Regulation of Fumarate Hydratase Gene Expression in Green Maize Leaves Under Hypoxic Conditions

The dynamics of fumarase activity in maize leaves under the conditions of different gas composition of the medium was studied. It is shown that under hypoxic conditions a decrease in this index of the enzyme under study is observed in comparison with normal conditions. It was found that in the environment of carbon dioxide and nitrogen two forms of the enzyme are observed, mitochondrial and cytoplasmic. The level of expression of fum1 and fum2 genes in green maize leaves was established in control and experimental samples. The dependence of the expression rate of fumarase genes in maize leaves is shown in different conditions of the gaseous medium

ЕКОЛОГІЧНА БЕЗПЕКА УРБАНІЗОВАНИХ ТЕРИТОРІЙ В УМОВАХ ІНТЕНСИВНОГО АНТРОПОГЕННОГО ПРЕСИНГУ

On the example of the urban area of city district of Voronezh, main factors shaping the ecological safety of the population in the terms of increasing the level of anthropogenic pressure, leading to a change in environmental conditions are studied. Based on GIS technologies common scientific and methodological approaches for assessing the ecological safety of the population in urban areas are developed. According to the results of a comprehensive evaluation of the factors shaping the ecological safety of the territory, geo-ecological zoning of the urban district of Voronezh is held.На прикладі урбанізованої території міського округу м. Воронежа досліджені основні чинники, що формують екологічну безпеку для населення в умовах зростання рівня антропогенного навантаження, що веде до зміни параметрів навколишнього середовища. На основі геоінформаційних технологій розроблені загальні науково-методичні підходи оцінки екологічної безпеки для населення урбанізованих територій. За результатами комплексної оцінки факторів, що формують екологічну безпеку території, проведено геоекологічне зонування території міського округу м. Воронежа

Regulation of Aconitate Hydratase Activity in Maize Leaves with Red and Blue Light

The dynamics of the activity of aconitate hydratase (AH, EC 4.2.1.3) in maize leaves under various light regimes was studied and it was established that red and blue light had an inhibitory effect on the functioning of the enzyme under study. Increased activity of AH in dark conditions is associated with activation of respiratory metabolism, as the main source of energy equivalents in the absence of light. The dependence of the expression rate of aco1 and aco2 genes in maize leaves on irradiation with light of different wavelengths is shown. The change in the expression rate of the aco1 gene, depending on the state of the phytochrome and cryptochromic systems, correlates with the activity of the encoded enzyme, indicating a phytochrome- and cryptochrome-mediated mechanism of regulation of the gene mediated. For the aco2 gene, the reverse dependence in phytochrome system regulation is shown

Organic Acids: The Pools of Fixed Carbon Involved in Redox Regulation and Energy Balance in Higher Plants

Organic acids are synthesized in plants as a result of the incomplete oxidation of photosynthetic products and represent the stored pools of fixed carbon accumulated due to different transient times of conversion of carbon compounds in metabolic pathways. When redox level in the cell increases, e.g., in conditions of active photosynthesis, the tricarboxylic acid (TCA) cycle in mitochondria is transformed to a partial cycle supplying citrate for the synthesis of 2-oxoglutarate and glutamate (citrate valve), while malate is accumulated and participates in the redox balance in different cell compartments (via malate valve). This results in malate and citrate frequently being the most accumulated acids in plants. However, the intensity of reactions linked to the conversion of these compounds can cause preferential accumulation of other organic acids, e.g., fumarate or isocitrate, in higher concentrations than malate and citrate. The secondary reactions, associated with the central metabolic pathways, in particularly with the TCA cycle, result in accumulation of other organic acids that are derived from the intermediates of the cycle. They form the additional pools of fixed carbon and stabilize the TCA cycle. Trans-aconitate is formed from citrate or cis-aconitate, accumulation of hydroxycitrate can be linked to metabolism of 2-oxoglutarate, while 4-hydroxy-2-oxoglutarate can be formed from pyruvate and glyoxylate. Glyoxylate, a product of either glycolate oxidase or isocitrate lyase, can be converted to oxalate. Malonate is accumulated at high concentrations in legume plants. Organic acids play a role in plants in providing redox equilibrium, supporting ionic gradients on membranes, and acidification of the extracellular medium

Light-Dependent Expression and Promoter Methylation of the Genes Encoding Succinate Dehydrogenase, Fumarase, and NAD-Malate Dehydrogenase in Maize (<i>Zea mays</i> L.) Leaves

The expression and methylation of promoters of the genes encoding succinate dehydrogenase, fumarase, and NAD-malate dehydrogenase in maize (Zea mays L.) leaves depending on the light regime were studied. The genes encoding the catalytic subunits of succinate dehydrogenase showed suppression of expression upon irradiation by red light, which was abolished by far-red light. This was accompanied by an increase in promoter methylation of the gene Sdh1-2 encoding the flavoprotein subunit A, while methylation was low for Sdh2-3 encoding the iron-sulfur subunit B under all conditions. The expression of Sdh3-1 and Sdh4 encoding the anchoring subunits C and D was not affected by red light. The expression of Fum1 encoding the mitochondrial form of fumarase was regulated by red and far-red light via methylation of its promoter. Only one gene encoding the mitochondrial NAD-malate dehydrogenase gene (mMdh1) was regulated by red and far-red light, while the second gene (mMdh2) did not respond to irradiation, and neither gene was controlled by promoter methylation. It is concluded that the dicarboxylic branch of the tricarboxylic acid cycle is regulated by light via the phytochrome mechanism, and promoter methylation is involved with the flavoprotein subunit of succinate dehydrogenase and the mitochondrial fumarase

Light Dependent Changes in Adenylate Methylation of the Promoter of the Mitochondrial Citrate Synthase Gene in Maize (Zea mays L.) Leaves

Limited methyl-specific restriction of genomic DNA by endonuclease MAL1 revealed the changes in its methyl status caused by adenine modification in maize (Zea mays L.) leaves under different light conditions (dark, light, irradiation by red and far-red light). Incubation in the light and irradiation by red light exhibited an activating effect on DNA adenine methylase activity, which was reflected in an increase in the number of methylated adenines in GATC sites. Far-red light and darkness exhibited an opposite effect. The use of nitrite conversion of DNA followed by methyladenine-dependent restriction by MboI nuclease revealed a phytochrome B-dependent mechanism of regulation of the methyl status of adenine in the GATC sites in the promoter of the gene encoding the mitochondrial isoform of citrate synthase. Irradiation of plants with red light caused changes in the adenine methyl status of the analyzed amplicon, as evidenced by the presence of restriction products of 290, 254, and 121 nucleotides. Adenine methylation occurred at all three GATC sites in the analyzed DNA sequence. It is concluded that adenylate methylation is controlled by phytochrome B via the transcription factor PIF4 and represents an important mechanism for the tricarboxylic acid cycle regulation by light