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Expression of Arabidopsis thaliana glutamate dehydrogenase genes is very low in the light and high in the dark. The molecular signals and mechanisms that provide the light-dependent glutamate dehydrogenase genes regulation remain unknown. The aim of this work was to study a role of redox signals which occur during light shifts in the regulation of the glutamate dehydrogenase genes expression. Using photosynthetic electron transport inhibitors 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl benzoquinone (DBMIB) we demonstrate that transcript levels of the GDH1 and GDH2 genes in Arabidopsis leaves change in accordance with a redox state of plastoquinone pool: they are low when it is highly reduced and high when it is oxidized. Hydrogen peroxide or high light treatment did not result in decreasing of GDH1 or GDH2 expression, so reactive oxygen species cannot be the signals that reduce expression of these genes during dark-to-light shifts. There was no significant difference between the glucose content in the leaves of plants treated with DCMU and the plants treated with DBMIB, so glucose is not the only or the main factor that regulates expression of the studied genes. We presume that expression of Arabidopsis GDH1 and GDH2 genes depends on the plastoquinone pool redox state. Expression of Arabidopsis glutamate dehydrogenase genes during light-to-dark and dark-to-light shifts depends on chloroplast electron transport chain redox state rather than reactive oxygen species or glucose content.

Mitochondria possess transport mechanisms for import of RNA and DNA. Based on import into isolated Solanum tuberosum mitochondria in the presence of competitors, inhibitors or effectors, we show that DNA fragments of different size classes are taken up into plant organelles through distinct channels. Alternative channels can also be activated according to the amount of DNA substrate of a given size class. Analyses of Arabidopsis thaliana knockout lines pointed out a differential involvement of individual voltage-dependent anion channel (VDAC) isoforms in the formation of alternative channels. We propose several outer and inner membrane proteins as VDAC partners in these pathways.

Plant glutamate dehydrogenase is an enzyme interconverting L-glutamate and 2-oxoglutarate and providing a link between carbon and nitrogen metabolism. In Arabidopsis thaliana, this enzyme is encoded by three genes. Two of them, GDH1 and GDH2, provide most of the enzyme activity in plant leaves and roots. Expression of GDH1 and GDH2 genes is very low in the light and high in the dark. The molecular signals and mechanisms that provide the light-dependent GDH genes regulation remain unknown. Using photosynthetic electron transport inhibitors 3-(3.4-dichlorophenyl)-1.1-dimethylurea (DCMU) and 2.5-dibromo-3-methyl-6-isopropyl benzoquinone (DBMIB) we demonstrate that transcript levels of the GDH1 and GDH2 genes in Arabidopsis leaves change in accordance with a redox state of chloroplast electron transport chain: they are low when it is highly reduced and high when it is oxidized. Hydrogen peroxide or high light treatment did not result in decreasing of GDH1 or GDH2 expression, so reactive oxygen species cannot be the signals that reduce expression of these genes during dark-to-light shifts. There was no significant difference between the glucose content in the leaves of plants treated with DCMU and the plants treated with DBMIB, so glucose is not the only or the main factor that regulates expression of the studied genes. We presume that expression of Arabidopsis GDH1 and GDH2 genes depends on the chloroplast electron transport chain redox state. This regulatory mechanism could arise because of a need to avoid a competition for substrate between tetrapyrrole synthesis, glutathione synthesis and using of L-glutamate as an energy source during prolonged darkness.

The influence of low-intensity laser radiation (LILR) on the changes in the content of anthocyanins, kaempferol, quercetin and their glycosides in the leaves of 5-week-old plants of Arabidopsis thaliana L. was studied by means of methods of high-performance liquid chromatography and gas chromatography mass spectrometry (GC-MS). It was found that in the leaves subjected to a stimulating He-Ne laser radiation dose (3.6 J cm-2 , continuous wave radiation, wavelength-632.8 nm, exposure time-5 min), the radiation induced an increase in the content of such compounds, the most significant one being in the case of anthocyanins (9 times). The present study also revealed an increase in the antioxidant potential of kaempferol, quercetin and their glycosides as a result of laser exposure. This increase was due to the preferential synthesis of compounds with a larger number of OH-groups on the phenyl ring. Thus, the content of quercetin, which has five OH-groups in its structure, increased almost by three times as compared to the control.