CO<Subscript>2</Subscript> exchange and structural organization of chloroplasts under hypothermia in potato plants transformed with a gene for yeast invertase

Growth, CO₂ exchange, and the ultrastructure of chloroplasts were investigated in the leaves of potato plants (Solanum tuberosum L., cv. Désirée) of wild type and transformed with a gene for yeast invertase under the control of patatin class I B33 promoter (for apoplastic enzyme) grown in vitro on the Murashige and Skoog medium supplemented with 2% sucrose. At a temperature of 22°C optimal for growth, the transformed plants differed from the plants of wild type in retarded growth and a lower rate of photosynthesis as calculated per plant. On a leaf dry weight basis, photosynthesis of transformed plants was higher than in control plants. Under hypothermia (5°C), dark respiration and especially photosynthesis of transformed plants turned out to be more intense than in control material. After a prolonged exposure to low temperature (6 days at 5°C), in the plants of both genotypes, the ultrastructure of chloroplasts changed. Absolute areas of sections of chloroplasts and starch grains rose, and the area of plastoglobules decreased; in transformed plants, these changes were more pronounced. By some ultrastructural characteristics: a reduction in the cold of relative total area of sections of starch grains and plastoglobules (in percents of the chloroplast section area) and in the number of granal thylakoids (per a chloroplast section area), transformed plants turned out to be more cold resistant than wild-type plants. The obtained results are discussed in connection with changes in source-sink relations in transformed potato plants. These changes modify the balance between photosynthesis and retarded efflux of assimilates, causing an increase in the intracellular level of sugars and a rise in the tolerance to chilling.     

The arsenolysis reaction in the biotechnological synthesis of ribavirin. The in vitro and in vivo inhibition of influenza A virus replication with a combination of ribavirin and ozeltamivir

The biotechnological method of synthesis of the antiviral drug ribavirin based on the transglycosylation reaction was improved due to the addition of catalytic amounts of sodium arsenate. This approach allows us to hydrolyze the excess natural nucleoside guanosine, a ribose donor, and, hence, made the composition of the reaction mixture less complicated, thus facilitating the process of ribavirin isolation. It was shown that in cell cultures the combination of ribavirin and oseltamivir carboxylate inhibited the replication of the influenza A virus more effectively than each of them alone. Similar results were obtained in experiments on laboratory animals (mouse Balb/c) infected with the influenza A virus H3N2/Aichi/68 strain.     

Influence of Gold Nanoparticles on the Tolerance of Wheat to Low Temperature

Doklady Biochemistry and Biophysics - It was shown for the first time that the treatment of winter wheat (Triticum aestivum L.) seeds with gold nanoparticles (average diameter 15.3 nm; solution...     

Conditions that influence bacterial luminescence in the presence of blood serum

Conditions that influence the luminescence of natural and recombinant luminescent bacteria in the presence of blood serum were studied. In general, blood serum quenched the luminescence of the marine Photobacterium phosphoreum and the recombinant Escherichia coli strains harboring the luminescent system genes of Photobacterium leiognathi, but enhanced the luminescence of the soil bacterium Photorhabdus luminescens Zm1 and the recombinant E. coli strain harboring the lux operon of P. luminescens Zm1. The quenching effect of blood serum increased with its concentration and the time and temperature of incubation. The components of blood serum that determine the degree and specificity of its action on bacterial luminescence were identified.__________Translated from Mikrobiologiya, Vol. 74, No. 2, 2005, pp. 191–197.Original Russian Text Copyright © 2005 by Deryabin, Polyakov.     

Synchronization of tuber formation in potato grown in vitro by cell division synchronization in axillary meristems of stem explants

Optimization of in vitro tuberization (formation and growth of stolons and microtubers) by synchronization of cell divisions in axillary meristems of initial stem explants induced by low nonfreezing temperatures was studied in potato (Solanum tuberosum L., cv. Lugovskoi) plants. The proportion of simultaneously dividing cells in axillary meristems of stem explants subjected to 2-h cold treatment at 4°C was in 2.6 times greater than in control material (without chilling). The analysis of growth of stolons and microtubers produced from the explants exposed to cold showed that synchronization of cell divisions in the meristems of initial explants resulted in synchronization of stolon and microtuber formation and production of microtubers of identical physiological age.     

Impact of bacterial autoregulatory molecules (homoserine lactones and alkylhydroxybenzenes) on the oxidative metabolism of the cell effectors of natural immunity

We investigated the impact of bacterial regulators homoserine lactones (HSLs) and alkylhydroxybenzenes (AHBs) (which are present in human fluids at pico- and nanomolar concentrations) on neutrophile oxidative metabolism. The HSL and AHB effects were determined using a test based on induced luminol-dependent chemoluminescence of neutrophiles in human peripheral blood. In this test, neutrophiles were preincubated with chemical analogs of bacterial autoregulators with different lengths of the hydrocarbon radical, such as HSL · HCl, C6- and C12-HSL, and C1-, C6-, and C12-AHB. We revealed that they suppressed the chemoluminescence and, accordingly, the oxidative metabolism of neutrophiles. This effect was more significant with HSLs than with AHBs. Within each of the two groups, the effect increased with an increase in the length of the hydrocarbon chain of the homologues. High concentrations of long-chain autoregulators of both types produce a cytotoxic effect that is associated with apoptosis in the case of C12-HSL and with cell membrane damage in the case of C12-AHB. The effects of low HSL and AHB concentrations involve their protein-modifying properties and result in changes in the activities of neutrophile oxidative enzymes. To a lesser extent, these effects are due to the pro- and antioxidant activities of HSLs and AHBs, respectively. In light of the results obtained, the HSL and AHB effects are to be considered as a novel mechanism of regulating the activities of cell effectors of natural innate immunity. In symbiotic and parasitic systems, the mechanism involves the bimodal pattern of the effects of HSLs and AHBs that vary depending on their structure and concentrations.     

To Find and Destroy: Identification and Elimination of Senescent Cells

“Our oldness is a disease that has to be treated like any other one,”—this statement formulated about a hundred years ago seems to be of current interest in the context of modern investigations. Recently, it has been established that accumulation of senescent cells in various organs and tissues is one of the main causes for the organismal aging, as well as for the progression of multiple age-related pathologies. On the one hand, this observation brings us one step closer to the desired goal—reversal or slowing down of aging. On the other hand, this raises a number of complicated questions: in what essentially lies the difference between senescent and normal cells and how they can be identified; whether senescent cells can be eliminated from the body and can this elimination stop/reverse aging; can such a targeted removal of senescent cells be accompanied by negative consequences, in particular, by an increase in the cancer incidence? This review summarizes the main features of senescent cells, surveys the existing approaches of targeted elimination of senescent cells in vivo, and highlights their advantages and disadvantages.     

Alternative pathways of photosystem I-dependent electron transport in two genetically different potato cultivars in vitro

Alternative pathways of electron transport involving photosystem I (PSI) only were studied in leaves of potato plants (Solanum tuberosum L., cv. Desiree), modified by yeast invertase gene, controlled by tuber-specific class I patatin B33 promoter with proteinase II signal peptide for apoplastic localization of the enzyme. Nontransformed (wild-type) potato cultivar Desiree was used as a source of control plants. Phototrophic cultures grown in vitro on the sucrose-free Murashige and Skoog medium, as well as plants grown on the medium with 4% sucrose were examined. Various PSI-dependent alternative pathways of electron transport were discriminated by quantitative analysis of kinetic curves of dark reduction of P700⁺, the primary electron donor of PSI, oxidized by far-red light known to excite selectively PSI. In potato plants with two different genotypes, four exponentially decaying kinetic components were found, which suggests the existence of multiple alternative routes for electron input to PSI. Inhibitor analysis (with diuron and antimycin A) allowed identification of each route. A minor ultra-fast component originated from weak residual excitation of PSII by far-red light and represented electron flow from PSII to PSI. Ferredoxin-dependent cyclic electron flow around PSI accounted for the middle component, and two slower components were assigned to donation of electrons to PSI from reductants localized in the chloroplast stroma. The rates of all components were somewhat higher in leaves of the transformed plants than in the wild-type plants. However, relative contributions of separate components to the kinetics of dark P700⁺ reduction in leaves of both potato genotypes were similar. Growing plants on the medium with sucrose dramatically increased the amplitude of absorbance change at 830 nm in the transformed (but not in wild type) plants, which indicated a drastic increase in P700 concentration in their leaves.