The cytoprotective effect of the phytoestrogen genistein on tumor cells

In order to determine the cytotoxic or cytoprotective effect of the synthetic isoflavonoid genistein, we studied its effect on HeLa tumor cells, which contain estrogen alpha receptors and do not contain estrogen beta receptors. It was shown that the genistein concentration (IC ₅₀ = 0.2 mM) at which the half maximal inhibition of the HeLa cell viability is achieved is ten times higher than the concentrations of tamoxifen and cisplatin, which are reference agents with a cytotoxic effect. At micromolar concentrations (0.1–10 µM) genistein decreased the cytotoxic effects of cisplatin and tamoxifen. We found the reduced Bax mRNA expression and increased Bcl-2 mRNA expression during incubation of the cells with genistein, which also indicates its cytoprotective anti-apoptotic effect. Genistein, even in high concentrations, had no effect on the membrane potential and calcium capacity of isolated mitochondria and did not activate the opening of the Ca²⁺-induced mitochondrial pore. Thus, the data show a protective effect of the isoflavonoid genistein on tumor cells.     

Chemical and enzymatic probing of spatial structure of the omega leader of tobacco mosaic virus RNA

The 5′-untranslated sequence of tobacco mosaic virus RNA — the so-called omega leader — exhibits features of a translational enhancer of homologous and heterologous mRNAs. The absence of guanylic residues, the presence of multiple trinucleotide CAA repeats in its central region, and the low predictable probability of the formation of an extensive secondary structure of the Watson-Crick type were reported as the peculiarities of the primary structure of the omega leader. In this work we performed chemical and enzymatic probing of the secondary structure of the omega leader. The isolated RNA comprising omega leader sequence was subjected to partial modifications with dimethyl sulfate and diethyl pyrocarbonate and partial hydrolyses with RNase A and RNase V1. The sites and the intensities of the modifications or the cleavages were detected and measured by the primer extension inhibition technique. The data obtained have demonstrated that RNase A, which attacks internucleotide bonds at the 3′ side of pyrimidine nucleotides, and diethyl pyrocarbonate, which modifies N7 of adenines not involved in stacking interactions, weakly affected the core region of omega leader sequence enriched with CAA-repeats, this directly indicating the existence of a stable spatial structure. The significant stability of the core region structure to RNase A and diethyl pyrocarbonate was accompanied by its complete resistance against RNase V1, which cleaves a polyribonucleotide chain involved in Watson-Crick double helices and generally all A-form RNA helices, thus being an evidence in favor of a non-Watson-Crick structure. The latter was confirmed by the full susceptibility of all adenines and cytosines of the omega polynucleotide chain to dimethyl sulfate, which exclusively modifies N1 of adenines and N3 of cytosines not involved in Watson-Crick interactions. Thus, our data have confirmed that (1) the regular (CAA)_n sequence characteristic of the core region of the omega leader does form stable secondary structure, and (2) the structure formed is not the canonical double helix of the Watson-Crick type.     

Actinomycete complexes in the rhizosphere of winter rye on soddy podzolic soil

The structure of actinomycete complexes in the rhizosphere of winter rye (Secale cereale L.) varieties originating from different ecosystems and geographical zones was studied in field experiments on soddy podzolic soil. In addition to streptomycetes, the complexes studied contained actinomycetes of the genera Micromonospora and Streptosporangium, represented at high occurrence and comparable abundance rates. The rhizosphere of most of the studied rye varieties was dominated by micromonosporas. The antifungal potential of mycelial prokaryotes associated with winter rye was assessed. The taxonomic and functional structure of actinomycete complexes was shown to be similar in rye varieties originating from the nonchernozem zone of Russia. However, the actinomycete complex proved to be much different in the rye variety that developed in the steppe zone of the lower Volga region.     

Actinomycetes in the rhizosphere of barley plants grown in the strongly acidic soddy podzolic soil

The study of various factors (soil acidity, the variety of barley plants, and their developmental phases) on the rhizosphere actinomycete complex showed that it is soil acidity that substantially influences the population of rhizosphere actinomycetes. The effect of soil acidity was most likely due to the different tolerance of rhizosphere actinomycetes to high concentrations of the aluminum and hydrogen ions. The developmental phases of barley plants correlated with the population indices of only one genus of actinomycetes, Micromonospora.     

Leader sequences of eukaryotic mRNA can be simultaneously bound to initiating 80S ribosome and 40S ribosomal subunit

Binding of mRNA leader sequences to ribosomes was studied in conditions of a cell-free translation system based on wheat germ extract. Leader sequence of TMV mRNA (the so-called omega-RNA sequence) was able to bind simultaneously 80S ribosome and 40S ribosomal subunit. It was found that nucleotide substitutions in omega-RNA resulting in destabilization of RNA structure have no effect on the complex formation with both 80S ribosome and 40S ribosomal subunit. Leader sequence of globin mRNA is also able to form a similar joint complex. It is supposed that the ability of mRNA leader sequences to bind simultaneously 80S ribosome and 40S subunit is independent of leader nature and may reflect previously unknown eukaryotic mechanisms of translation initiation.     

Biochemical and physiological estimation of barley regenerants obtained in selective systems

Callus lines of barley (Hordeum vulgare L.) resistant to aluminum toxicity and osmotic stress from which plants regenerated were obtained in selective systems. Comparative estimation of the intensity of lipid peroxidation, the content of anthocyans and ascorbic acid in leaves, the parameters of CO₂/H₂O gas exchange in leaves of regenerant plants obtained in selective mediums with gradual addition of aluminum ions and polyethylene glycol and in mediums without selective agents was performed in conditions of an artificial climate. The obtained data were compared with biochemical and physiological parameters of barley plants of the initial genotypes grown in the same conditions. Significant changes in the intensity of apparent photosynthesis, transpiration, and efficacy of water use by barley leaves were revealed as a result of callus culturing and especially due to the use of selective systems in vitro.     

Colonization of plant rhizosphere by actinomycetes of different genera

The survival of environmental isolates of actinomycetes introduced with the seeds of agricultural plants in root-free soil and in the rhizosphere and rhizoplane was studied. Different strategies of colonization of the rhizosphere were revealed for the representatives of the genera Streptomyces, Micromonospora, and Streptosporangium, organisms typical for the moderate climate rhizosphere. The plants of winter rye (Secale cereale L.) inoculated with actinomycetes were shown to have growth advantages, while the cow clover plants (Trifolium pratense L.) had no growth advantages compared to uninoculated plants. The role of the plant component in the interaction with mycelial prokaryotes is discussed.     

Anti-Fusarium activity of cyanobacteria and actinomycetes in soil and rhizosphere

The effect of cyanobacteria (Nostoc linckia, N. commune, and Microchaeta tenera) and streptomycetes on the pathogenic micromycete Fusarium was studied in laboratory simulation experiments. Interpopulational relationships in the rhizosphere of spring wheat (Triticum aestivum L.) and in soddy-podzolic soil were investigated.