidases, favored lowering the hydrogen peroxide level in comparison with the initial values. For the first time, electrophoresis revealed two catalase isoforms, CAT1 and CAT2, in leaves of both potato lines. The significance of CAT1 was greater than that of CAT2 in the total catalase activity during the hardening period. It is concluded that, under the long-term cold hardening of potato plants, the content of hydrogen peroxide is determined by highly active guaiacol peroxidases and Class I catalase exerting energy-independent H₂O₂ decomposing. In this case, in the transformants that are rich in membrane lipids, where polyunsaturated fatty acids predominate, the activity of H₂O₂-scavenging enzymes increased significantly more than in the control, which is why the hardening of the transformants is more effective.     

Effect of the <Emphasis Type="Italic">desA</Emphasis> gene encoding Δ12 acyl-lipid desaturase on the chloroplast structure and tolerance to hypothermia of potato plants

Effects of the desA gene from the cyanobacterium Synechocystis sp. encoding Δ12 acyl-lipid desaturase and increasing the level of unsaturated fatty acids (linoleic acid (18:2) primarily) in membrane lipids, which was inserted into potato (Solanum tuberosum L., cv. Desnitsa) plants, on chloroplast ultrastructure and plant tolerance to low temperatures were studied. The main attention was focused on modifications in the chloroplast structure and their possible relation to potato plant tolerance to oxidative and low-temperature stresses under the influence to their transformation with the Δ12 acyl-lipid desaturase gene from cyanobacterium (desA-licBM3-plants). Morphometric analysis showed that, in comparison with wild-type (WT) plants, in desA-licBM3-plants the number of grana in chloroplasts increased substantially. The total number of thylakoids in transformant chloroplasts was almost twice higher than in WT plants. The number of plastoglobules per chloroplast of transformed plants increased by 25%. A marked increase in the number of grana, total number of thylakoids, and the number of plastoglobules in chloroplasts of desA-licBM3-plants indicates their more intense lipid metabolism, as compared with WT plants, and this resulted in the conservation of some part of lipids in plastoglobules. In addition, the expression of heterological desA gene encoding Δ12 acyl-lipid desaturase positively influenced stabilization of not only structure but also functioning of chloroplast membranes, thus preventing a transfer of electrons from the ETR to oxygen and subsequent ROS generation at hypothermia. This was confirmed by the analysis of the rate of superoxide anion generation in tested genotypes.     

Dynamics of human telomerase RNA structure revealed by antisense oligonucleotide technique

Telomeres are the nucleoprotein complexes that cap the linear chromosome ends. Telomerase is a ribonucleoprotein that maintains telomere length in stem, embryonic and cancer cells. Somatic cells don't contain active telomerase and telomere function as mitotic clock and telomere length determines the number of cell divisions. Telomerase RNA (TER) contains the template for telomere synthesis and serves as a structural scaffold for holoenzyme assembly. We compared different oligonucleotide based methods for telomerase RNA inhibition, such as antisense oligonucleotides, knockdown by transient siRNA transfection and silencing by miRNA derived from short expressed RNA hairpin in HEK293 cells. All of these methods were applied to different TER regions. Our results revealed that CR2/CR3 domain of TER is accessible in vitro and in vivo and could serve as an optimal site for oligonucleotide-based telomerase silencing.     

The effect of potato plant transformation with the gene encoding Δ12-acyl-lipid desaturase on the CO2 exchange and activities of antioxidant enzymes under hypothermia

The effects of potato (Solanum tuberosum L., cv. Desnitsa) plant transformation with the desA gene encoding Δ12-acyl-lipid desaturase from Synechocystis sp. PCC 6803 on the regulation of free-radical processes in relation to plant tolerance to hypothermia are considered. It was shown that the content of polyunsaturated fatty acids (PUFA) in transformed plants was higher than in wild-type ones. In particular, the content of linoleic acid in transformants was higher by 35% and the content of linolenic acid was by 41% higher than in untransformed plants. In addition, transformation induced an increase in the absolute content of C₁₆-PUFA and on the whole resulted in a marked accumulation of membrane lipids. As judged from the values of the damage index and the ratio of photosynthesis to respiration in wild-type and transformed plants under cold treatment, these changes in lipid metabolism favored the protection of coupling membranes, thus preventing plants against free-radical oxidation under low-temperature stress. As a result, the intensity of oxidative stress in transformed plants was much lower than in wild-type ones, whereas antioxidant enzymes (superoxide dismutase, catalase, peroxidase) were not substantially activated under hypothermia.     

Role of Fatty Acid ω3 Acyl-Lipid Desaturases in Low-Temperature Hardening of Solanum tuberosum L.

Russian Journal of Plant Physiology - The role of fatty acid ω3 acyl-lipid desaturases in low-temperature hardening (7 days at 3°C) of potato plants (Solanum tuberosum L., cv. Yubilei...     

Changes in Fatty Acid Composition and Lipid Content Occurring in Potato Leaves during Cold Hardening: the Role of ∆12-Acyl-Lipid Desaturase

Russian Journal of Plant Physiology - The qualitative composition and changes in the total fatty acid (FA) content in leaves of wild-type potato (Solanum tuberosum L., cv. Desnitsa) plants and...