Role of Plant Carbonic Anhydrases under Stress Conditions

Carbonic anhydrases (CAs) are enzymes catalyzing the reversible hydration of carbon dioxide with the generation of protons and bicarbonate. The components of the reaction are involved in almost all metabolic processes in higher plants and algae, maintaining the balance of electrolytes and pH, gluconeogenesis, lipogenesis, ethylene synthesis, and others. The CAs may take part in transmitting signals to activate cascades of protective response genes. Our findings reveal significant changes in the content of carbonic anhydrase gene transcripts in response to changes in environmental conditions. Here we discuss the functions of CAs located in the plasma membrane, chloroplast envelope, chloroplast stroma, and in thylakoids in plant protection under stress conditions, such as high illumination, low and high concentration of carbon dioxide in the environment, drought, and salinity

Comparison of the Functional Activities of Xanthine Oxidases Isolated from Microorganisms and from Cow’s Milk

© 2018, Pleiades Publishing, Inc. The characteristics of the formation of the superoxide radical anion (O2∙−) and hydrogen peroxide by xanthine oxidases isolated from microorganisms and from cow’s milk were investigated. The increase in pH led to an increase in the rate of xanthine oxidation with oxygen by both xanthine oxidases. The functioning of xanthine oxidase from milk along with the two-electron reduction of O2 to H2O2 carries through the one-electron reduction of O2 to O2∙−, and the rate and the fraction of generation of O2∙− increased with increasing pH. Under operation of the microbial xanthine oxidase, the O2∙− radical was not detected in the medium. The results suggest a difference in the operation of active centers of enzyme from different sources

Ways to Protect People in Emergency Situations

В данной статье рассмотрены актуальные проблемы увеличения роста чрезвычайных происшествий, проанализированы методы и способы защиты людей от опасных катастроф, которые имеют большое влияние на здоровье.This article discusses the current problems of increasing the growth of emergencies, analyzes methods and methods of protecting people from dangerous disasters that have a great impact on health

Photosynthetic Antenna Size Regulation as an Essential Mechanism of Higher Plants Acclimation to Biotic and Abiotic Factors: The Role of the Chloroplast Plastoquinone Pool and Hydrogen Peroxide

The present chapter describes the mechanisms of reactive oxygen species formation in photosynthetic reactions and the functional significance of reactive oxygen species as signal messengers in photosynthetic cells of plants. Attention is given to the acclimation mechanisms of higher plants to abiotic and biotic factors such as increased light, drought, soil salinity and colonization of plants by rhizosphere microorganisms. Special attention is paid to the reactions of reactive oxygen species with the components of the chloroplasts plastoquinone pool leading to production of hydrogen peroxide as a signal molecule, which is involved in acclimation of plants to these stress conditions. The chapter also presents the data demonstrating that regulation of the size of the light-harvesting antenna of photosystem II is one of the universal mechanisms of the structural and functional reorganization of the photosynthetic apparatus of higher plants exposed to the abiotic and biotic factors. These data were obtained for both model Arabidopsis (Arabidopsis thaliana) plants as well as for agricultural barley (Hordeum vulgare) plants. It is hypothesized that hydrogen peroxide, produced with involvement of the plastoquinone pool components, plays the role of a signaling molecule for regulation of the photosystem II antenna size in higher plants when environmental conditions change

Photosynthesis-dependent H₂O₂ transfer from chloroplasts to nuclei provides a high-light signalling mechanism

Chloroplasts communicate information by signalling to nuclei during acclimation to fluctuating light. Several potential operating signals originating from chloroplasts have been proposed, but none have been shown to move to nuclei to modulate gene expression. One proposed signal is hydrogen peroxide (H2O2) produced by chloroplasts in a light-dependent manner. Using HyPer2, a genetically encoded fluorescent H2O2 sensor, we show that in photosynthetic Nicotiana benthamiana epidermal cells, exposure to high light increases H2O2 production in chloroplast stroma, cytosol and nuclei. Critically, over-expression of stromal ascorbate peroxidase (H2O2 scavenger) or treatment with DCMU (photosynthesis inhibitor) attenuates nuclear H2O2 accumulation and high light-responsive gene expression. Cytosolic ascorbate peroxidase over-expression has little effect on nuclear H2O2 accumulation and high light-responsive gene expression. This is because the H2O2 derives from a sub-population of chloroplasts closely associated with nuclei. Therefore, direct H2O2 transfer from chloroplasts to nuclei, avoiding the cytosol, enables photosynthetic control over gene expression

ЭФФЕКТ РАЗЛИЧНЫХ ФЕРМЕНТОВ-АНТИОКСИДАНТОВ НА РЕГЕНЕРАТИВНЫЕ ПРОЦЕССЫ В ЭПИТЕЛИИ ТРАХЕИ ПОСЛЕ ХИМИЧЕСКОГО ОЖОГА

The aim of the study was to investigate a role of different antioxidant enzymes for tracheal epithelium regeneration after chemical burn.Methods. The study was conducted in a rat model of chemical burn of the upper airways caused by inhaled hydrochloric acid.Results. According to results of histological examination, to the 2nd day after the exposure approximately 70 % of the epithelial surface remained injured, mostly due to death of the ciliated cells. The degree of the damage was unchanged to the 4th day after the exposure. Visible regeneration of the tracheal epithelium began to the 7th day. The death of the tracheal epithelial cells was generally due to necrosis though cell apoptosis also occurred. The expression of all antioxidant enzymes was greatly decreased during the 1st day after the exposure followed by its growth to maximum to the 7th day and normal level to the 15th day after the burn. Exposition of superoxide dismutase to the trachea resulted in a significant epithelium destruction. On contrary, peroxiredoxin 6 and a chimeric protein containing peroxiredoxin / superoxide dismutase significantly protected the tracheal epithelium.Conclusion. Peroxiredoxins and their derivates could be used as highly efficient therapeutic agents with potent antioxidant action in patients with burn injury of the upper airways.Проведено исследование на модели химического ожога парами соляной кислоты верхних дыхательных путей (ВДП) крысы. В результате гистологического анализа показано, что после 1-го дня после ожога » 70 % поверхности эпителия остается поврежденной. При этом в основном гибнут реснитчатые клетки, степень повреждения остается приблизительно такой же на 3-и сутки после ожога. Видимая регенерация эпителия трахеи наблюдается на 7-е сутки после ожога. Гибель клеток эпителия трахеи происходит в основном по некротическому пути, хотя наблюдается также апоптоз клеток. В 1-й день после ожога наблюдается резкое снижение экспрессии всех ферментов-антиоксидантов, максимум экспрессии достигается на 7-й день и приходит в норму на 15-й день после ожога. Аппликация суперок-сиддисмутазы (СОД) в обожженную трахею вызывала значительное разрушение эпителия трахеи. В противоположность этому при аппликации в трахею пероксиредоксина (Prx) 6 и химерного белка с Prx-СОД практически полностью сохранялся эпителий трахеи. Таким образом, Prx и его модификации – перспективные эффективные лекарственные средства мощного антиоксидантного действия для лечения ожогов ВДП

ROS-dependent signaling pathways in plants and algae exposed to high light: Comparisons with other eukaryotes

Abstract Like all aerobic organisms, plants and algae co-opt reactive oxygen species (ROS) as signaling molecules to drive cellular responses to changes in their environment. In this respect, there is considerable commonality between all eukaryotes imposed by the constraints of ROS chemistry, similar metabolism in many subcellular compartments, the requirement for a high degree of signal specificity and the deployment of thiol peroxidases as transducers of oxidizing equivalents to regulatory proteins. Nevertheless, plants and algae carry out specialised signaling arising from oxygenic photosynthesis in chloroplasts and photoautotropism, which often induce an imbalance between absorption of light energy and the capacity to use it productively. A key means of responding to this imbalance is through communication of chloroplasts with the nucleus to adjust cellular metabolism. Two ROS, singlet oxygen (1O2) and hydrogen peroxide (H2O2), initiate distinct signaling pathways when photosynthesis is perturbed. 1O2, because of its potent reactivity means that it initiates but does not transduce signaling. In contrast, the lower reactivity of H2O2 means that it can also be a mobile messenger in a spatially-defined signaling pathway. How plants translate a H2O2 message to bring about changes in gene expression is unknown and therefore, we draw on information from other eukaryotes to propose a working hypothesis. The role of these ROS generated in other subcellular compartments of plant cells in response to HL is critically considered alongside other eukaryotes. Finally, the responses of animal cells to oxidative stress upon high irradiance exposure is considered for new comparisons between plant and animal cells