A comparison of partial dehydration and hydrated storage-induced changes in viability,reactive oxygen species production,and glutathione metabolism in two contrasting recalcitrant-seeded species

This study compared the responses of Avicennia marina and Trichilia dregeana seeds, both of which are recalcitrant, to partial dehydration and storage. Seeds of A. marina exhibited a faster rate of water and viability loss (± 50% viability loss in 4 days) during partial dehydration, compared with T. dregeana (± 50% viability loss in 14 days). In A. marina embryonic axes, reactive oxygen species (ROS) production peaked on 4 days of dehydration and was accompanied by an increase in the GSH:GSSG ratio; it appears that the glutathione system alone could not overcome dehydration-induced oxidative stress in this species. In A. marina, ROS and axis water content levels increased during hydrated storage and were accompanied by a decline in the GSH:GSSG ratio and rapid viability loss. In T. dregeana embryonic axes, ROS production (particularly hydrogen peroxide) initially increased and thereafter decreased during both partial dehydration and hydrated storage. Unlike in A. marina embryonic axes, this reduced ROS production was accompanied by a decline in the GSH:GSSG ratio. While T. dregeana seeds may have incurred some oxidative stress during storage, a delay in and/or suppression of the ROS-based trigger for germination may account for their significantly longer storage longevity compared with A. marina. Mechanisms of desiccation-induced seed viability loss may differ across recalcitrant-seeded species based on the rate and extent to which they lose water during partial drying and storage. While recalcitrant seed desiccation sensitivity and, by implication, storage longevity are modulated by redox metabolism, the specific ROS and antioxidants that contribute to this control may differ across species.     

<Emphasis Type="Italic">Mycobacterium avium</Emphasis> MAV2052 protein induces apoptosis in murine macrophage cells through Toll-like receptor 4

Mycobacterium avium and its sonic extracts induce apoptosis in macrophages. However, little is known about the M. avium components regulating macrophage apoptosis. In this study, using multidimensional fractionation, we identified MAV2052 protein, which induced macrophage apoptosis in M. avium culture filtrates. The recombinant MAV2052 induced macrophage apoptosis in a caspase-dependent manner. The loss of mitochondrial transmembrane potential (ΔΨ_m), mitochondrial translocation of Bax, and release of cytochrome c from mitochondria were observed in macrophages treated with MAV2052. Further, reactive oxygen species (ROS) production was required for the apoptosis induced by MAV2052. In addition, ROS and mitogen-activated protein kinases were involved in MAV2052-mediated TNF-α and IL-6 production. ROS-mediated activation of apoptosis signal-regulating kinase 1 (ASK1)-JNK pathway was a major signaling pathway for MAV2052-induced apoptosis. Moreover, MAV2052 bound to Toll-like receptor (TLR) 4 molecule and MAV2052-induced ROS production, ΔΨ_m loss, and apoptosis were all significantly reduced in TLR4^?/? macrophages. Altogether, our results suggest that MAV2052 induces apoptotic cell death through TLR4 dependent ROS production and JNK pathway in murine macrophages.     

Fish assemblage structure in an estuary of the Atlantic Forest biodiversity hotspot (southern Brazil)

We described the fish assemblage in the estuary of the Guaraguaçu River (one of the largest tributaries of the Paranaguá Bay Estuary, located within Brazil’s Atlantic Forest Biosphere Reserve) from June 2005 to May 2006, and assessed the seasonal and spatial effects of abiotic environmental attributes on the fish assemblage structure. Despite some oscillations in salinity, the upper and lower estuaries had year-round persistent oligohaline and polyhaline conditions, respectively. Despite high species richness (55 species), the Guaraguaçu River Estuary fish community contains a few dominant taxa; 11% of the richness accounts for >60% of its density and biomass. The most abundant species (in terms of both biomass and density) was Atherinella brasiliensis. Species whose densities were most strongly associated with the upper estuary were Centropomus parallelus, Ctenogobius schufeldti, Eucinostomus melanopterus, Platanichthys platana, Trinectes paulistanus, and Eugerres brasilianus. Those whose densities were most strongly associated with the lower estuary were A. brasiliensis, Sphoeroides greeleyi, Eucinostomus argenteus, Sphoeroides testudineus, Diapterus rhombeus, and Harengula clupeola. Throughout the year, canonical correspondence analysis identified: (1) the pattern of horizontal stratification of salinity along the river as being the most important variable for explaining most of the fish fauna structure; and (2) a strong relationship between the fish fauna and the salinity gradient along the estuary. Analysis of similarity further confirmed that each estuarine zone supports a year-round persistent and relatively homogeneous fish species assemblage. Total mean density and biomass remained constant over time in each estuarine habitat, but density shifted in the most abundant species, which appears related to recruitment patterns. Such species and abundance persistence likely occurs because seasonal rainfall-induced changes in river discharge are not sufficient to significantly shift runoff and salinity and thus fish assemblage structure (species composition, density and biomass) along the estuary. Such a lack of seasonal fish fauna movement as a response to changes in river flow contrasts with other estuarine systems around the world.     

Programmed cell death in the cyanobacterium <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> induced by allelopathic effect of submerged macrophyte <Emphasis Type="Italic">Myriophyllum spicatum</Emphasis> in co-culture system

This investigation demonstrates that programmed cell death (PCD) in a cyanobacterium, Microcystis aeruginosa, resulting from allelopathic stress induced by a submerged macrophyte, Myriophyllum spicatum, in a co-culture system. The hallmarks of PCD, caspase-3-like protease activity, DNA fragmentation, and destruction of cell ultrastructure, as well as intracellular PCD signaling radicals, reactive oxygen species (ROS), and nitric oxide (NO), were measured in M. aeruginosa cells co-cultured with M. spicatum for 7 days. The results showed a dose–response relationship between M. spicatum biomass and M. aeruginosa mortality. A caspase-3-like protease was activated and elevated from day 3. Thylakoid disintegration, cytoplasmic vacuolation, and fuzzy nuclear zone were observed by transmission electron microscopy, and distinct DNA fragmentation was detected in M. aeruginosa cells at a M. spicatum biomass of 6.0 g fresh weight (FW) L^?1 during the 7 days. Allelochemicals of total phenolic compounds (TPCs) were determined in co-culture water, and the concentration increased with increasing of M. spicatum biomass and co-culture time. Compared with the level of ROS production in the control group, a significant overproduction of ROS was detected in M. aeruginosa cells in the treatment group, and this was positively correlated with TPC concentration. Furthermore, the level of intracellular NO increased with the percent mortality of M. aeruginosa. The results indicated that a PCD pathway was induced in the cyanobacterium M. aeruginosa when co-cultured with the submerged macrophyte M. spicatum.     

Similar behavior,different mechanisms: the research of the style bending of <Emphasis Type="Italic">Alpinia</Emphasis> species

The styles of the plants of genus Alpinia show a similar bending behavior. Each species has two types—hyper-type and cata-type. The styles of hyper-type bend downward first, and then bend upward second. The styles of cata-type also bend twice, but the bending direction is opposite to hyper-type. We tested the effects of light, IAA, and NPA on the style movement of Alpinia oxyphylla and Alpinia galanga, and analyzed the IAA distribution in their styles. We found that the effects of light were similar for the two species, but the two types of each species responded differently. The first style bending of hyper-type was downward when it was in dark, and was upward when in light; the second bending was upward if in light, and did not move if in dark. The two bendings of cata-type showed no obvious difference between in dark and in light. Effects of IAA and NPA were different for two species. For A. galanga, neither IAA nor NPA had obvious effects on the style bending. For A. oxyphylla, IAA enhanced the second bending of hyper-type and the two bendings of cata-type. NPA enhanced the second bending of hyper-type and the first bendings of cata-type, and significantly inhibited the second bending of cata-type. The results of IAA immunolocalization indicated that IAA was symmetrical in the styles of A. galanga both before the first bending and before the second bending in two types. However, in A. oxyphylla, IAA asymmetry was found in two types. Therefore, we hypothesize that the mechanisms of the style bending of Alpinia plants are different, not only between two types of each species, but also among species.     

Effect of Reducing Nitric Oxide in <Emphasis Type="Italic">Rumex</Emphasis> K-1 Leaves on the Photoprotection of Photosystem II Under High Temperature with Strong Light

The purpose of this study was to explore the effect of reducing nitric oxide (NO) in Rumex K-1 leaves on the photoprotection of photosystem II (PSII) under high temperature with strong light. Reducing the content of NO in Rumex K-1 leaves significantly aggravated the PSII photoinhibition and net degradation of D1 protein under high temperature with strong light, but not under high temperature in the darkness. The reduction of NO remarkably inhibited the electron transport of PSII in the leaves under high temperature and strong light, which resulted in an increase in excitation pressure and an over-accumulation of reactive oxygen species (ROS). The over-accumulation of ROS further damaged PSII. However, when the synthesis of D1 protein was inhibited, the D1 protein content and PSII activity were no longer influenced by reducing NO content in the leaves. The reduction of NO in leaves decreased the activities of ROS scavenger enzymes after treatment with high temperature and strong light for 2 h, which enhanced the over-accumulation of ROS to damage photosynthetic apparatus severely. All of these results suggest that NO was involved in the synthesis of D1 protein. Maintaining physiologically appropriate NO content in leaves will alleviate net degradation of D1 protein under high temperature with strong light to keep photosynthetic electrons flowing smoothly, which mitigates the accumulation of ROS in photosystems to avoid damage to the photosynthetic apparatus. Therefore, NO plays an important role in maintaining higher PSII photosynthetic performance under high temperature with strong light.     

Phagocytosis influences the intracellular survival of <Emphasis Type="Italic">Mycobacterium smegmatis</Emphasis> via the endoplasmic reticulum stress response

Background

Mycobacterium smegmatis, a rapidly growing non-tuberculosis mycobacterium, is a good model for studying the pathogenesis of tuberculosis because of its genetic similarity to Mycobacterium tuberculosis (Mtb). Macrophages remove mycobacteria during an infection. Macrophage apoptosis is a host defense mechanism against intracellular bacteria. We have reported that endoplasmic reticulum (ER) stress is an important host defense mechanism against Mtb infection.

Results

In this study, we found that M. smegmatis induced strong ER stress. M. smegmatis-induced reactive oxygen species (ROS) play a critical role in the induction of ER stress-mediated apoptosis. Pretreatment with an ROS scavenger suppressed M. smegmatis-induced ER stress. Elimination of ROS decreased the ER stress response and significantly increased the intracellular survival of M. smegmatis. Interestingly, inhibition of phagocytosis significantly decreased ROS synthesis, ER stress response induction, and cytokine production.

Conclusions

Phagocytosis of M. smegmatis induces ROS production, leading to production of proinflammatory cytokines. Phagocytosis-induced ROS is associated with the M. smegmatis-mediated ER stress response in macrophages. Therefore, phagocytosis plays a critical role in the induction of ER stress-mediated apoptosis during mycobacterial infection.

     

Reactive oxygen and nitrogen (ROS and RNS) species generation and cell death in tomato suspension cultures—<Emphasis Type="Italic">Botrytis cinerea</Emphasis> interaction

This article reports events connected to cell survival and Botrytis cinerea infection development in cell suspension cultures of two tomato cultivars which show different levels of susceptibility to the pathogen: cv. Corindo (more susceptible) and cv. Perkoz (less susceptible). In parallel changes in reactive oxygen (ROS) and nitrogen (RNS) species generation and in S-nitrosoglutathione reductase (GSNOR) activity were studied. In vivo staining methods with acridine orange (AO) and ethidium bromide (EB) as well as fluorescent microscopy were used to assess tomato and B. cinerea cells death. The biochemical studies of ROS and RNS concentrations in plant cell extract were complemented by in vivo ROS and nitric oxide (NO) imaging using nitro blue tetrazolium (NBT), diaminobenzidine (DAB) and diaminofluorescein diacetate (DAF-DA) staining methods, and confocal microscope technique. B. cinerea infection proceeded slower in Perkoz cell cultures. It was evidenced by measuring the pathogen conidia germination and germination tube development in which nuclei revealing cell death dominated. Two different types of tomato cell death were observed: cells with necrotic nuclei dominated in Corindo whereas in Perkoz cells with characteristic of vacuolar death type prevailed. In Perkoz cells, constitutive levels of NO and S-nitrosothiols (SNO) were significantly higher and hydrogen peroxide (H₂O₂) and superoxide anion (O₂ ^?) concentrations were slightly higher as compared with Corindo cells. Moreover, increases in these molecule concentrations as a result of B. cinerea inoculation were observed in both, Perkoz and Corindo cell cultures. The enzymatic GSNOR activity seems to be an important player in controlling the SNO level in tomato cells. Involvements of the studied compounds in molecular mechanisms of tomato resistance to B. cinerea are discussed in the paper.     

Changes in the structural parameters of the summer zooplankton in the pelagic zone of Lake Sevan (Armenia) during an increase in fish abundance and biomass

Features of the composition and structure of the summer zooplankton in the pelagic zone of Lake Sevan in years that were characterized by different abundances and biomasses of fish are described. It is shown that the species diversity of the community and the specific number of species of zooplankteurs, the quantity of Copepods in the total abundance and biomass of zooplankton, as well as the value of the Shannon index and the trophic coefficient, increased upon an increase in the fish abundance. At the same time, the total biomass of zooplankton and biomass of cladocerans decreased, among which the density and biomass of the larger and more colored Daphnia (Ctenodaphnia) magna Straus decreased, but the density and biomass of D. (Daphnia) hyalina Leydig and Diaphаnosoma brachyurum Lievin increased.     

Nitric oxide–cytokinin interplay influences selenite sensitivity in <Emphasis Type="Italic">Arabidopsis</Emphasis>

Key message

Selenite oppositely modifies cytokinin and nitric oxide metabolism in Arabidopsis organs. A mutually negative interplay between the molecules exists in selenite-exposed roots; and their overproduction causes selenite insensitivity.

Abstract

Selenium-induced phytotoxicity is accompanied by developmental alterations such as primary root (PR) shortening. Growth changes are provoked by the modulation of hormone status and signalling. Cytokinin (CK) cooperates with the nitric oxide (NO) in many aspects of plant development; however, their interaction under abiotic stress has not been examined. Selenite inhibited the growth of Arabidopsis seedlings and reduced root meristem size through cell division arrest. The CK-dependent pARR5::GUS activity revealed the intensification of CK signalling in the PR tip, which may be partly responsible for the root meristem shortening. The selenite-induced alterations in the in situ expressions of cytokinin oxidases (AtCKX4::GUS, AtCKX5::GUS) are associated with selenite-triggered changes of CK signalling. In wild-type (WT) and NO-deficient nia1nia2 root, selenite led to the diminution of NO content, but CK overproducer ipt-161 and -deficient 35S:CKX2 roots did not show NO decrease. Exogenous NO (S-nitroso-N-acetyl-DL-penicillamine, SNAP) reduced the pARR5::GFP and pTCS::GFP expressions. Roots of the 35S:CKX and cyr1 plants suffered more severe selenite-triggered viability loss than the WT, while in ipt-161 and gsnor1-3 no obvious viability decrease was observed. Exogenous NO ameliorated viability loss, but benzyladenine intensified it. Based on the results, selenite impacts development by oppositely modifying CK signalling and NO level. In the root system, CK signalling intensifies which possibly contributes to the nitrate reductase-independent NO diminution. A mutually negative CK-NO interplay exists in selenite-exposed roots; however, overproduction of both molecules worsens selenite sensing. Hereby, we suggest novel regulatory interplay and role for NO and CK in abiotic stress signalling.

     

The involvement of reactive oxygen species in defense of wheat lines with the genes introgressed from <Emphasis Type="Italic">Agropyron</Emphasis> species contributing the resistance against brown rust

The role of reactive oxygen species (ROS) in the defense of nearly isogenic lines of common wheat (Triticum aestivum L., cv. Thatcher) with the genes of resistance to brown rust introgressed from Agropyron species was studied using light microscopy. This disease is induced by the fungus Puccinia triticina Erikss. The presence of superoxide anion in the sites of infection was detected with the dye nitro blue tetrazolium. In addition, we studied fungus development on plants treated with the inhibitor of Ca²⁺-channels, verapamil, disturbing penetration into the cells of Ca²⁺ required for ROS generation. During fungus development in the immune line with the Lr38 resistance gene (from A. intermedium (Host) Beuv.), oxidative burst developed at the sites of contacts of appressoria with stomata and exerted a fungicidic effect. When ROS generation was suppressed, the fungus developed haustoria in the mesophyll cells. In plants with the Lr19 gene (from A. elongatum (Host) Beuv.), only moderate amount of superoxide anion accumulated on the cell walls of stomatal guard cells and in the infection structures when the fungus penetrated into the substomatal cavity and in mesophyll cells. In plants with the Lr24 gene (from A. elongatum), superoxide anion was detected only around haustoria. Suppression of ROS generation in plants harboring the Lr19 and Lr24 genes did not affect fungus entrance into the substomatal cavity but facilitated penetration of haustoria into the mesophyll cells. At the same time, in the lines with the Lr1 gene (from T. aestivum), cytological examination did not detect O ₂ ^? accumulation in plant cells, whereas treatment with verapamil enhanced mycelium development. In all lines, the suppression of oxidative burst slowed the development of hypersensitive response.     

Cassava <Emphasis Type="Italic">C-repeat binding factor 1</Emphasis> gene responds to low temperature and enhances cold tolerance when overexpressed in Arabidopsis and cassava

Key message

Reactive oxygen species (ROS) oxidize methionine to methionine sulfoxide (MetSO) and thereby inactivate proteins. Methionine sulfoxide reductase (MSR) enzyme converts MetSO back to the reduced form and thereby detoxifies the effect of ROS. Our results show that Arabidopsis thaliana MSR enzyme coding gene MSRB8 is required for effector-triggered immunity and containment of stress-induced cell death in Arabidopsis.

Abstract

Plants activate pattern-triggered immunity (PTI), a basal defense, upon recognition of evolutionary conserved molecular patterns present in the pathogens. Pathogens release effector molecules to suppress PTI. Recognition of certain effector molecules activates a strong defense, known as effector-triggered immunity (ETI). ETI induces high-level accumulation of reactive oxygen species (ROS) and hypersensitive response (HR), a rapid programmed death of infected cells. ROS oxidize methionine to methionine sulfoxide (MetSO), rendering several proteins nonfunctional. The methionine sulfoxide reductase (MSR) enzyme converts MetSO back to the reduced form and thereby detoxifies the effect of ROS. Though a few plant MSR genes are known to provide tolerance against oxidative stress, their role in plant–pathogen interaction is not known. We report here that activation of cell death by avirulent pathogen or UV treatment induces expression of MSRB7 and MSRB8 genes. The T-DNA insertion mutant of MSRB8 exaggerates HR-associated and UV-induced cell death and accumulates a higher level of ROS than wild-type plants. The negative regulatory role of MSRB8 in HR is further supported by amiRNA and overexpression lines. Mutants and overexpression lines of MSRB8 are susceptible and resistant respectively, compared to the wild-type plants, against avirulent strains of Pseudomonas syringae pv. tomato DC3000 (Pst) carrying AvrRpt2, AvrB, or AvrPphB genes. However, the MSRB8 gene does not influence resistance against virulent Pst or P. syringae pv. maculicola (Psm) pathogens. Our results altogether suggest that MSRB8 function is required for ETI and containment of stress-induced cell death in Arabidopsis.

     

Medium composition for effective slow freezing of embryonic cell lines derived from marine medaka (Oryzias dancena)

This study was conducted to identify optimal medium composition for freezing Oryzias dancena embryonic cell lines. Different freezing media consisting of various concentration of dimethyl sulfoxide (DMSO), fetal bovine serum (FBS), and trehalose were prepared and long-term cultured embryonic cell line was frozen in each freezing medium by conventional slow freezing program for 7 days. Through measurement of viability and growth of post-thaw cells frozen in each freezing medium, it was determined that optimal composition of three components was 10 % DMSO, 20 % FBS, and 0.1 M trehalose. The post-thaw cells frozen in optimal freezing medium showed similar morphology and growth rate with non-frozen cells. Next, this condition was applied to two different sets of experiment; (1) freezing of the same cells during expanded period (57 days) and (2) freezing of short-term cultured cells from other batches for 7 days. The viability of post-thaw cells was significantly low and comparable in set 1 and 2, respectively, when compared with the result of long term-cultured cells frozen in optimal freezing medium for 7 days and similar morphology and growth rate with non-frozen counterparts were detected in the post-thaw cells from both sets. In conclusion, this study first reports the optimal medium composition for freezing O. dancena embryonic cells, which can contribute to fish species preservation as well as improvement of cell-based biotechnology by providing stable cell storage.     

Immunostimulatory Effect of Enzyme-Modified <Emphasis Type="Italic">Hizikia fusiforme</Emphasis>in a Mouse Model In Vitro and Ex Vivo

Hizikia fusiforme, a brown seaweed, has been utilized as a health food and in traditional medicine. In this study, we investigated whether enzyme-modified H. fusiforme extracts (EH) have immunological effects compared with normal H. fusiforme extracts (NH). The effects of NH and EH on immune responses were investigated by assessing nitric oxide (NO) production, phagocytosis, and cytokine secretion in RAW 264.7 murine macrophages and mice. Also, fucosterol was evaluated to find the active component of NH and EH by addressing cytotoxicity test and NO production. Both of NH and EH significantly increased cell viability and NO synthesis. Tumor necrosis factor-α (TNF-α) expression was more induced by EH with LPS treatment. Phagocytic activity, as the primary function of macrophages, was markedly induced by EH treatment. Additionally, EH encouraged splenocyte proliferation and recovered the levels of cytokines IL-1β, IL-6, and TNF-α in mice. Finally, fucosterol increased NO production with no cytotoxicity, which means that fucosterol is an active component of EH. In conclusion, EH has the potential to modulate immune function and could offer positive therapeutic effect for immune system diseases.     

A new species of labrid fish <Emphasis Type="Italic">Oxycheilinus samurai</Emphasis> from the western Pacific Ocean

A new species of labrid fish Oxycheilinus samurai sp. nov. is described on the basis of five specimens from the Ryukyu Islands, Japan, and Panay Island, the Philippines. The new species is most similar to the Indo-West Pacific species Oxycheilinus orientalis in having a slender compressed body, 12 pectoral-fin rays, a blackish blotch around the anterior portion of the lateral-line anterior series, and a dark blotch basally on the membrane between the first and second dorsal-fin spines. However, O. samurai can be distinguished from O. orientalis by the following combination of characters: gill rakers 4 + 7–8; snout rounded with maximum circumference 49.8–63.5 % of standard length (SL); interorbital width 7.7–9.2 % of SL; caudal-peduncle depth 13.8–15.3 % of SL; posterior margin of caudal fin white; black or dark red area just before white posterior margin of caudal fin; poorly defined blackish blotches on inner surface of opercle in preserved specimens.     

Necrotic and apoptotic cell death induced by Captan on <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Captan is one of the most widely used broad-spectrum fungicide applied to control several early and late diseases of grapes, apples, and other fruits and vegetables, and as other phthalimide fungicides is defined as a multisite compound with thiol-reactivity. Captan can affect non-target organisms as yeasts, modifying microbial populations and fermentation processes. In this study, we asked whether Captan thiol-reactivity and other mechanisms are involved in acute Captan-induced cell death on aerobic growing Saccharomyces cerevisiae. Thus for, we analyze cellular protein and non-protein thiols, cell membrane integrity, reactive oxygen species accumulation, phosphatidylserine externalization, and apoptotic mutants behavior. The results showed that when submitted to acute Captan treatment most cells lost their membrane integrity and died by necrosis due to Captan reaction with thiols. However, part of the cells, even maintaining their membrane integrity, lost their culture ability. These cells showed an apoptotic behavior that may be the result of non-protein thiol depletion and consequent increase of reactive oxygen species (ROS). ROS accumulation triggers a metacaspase-dependent apoptotic cascade, as shown by the higher viability of the yca1-deleted mutant. Together, necrosis and apoptosis are responsible for the high mortality detected after acute Captan treatment of aerobically growing cells of S. cerevisiae.     

Carbohydrate metabolism of the phase variants of purple photosynthetic bacteria

The R and M phase variants of Rhodobacter sphaeroides and Rhodobacter capsulatus were isolated. The growth rates in the dark and in the light in glucose-containing media were much higher for the Rba. sphaeroides R variant than for the M variant. For the Rba. capsulatus R and M variants, growth rates in the dark and in the light in fructose- or glucose-containing media differed insignificantly. The cells of Rba. sphaeroides and Rba. capsulatus phase variants growing in media with glucose and fructose exhibited differences in activity of the key enzymes of the Embden–Meyerhof–Parnas (EMP) and Entner–Doudoroff (ED) pathways. The oxidative pentose phosphate pathway (PPP) does not participate in glucose and fructose metabolism in the studied bacteria. Specific activity of the ED pathway enzymes was higher in dark-grown R and M variants of both Rba. sphaeroides and Rba. capsulatus than in the cells grown under light. Specific activity of the EMP enzymes was higher for the R and M variants of both cultures grown in the light than for those grown in the dark. Activities of the 2-keto-3-deoxy-6-phosphogluconate and fructose bisphosphate aldolases, the key enzymes of the ED and EMP pathways in Rba. sphaeroides M variant grown in the medium with glucose in the light or in the dark, were approximately twice those of the R variant. In the medium with fructose activities of these enzymes in both R and M variants did not change significantly depending on growth conditions. Activities of the enzymes of the EMP and ED pathways in the extracts of the Rba. capsulatus R and M cells grown with glucose or fructose did not change significantly. Cultivation of Rba. sphaeroides and Rba. capsulatus phase variants in the medium with fructose resulted in a considerably increased synthesis of 1-phosphofructokinase. Induction of 1-phosphofructokinase synthesis in Rba. sphaeroides occurred only in the light, while in Rba. capsulatus induction of this enzyme in the medium with fructose was observed both in the dark and in the light. Thus, under aerobic conditions in the dark the phase variants of both bacteria probably assimilated glucose and fructose via the ED pathway, while in the light the EMP pathway was active.     

<Emphasis Type="Italic">Xenopus laevis</Emphasis> peroxiredoxins: Gene expression during development and characterization of the enzymes

Reactive oxygen species (ROS) are produced via catabolic and anabolic processes during normal embryonic development, and ROS content in the cell is maintained at a certain level. Peroxiredoxins are a family of selenium-independent peroxidases and play a key role in maintaining redox homeostasis of the cell. In addition to regulating the ROS level, peroxiredoxins are involved in intracellular and intercellular signaling, cell differentiation, and tissue development. The time course of peroxiredoxin gene (prx1–6) expression was studied in Xenopus laevis during early ontogeny (Nieuwkoop and Faber stages 10–63). The highest expression level was observed for prx1 at these developmental stages. The prx1, prx3, and prx4 expression level changed most dramatically in response to oxidative stress artificially induced in X. laevis embryos. In X. laevis adults, prx1–6 were all intensely expressed in all organs examined, the prx1 expression level being the highest. The X. laevis prx1–6 genes were cloned and expressed in Escherichia coli, and physico-chemical characteristics were compared for the recombinant enzymes. The highest peroxidase activity and thermal stability were observed for Prx1 and Prx2. It was assumed that Prx1 plays a leading role in X. laevis early development.