Hydrogen peroxide as a signal mediator at inducing heat resistance in wheat seedlings by putrescine

Polyamines are multifunctional stress metabolites of plants. However, information on the effect of exo­genous polyamines on plant resistance to high temperatures is contradictory, and it remains unclear which signal mediators are involved in the realization of their physiological effects. The possible involvement of hydrogen peroxide as a mediator under the action of exogenous diamine putrescine on the resistance of etiolated wheat seedlings (Triticum aestivum L.) to hyperthermia (10-minute heating at 46°C) and the functioning of antioxidant system was investigated. It was established that the treatment of seedlings with putrescine in 0.25–2.5 mM concentrations caused a significant increase in their heat resistance. In response to the putrescine effect, a transient increase in the H2O2 content occurred in the root cells. This effect was eliminated by treatment of seedlings with a diamine oxidase inhibitor aminoguanidine and an NADPH oxidase inhibitor imidazole. These inhibitors, as well as the scavenger of hydrogen peroxide dimethylthiourea (DMTU), mitigated the effects of increased heat resistance of seedlings and increased activity of superoxide dismutase and catalase caused by putrescine. Under the influence of DMTU and imidazole, but not aminoguanidine, the effect of increasing the activity of guaiacol peroxidase in the roots of seedlings treated with putrescine was eliminated. The conclusion was made about the role of hydrogen peroxide and the possible participation of diamine oxidase and NADPH oxidase in its formation during the implementation of the stress-protective effect of putrescine on wheat seedlings

Phenylalanine ammonia-lyase activity and content of flavonoid compounds in wheat seedlings at the action of hypothermia and hydrogen sulfide donor

At present hydrogen sulfide (H2S) is considered as one of the signal mediators in plant cells. However, its role in formation of plant resistance to low temperatures and, in particular, in regulation of secondary metabolism under stress conditions remains poorly understood. The influence of H2S donor sodium hydrosulfide (NaHS) on phenylalanine ammonia-lyase (PAL) activity and content of flavonoids in wheat seedlings at normal temperature (21 °C) and under cold hardening conditions (7 days at 3 °C) was studied. After 2 days of the hardening temperature, a transient increase in PAL activity was noted. Also, activity of the enzyme was increased by treatment of plants with 0.1 or 0.5 mM NaHS under normal temperature conditions and especially at the background of cold hardening. By themselves, the cold hardening and the action of H2S donor caused an increase in total content of flavonoids and amount of anthocyanins. With the combination of hypothermia and treatment of seedlings with NaHS, this effect enlarged and the total content of flavonoids increased by 3.8, and anthocyanins increased by 1.8 times in comparison to the control. Treatment with the H2S donor caused a decrease in content of the lipid peroxidation product malonic dialdehyde in seedlings after the action of hardening temperature, and especially after their freezing at –5 °C. Also, under the influence of NaHS, survival of hardened and unhardened seedlings after cryostress increased. It was concluded that one of the mechanisms of the positive influence of the H2S donor on resistance of wheat seedlings to hypothermia is the PAL-dependent accumulation of flavonoid compounds, which have a high antioxidant activity, and a decrease in effects of secondary oxidative stress

Three-loop verification of a new algorithm for the calculation of a β\beta-function in supersymmetric theories regularized by higher derivatives for the case of N=1{\cal N}=1 SQED

We verify a recently proposed method for obtaining a $\beta$-function of ${\cal N}=1$ supersymmetric gauge theories regularized by higher derivatives by an explicit calculation. According to this method, a $\beta$-function can be found by calculating specially modified vacuum supergraphs instead of a much larger number of the two-point superdiagrams. The result is produced in the form of a certain integral of double total derivatives with respect to the loop momenta. Here we compare the results obtained for the three-loop $\beta$-function of ${\cal N}=1$ SQED in the general $\xi$-gauge with the help of this method and with the help of the standard calculation. Their coincidence confirms the correctness of the new method and the general argumentation used for its derivation. Also we verify that in the considered approximation the NSVZ relation is valid for the renormalization group functions defined in terms of the bare coupling constant and for the ones defined in terms of the renormalized coupling constant in the HD+MSL scheme, both its sides being gauge-independent.Comment: 19 pages, 8 figures; title changed, minor corrections; the final version to appear in Nuclear Physics

ИНДУЦИРОВАНИЕ СОЛЕУСТОЙЧИВОСТИ 24-ЭПИБРАССИНОЛИДОМ ПРОРОСТКОВ ПРОСА (Panicum miliaceum) С УЧАСТИЕМ АКТИВНЫХ ФОРМ КИСЛОРОДА

The treatment of millet seedlings with 24-epibrassinolide (24-EBL) was shown to cause a transient increase in their hydrogen peroxide content, the subsequent activation of antioxidant enzymes (superoxide dismutase, catalase, guaiacol peroxidase) and the development of their resistance to salt stress. Antioxidant dimethylthiourea and NADPH oxidase inhibitor imidazole leveled these processes. It was concluded that the induction of millet salt tolerance by exogenous 24-EBL was mediated by the enhancement of reactive oxygen species level associated with the increased activity of NADPH oxidase.Показано, что обработка проростков проса 24-эпибрассинолидом (24-ЭБЛ) вызывала транзиторное увеличение в них содержания пероксида водорода, последующую активацию антиоксидантных ферментов (супероксиддисмутазы, каталазы, гваяколпероксидазы) и развитие устойчивости к солевому стрессу. Антиоксидант диметилтиомочевина и ингибитор НАДФН-оксидазы имидазол нивелировали эти процессы. Сделано заключение, что индуцирование солеустойчивости проса экзогенным 24-ЭБЛ опосредовано усилением генерации активных форм кислорода, связанным с повышением активности НАДФН-оксидазы

Reactive oxygen species and stress signaling in plants

Data on the basic processes and the compartments, involved in formation of reactive oxygen species (ROS) in plant cells, are generalised. The features of structure and regulation of NADPH-oxidase as the one of main enzymatic producers of ROS are characterized. The two-component histidine kinases, ROS-sensitive transcript-factors, ROS-sensitive protein kinase and redox-regulated ionic channels are discussed as the possible sensors of redox-signals in plant cells. The interaction between ROS and other signal mediators, in particular nitric oxide and calcium ions, is discussed. The ROS role as the signal mediators in the development of plant resistance to hyperthermia, osmotic shock and other abiotic stressors is analyzed

Signal mediators at induction of heat resistance of wheat plantlets by short-term heating

The effects of functional interplay of calcium ions, reactive oxygen species (ROS) and nitric oxide (NO) in the cells of wheat plantlets roots (Triticum aestivum L.) at the induction of their heat resistance by a short-term influence of hyperthermia (heating at the temperature of 42 °С during 1 minute) have been investigated. The transitional increase of NO and H2O2 content, invoked by heating, was suppressed by the treatment of plantlets with the antagonists of calcium EGTA (chelator of exocellular calcium), lanthanum chloride (blocker of calcium channels of various types) and neomycin (inhibitor of phosphatidylinositol-dependent phospholipase C). The rise of hydrogen peroxide content, caused by hardening, was partially suppressed by the action of inhibitors of nitrate reductase (sodium wolframate) and NO-synthase (NG-nitro-L-arginine methyl ester – L-NAME), and the increasing of nitric oxide content was suppressed by the treatment of plants with the antioxidant ionol and with the scavenger of hydrogen peroxide (dimethylthiourea). These compounds and antagonists of calcium also partially removed the effect of the rise of plantlets’ heat resistance, invoked by hardening heating. The conclusion on calcium’s role in the activation of enzymatic systems, generating reactive oxygen species and nitric oxide, and on the functional interplay of these signal mediators at the induction of heat resistance of plantlets by hardening heating is made

Induction of plant cells heat resistance by hydrogen sulfide donor is mediated by H(2)O(2) generation with participation of NADPH oxidase and superoxide dismutase

The participation of enzymatic systems carrying out generation and conversion of reactive oxygen species (ROS), in realization of the stress-protective effect of hydrogen sulfide (H2S) on wheat coleoptile cells was investigated. It has been shown that the treatment of isolated coleoptiles with a 100 μM hydrogen sulfide donor sodium hydrosulfide (NaHS) caused a transient enhancement of the generation of superoxide anion radical (O2•–), an increase of hydrogen peroxide content and superoxide dismutase (SOD) activity in them. The increase in ROS generation was eliminated by the inhibitor of NADPH oxidase imidazole, but not by the peroxidase inhibitor sodium azide. Treatment of coleoptiles with SOD inhibitor sodium diethyldithiocarbamate (DDC) enhanced the generation of O2•– and neutralized the effect of increasing H2O2 content induced by NaHS. One day after treatment with the H2S donor, the generation of ROS decreased to a control level, while the activity of antioxidant enzymes increased markedly and the resistance of coleoptiles to damaging heating­ was increased. These effects of the hydrogen sulfide donor were eliminated by coleoptiles’ treatment with inhibitors of NADPH oxidase (imidazole) and SOD (DDC). It was concluded that both NADPH oxidase, genera­ting O2•– , and SOD, which turns it into H2O2 performing signaling functions, are involved in the formation of a signal that induces protective systems and causes an increase in heat resistance of plant cells

Використання методу чисельно-асимптотичного наближення для дослідження процесу взаємодії β⁻-випромінювання з лінійними гнучколанцюговими полімерами

An algorithm for asymptotic approximation of the solution to one class of model nonlinear singularly-perturbed boundary problems in radiation physics of spatially-nonuniform linear flexible-chain polymer systems has been constructed. The obtained numerical data on the interaction of β⁻-radiation with polyvinylchloride are presented.Построен алгоритм асимптотического приближения решения одного класса модельных нелинейных сингулярно возмущенных краевых задач радиационной физики пространственно-неоднородных линейных гибкоцепных полимерных систем. Приведены результаты численных исследований взаимодействия β⁻-излучения с поливинилхлоридом.Побудовано алгоритм асимптотичного наближення розв’язку одного класу модельних нелінійних сингулярно збурених крайових задач радіаційної фізики просторово-неоднорідних лінійних гнучколанцюгових полімерних систем. Наведено результати чисельних досліджень взаємодії β⁻‑випромінювання з полівінілхлоридом

State of enzymatic antioxidative system and heat resistance of wheat plantlets treated by combination of 24-epibrassinolide and NO donor

The influence of 24-epibrassinolide (24-EBL) and nitric oxide donor sodium nitroprusside (SNP) on the state of antioxidative system and heat resistance of wheat (Triticum aestivum L.) plantlets has been investigated. The treatment with 24-EBL (20–200 nM) or with SNP (0.1–2.0 mM) increased the survival of plantlets after 10-min damaging heating at 46 °C in the water thermostat. The cotreatment with 20 nM of 24-EBL and 0.2 mM of SNP caused more essential protective influence in comparison with the treatment by each compound separately. At the same time, joint influence of high concentrations (200 nM of 24-EBL and 2 mM of SNP) reduced the heat resistance of plantlets. Under the influence of 24-EBL and SNP in concentrations that have protective effect, as well as their combinations, the activity of superoxide dismutase (SOD) in roots increased. After damaging heating, the highest value of SOD activity remained in the variant with cotreatment of plantlets with 20 nM of 24-EBL and 0.2 mM of SNP. The activity of catalase and guaiacol peroxidase (GPX) in plantlets roots increased under the influence of various concentrations of SNP and its combinations with 24-EBL. At the same time, 24-EBL alone did not exert the impact on the catalase activity and caused the decrease in GPX activity. The activity of these enzymes decreased in all variants of experiment after heating. The heat stress caused the increase in the content of lipid peroxidation product malonic dialdehyde. The treatment of plantlets with 24-EBL and also its combination with SNP in low concentrations removed this effect, but in high concentrations, on the contrary, increased it. The conclusion was made that intensifying of protective influence of 24-EBL and SNP on wheat plantlets at their combined application in low concentrations is substantially caused by stabilization of pro-/antioxidative balance

State of antioxidant system in triticale seedlings at cold hardening of varieties of different frost resistance

Efect of cold hardening on state of antioxidant system (AOS) of triticale (×Triticosecale Wittmack) seedlings of varieties, difered in frost resistance, namely Buket and Raritet (winter, high-frost-resistant), and Alexandra and Pidzymok Kharkovskiy (facultative, less resistant) was studied. In absence of cold hardening, a clear connection between studied indicators of the AOS state and frost resistance of the varieties was not observed. After hardening of seedlings at 2–4 °C for 6 days, the activity of superoxide dismutase (SOD) and catalase increased in the high-frost-resistant varieties Buket and Raritet. In less resistant ones—Alexandra and Pidzymok Kharkovskiy—the activity of these enzymes changed less signifcantly. At the same time, the activity of guaiacol peroxidase increased more noticeably after hardening in these varieties. Hardened seedlings of the Buket, Raritet and Alexandra varieties had signifcantly higher sugar content than the Pidzymok Kharkovskiy. The proline content in response to cold hardening increased in all varieties, while the absolute values in the varieties Buket, Raritet and Pidzymok Kharkovskiy were signifcantly higher than in the Alexandra. Cold hardening caused a signifcant increase in the content of anthocyanins and favonoids, absorbing in UV-B, in the Buket, Raritet and Alexandra, but not in the Pidzymok Kharkovskiy. The content of lipid peroxidation product malondialdehyde after a 6-h damaging action of −7 °C increased in the varieties Alexandra and Pidzymok Kharkovskiy and slightly changed in the Buket and Raritet. In general, a positive relationship was found between AOS activity and frost resistance of hardened triticale seedlings. This relationship was most clearly manifested for indicators of SOD activity and favonoid content